#outdoor-ops — Public Fediverse posts

The magic carpet ground plane is grounded, but the GTU keeps flying.

Ham Radio Outside the Box receives quite a lot of email every week from readers with questions, comments and suggestions. One such email came about as a result of an article in the outstanding newsletter from the Surrey Amateur Radio Club called the Communicator. The editor of the Communicator is Canadian Amateur Radio Hall of Fame member John Schouten VE7TI. John approached me some time ago to see if I would be willing to be a regular contributor to the Communicator. I readily accepted and I am indebted to the Communicator for publishing a regular series of posts from this blog to the Communicator’s international readers in over 150 countries.

A recent article in the Communicator triggered an email from Guy VA7GI and that sparked a chain of correspondence beginning with a request for more details of the Ground Tuning Unit featured in recent posts on this blog. Then Guy suggested I conduct a test to compare a GTU combined with a Faraday cloth (“Magic Carpet”) capacitance plate on the ground, to a regular set of radials. That sounded like an interesting challenge so I set up a test antenna out in the backyard to find out how the two compared.

An old, bruised and battered, long retired MFJ 20m telescopic whip was mounted on a tripod and promptly caught a gust of wind which sent it crashing to the ground. Fortunately it just missed a large birch tree and landed softly on the grass. More bruises! It was re-erected and secured with cordage to prevent any further falls. Then a 17ft raised wire counterpoise was attached via an RF current sensor.

RF current sensor and RigExpert antenna analyzer pictured in another experiment

RF was applied to the antenna by a RigExpert antenna analyzer and a strong deflection was observed on the current sensor. The meter reading was set to mid-scale by adjusting the instrument’s sensitivity control. Now it would be possible to determine whether the current through the GTU/Faraday cloth was higher or lower than the current passing into the wire counterpoise.

Next step; the counterpoise wire was disconnected and the GTU was attached with a wire to the Faraday cloth on the ground. Once again RF was applied and the relative current was observed on the meter. NB: the current sensor does not measure absolute current values; its job is only to compare relative values. I expected the GTU/Faraday cloth ground arrangement to compare favorably with the wire counterpoise, after all I had made multiple contacts with this arrangement. But, to my surprise, the ground current was now lower than the wire counterpoise result.

Linear-loaded monopole with Magic Carpet held down with rocks to withstand the wind coming across 100 miles of Lake Huron!

My “magic carpet”, made of Faraday cloth ordered from the company named after a Brazilian River, was a purchase made for the purpose of experimentation. To its credit, it served its purpose, but I had some reservations about its suitability for field portable radio operations. The first time I laid it out on my backyard lawn was during a day of bright sunshine. I was dazzled by the sunlight reflected from its surface. Those reflections were probably observable from Earth orbit and certainly detracted from the stealth of a field installation. Stealth was restored with a coat of dark green, non-reflective spray paint.

The outdoor environment challenged the installation with another trial – wind. The wind had already laid the antenna whip down, now it blew under and around my one square meter of Faraday cloth making it difficult to secure it to the ground. No spring gusts were going to defeat this scientific experiment, so reinforced grommets were attached to each corner of the cloth which was then tightly and securely held in its place with tent stakes.

After a few deployments the edges of the Faraday cloth began to fray and were secured with Gorilla tape, but the non-reflective paint was beginning to crack where the magic carpet was folded between uses. And then it failed the current test!

The image shows the Ham Radio Outside the Box Linear-Loaded Monopole with Magic Carpet deployed along the shore of Lake Huron during a recent OOTA activation. No, that’s not a typo, OOTA is “Out On The Air”. Check it out online.

So is the Magic Carpet idea dead in the water? Guy VA7GI had another suggestion: “I have two friends with ham rigs on sailboats. They each use a backstay with insulators as a vertical antenna. You’d think with a saltwater ground they have the perfect ground plane. But it’s not that simple. They use folded copper wire in the bilge for a ground. They don’t want to drill a hole in the hull or dangle a wire near the prop. Alternatively, they could use Faraday cloth and your GTU. I bet that’d make a huge difference, especially for trans-ocean sailing.”

So magic carpet rides on the wayward wind are grounded, at least for now. My home QTH is surrounded by the Great Lakes so maybe the the idea of a “floating ground” is worth exploring?

The magic carpet is grounded, but not the GTU!

In a later email Guy VA7GI said: “My intuition is that most verticals have compromised radials, placed wherever convenient or possible. Perhaps all vertical antennas would benefit from a GTU.” On the first point Guy may be right. There is a lot of discussion online about the placement of radials. On the ground, or raised above ground? Positioned to direct an antenna’s radiation in a particular direction? Or spread evenly to enhance the widest ground coupling? And, of course, how many radials?

Guy’s second point: “Perhaps all vertical antennas would benefit from a GTU” got me thinking. Could that idea be of benefit in implementing a limited footprint, vertical quarter-wave field antenna? How does a Ground Tuning Unit work? It resonates a capacitive ground path which increases the current in “the other half” of an antenna. That is an idea worth exploring, so a further test was conducted.

A new, improved linear-loaded monopole was erected. The ham-made ladder line previously used has been replaced with a slightly longer (11.5ft) section of 450 ohm commercial window line. When erected as a quarter-wave vertical worked against a GTU tuned counterpoise, the length is not critical within certain restraints because the electrical length of “the other half” is adjustable by the GTU. A shorter radiating element with a longer counterpoise works, as does a longer radiator with a shorter counterpoise. The antenna impedance changes, but unless taken to extremes, it remains close enough to keep the SWR presented to the transceiver within acceptable limits.

This new test was designed to discover whether a GTU could resonate short raised radials sufficiently well to make the antenna an efficient radiator. This arrangement would get a passing grade if the current through the GTU/short radials combination matched the current passing through full-length radials. It didn’t work out too well with the Faraday cloth so I was skeptical about the outcome of this test.

My 11.5ft linear-loaded monopole was paired with two raised radials each 16.5ft long but with links at 11ft and 13ft. Once again, the current was monitored with the full-length radials and set to mid-scale on the meter as a benchmark. Then the radial links were opened at the 11ft point and the GTU was adjusted for maximum current. This time there was a different outcome. The current matched the result obtained with the full-length radials. So Guy – you were right!

Further tests will be conducted with even shorter raised radials to determine whether the current can be maintained with a minimum possible ground footprint. The objective is to design a simple pedestrian portable antenna that can be deployed in a limited space environment such as small clearings in the woods.

The man from the future

Another project remains on the slate and that is the idea of using a helically wound radiating element as suggested by a reader in New Zealand (the “man from the future” – New Zealand is 16 hours ahead of the Eastern Time Zone). Ham Radio Outside the Box will cover that in a later post.

Meanwhile a package arrived in the mail

I was very pleased to receive a package in the mail from Tim KQ4TQ. Tim sent me a GTU he had built himself and asked me to evaluate it. Tim’s GTU is a slightly different build to my own and I will certainly evaluate it fully and report back here soon. Thanks Tim!

Thanks to all Ham Radio Outside the Box subscribers

I put a lot of work into preparing posts for this blog, but it is a labor of love. I seek no financial return, nor will I accept any; this is a hobby not a business. My motivation is to stimulate discussion and learn from experiments and the feedback of other hams. So it was gratifying when WordPress informed me recently that Ham Radio Outside the Box has now surpassed the modest level of 1000 subscribers. Knowing there is a steadily growing interest in the content generated here makes all the work worthwhile. Thank you!

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #Antennas #Counterpoise #Ground #OutdoorOps

Shacks On The Air anyone?

There has been an explosion of “On The Air” programs lately. I think SOTA (Summits On The Air) may have kick started the trend. To my mind SOTA remains the purest and best of them all. Although there are many drive-up summits, many others require strenuous effort to reach the “activation zone” on foot. Unfortunately, here in southern Ontario, we have very few high elevation points. Some peaks over 500 meters (1600 feet) can be found, but without the required “prominence” to qualify for the SOTA program. I visited one of the few SOTA peaks in my area once. It was hard to see why it was classified as a peak. The activation zone was a section of flat road. SOTA forbids activating from inside a vehicle so all an activator has to do is park at the side of the road, get out and play radio at the roadside. Piff!

Woof Woof

Some friends and I enjoy a leisurely CW rag chew once a week. We have one thing in common – mourning the loss of once-loved canine friends. At the end of every session we sign off with “woof”. So when I think of the World Wide Flora and Fauna program (WWFF) my mind interprets that as “Woof-Woof”.

WWFF is very popular in Europe and to a lesser extent in North America. If you hear a station signing off with “73 44” you will know it is a WWFF QSO in which 44 contacts are required to activate a park. Some of the “Woof-Woof” program rules are quite strict. If you are operating from inside multiple parks you can only claim one for your activation, unlike POTA where one set of contacts can qualify for multiple activations in the right location. SSB participants in xOTA programs greatly outnumber CW operators so, although getting 44 contacts by phone may be relatively easy, getting the same QSO count by CW is sometimes more challenging. Fortunately, QSO counts for operating sessions are cumulative so you can return to the same park as many times as is necessary to validate an activation.

POTA

From humble beginnings the Parks On The Air program has exploded to become a formidable force in amateur radio. Every day there are multiple parks being activated around the world. The required QSO count to qualify an activation is 10. Ten is much more attainable than 44, but even so, there are days when even that number is a challenge. For those of us who like to handicap our operations by using QRP, a day of poor propagation conditions can bury our signals in the noise. I have participated in POTA for the last few years and have had very few outings in which I experienced a “busted activation”, i.e. made fewer than 10 contacts. Some operators avoid busted activations by making HT to HT VHF simplex contacts with other hams in their group. If you think that’s a good idea there is a way to make every POTA session an effortless success regardless of propagation conditions.

In days gone by the local indigenous hunters would drive herds of buffalo over a cliff where young braves would finish the kill. The hunt provided food for a whole winter. During one hunt a young brave was crushed by a falling buffalo and suffered the injury that gave this Alberta park its name.

POTA was predicated on the idea that fewer rules makes for better participation. That’s a good premise and has worked well making POTA the “elephant outside the room”. On the downside, even the few rules that are in place are not enforced. When I made the suggestion that a Park to Park contact should mean a contact between two different parks, POTA management politely suggested I should forget about it and just enjoy my own operations.

I read one account of an “activation” completed within 100 feet (30m) of a park boundary. That is valid for trails, but not for actual parks. I know that particular park and it does not qualify for the 100 feet rule. Generally, an operator and all their equipment must be completely within a park’s boundary. But perhaps, if that rule doesn’t work for you, “forget about it” and enjoy yourself.

The Drive-Thru activation

Unlike SOTA, POTA does not forbid operating from inside a vehicle. This has led to something variously called “Parking Lots On The Air (PLOTA)” or “Drive-Thru” activations. Mea Culpa; I have been guilty of this several times but I try to avoid drive-thru activations except in winter. In winter, brave Canadians don’t even button up our Mackinaws until it gets to 100 below, and we stir our coffee with our thumbs. It is only out of respect for our radio equipment that we would even consider operating from inside the comfort of a vehicle when the howling wind is blowing the snow horizontally and the mercury in the thermometer is frozen solid.

Kakabeka Falls, northern Ontario, the “Niagara of the North”.
If you gotta moment during your PLOTA activation, step outta the car and take a look.

In summer many of us prefer to enjoy a hike or visit some of the spectacular scenery in our parks before or after a radio session. But for some diehard POTA activators, the name of the game is contacts – lots of ’em – then drive on to the next park where once again its eyes down, antennas up; no time to get out of the car. We each enjoy our hobby in our own way.

All the other OTAs

There are so many OTA programs these days it’s getting out of hand. How about TOTA? Did you think it means Towers On The Air? You are correct. But it also means Toilets On The Air. How about that; you can play radio while attending to your bodily functions. I know of one ham who takes his Handy-Talkie into the shower so he doesn’t miss any calls from his buddies; SHOTA anyone? TOTA also means Tiles On The Air. A Tile is a Maidenhead subsquare about 5km by 7km.

I am surprised nobody has thought of What 3 Words On The Air (W3WOTA?, WWWOTA?). W3W is a ridiculous (my opinion) method of dividing the world up into small squares each designated by three unique words. A lot of words are needed to identify all the world’s locations so some very rare and unusual words are employed. The English language is pronounced very differently around the world, and even within the United States. I met a very interesting fella who proudly came from “the South” once. He explained that the words “pin” and “pen” are pronounced exactly the same where he came from. Imagine trying to battle poor propagation conditions while interpreting a strange dialect relaying a rare and unusual word. When I posted on this topic some time ago I received a comment that W3W is universally accepted by emergency responders and we should just get used to it. Yay, let’s all get used to confusion and damn the torpedoes.

The spectacular Athabasca Glacier along Icefields Parkway, Alberta. Maybe worth stepping out of the car to take a look. It is possible to hike right up to the base of the glacier, or take a specially-equipped bus ride out on the ice.

Don’t laugh please

Try not to titter when I introduce the next OTA. It is called HEMA and stands for “Humps Excluding Marilyns”. I believe it is a European program but I haven’t come across it on this side of the Atlantic. My first reaction was to wonder why Marilyn’s humps were excluded. I am sure HEMA has attracted a lot of jokes but it is actually a serious program. A “hump” is a summit with at least a 100 meter prominence, while a “marilyn” is a summit with at least a 150 meter prominence. So a hump excluding marilyns is a summit with a prominence between 100 and 150 meters. Robert Ripley might have made a TV episode about this one.

I’m OOTA here

I have become involved with one of the new OTAs and have filed my first couple of logs. It is called “Out On The Air (OOTA)“. As “the seasons go round and round and the painted ponies go up and down” (Joni Mitchell) the carousel of time begins to take its toll and I have less energy than I used to have. Just a few winters ago I would strap on snowshoes and haul a sled full of radio equipment across the deep and crisp and even white landscape to do an outdoor winter activation. No more. Maybe less inclination to join the OTA rat race too. Now I am content to set up in the sunshine and enjoy just being outdoors with my radio, and maybe a newly built antenna. If I make a few contacts I am satisfied. The great thing about OOTA is that there is really only one rule – just get out of the shack and make at least one contact. That’s just fine with me. If you do a POTA or “Woof Woof” activation, or you activate a hump that wasn’t Marilyn’s that counts too. Softly, softly, catchee monkey; relax, breathe; soak up the summer sun; enjoy life, it doesn’t last forever.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #CW #OutdoorOps #POTA

A Mini Ground Tuning Unit and a magic carpet for portable ops

In the last couple of posts I discussed my quest for a simple portable antenna that could be rapidly deployed in a very limited space, for example in a small clearing while hiking through the woods. Such an antenna would have to be a short, yet efficient, vertical that occupies a very small footprint on the ground.

The first successful candidate is a Linear-Loaded Monopole which meets all the design criteria and has performed surprisingly well in initial field tests. Ham Radio Outside the Box has received another suggestion from a reader who lives in the future (I’ll explain in an upcoming post) for a helical antenna. We’ll be hitting the outback (out in the backyard) to experiment with that idea very shortly.

Meanwhile, another design criterion is that a hiking antenna should occupy a very small footprint on the ground. My local woodlands sit atop the Niagara Escarpment and are often very rocky – sometimes with wide and dangerous cracks in the bedrock. There is often nowhere to set up ground radials and limited options for raised radials, so an alternative arrangement for “the other half” of a vertical quarter-wave antenna is necessary.

The solution that has been discussed here on Ham Radio Outside the Box is to use a Ground Tuning Unit (GTU) coupled to a small capacitive plate on the ground. There is some spooky physics associated with how a GTU works which we’ll discuss later in this post. But don’t let that discourage you; the science of physics is full of mind-mending spooky stuff.

Introducing the Mini GTU

I built a GTU some years ago which has seen a lot of use. Unfortunately it is rather big for carrying on a hike through the woods. I needed a small, lightweight version for this new use case. The Mini GTU is a simple device as can be seen from the wiring diagram here:

The device comprises four inductances – 4, 2, 1 and 0.5 microhenries. Each inductor has a SPST switch that can be used to short circuit it and thereby bypass it from the inductance selection. This arrangement allows binary selection of inductance from 0.5 to 7.5 microhenries in 0.5 microhenry increments. For this application it was considered unnecessary to increase the inductance any further, but more inductance could be added by doubling the value of each added inductor.

The Mini GTU is connected to the shield side of the coax that connects the antenna to the radio. This is exactly where you would normally connect radials. The other end of the Mini GTU connects to a capacitive plate laid directly on the ground.

What? No ground current meter?

A GTU usually has a ground current meter in series with the current path. That is achieved by adding a sampling circuit – a small toroidal core inductor with a single secondary turn, a diode rectifier and meter. Again, unnecessary in this application because as the current through the GTU increases, so does the current in the radiating part of the antenna. This is indicated by observing the SWR indicator on the radio.

Construction of the Mini GTU

I built the device on a small piece of perfboard. The following two pictures show the layout of the components. As usual, my collection of T37-2 and T37-6 powdered iron cores were deployed. The smallest inductor (0.5uH) was wound on two stacked T37-6 cores. The 1uH and 2uH inductors were each wound on two stacked T37-2 cores. For the 4uH inductor I redeployed the six T37-2 binocular style cores I had used on the 2T2C inductor discussed in a recent post.

Why not just use one tapped inductor and a rotary switch?

That’s a good question. I could have wound a single 7.5 uH inductor with taps every 0.5 microhenries and used a rotary switch to select the appropriate inductance. But that would require good precision in locating the tap points since 0.5uH is a very small inductance that is more easily wound on a small core.

It is unnecessary to wind these smaller inductors to the precise values specified. Even using tiny T37 cores, a single turn can change the inductance quite a bit. I strove for a precision of about 10% which turned out to be very achievable.

Mini GTU top side showing polyvaricon and inductance selector switches Mini GTU bottom side showing inductors and switch wiring

About that capacitive plate on the ground …

Various different types of plate were tried. Pizza trays, hardware cloth and chicken wire all sorta worked. I wasn’t happy with any of them though. They are not very easily carried on a hike and one, the hardware cloth, had sharp cut steel wire edges that attacked me viciously when I handled it. A better solution had to be found.

Why don’t you come with me … on a magic carpet ride

I bought a piece of Faraday cloth to try out. This material is very light and easy to pack away in a backpack while hiking. Faraday cloth is sometimes referred to as “magic carpet” in ham radio circles and perhaps with good reason. It is made of several layers with interwoven dense conducting material. I purchased a piece of magic carpet from the “Brazilian River” company. It measures 39×43 inches (very nearly 1 square meter).

One square meter is a little larger than I had hoped for in this application so I folded it twice to created a nearly square smaller footprint. If that worked the plan was to cut the sheet into four pieces and use just a single piece for my hiking antenna. Did it work? With the smallest footprint and adjustment of the Mini GTU for best SWR indication on the radio an SWR of 1.68:1 was obtained. Not bad, in fact very usable, but could a bigger magic carpet go even better?

Second test: the magic carpet was folded in half. Now it was a rectangle and with the Mini GTU adjusted the best SWR dropped to 1.45:1. Obviously a trend had been established. Could the whole sheet of magic carpet top the trend?

Third test: now the whole square meter of Faraday cloth lay spread on the ground, secured from the wind with some rocks surreptitiously borrowed from my wife’s garden bed (thanks to all the ancient Norse gods she doesn’t read my blog). The SWR dropped again to 1.13:1. Jingolaba!

Conclusion: “magic carpet” seems to be best solution. If the available trail-side operating site is too small for the whole one square meter of cloth, it can be folded once or even twice while keeping the SWR well below 2:1.

Other hams have tried even larger sheets of Faraday cloth for a ground plane and achieved good results, but without a GTU. The advantage of the GTU is that only a very small capacitive ground plate is required to achieve the same or better results.

One more final note: antenna physicists will note I have been using SWR as a measurement of the effectiveness of the hiking antenna. Of course, lowest SWR does not imply resonance, but radios do not have any way of measuring and displaying complex impedance values and an antenna analyzer would add to the weight needed to be carried into the field when hiking.

Addendum: a bit of spooky physics to (explain?) how a GTU works

A quarter-wave vertical antenna radiates sinusoidal voltage and current waves into an imaginary medium called the “ether”. At the same time a mirror image of these waves is generated in the ground. These mirror image waves are as real as the “ether”. If we were to bury a current meter in the ground beneath the antenna would it record the mirror image? Unrenowned scientists like myself (I earned a bachelor’s degree in physics way back when) say no.

There are three reasons why not. First, and most obvious, we cannot read a meter buried in the ground. Second, no because the mirror image is virtual not real. And the third reason is really spooky. If you search on the Whirled Wild Web for the “double slit” experiment you will learn that spooky physics stuff only happens when scientists don’t try to monitor it. That experiment is one of the most mind-bending, unexplained phenomena that even amateur scientists can attempt to reproduce. So what happens to the real current flowing through the GTU? RF gotta go somewhere.

The concept of virtual images can be seen in this picture of looking at a transceiver in a mirror. If we trace the path of the light rays through the mirror we can see a mirror image of the transceiver at the same distance behind the mirror as the actual transceiver is in front of the mirror. Step behind the mirror and you won’t find the virtual mirror image. A fanciful thought emerges here. Maybe science will one day find a way to create that expensive radio you can’t afford using a virtual image held behind a mirror.

Mirror image – is it real or virtual?

Physics can take spookiness to extremes. My own favorite is a topic called quantum entanglement. If really mind-bending science interests you, try typing that into your search engine. Even one of the greatest scientific minds of all time, Albert Einstein, called that “spooky action at a distance”.

Back to the future

My next project will be developing this week. I replied to the reader “from the future” and will be exploring his ideas in my backyard where intermittent snow cover is heralding the very slow birth of another spring season. Stayed tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #Antennas #Ground #OutdoorOps #Portable

A Linear-Loaded Monopole antenna for hiking

There is a lot of information online about Linear-Loaded Dipoles, but I haven’t found anything at all about cutting a Linear-Loaded Dipole in half to create a Linear-Loaded Monopole worked against ground. The legendary L.B. Cebik (W4RNL, SK) published a design philosophy for an 80m Linear-Loaded Monopole, but it didn’t match what I had in mind. So I decided to build one for the purpose of experimentation. Maybe I could make it into a compact, lightweight antenna capable of rapid deployment while hiking – maybe.

What is Linear-Loading?

According to my search engine’s “Search Assist”, “Linear loading is a technique used in antenna design where a portion of the antenna wire is folded back on itself to reduce its overall length while maintaining good electrical performance. This method allows for a shorter antenna that can still operate effectively on the desired frequency.”

Sounds very simple doesn’t it? In the real world, where the RF hits the ether, it gets a little more complicated – especially when venturing outside the box. I could have made life nice and simple by building a Linear-Loaded Dipole; there are lots of designs available online that I could have used. But a dipole is too large for agile, rapid deployments; it needs a taller pole which, in turn, requires pegging into the ground and guy wires. I could use a tree limb for support, but only if suitable trees are available; often they are not. No, my requirement for a very simple hiking antenna implies a vertical antenna – a short vertical antenna.

Short antennas are easy to build; simply add a loading coil at the base and Bob’s your uncle. But that won’t qualify for my purposes. Short loaded antennas have a reduced radiation resistance and ohmic loss in the coil – they are inefficient. So how to shorten an antenna while maintaining efficiency? That’s where linear loading comes into play. A linear-loaded antenna is almost as efficient as a regular version.

How to build a Linear-Loaded Monopole?

It should have been “EZ-PZ”. Just take the dimensions from any of the online designs for a Linear-Loaded Dipole and cut them in half. That’s where I started. For a 20 meter antenna, a length of around 11 feet of window line, shorted at one end, is a good starting point. I hauled it up the mast in my newly glacier-free backyard, attached a counterpoise wire and started trimming. Between snips the resonant frequency was monitored on my RigExpert antenna analyzer. I use the term “resonant frequency” loosely in this context. The expected impedance of a quarter-wave vertical is around 37 ohms which implies there will be some reactive component to the impedance. I searched for a dip in SWR over a wide frequency range until it was possible to locate where the antenna was “resonant”.

Home made ladder line. The separators are made of shrink wrap heated with a Weller soldering gun with plastic welding tip. Lots of work and not very elegant, but practical and cheap!

So long John?

A low SWR in the region of the bottom end of the 20 meter band was the target, but the dip in the curve was below the bottom of the band – way below. I snipped and snipped until that dip fell where it was needed. Then the counterpoise length was adjusted until the lowest SWR was obtained. How long was my ladder line? A large pile of snipped ladder line lay on the grass beneath the pole. When I took the antenna down, laid it out on the ground and measured its length it was quite a surprise to see the ladder line radiator was only 8.67ft (2.64m) long. And the counterpoise length was 18ft (5.5m).

Jingo-la-ba!

Will it QSO? I fired a smidgen less than five watts into it and received a response from a station somewhere in the US with an encouraging signal report. Well, at least it “works”. But now came the next step. That pesky 18ft counterpoise had to go, to be replaced with the 2T2C (Tuned Tank Circuit Coupler) described in the last post.

A new challenge

The 2T2C ground coupler was directly connected to the ground side of the short coax feedline and a further wire was added to connect to a small capacitance plate on the ground. Life is complicated and then you die, so why do I insist on adding more complications? It’s called experimentation – experiment and learn! I learned. I learned that my choice of inductance and capacitance for the 2T2C resulted in impossibly sharp tuning of the ground circuit. The 2T2C needed a design modification to reduce the inductance and increase the capacitance. Spreadsheet modeling suggested this would make the 2T2C easier to adjust. I needed to confirm that before rebuilding the 2T2C, but how?

L-match innovation

The answer came in the form of a variable L-match that I built quite recently. It has switch selectable inductors and a variable capacitor. It could be adapted to fit this bill very nicely.

This idea was inspired by VK3YE who published a YouTube video about it some time ago. At one terminal of the L-match a connection is made to the BNC center conductor. At the other terminal, a connection is made to the shield side of the BNC. If you trace the signal path through the device it can be seen that the inductors and capacitor are in series. Now we have a Ground Tuning Unit (GTU) and can use binary selection of the inductances, together with rotating the variable capacitor, to determine the combination of inductance and capacitance for easiest tuning of the ground connection.

The inductances available on my L-match are 0.5, 1, 2, 4, 8 microhenries, allowing the inductance to be varied up to 15.5 microhenries in 0.5 microhenry increments. The variable capacitor is a 30-160pF polyvaricon.

Now, with the 8.67ft linear-loaded vertical erected and the “L-match GTU” making the ground connection via a capacitance plate on the ground, it was easy to select values that would allow smooth adjustment of the antenna SWR. It was found that 1 or 1.5 microhenries worked best. With these values selected the polyvaricon could be adjusted around mid-range to easily select best SWR.

A caution!

There’s a gotcha with this technique. My L-match has a switch to connect the top end of the variable capacitor to either the input or output. This is used to enable fast selection of either high or low impedance antennas. Referring to the diagram above, if the switch (not shown) is set to connect the variable capacitor to the left side of the inductors, this technique will not work. The inductors will be out of circuit and only the variable capacitor will be in circuit.

Will it still QSO?

My low-band QMX was dug out of its field pack and hooked up to the revised antenna (8.67ft of vertical window line with the “L-match GTU” providing the “other half” of the antenna. Using the “Tune SWR” feature of the QMX, the best SWR of 1.36:1 was obtained by a very small adjustment of the variable capacitor in the L-match GTU. Then it was time to go hunting. My best contact was in the state of Arizona (the “Arid Zone”?) almost 3000km away from my station in Southern Ontario. Signal reports were 599 each way. My sent report was a genuine 599 suggesting the antenna has good ears. The 599 report I received may have been genuine or perhaps it was just a “contest report”. In any event a good solid contact was made. A second contact into North Carolina only yielded a 549 signal report, but perhaps the low angle radiation pattern favored longer distance contacts.

Notice that the L-match GTU has no RF current meter. I could perhaps have inserted my home brewed RF current meter in circuit, but it wasn’t really necessary. Adjusting the ground current also regulates the radiating element current. Simply adjusting for lowest SWR indication on the radio peaks the radiated energy.

For practical outdoor use while hiking through the woods and rapidly deploying the antenna in clearings, the L-match GTU will be replaced with a much smaller series L-C coupler (2T2C). A 13ft Crappie pole is used to support the antenna. It collapses to the perfect length for carrying inside a fishing pole bag (no surprise there then) and is very lightweight.

There’s another gotcha

When the current distribution on the antenna was viewed in EZNEC it was discovered that the current maximum is in the ground circuit instead of in the radiator. Just like any ground-mounted antenna, this can lead to ground losses and inefficiency. However, the primary design objective was not to seek a Nobel Prize in antenna physics, but to come up with a design that meets the objective of a rapid deployment, simple antenna for hiking through the woods. The Linear-Loaded Monopole may just meet that requirement, but I have other ideas to try first. Stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #Antennas #Counterpoise #Ground #OutdoorOps #Portable #QMX

The “tootie-toosie” and the Hiking Antenna

My favorite way of operating is to hike into the woods, find a clearing, set up a quick and easy antenna, make one or more contacts and move on. Well, to be honest, I might pause long enough at a back country waypoint to get out my Aeropress and brew up a refreshing cup of Joe.

To do this my antenna must be simple, compact, lightweight and (hopefully) efficient. The simplest arrangement that meets those criteria is an end-fed wire, but quite often the trees are not tall enough, or contain dense brush in which wires can become entangled. I needed something compact and self-contained that is easy to carry into and set up in a dense wooded area.

I came up with a couple of ideas. First up to bat was a Linear-Loaded Monopole (LLM: no, not a Lunar Landing Module). The LLM is a recent bizarre invention that escaped from my basement skunk works lab and made its virgin QSO in the outback (out in my backyard). But I also had another idea on deck – a converted photo lighting tripod with short whip that I used very successfully out in the field last summer.

Hiking antenna 01: a Linear-Loaded Monopole Hiking antenna 02: 13ft tripod/whip

Other craft ale inspired ideas may enter the fray during the course of the coming weeks and months but, for now, let’s discuss these two strange RF launch systems.

A rapid deployment hiking antenna does not share the same design imperatives as other less temporary antennas. The efficiency – the proportion of energy radiated compared to the amount delivered to the antenna by the transceiver – is obviously important, especially since my transient operating base will be primarily QRP. Rapid deployment is the key objective; it must be very fast to set up and tear down. Hiking expeditions often take me well away from my vehicle and any road. I operate in areas that are heavily forested and patrolled by sometimes aggressive black-coated guardians with big teeth and long sharp claws.

Another requirement that factors into the design is a small ground footprint. Trails in these parts are often shrinkingly narrow, rocky, uneven and sometimes covered in mud or pools of rainwater. Laying out a system of radials on the ground is not an attractive proposition and sometimes it is next to impossible. In a recent post (Link: Be gone pesky radials!) we introduced an alternative using a Ground Tuning Unit (GTU). Well, that’s all fine and dandy but the GTU I had built is a a little big and heavy for carrying down a trail. I challenged myself to come up with an alternative.

Most of my outdoor operating time is spent on one band: 20 meters, so I wondered whether it would be possible to design and build a much simplified alternative to the GTU that would be very small, very light and serve the same purpose. I came up with something that met those criteria very well indeed.

Enter the “tooty-toosie”

The “tootie-toosie”, or 2T2C is a Tuned Tank Circuit Coupler. The idea involves a tank circuit designed to resonate at a desired frequency. The frequency I targeted was 14.060 MHz which is the CW calling frequency in the 20-meter band. This L-C circuit is actually a series connected resonator so maybe not strictly a “tank” circuit but I liked the “tootie-toosie” name anyway.

It is actually quite difficult to wind an inductor and select a capacitance for resonance on a specific frequency. Instead I targeted the bottom end of 20m (I am a CW op). Component tolerances limit the accuracy so I gave it my best shot and the end result was quite good. A simple L-C resonant circuit will have a fairly low Q and that will give some leeway in the frequency response. I measured the finished project on a nanoVNA and the peak in the curve showed a useful bandwidth at the bottom end of 20m.

I had already designed a great little tool to assist in a project like this. It is a LibreOffice Calc spreadsheet that will compute the resonant frequency of an L-C tank circuit, or the capacitance required with a known inductance to resonate at a desired frequency; or the inductance required with a known capacitance to resonate at a desired frequency.

I plugged in some parameters to come up with component values needed then began construction.

20m 2T2C ground coupler

Just like with previous projects I didn’t have the correct toroidal cores in my component drawer. And just like with those previous projects I leaned on my inner MacGyver to find a solution. T37-2 powdered iron cores were the best I could find and, just like before, I stacked multiple cores together to make a bigger aggregate core. As I understand it, inductors wound on toroidal cores perform best when as much of the winding as possible lies within the core. That gave me an idea. If I built a MacGyver version of a binocular core most of the winding will be inside the core. Could that work?

MacGyver inspired binocular core

Here is how it came together. Two tightly stacked sets of three T37-2 powdered iron cores were put together and secured with electrical tape. Then thin enameled copper wire was wound through the cores until the cores were full of wire. [By the way, the enameled copper wire was scrounged by unwinding old surplus transformers I had in my junque drawer]. I had no idea whether this would work but I gave it a try anyway. The inductance measured on my L, C meter was 29 microhenries.

The tuned circuit calculator told me that was probably too much inductance, but it would be easy to reduce it by unwinding a few turns of wire. I wanted to use a 10pF ceramic capacitor (I have hundreds of them) so I needed only about 13 microhenries in the inductor.

After carefully unwinding the cores and measuring the inductance I got it down very close to 13 microhenries. The capacitor and inductor were quickly soldered together in series to create my tuned circuit.

About that capacitor

A tiny ceramic disc capacitor looks a little dodgy in this application. It has to carry the full AC current flowing in the ground circuit of whichever hiking antenna is chosen. Operating QRP puts less stress on the capacitor so I am hoping it can carry the load. As a backup a short length of thin speaker wire, or maybe even coax can be substituted in place of the ceramic capacitor.

[UPDATE: the ceramic capacitor has now been replaced with a compression trimmer. The only value I had available is 3-30pF so I reduced the number of turns on the coil so that the trimmer could be adjusted near its top end. Adjustment is quite coarse but it gives some flexibility to peak the ground current fairly accurately.]

First field test

Most of the winter snow that was in my backyard has now melted so I was able to set up the tripod/whip antenna shown in the picture at the top of this post. Last summer this antenna was used with either two raised radials, or four ground radials. Will it work with the 2T2C ground coupler? On the day of the test there was a major solar storm and the bands were silent, but at least it would still be possible to see if the antenna would tune up with the radials replaced by this new arrangement.

This antenna has a radiating element only 13ft long made up of a 9ft Buddipole whip with the remainder coming from the tripod main tube itself. It requires a 4:1 unun and a tuner but has the advantage of operating on multiple bands from 20m up to 10m (but used as a fixed 20m antenna in this experiment).

The test was successful in demonstrating that the antenna with this new fixed, tuned ground system would deliver a low SWR (1.3:1) to keep the transceiver happy. The next step, when the bands cooperate, is a full magic smoke test.

Ham Radio Outside the Box will report back when the hiking antenna options have been exposed to full field conditions. I am looking forward to getting back into the woods with my radio gear after another long, snowy winter!

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #Antennas #Counterpoise #CW #Ground #OutdoorOps #Portable

Isn’t every quarter-wave antenna really a half-wave antenna?

It’s a bit early for April Fool’s jokes so this is a perfectly serious discussion. Just maybe, the distinction between a quarter-wave and a half-wave antenna is a bit more obscure than we thought. Which is better; a quarter-wave or a half-wave antenna? Does it even matter if indeed every quarter-wave antenna really is a half-wave antenna? The answer is not straightforward and we will explore why in this week’s post.

Let’s all use our noddles

An expert could be defined as somebody who knows at least a little more about a subject than most other people. I am not an expert, but I do have a very inquiring mind. Don’t accept anything you read here without question. Science is the process of submitting a hypothesis which can be challenged, refuted, updated or even discarded. New hypotheses can replace old ones as further studies are completed. Treat everything you read here as a hypothesis; it might be completely wrong, partially right or even brilliantly correct. Challenge it with your own critical thought because I thought I was wrong once – but I was mistaken 😉

How to improve the efficiency of an antenna by burying half of it in the ground

Sounds ridiculous doesn’t it? But isn’t that exactly what we do when we erect a ground-mounted quarter-wave whip with a set of radials? What role do the radials play? Do they reflect the signal away from the ground? “Experts” say no, so my hypothesis suggests that an efficient set of radials establishes a ground plane that is better (or worse) than the actual ground itself.

Current in a ground-mounted quarter-wave antenna. Green line represents ground.

The Good Earth

The problem with “the good Earth” is that it isn’t always. It depends on the conductivity of whatever our antenna is mounted on. Seawater could be considered the best ground plane but it has an unfortunate habit of being a slightly unreliable support for antennas. Moving inland a little we have sand, nice firm sand. The sea is still close by and helps with antenna efficiency and directionality, that is if you wish to send your signal in the direction of where the sea is.

Unfortunately for me, the closest sea (James Bay in the near Arctic) is over a thousand kilometers to the north and is frozen for much of the year. So I have to rely on the conductivity of the soil in my area. I live in the Great Lakes region and I am surrounded on three sides by the waters of mighty Lake Huron. Pure freshwater is almost a perfect insulator, but I have the advantage of living on the Niagara Escarpment and water from my well contains over 2000 parts per million of dissolved solids. That may improve my soil conductivity for ham radio purposes but it cost me a small fortune in water treatment equipment to get rid of those dissolved solids to make the water drinkable.

Whenever I wish to deploy a ground-mounted antenna I have to rely on ground radials because sometimes my portable operations take me to locations where I set up on the ancient bedrock of the Canadian Shield, or sandy lakeside beaches where the ground conductivity is not so good.

How do ground radials really work?

I hypothesized earlier that radials establish a ground plane. Their purpose is to give the antenna – and it’s image in the ground – a zero reference point. If this ground plane is efficient (i.e. lots of radials) the current in both the ground and the antenna will increase. Higher current in the antenna means more signal is radiated. And what about that higher current in the ground? The earthworms will thank you for the extra warmth.

By the way, counterpoise or radials?

The two terms are often confused. When I use the term “counterpoise” I use it to mean “the other half of the antenna” which may be made up of a set of radial wires, or a blanket of Faraday cloth, or AA1AR, Bruce’s copper mesh.

End-Fed Half-Wave antenna current distribution

What’s to be done?

If half our signal is warming the winter nightcrawlers what can we do to redirect the crown joules in a more useful direction? First, let’s examine the current distribution in a half-wave antenna wire.

Let’s call it a “voltage-fed” antenna because a lot of half-wave antennas are end-fed. It could equally be a center-fed dipole which is also a half wavelength long. There are several different ways to erect an End-Fed Half-Wave antenna:

• Vertical
• Flat top
• Inverted-V
• Inverted-L
• Sloper

Notice that however we erect it, the entire antenna remains above ground. Some online advice suggests the ends of the wire can be placed close to the ground because there is almost no current there. Others disagree and note that the ends of a half-wave wire are high voltage points and should be kept above head height. And it isn’t just for safety reasons. What are the effects of placing a high voltage point close to ground? Could there be some ground interaction that affects the antenna performance. Any experts care to comment?

Enter the Dipole

A dipole or an EFHW can be erected vertically. Let’s talk about the dipole. It is a center-fed half-wave (a CFHW if you like acronyms). A vertical dipole could be described as a quarter-wave vertical antenna with a quarter-wave counterpoise. Can’t see it? Suppose the counterpoise section is tilted away from vertical. Now it looks more like quarter-wave with a counterpoise. But, the whole antenna is still a half-wave, isn’t it?

Bifurcate that counterpoise

A bifurcated counterpoise is a fancy way of saying split it in two, or in other words, duplicate it. Why? Well again, this is my personal theory. The lower half of a vertical dipole may come close to ground unless it is raised high enough. Ground effects may distort the radiation pattern. If we add an extra wire to the counterpoise section the antenna looks like an Inverted-Y and the current in the counterpoise is split between two conductors. If the current in each conductor is half that of a single conductor the resistive loss in the counterpoise section will be lower, and any ground interaction may be mitigated.

I have occasionally used an Inverted-Y for many years. It was one of the earliest antennas I ever built and performs well. An Inverted-Y built for 20m has to be erected at a height of at least 30 feet (~10m). At that height the feedpoint sits about 13ft above ground and the two radials must be spread at quite a wide angle to remain clear of the ground. I wonder whether we could make this antenna more stealthy? A 30ft mast in a busy public place tempts unwelcome attention from passers-by and park officials. Some ideas rattling around in my old, grey noddle are:

• Lower the apex by shortening the radiating element with a low-loss capacitance hat at the apex
• Reduce the length of the radiating element AND the radial wires using linear loading (folding the wires back on themselves with a small spacing)

Any other ideas from readers would be most welcome. Let me know what you think in the comments.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #Antennas #Counterpoise #Ground #OutdoorOps #Portable

Be gone pesky radials!

One of the biggest bugbears of portable operations in a public space when using a vertical antenna is having to lay out radials – either on the ground, or raised. I have told the story of the dancing lady before on this blog; she performed a little jig when advised to be careful of the wires on the ground. Some of the parks I frequent are quite small and busy in the summer months, so I always have to be cautious about creating a potential hazard for other park users.

Even if I find a nice quiet area along a trail, there is often limited space in which to spread my wires. Alternatively, I may be on a mission to operate with multiple rapid deployments – drop my pack, super fast setup, operate, move on. A small vertical antenna is a very convenient way of getting on the air with minimum fuss – except for the radials.

What is the function of radials?

It doesn’t matter whether the radials are on the ground or raised, they form a counterpoise – “the other half” of an antenna. The current flowing through the radial system controls the current flowing into the radiating element. An efficient set of radials allows maximum current to flow through the whole antenna system. The current flowing in the radiating element is equal to the current flowing into the radials. More current equals more signal being radiated.

We can throw a single wire on the ground and call it a counterpoise – there seems to be a magic length of 17 feet, at least that’s what we may be led to believe from reading many online accounts. Seventeen feet may be approximately a quarter wave on 20m, but it is detuned by proximity to the ground. Is it efficient? Well, it’s better than nothing. Without that wire the operator may become the counterpoise – RF gotta go somewhere.

Transceivers can’t count radials

Let’s pretend that transceivers have eyes for a minute. When the transceiver looks at a counterpoise – whether its made of wire radials, or has a callsign – all it really “sees” is a combination of Resistance, Inductance and Capacitance (RLC). Transceivers can’t count radials – you read it here first! Resistance, Inductance and Capacitance are seen as impedance. An efficient set of radials has a low impedance to RF which allows maximum current to flow. So isn’t the current flowing into the counterpoise system really the most important factor in determining its efficiency?

Hams endlessly debate about how many radials make an efficient counterpoise. Is it 4; is it 16, or maybe 128? The debate is pointless unless other factors are also considered. The correct number is just ONE – if your antenna is erected in seawater. I want to propose another number – ZERO and, in the true spirit of scientific endeavor, I have empirical evidence to support my assertion. If an assertion cannot be verified by experiment it just ain’t so.

“I would rather have questions that can’t be answered than answers that can’t be questioned.”
― Richard Feynman

Here is the experiment

The SWR is hard to read due to the bright sunlight – it is 13. The GTU had not yet been adjusted for maximum counterpoise current. Observe the small deflection on the RF current meter. The SWR is difficult to read due to the bright sunlight; it reads 1.79.
The strange blue thing in the antenna wire is a small loading coil.
Observe the higher deflection on the RF current meter after the GTU had been adjusted for maximum current in the counterpoise.

The experiment was conducted in the Ham Radio Outside the Box outdoor laboratory (my driveway). A welcome rise in temperature had melted the ice from my concrete driveway and, for once, the Sun was shining. I wanted to test a “de minimis” rapid deployment antenna that would also serve to verify my assertion about counterpoise efficiency.

The initial test was conducted with my 20m emergency wire antenna (a coil-loaded 13ft wire). Instead of radial wires I used my GTU (Ground Tuning Unit).

A GTU is a series connected L-C device. There is a sensor circuit connected to a small analog meter for observing the current passing through the device. The GTU case is a Hammond aluminum box which is electrically connected to the ground side of the GTU. The input to the GTU is a short wire connected to the shield of the coax at the antenna end.

To monitor the current in the radiating element an RF current meter was inserted into the radiator wire. The current meter is basically a GTU without the tuned circuit.

The GTU was placed directly on the concrete driveway; its aluminum box forming a capacitive connection to ground. It would have been more effective to perform the experiment on grass, but my lawn is still buried under a miniature glacier formed by another dreadful winter that isn’t over yet.

The 20m emergency antenna is nominally resonant when a counterpoise is attached so no further tuning was required. The absence of radials required the GTU to do the job of maximizing the current flow on the ground side of the antenna.

At the start of the experiment there was a small current flowing to ground. A similarly small current was observed flowing into the radiator wire (see images). The antenna analyzer recorded an SWR of 13:1.

As the GTU was tuned the ground current increased. It was observed that the current in the radiator also increased. Neither meter was capable of measuring the value of current, so the readings simply represented the relative flow of currents in the counterpoise and radiator. As the ground current peaked the antenna analyzer showed a much improved 1.79:1 SWR.

Quod Erat Demonstrandum?

So did that little semi-scientific experiment prove the point? Well kinda sorta. It established a correlation between ground side current and radiator current. But would it QSO? No, definitely not; it’s just a dumb collection of wire and electronic components – I make the QSOs eh?

Next step – hook up a radio

This is the bit where I boldy went on to risk a radio in pursuance of scientific inquiry. First, the antenna was replaced with my “tactical” 9.5ft whip wearing its finest top hat. The whip was mounted on a small tripod out on the driveway. Even with a googol (10e100) of radials this antenna would not be resonant on the 20m band. That called for deployment of my QROp L-match tuner. The radio called into service for the experiment was my old Yaesu FT-897 set for a blistering 20 watts. Since the antenna is a compromised short vertical my QRP radios were granted liberty for the day. A little muscle was called for to ensure a decent signal could be launched up to the edge of space to pound the ionosphere.

The L-match was adjusted for resonance (X=0 @ 14.113MHz), a low SWR reading on the radio, then the GTU was adjusted to max out the ground current, which lowered the SWR reading on the radio even further. Everything was ready for launch but countdown was paused for one further refinement.

A large plate for pizza?

A GTU is usually used in combination with a capacitance plate laying on the ground. The GTU body is itself a very small capacitance plate, but maybe a larger plate would enhance the ground side current flow. A quick hunt around the Ham Radio Outside the Box HQ turned up a number of options. One of the options was an old pizza pan. It worked – i.e. it raised the ground current a little, but I really couldn’t see carrying a disgusting retired old pizza pan around as part of my portable ops kit. A little further searching resulted in a small piece of what looked like chicken wire. It looked much nicer and it worked even better than the pizza pan.

GTU atop its chicken wire capacitance plate. The large toggle switch bottom right is a bypass switch. The knob under the meter selects one of three inductors. The knob at top right adjusts the deflection of the meter needle. The large knob is for the tuning capacitor.

The final setup – will it QSO?

Final setup. This picture was taken before the chicken wire capacitance plate was in place. The antenna was fed by a 10ft RG-8 coax through a Common Mode Current choke (on a FT240-31 toroid)

Do I have to say it again? I make the QSOs not the dumb bits of wire. Well, could I make some contacts with this ZERO radial short vertical antenna system? Here is a picture of the setup.

Once again, a concrete driveway is not the best test of a GTU-based zero radial counterpoise system. The glacial layer of frozen, compressed snow on my lawn may not melt for another few weeks so one has to just make do with whatever nature allows.

I scanned the bands seeking somebody calling CQ and found a station in Connecticut doing a POTA activation. Grabbing my CWMorse paddle key I threw out my callsign and waited to hear if he heard me. Connecticut might be a little close to my QTH in southern Ontario for a vertical antenna with low angle radiation. Anyway, he heard me and sent me a 539 report. I responded with a 579. Contact was made.

A popular mantra among hams is “one is none and two is one” so I figured another contact would hammer a nail in it and seal the proof.

A little more search and pounce revealed another POTA activator in Virginia. Still quite close but my contact there earned my modest setup a 579 report.

Both those contacts were on 20m and I wondered whether another band would also work. I tuned up on 15m but the band was frantically busy with high speed CW traffic and I didn’t want to slow anybody down with my low power into an experimental antenna so I pulled the plug.

So there we have it. A very simple, rapid deployment field portable vertical antenna with zero radials. Now how am I going to make the ladies dance?

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #Antennas #Counterpoise #CW #Ground #OutdoorOps #Portable #POTA

A highly efficient multiband QRP L-match builder project

Here is a project that provides a much more efficient way of matching an End-Fed Half Wave antenna than the usual 49:1 impedance transformer. High ratio transformers are prone to inductance leakage, core saturation and overheating leading to low efficiency. Although a 49:1 (or similar high ratio) transformer can present a low SWR to a transceiver, that is not a good indicator of the transformer’s efficiency. It only tells us our radio will not be damaged; it provides no useful information about how much of our signal will actually be radiated. Also, even though a low SWR can be obtained on multiple bands, the radiation pattern breaks up into multiple lobes and nulls on the higher harmonics. End-Fed Half-Wave antennas should really only be used on their fundamental frequency band and its second harmonic.

This L-match can also be used with other high impedance long wire antennas, for example, random wires. With the flick of a switch it can also be used to match low impedance antennas such as verticals.

Here is an interior view of the L-match. Note the “expedient” use of T37 toroids since I didn’t have any larger ones. To compensate I used 2 T37-6 toroids for the 0.5uH inductor; 2 T-37-2 toroids for each of the 1.0 – 4.0uH inductors and 4 T37-2 toroids for the 8uH inductor. I have tested the device using 4.5 watts into a dummy load and noted stable SWR with no noticeable core heating. I recommend the use of T50 or T68 toroid cores for anybody wanting to build their own version. The variable capacitor is a 160pF polyvaricon.

There are 10 kinds of people ... those who understand binary notation and those who don’t.

It’s an old joke but it’s quite true. In the binary system there are only two digits to remember: “1” and “0”. We can count from decimal 0 to 31 using only 5 binary digits.

Therefore, with only 5 inductors: 0.5uH, 1.0uH, 2.0uH, 4.0uH and 8.0uH we can select up to 32 values of inductance by binary operation of the switches (NB: “u” in this post represents the Greek letter “mu”, uH referring to microhenries). Inductance values can be selected in increments of only 0.5uH for fairly precise tuning.

L-match with binary selectable inductance. NB: Not shown is a switch connecting the variable capacitor to either the input (for low impedance antennas) or the output (for high impedance antennas). The switch can be omitted by simply reversing the input/output connections.

A few years ago I built a “Super Tee” QRP tuner that has 7 coils and 7 switches. Additional 0.25uH and 0.125uH inductances were available providing 128 different selectable inductances in increments of 1/8 of a microhenry. My experience has been that it is rarely necessary to use that level of precision in inductance values.

The table below shows how binary selection can vary the inductance between zero (all switches closed) and 31.5 uH in 32 increments of 0.5uH.

8uH coil4uH coil2uH coil1uH coil0.5uH coilTotal inductanceSwitch closedSwitch closedSwitch closedSwitch closed0.5uH0.5uHSwitch closedSwitch closedSwitch closed1uHSwitch closed1uHSwitch closedSwitch closedSwitch closed1uH0.5uH1.5uHSwitch closedSwitch closed2uHSwitch closedSwitch closed2uHSwitch closedSwitch closed2uHSwitch closed0.5uH2.5uHSwitch closedSwitch closed2uH1uHSwitch closed3uHSwitch closedSwitch closed2uH1uH0.5uH3.5uHSwitch closed4uHSwitch closedSwitch closedSwitch closed4uHSwitch closed4uHSwitch closedSwitch closed0.5uH4.5uHSwitch closed4uHSwitch closed1uHSwitch closed5uHSwitch closed4uHSwitch closed1uH0.5uH5.5uHSwitch closed4uH2uHSwitch closedSwitch closed6uHSwitch closed4uH2uHSwitch closed0.5uH6.5uHSwitch closed4uH2uH1uHSwitch closed7uHSwitch closed4uH2uH1uH0.5uH7.5uH8uHSwitch closedSwitch closedSwitch closedSwitch closed8uH8uHSwitch closedSwitch closedSwitch closed0.5uH8.5uH8uHSwitch closedSwitch closed1uHSwitch closed9uH8uhSwitch closedSwitch closed1uH0.5uH9.5uH8uhSwitch closed2uHSwitch closedSwitch closed10uH8uhSwitch closed2uHSwitch closed0.5uH10.5uH8uhSwitch closed2uH1uHSwitch closed11uH8uhSwitch closed2uH1uH0.5uH11.5uH8uh4uHSwitch closedSwitch closedSwitch closed12uH8uh4uHSwitch closedSwitch closed0.5uH12.5uH8uh4uHSwitch closed1uHSwitch closed13uH8uh4uHSwitch closed1uH0.5uH13.5uH8uh4uH2uHSwitch closedSwitch closed14uH8uh4uH2uHSwitch closed0.5uH14.5uH8uh4uH2uH1uHSwitch closed15uH8uH4uH2uH1uH0.5uH15.5uH

If we look at the table below we can see that it would be possible to use even fewer coils and switches if we wanted to operate on fewer bands. For example, if we wanted to operate only on the 20m, 30m and 40m bands we would need only three values of inductance. With five inductances and five switches we can operate on seven bands: 80m, 40m, 30m, 20m, 17m, 15m and 12m. It might be possible to also get a match on the 10m band. The maximum inductance in this project is 15.5uH, but there is additional stray inductance within the internal wiring.

Frequency (MHz)Inductance (microhenries)Capacitance (picofarads)3.715.11207.157.86210.1255.54414.153.93118.113.12521.22.62124.932.21828.52.016

Why choose binary selection?

Many designs for L-match devices use a single toroid core inductance with selectable taps as shown in the diagram below. I have built one myself, but as Shakespeare would have said: “Here’s the rub”. It is not easy to build a single inductor with 32 taps at 0.5uH increments. Even if that could be achieved where would we source a 32-way switch? We could use a lead with an alligator clip to select the taps but that would be inconvenient and potentially unreliable out in the field for portable operations.

My own version of this kind of L-match had only 12 taps with a 12-way rotary switch and worked fairly well but was not as versatile as binary selection.

L-match with tapped coil

I would like to add my gratitude to Martin K1FQL who provided the math equations and a lot of guidance to me in understanding how L-matches work. I have not included the equations in this post, but if anybody is interested I recommend reading Martin’s post at this link: Highly Efficient L-Matching Networks for End-Fed Half-Wave Antennas.

Coming up on Ham Radio Outside the Box

— Improving the efficiency of an antenna – by burying half of it underground? —

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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Escaping from the shack between snowstorms

HamClock – or Open Ham Clock?

It was recently announced that the popular HamClock program will cease to function in June 2026 due to the death of its creator. HamClock has been running on an Inovato mini computer in my shack for a long time now. It has given instant access to a wealth of information important to the operation of my home shack. A rescue attempt has been announced that will restore access to the databases HamClock relies on to display its information. I hope that attempt is successful and will follow that project closely.

Meanwhile, there is now a competitor called Open Ham Clock. For the last few days I have been displaying both HamClock and Open Ham Clock on my shack computers and I have to say that I currently find the open version more useful and much more informative than the original. Both programs provide a VOACAP display that provides an instant view of band conditions for a selected “DX” location. In this context “DX” refers to any station or location selected by clicking on the map display, but not necessarily a long distance location.

Have you tried either program; if so what is your opinion? Let me know in the comments.

Screenshot of Open Ham Clock at VA3KOT’s QTH (“DE” on map)

Life is tough and then it’s winter again

I am not a great fan of winter. I might think differently if I owned a snowmobile and could carry my portable radio gear for miles and miles along the extensive network of trails that cover the area where I live. Unfortunately I do not own such a vehicle and I’m a bit long in the tooth for snowshoeing through the woods wearing a backpack full of gear. Even if I did still have the stamina to get out into the back country in winter it would still be difficult to erect an antenna. Canada’s (literally) billions of evergreen trees have dense brush that catches the snow. Try to launch a wire up into the tree canopy and you can expect a small, cold avalanche to come tumbling down on top of your head. Guying a mast takes a lot of ingenuity because trying to drive stakes into the ground at this time of year requires something like a jack hammer – and that’s if you can even find the ground beneath a couple of feet of icy compressed snow.

But then, sometimes an idea occurs which is borderline genius but, at the same time, very simple. So when I wanted to take advantage of a recent day when the temperature managed to creep above freezing for the first time in weeks, this happened. I carried my Spiderbeam mast out onto my driveway looking for a way to secure it well enough to test an antenna idea. My driveway is regularly plowed and although I haven’t seen the concrete for months, the compressed layer of icy precipitation is sufficiently thin that my 4×4 truck can complete its passage between house and road without difficulty. But the rest of my suburban lot still carries the accumulated snowfall from weeks of winter weather. At the side of my driveway the snow is a couple of feet deep. Would it be firm enough to support my mast I wondered? I decided to find out. I pushed the mast down into the compressed snow and it felt firm enough. It penetrated 19 inches into the snow before meeting a firmer layer. A swift encouragement with my right foot inside a heavy snow boot sealed the hole at the top.

Base of Spiderbeam sticking out of the snow

This particular mast is Spiderbeam’s 7 meter (23 feet) model. Would the snow holding less than 2 feet of mast at the bottom be sufficient to support the full extended length? Yes. Not only that but when I used it to support a 40m EFHW wire the mast bowed with the strain of the long wire, yet did not show any sign of dislodging from its nature-supplied support. Success! Maybe winter ain’t so bad after all!

The antenna was a half wavelength long on 40m, with links for 30m and 20m. It allows me to set up the antenna for operation on its fundamental frequency for the 20m, 30m and 40m bands without relying on harmonics, although it does also work on the 2nd harmonic of 40m (i.e. 20m) when operated at its full length. Note that the CW QRP calling frequencies of 7.030 and 14.060 are very conveniently precisely related.

I have used this wire many times for POTA activations but on this occasion I wanted to test the ability of my version of AA5TB’s parallel tuned circuit to find a match on each of the three bands (it did, easily). I also used the occasion to test my newly completed QRP L-match (with binary selectable inductances) to see if that would also find a match on the same three bands. It did, again easily. I’ll be writing more about that project in an upcoming post.

What happened?

I skipped a light Fandango when I received this week’s report from WordPress. Although I don’t fixate on Ham Radio Outside the Box’s visitor numbers, subscriber count etc, something unusual must have happened. In the last 7 days this humble little blog received 5,350 page views which is more than double the regular weekly number. Compared to major websites that statistic may be underwhelming, but for a tiny one person amateur radio hobby blog from the Great White North it’s an achievement. A big thanks to all Ham Radio Outside the Box subscribers and visitors; it is folks like you who make writing this blog so worthwhile.

I don’t want to belabor the point but this is a non-commercial site. Any links in the posts here are not “affiliate links”. I do not solicit or accept financial donations from any source. Amateur radio is my hobby, not a business. Participating in the hobby often costs money – particularly for experimenters like myself. The costs associated with maintaining a domain registration and site hosting fees are just part of the investment in a hobby that carries its own reward through the enjoyment and thrill of communicating with others by radio. We should keep in mind the definition of “Amateur service” from the FCC Part 97 rules (para 97.3, section 4). Note in particular the phrase “without pecuniary interest”.

Amateur service. A radiocommunication service for the purpose of self-training, intercommunication and technical investigations carried out by amateurs, that is, duly authorized persons interested in radio technique solely with a personal aim and without pecuniary interest.

Feedback

If you choose to leave a comment on any post on this blog, WordPress will ask you to set up an account. This has two benefits; it helps to prevent bots and other undesirable sources from flooding the site with spam. It also allows you to be notified of follow-up comments (e.g. my reply) when posted.

Some spam does still get through but is caught in the spam filter. Unfortunately some genuine comments also occasionally get trapped in the spam filter. If your comment does not appear within 24 hours please let me know by email.

If you prefer to use email to send feedback please ensure to include your callsign or “SWL” if you are not a ham. Many subscribers have cryptic IDs such as “pickledwalnut037az2”. You will be sure to get a reply if I know I am dealing with a real person. Thanks.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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#AmateurRadio #HamClock #OpenHamClock #OutdoorOps

Engineering challenges of the completed QRP EFHW coupler

Kudos to Kits and Parts, the United States Postal Service and the Canada Post dog sled teams who fearlessly fought their way through blizzards on the frozen barren tundra into the wild white yonder to safely deliver my package of toroid cores. But, as soon as I had unpacked the goodies I realized I may have fired off the order with excessive haste. I ordered some medium sized Type 2 and Type 6 powdered iron toroids for my occasional QROp (20 watts) projects and some smaller ones for QRP. How small? Too small! In my haste I had ordered 25 T37-2 and 25 T37-6 cores. These cores are so small that winding inductors on them requires a great deal and patience and dexterity – I have neither.

When life hands you lemons …

When life hands me self-inflicted lemons I tend to fill my head with expletives that are best not spoken in polite company. Then I find ways to cover up my mistakes. T37 cores are really only suitable in the stages of a transceiver prior to the final PA. Could they possibly be persuaded to handle the full 4.5 watts output of my revered antique Yaesu FT-817?

I reminded myself that this is Ham Radio Outside the Box and in that spirit I would find a way to use those lilliputian cores in my project. There were two screaming demons haunting my thoughts on this. A toroidal core can overheat due to being too small to handle the power applied to it. Or it can simply reach magnetic saturation causing it to fail to perform as expected.

I remembered an old trick used by hams who enjoy pumping out so much power they risk blowing holes in the ionosphere. They use multiple stacked toroid cores to share the load. Would that work with the tiny cores I had at my disposal? I decided to take the risk, but first test the idea on the bench before venturing out into the Big Blue Sky Shack.

But how to test the idea?

If a core can’t handle the power applied to it it will get hot. If the core reaches magnetic saturation it will no longer function as expected. I figured a simple way to test for these conditions on the bench would be a keydown test into a 2.5Kohm dummy load. I used two stacked T37-6 cores, held together with electrical tape and then by the wire wound through them. The setup was almost identical to the “20 minute” version published in the previous post, except that the inductor was now the toroidal core version.

The tuned circuit, dummy load and transceiver were hooked up on the bench and then, with very little trepidation (if I blew up the inductor I had more wire, more cores), I keyed up the full four and a half watts from the transceiver for 30 seconds while monitoring the SWR on my Norcal QRP power meter. Did it survive the test?

The Norcal QRP power meter indicated a rock steady SWR throughout the test. The cores may have increased in temperature but not enough to be detectable when touched with my fingers at the end of the keydown. Not a scientifically rigorous test but it inspired confidence in the viability of the solution. Stacking two cores increases the depth through which the wires pass through the core and that may compensate for the smaller diameter.

And now – that pesky polyvaricon

The 3D printing revolution hasn’t yet penetrated the basement laboratories of Ham Radio Outside the Box. Instead I am limited to good old-fashioned engineering techniques in my build projects. It is amazing what can be achieved with an extensive collection of materials and a few simple tools. That is exactly how I approached the challenge of attaching a regular quarter-inch knob to the stubby, irregular shaft of a polyvaricon.

The basic idea has already been covered on this blog but it has now been refined into a reproducible technique that is rugged and reliable enough to survive the rigors of being bumped over the steep and rocky terrain encountered along the north end of the Niagara Escarpment. The solution to the challenge is to construct a short quarter-inch diameter adapter shaft than can be securely attached to the polyvaricon. The basic material used is a steel drinking straw. Now that plastic straws have been declared a deadly hazard to the survival of the human race, steel straws are becoming quite easy to find.

Two tools were required; a Dremel for cutting a slot in one end of a section of the straw, and a small tube cutter for cutting the adapter shaft to the correct length. The adapter shaft is secured to the polyvaricon by means of a long, fine bolt and a small washer. Scavenging polyvaricons from dirt cheap thrift store AM/FM radios ensures the correct size of bolt is obtained. I did have to grind down the washer a little when the adapter shaft was fitted to ensure it slid into the knob nicely. Building the adapter shaft took about a half hour of delicate work while wearing a magnifying lens to enhance my degenerating vision. I imagine making something similar with a 3D printer would take as long.

I have another project developing on the workbench which involves the same inductor core tricks and polyvaricon mods as outlined here. It is a wideband L-match and if it works I’ll publish the details here in a couple of weeks. On the other hand, if it doesn’t work …

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No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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#AmateurRadio #EFHW #OutdoorOps #Portable

A 20-minute QRP End-Fed Half-Wave antenna coupler

It was almost time to make lunch but I had an idea that just wouldn’t wait. I figured I had 20 minutes to zip down to the basement shack/development lab and throw a simple circuit together on the workbench. I had been re-reading (for the 1000th time) AA5TB’s website about using a parallel tuned circuit to transform the high impedance of an End-Fed Half-Wave antenna down to 50 ohms. I had built a QRO version already but now I need a QRP version.

Why use a parallel tuned circuit coupler?

The objective was to avoid the use of very high impedance ratio transformers (e.g. 49:1). These transformers have received heavy criticism in online forums for numerous reasons that I won’t go into here. An alternative that is often considered to be the best option is an L-network. According to Steve AA5TB, an L-network provides better bandwidth but less feedline isolation.

I do have a QRP tunable L-network coupler on the drawing board. It will use series toroidal inductors where each inductance can be shorted out using a toggle switch. A broad range of inductance values will be selectable in binary fashion by opening and closing the toggle switches. A polyvaricon will provide variable capacitance. It’s a bit of a complicated and slow arrangement compared to the tuned circuit coupler where the only adjustment needed is the variable capacitance. So back to AA5TB’s design.

In a rush (I was hungry) I dived into my component and junque drawers, found a polyvaricon with a range of about 16-160pF, then a 2.7Kohm resistor and a BNC jack. But I still needed a coil. I have wound many coils over the years and they fill the graveyard drawer in my shack closet. I picked up one that looked like it might do the job, even though it’s a scrappy, ugly beast. When I built it I used a small cutoff of the kind of plastic board that realtors use for their “For Sale” signs. I wound 19 turns of thin solid core telephone wire around it. The winding measured 4 microhenries on my Almost All Digital Electronics L/C meter IIB.

The coil still needed a secondary winding so I wound 3 turns of the same wire over the center of the primary and connected the ends to the BNC jack. The primary winding and the 2.7Kohm resistor (simulating the impedance of the EFHW) were connected in parallel with the polyvaricon. I didn’t really expect this rushed, kluge matching circuit to work but it was a first step. I could improve the coil later once I had the initial measurements.

You heard the expression “looks like a million dollars”? Well this looks like a single solitary buck – but it works!

I love it when a project just works!

I hooked the ugly bench project up to my RigExpert AA-55 Zoom antenna analyzer and performed a quick SWR measurement on 40m, 30m, 20m, 17m, 15m, 12m and 10m. On each band the SWR could be adjusted to 1.5:1 or less. The polyvaricon does not allow very fine adjustment so tuning is a little touchy. Feeling lucky I also checked 80m – well maybe that was over-optimistic, so no joy there.

Next, I checked for resonance on each band by looking at the R and X measurements on the analyzer. Sure enough I could get resonance (i.e. X=0) on 40m, 30m and 20m. I could not tune X down to zero on the higher bands but came pretty close.

N.B. I am not implying that a single end-fed wire can be used on all bands from 40-10m using this coupler. An EFHW antenna may be tunable on multiple bands but its radiation pattern becomes distorted on its 3rd and higher harmonics. Low SWR does not indicate the antenna is useful on other than its fundamental frequency and its 2nd harmonic.

Gone to the dogs

I have placed an order for quite a lot of toroid cores from Kits and Parts. When my order makes its way through the United States Postal Service and over the border, Canada Post will take charge of it and load it onto a dog sled. It will then be hauled through the frozen barren tundra, crossing multiple time zones and finally end up at my door. No doubt the “postie” will ring my bell and seek payment of further taxes before handing over the package. When that happy day arrives – assuming the dog sled isn’t ambushed by hungry polar bears en route – I will replace the coil with a much nicer one wound on a type-2 powdered iron toroid.

Times are hard, so I’m a scavenger

It would be nice if I could find another polyvaricon to wire in parallel with the main one. A lower capacitance device would allow me to make both coarse and fine tuning adjustments. I tear apart old AM/FM radios to scavenge the components so there may be just the part I need sitting in the junque drawer already.

And, of course, the project will get a nice enclosure to make it look nice and protect it against the bumps and grinds it will incur during my back country ham radio missions.

Finally, when the second consecutive Arctic weather season is finally over and I can get outside without wearing parka, mukluks and snowshoes, I will hook up various wires to what I hope will be the finished product. I have prepared a 40m half-wave wire already. It has links for 30m and 20m so it can be used on its fundamental frequency on each of those three bands. And, of course, a 0.05 wavelength counterpoise too.

How to look simply radiant

If the counterpoise is omitted the antenna may still “tune” but the coax becomes the counterpoise and will radiate. Since a lot of portable operators, like myself, like to directly connect the coupler to the radio (or via a very short coax) the operator becomes the counterpoise and will radiate. That thought is perhaps the ultimate endorsement for QRP!

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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#AmateurRadio #Antennas #Counterpoise #OutdoorOps #Portable

My FT-891 has been retired from POTA service … why?

Following high level, wide-ranging, bilateral talks with senior management (XYL) a far-reaching, binding agreement was today handed down to me. The focus of the agreement is contained in the executive summary which reads: “ya got enough radios already”.

And it’s true

I own more radios than I really use. Nearly all of my radios are of the vintage variety. The sole exception is my QRP Labs QMX. The QMX is unique in that it is an SDR radio so it can be updated as needed. One day, perhaps, even the hardware will become obsolete although it is more likely to succumb to the fragility of its low-cost construction – or the indelicate treatment to which it is subjected in the rigorous outdoor environment where I like to operate.

Radios become obsolete quite quickly as technologies evolve. Many modern rigs incorporate what I like to call a “fish finder” – a waterfall display enabling an operator to “catch” another station with a simple tap on a touchscreen. Fantastic yes, but is it just “nice to have” or an essential convenience for modern operating?

Most of my own outdoor operations are related to POTA. Once out in the Big Blue Sky Shack, preferably far from the madding crowd, in a location accessible only via Shanks’ Pony (an old Scottish expression – “shanks” are legs), I set up my station, find an open frequency, call CQ and work the hunters until they quit coming. What level of technological sophistication does that require? Even a very basic, unsophisticated, boat anchor rig can accomplish that. Does it really require a “fish finder”? Well, a fish finder would be nice, but spinning the dial and listening up for active stations worked for many years. Wanna go high tech? Check the clusters on a mobile phone.

Technological advances can even be detrimental. Remember old tube rigs? They were robust (until the tubes needed replacing). Tube rig operators never had to obsess about SWR. High SWR in a modern radio can result in voltage peaks that can send delicate FET PA transistors to the semiconductor cemetery. Sure tubes (or “thermionic valves” as they are known in the Land of Hope and Glory) can be big and fragile. I remember, when I was a kid exploring the thrill of electromagnetrickery, I owned a receiver with tiny, wire-ended tubes. But this isn’t a post about boat anchor technology – no matter how our romanticized recollections of youth bring out fond memories of days gone by.

Back to the future

I bought my Yaesu FT-891 a few short years ago based on recommendations I read online. I wanted a radio that would pack a punch and make getting QSOs from a campsite almost a sure thing. I remember self-spotting on the POTA website with the comment “100 watts!”. I wanted to attract hunters who wouldn’t have to struggle to hear me. A hundred watts for a CW signal is equivalent to AM broadcast signal strength compared to SSB. Alright, I exaggerate, but it quickly occurred to me that a QRP CW signal into an efficient antenna would get the job done equally well. Since that time I have rarely strayed from QRP – or sometimes QROp (20 watts for a 1 S-unit signal boost) when conditions are bad.

The new shack star – Yaesu FT-891

The Yaesu FT-891 is an interesting radio. It’s compact format makes it easy to carry into the field, but also has a downside. Small radios bury most of their impressive set of features in layers of menus. And the FT-891 has an impressive set of features. Audio bandwidth can be set as wide as the mighty Mississippi or as tight as Scrooge’s purse strings. Zero beating the other station’s frequency can be accomplished in a single button press if the “ZIN” function is programmed to one of the A, B, C buttons on the front panel. Then pressing the <F> key repeatedly brings up another four layers of menus. These menus allow the operator to select and adjust other levels of IF filtering like “APF – Audio Peak Filter”, “CNT – Contour”, “SFT – IF shift”, “IPO – Intercept Point Optimization” and “NCH – Notch”.

Filters can get you into trouble

During one POTA activation I recall hearing a hunter respond to me, but his signal sounded like a series of atmospheric clicks. “What the heck is that?” I remember thinking. “Is he testing whether I can copy railroad code?” (I can’t). I set my RIT (Receiver Incremental Tuning) a little off frequency and suddenly his signal was perfectly clear. The problem was my filter was set too narrow. Responding to an activator a little away from zero beat is a technique often used to stand out in a pile-up; it works in SSB too. Since my filter was too narrow the hunter’s signal was just outside my passband. Some CW operators are able to use the filter between their ears to separate a signal in a busy band. It takes some concentration – more than I have.

Tis a gift to be simple

All those menus are such fun to play with while working a pile-up out in the back country with mosquitoes, deer flies and other winged pestilences trying to have lunch on the back of your neck. As you swing an arm wildly to crush the airborne assault your CW key crashes to the forest floor and the contacts fill with wet sand and soil turning dits and dahs into incomprehensible gibberish. The hunters have fled and you are back to sending CQ trying to entice them to return. Wouldn’t it be nice to have a simple radio instead?

It get’s worse

It’s fine and dandy reducing a QRO rig’s power to peanut level. On the FT-891 it’s a simple matter of holding the <F> key down for 2 seconds, rotating the Multifunction knob to select section 16 of the Mariana Trench level menus, then choosing which of the six HF power sub-menus to adjust. Then click the Multifunction knob again, rotate it to the desired power output, from 5 watts to 100 watts; click the <F> key again and in no time at all you’re all set.

But there’s still a problem. The FT-891, like many other QRO radios adjusted for low power, still sucks power out of your battery like a camel filling its hump before a trek across the desert. The FT-891 draws over 5 amps even when the output power is wound down to 5 watts. By contrast, the QMX and other QRP radios can run when powered by a tiny 9 volt alkaline battery.

Big eyes, small wallet

Twenty years ago I worked for a few months in a Toronto establishment known to local hams as “the candy store”. Every day I had every one of the big Japanese manufacturers radios to play with. The staff were encouraged to become familiar with all the radios on display so that we could offer expert advice to customers. My big wide eyes fell on one particular radio from Yaesu; it was the FT-897 – a radio that I began to covet but couldn’t afford to buy at that time. I left that employment to start my own business and after a while I had the funds to buy that rig.

FT-897 Old faithful, now assigned to occasional portable use

The Yaesu FT-897 is a big and chunky, yet rugged looking QRO radio that was intended for use in the field. I used it as a base station radio instead and it served that purpose until quite recently. It is old-tech now but maybe that’s a bit of an advantage. You see, it is relatively simple compared to the later FT-891. The FT-897 was introduced before IF filtering was widely available to the low budget ham market. Instead it has audio frequency filtering – accessible from the front panel – that works remarkably well. I can narrow the CW receive bandwidth down to 60Hz (danger of missing calls), 120Hz or 240Hz very easily without diving deep into a menu system.

The FT-897 does not integrate very well with common programs like FLrig and FLdigi. Too few functions can be controlled with CAT commands – unlike the newer FT-891. So the momentous decision was made to switch the two radios. Who cares if it takes a lot of clicks, twiddles and turns to select a desired feature on the FT-891 if the clicks, twiddles and turns are replaced with on-screen slider controls? The FT-891 is now my shack radio and I am very happy with it in this role. My XYL is equally happy that we don’t have to have another full and frank discussion about my urge to deplete our retirement savings to buy yet another whizz-bang box of tricks that will only keep me happy until the next whizz-bang box appears.

And the old FT-897? Is that going to be my regular portable rig now? Sorry old fella, you’re still a little hungry on battery amps. Maybe field day, perhaps.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#amateurRadio #CW #FT891 #FT897 #OutdoorOps #POTA #QMX

The ultimate rebuild of an ancient Yaesu FT-817.

I think it was a couple of years ago now I ordered a QRP Labs QMX transceiver. It quickly, but temporarily, became my favorite radio for portable field operations. I have written before about why I believe the QMX is a mighty fine piece of miniaturized technology but is less suitable for the rigors of being operated in the kind of field operating environment to which I expose my radios. My QMX is the low-band version and I also miss the opportunity to explore the higher bands when propagation conditions permit.

What’s a poor Ham to do?

I could buy another QMX, but order the high band version this time. It would be a very modest investment, but would still require ruggedizing. Another downside is the long, long wait time betwixt ordering and receiving the tiny parcel from Turkey. I could also order a QMX+ which is a fine all HF band radio, but then what to do with the QMX low band? There is another solution.

The Paranoid Android

I recall a quote from the book “The Hitchhikers Guide to the Galaxy” by Douglas Adams in which the perenially depressed robot “Marvin the Paranoid Android” moans: “The first ten million years were the worst.” When I look at the front panel of my ancient Yaesu FT-817 non-ND version it kinda has a Marvin look about it. It has spent almost a quarter of a century waiting patiently in a drawer for the day when it might be called into action again. Many radios have come and gone during that time but – even though I had planned to sell it on many occasions – I still own it and it’s day to see the sunshine again has finally come.

Where are the features?

The non-ND version of the FT-817 is a barebones rig. I needed a CW memory keyer – it doesn’t have one. Activating a POTA park sometimes requires great patience and many, many CQs. My QMX at least has that covered. I also needed an audio filter. It used to be possible to buy a Collins mechanical filter but they are no longer made. My QMX also has that feature covered, but the FT-817 requires an external audio filter.

Failure is not an option

The FT-817 does have a higher level of ruggedness than the QMX. With a few extra precautionary measures it can be protected from the ingress of sand particles during a beach activation, or unexpected spray from waves on the shores of the Great Lakes. The QMX will not tolerate wide variations in DC supply voltage; the FT-817 has that covered. The QMX uses inexpensive but fragile PA transistors (mine have not succumbed to failure – yet). Well, the FT-817 also had fragile PA transistors in its early days and mine did indeed fail during a field deployment. The FT-817’s PA board is a small module that is easily replaced with the new upgraded module – as was mine.

Assembled rebuilt FT-817 portable operations rig. The battered, field protective canvas pouch on the right contains a Talentcell LiFePO4 battery. Right hand side view of the “helper modules” showing the input jack for connecting a cable from the headphone output of the FT-817. The switch allows the K4ICY AF filter to be bypassed for a barn door wide audio bandwidth. Left hand side view of the “helper modules” showing the switch allowing selection of 2-stage or 4-stage audio frequency filtering. To the right of the switch is the AF output jack for connecting headphones. The jack on the K3NG keyer connects to the “Key” jack on the FT-817. On the back of the AF filter module is the power switch controlling the internal
9-volt battery (now replaced by a buck converter) which supplies both modules. Internal view of the keyer module and the filter module. The 9 volt battery has now been replaced with a buck converter that converts the radio’s DC supply from 12.6 volts down to 9 volts to power the helper modules.

I get by with a little help from my friends

The feature shortcomings of the FT-817 have been overcome with two “helper modules” assembled inside aluminum Hammond project enclosures. The front enclosure contains a K3NG Arduino nano based CW keyer and a very simple no-thrills set of 3D printed paddles. Well who really needs to spend $300 on a fancy set of paddles for a brief POTA exchange? These paddles get the job done FB. The same cannot be said about the fist that operates them!

The front panel controls are very simple. The paddles protrude through a cutout in the Hammond enclosure.

Beside the paddles is a knob. This knob is used to operate a rotary encoder inside. Clicking the knob operates the switch built into the rotary encoder and triggers the sending of a “CQ CQ POTA de VA3KOT VA3KOT k” stored message in the Arduino keyer.

Rotating the knob adjusts the speed of the CW over a wide range. I have found this to be a very useful feature. I usually send at 20wpm and receive responses that are slower and faster than my sending speed. With this prominent control front-and-center I can quickly adjust my sending speed to suit.

I built the K4ICY audio frequency filter module around a quad op-amp DIL chip. This is a very simple circuit that provides 2 or 4 stages of filtering to narrow the bandwidth of a received signal. Each stage contains identical components whose values are selected according the operator’s desired sidetone frequency. The whole module can be bypassed if required allowing an audio bandwidth wide enough to pass a crosstown bus sideways.

Both modules are rigidly secured to each other using two aluminum rails made from scrap material. I hoard scraps of metal, plastic and other materials – you just never know when you’re gonna need ’em.

The dimensions of the two modules provide an ample flat surface on which to mount the ancient, but revered, transceiver. I purchased some “peel & stick” Gorilla brand “Slipstick” gripper pads and applied four of them to the base of the FT-817. This is a genuinely useful product I recommend to any hambrewer. The radio has been secured to the top of the helper modules with two woodland zip ties made from thin cordage. These simple cord fasteners work just as well as plastic zip ties and can be easily undone for servicing the modules.

I purchased a box load of these Hammond enclosures at an auction many years ago. They have proved very useful. In another build, using the same enclosures configured in an identical manner, I was able to construct two battery modules each containing four 18650 Lithium Ion batteries in 4S1P configuration for powering another one of my ancient QRP transceivers.

This is not the first time I have revived my FT-817, but previous rebuilds were clumsy. It is one thing to put together multiple modules on the shack bench. Clumsy, cluttered, loose modules might work in a picnic-tables-on-the-air type activation. But would it work in a situation where there are no convenient surfaces to mount the equipment; where – at any moment – we might be politely asked to vacate the area by a hungry bear looking for a space to eat his lunch? This new build is a grab-and-go package that works in small, tight spaces – even on top of a rock in the backcountry – and that’s the kind of environment where I like to operate.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #FT817 #OutdoorOps #POTA #QMX

This is still a hobby, isn’t it?

I used the mesh as below !!  I would like to propose you test and show in your fine public forum the use of copper mesh used to plug vermin holes for a counterpoise. , A link is attached . I’ve used this in the past 2 months with absolute success.  If the feed point is elevated I may run a wire with a alligator clip to the ground and attached the mesh. In my testing a 8.5 ft length of mesh (comes in rolls) is better by a .2 SWR compared to 5 17 ft radials doubled back on itself in the same approximate width as the 5″ mesh. The nice of the mesh is that it can roll out nice on the snow or ground  with a few rocks holding it in place. I claim it gives increased ” solidity” to the ground effects if there is such a thing.  Its a poor man’s Cameleon (sp) fabric counterpoise they sell for 100 + so USD. I find it hard to believe this is pure copper , I have not soldered it as a test. I’d suggest at least taping the cut ends with duct tape to stop the unravelling of the mesh . The other bad so to speak is that after a time the copper may wear and deposit itself as tiny ting shards  of wires , not too bad for the outside though not in the house  for the Doggies which I have.. This stuff may work  well for small inside verticals that need a easy counterpoise. Again the ease of rolling this out is great AND IT DRIES FAST IF WET  especially compared to the Cameleon  (sp) .   Respectively submitted, if you decide to use and test this on your site I will accept use of my call and name (AA1AR, Bruce) as the initial proposer of this mesh as once the INFLUENCERS grab this it will be their claim to fame and this needs to be stopped.  Some of them are fine like Waters though some have been compromised by “must use for POTA super yellow Poloni & XXXXX flexible cable”  which I think is rather sad.. They just push hardware . I wonder how much money they make from all this . This mesh could also be ELEVATED and used as part of a pota performer by hanging it with a string thru its mesh. An interesting test !!!  I really do need to suscribe (sp) to your channel.  Sorry for the mispelling its 5 am       Bruce S. AA1AR   https://www.amazon.com/Copper-Mesh-Prefect-Blocking-Eco-Friendly/dp/B08PSLHWZT/ref=sr_1_4?crid=1YF5QRR4AOAQR&dib=eyJ2IjoiMSJ9.YJEVFO30iuWfii-aS0LyZqhl2p3_NwqoH8sQCRMneSIClgbl8syNMcHSRx8otcrCk47fE7PJTPN0to4efyxLlpi8H4o7WkbI63QkXXnVYqNycW9YEpXiWU9JdypAK4UdOxO9vlNg0J60tJIrFDQuSE0KdXt3Ya08wB1tPy7PHPrTfqgwrKnvMJ7B8UHCQCQNTDEyRSR6g3OtBsnicIMe5DssvlAFr7k1EvLEEQMkO5c.vsa4EQ0FlfyhmO85psjNiTfPcPSBjTzzGATB4eRPoOs&dib_tag=se&keywords=copper%2Bmesh%2Brodent%2Bcontrol&qid=1765793755&sprefix=copper%2Bmesh%2Caps%2C148&sr=8-4&th=1

Ham Radio continues to change. Whether you believe the changes are good or bad depends on a lot on your perspective. But, no matter if you are a traditional brass pounder, or you believe the Internet is the future of ham radio, one question stands out as we enter another year. Is ham radio still just a hobby? Yes, there is always the public service aspect. Many of us still enjoy getting out to support our local charity run or bicycle race, but isn’t that still part of the hobby? The change that has surprised me the most brings the lure of money into the picture. Has the line between a pure hobby and a small business become blurred?

What indeed is a hobby? I found this definition online:

“A hobby is a regular activity that a person engages in for enjoyment and relaxation during their leisure time, rather than for financial gain or professional purposes.”

This isn’t meant to criticize those who seek financial reward from writing or posting videos about amateur radio. We each have our own circumstances and maintaining an online presence does cost money. Services such as Patreon have tempted many online content creators to invite followers to make a voluntary regular financial donation to “support the channel”. Has this turned our hobby into a micro business? One online source defines “business” as:

The activity of buying and selling commodities, products, or services.

If a website or video channel provides affiliate links to products, is that a business service? And are commissions earned and Patreon donations received taxable as business income? I don’t know. If there is a non-profit motive and a genuine need for assistance then a request to help cover the running costs would bI used the mesh as below !!  I would like to propose you test and show in your fine public forum the use of copper mesh used to plug vermin holes for a counterpoise. , A link is attached . I’ve used this in the past 2 months with absolute success.  If the feed point is elevated I may run a wire with a alligator clip to the ground and attached the mesh. In my testing a 8.5 ft length of mesh (comes in rolls) is better by a .2 SWR compared to 5 17 ft radials doubled back on itself in the same approximate width as the 5″ mesh. The nice of the mesh is that it can roll out nice on the snow or ground  with a few rocks holding it in place. I claim it gives increased ” solidity” to the ground effects if there is such a thing.  Its a poor man’s Cameleon (sp) fabric counterpoise they sell for 100 + so USD. I find it hard to believe this is pure copper , I have not soldered it as a test. I’d suggest at least taping the cut ends with duct tape to stop the unravelling of the mesh . The other bad so to speak is that after a time the copper may wear and deposit itself as tiny ting shards  of wires , not too bad for the outside though not in the house  for the Doggies which I have.. This stuff may work  well for small inside verticals that need a easy counterpoise. Again the ease of rolling this out is great AND IT DRIES FAST IF WET  especially compared to the Cameleon  (sp) .   Respectively submitted, if you decide to use and test this on your site I will accept use of my call and name (AA1AR, Bruce) as the initial proposer of this mesh as once the INFLUENCERS grab this it will be their claim to fame and this needs to be stopped.  Some of them are fine like Waters though some have been compromised by “must use for POTA super yellow Poloni & XXXXX flexible cable”  which I think is rather sad.. They just push hardware . I wonder how much money they make from all this . This mesh could also be ELEVATED and used as part of a pota performer by hanging it with a string thru its mesh. An interesting test !!!  I really do need to suscribe (sp) to your channel.  Sorry for the mispelling its 5 am       Bruce S. AA1AR   https://www.amazon.com/Copper-Mesh-Prefect-Blocking-Eco-Friendly/dp/B08PSLHWZT/ref=sr_1_4?crid=1YF5QRR4AOAQR&dib=eyJ2IjoiMSJ9.YJEVFO30iuWfii-aS0LyZqhl2p3_NwqoH8sQCRMneSIClgbl8syNMcHSRx8otcrCk47fE7PJTPN0to4efyxLlpi8H4o7WkbI63QkXXnVYqNycW9YEpXiWU9JdypAK4UdOxO9vlNg0J60tJIrFDQuSE0KdXt3Ya08wB1tPy7PHPrTfqgwrKnvMJ7B8UHCQCQNTDEyRSR6g3OtBsnicIMe5DssvlAFr7k1EvLEEQMkO5c.vsa4EQ0FlfyhmO85psjNiTfPcPSBjTzzGATB4eRPoOs&dib_tag=se&keywords=copper%2Bmesh%2Brodent%2Bcontrol&qid=1765793755&sprefix=copper%2Bmesh%2Caps%2C148&sr=8-4&th=1e a sincere and appropriate alternative.

If I had a million dollars, I’d be rich

When I read a blog or forum post that is full of links to affiliate services such as Amazon where we can purchase promoted products “at no additional cost” I wonder whether the product is being promoted because it truly is the best available product at the best price, or for some other reason. Last fall I stayed at a very nice hotel and posted a very positive review of my stay online. Shortly afterwards I received an email from the hotel offering me $20 if I posted a positive review on another specific online service. I was shocked and replied that I declined their offer and did not approve of businesses buying favorable reviews. I now tend to distrust online reviews of anything, including ham radio equipment.

Am I just a grumpy old curmudgeon?

Perhaps this is “progress”; the concept of a pure hobby activity may be fading into history. Perhaps I am simply too old-fashioned to keep up. I have owned and operated businesses – real bricks and mortar businesses – so I am not opposed to the concept of entrepreneurship. I am retired now and enjoy ham radio as an activity that I engage in purely for enjoyment and relaxation during my leisure time. Other people’s situations and motivations may differ from mine but, here on Ham Radio Outside the Box, I cover the costs out of my own pocket and am happy to carry on doing so.

And while I’m up on my soapbox …

Early in my ham radio activities I discovered that I enjoyed operating outdoors (out in the “Big Blue Sky Shack”) far more than sitting at home in my basement shack. But there was a problem. Quite often I would be sitting in a field calling CQ into a black empty void and getting no responses. Then along came a brilliant new activity that changed everything. Now I got contacts every time I stepped outdoors and fired up my rig – sometimes lots of contacts. That new activity was Parks on the Air, a.k.a. POTA.

This QTH is on the edge of a cliff on the Bruce Trail overlooking Georgian Bay reached after a short 1km hike through the county’s black bear hot spot. Great QRP DX from up here.

POTA fundamentally changed ham radio and has quickly become one of the most popular activities in ham radio. The rules are very simple and, quite frankly, open to interpretation. Adherence to the rules is left to the honor and honesty of participants. In June 2024 I wrote a post entitled: “How to really up your POTA game (and why you shouldn’t)“. I wrote: “There is a very simple way to get your activation complete in very short order – even during a complete HF blackout. And for a bonus you can get lots of Park to Park (P2P) credits along the way. And best of all you can do it all without violating any Parks on the Air rules. Oh, just one more thing, PLEASE DON’T EVER DO THIS!.”

I was, and remain, uncomfortable with the practice of two hams making an HT to HT VHF simplex contact with each other to complete an activation. It just doesn’t seem to be in the spirit of good operating practice to my way of thinking. Is leaving the park after a “busted activation” really so bad?

Taking it easy. A nice relaxed activation beside a beautiful lake. No rush, just enjoy the sunshine and the scenery and let the contacts roll in.

My personal preference is to hike into the backcountry, find a secluded spot away from the public eye and set up my radio. But it seems that approach is rare among POTA operators. Many prefer what Ed Durrant DD5LP has dubbed “PLOTA” (Parking Lots on the Air). I have also heard it called “Drive-Thru activations”. Sometimes the parking area is actually outside the park boundary, but what the heck eh? I read one POTA activation account in which the activator was within 100 feet of the park entrance and claimed a valid activation. For the record, the activator and all their equipment must be entirely inside the park boundary. The only exception to this rule is for trails where the 100ft exemption applies.

If too many hams activate a park from the parking lot, or adjacent picnic tables, or set up poles and antennas in public areas, other park users may start to complain. Could it happen? You bet it could; witness what happened in the State of Virginia recently as reported by, among others, fellow blogger Stuart VE9CF on his blog “Out n Aboot”. People who visit parks for quiet enjoyment may not appreciate hams hollerin’ into microphones trying to complete a contact when the bands are bad. Perhaps consider operating CW or digital modes and wearing headphones. People may construe your unobtrusive, totally silent radio activity as some kind of scientific study and pass on by.

It really is fun to operate outside in a park. We can soak up the sunshine, enjoy the trails and the wildlife and play radio too. Del N2NWK who is an avid POTA activator disagrees and wrote in a comment here on Ham Radio Outside the Box:

“There is no such thing as in the spirit of POTA. POTA is not about going to the park to enjoy nature. POTA is about operating your radio in the park to make at least 10 contacts in order to have a valid activation.

POTA rules states that you and all your equipment must be within the boundaries of the park. There is nothing in the POTA rules that say you must hike, or go a certain distance in the park to activate. Just operate you radio in the park and have fun. POTA allows you to choose however you feel to activate your park.

Too many people trying to make rules for POTA that does not exist. Park to Park is operators making contacts with each other from a park, it does not matter if it is the same park or not.”

So Del and many other hams like him I suspect, participate in POTA simply to rack up as many contacts as possible, as quickly and efficiently as possible. Nothing wrong with that I guess, I just see things differently.

I used to be drawn to the competitive aspects of POTA. I checked the POTA website regularly to make sure I was still listed as the “Park Leader” at my local parks. If not, I would schedule another activation to restore my status. After a while the allure of yet another activation waned. Now I am content to go to a park, or a trail, or wilderness area to test a new antenna design by making some contacts. Maybe I am slowing down with age who knows. I am glad POTA is still around and I really hope the Virginia experience doesn’t lead to further restrictions on ham radio activities in public spaces.

As always, if you disagree, or have another perspective to consider, please leave a comment below.

Coming up on Ham Radio Outside the Box

Adam K2CAT wrote to me about a new iOS/Mac app he has written to help hams. I am not an iOS/Mac user myself so I cannot comment on how good it is, but next week Ham Radio Outside the Box will post Adam’s description so you can try it out for yourself.

Also in next week’s post, another great idea from a reader. Bruce AA1AR has come up with an original and very clever idea for constructing radials. Read all about it next week.

Coming up later this month; it is another bitter winter here in southern Ontario; cold temperatures, biting winds and lots of snow. I set up my ancient Yaesu FT-817 in the back seat of my RAM 1500 truck for shelter and found I was juggling paddles, battery and assorted other bits and pieces that were falling from my frozen hands and finding cunning hiding places under the seat, or in awkward crevices that were hard to reach. After a rethink and a bit of metalwork in my garage workshop I found a better way to get my portable winter gear organized. Details in an upcoming post.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #Antennas #CW #OutdoorOps #Portable #POTA

A Year End Compendium of Outside the Box Antenna Ideas

We have reached the end of another year of crazy ideas here at Ham Radio Outside the Box and a repeat of last year’s severe winter has gotten underway in southern Ontario. The daily temperature high remains well below freezing and the ground is buried under a thick blanket of snow already. I have tried to “Keep Warm and Carry On” with more off-the-wall outdoor antenna experiments but succumbed to the biting wind and had to retreat to the warmth of the shack.

Here in the nice toasty warmth of my basement “Comms Room” I am surrounded by radio equipment, electronic gizmos, tools and almost enough wire to lay a new transatlantic cable. I also have computers. One of the computers runs the incredible HamClock program giving me instant access to updated solar propagation conditions, the current location of the International Space Station and real time data on the International HF beacon project.

Another computer is the one on which I am typing this post now. I recently realized that I have written so many posts related to field portable antennas I have built and tried that it would be a useful exercise to re-read them all. Heck, I surprised myself with some of the ideas that were posted and forgotten, but will now be resurrected. So, to end the year, I have composed a compendium of 35 of those posts – old and not-so-old – as a reference for readers to explore. I hope you may find some useful information for your own deployments.

I should stress that these are not all tried and tested designs. Some have worked so well I intend to keep them in my hambag for field portable radio operations. Others … well they were useful learning opportunities. Even if you only pick up a couple of tips such as the simplest, quick release method of attaching an antenna wire to the top of a pole the read will be worth your time.

NB: If you find any of these posts particularly interesting you can use the “Print” function on your computer and select “Save to PDF” or “Print to file” to keep a local copy.

ZZZZZ … ZZZZ … ZZZ

Ham Radio Outside the Box will now go into hibernation until the new year. Until then my best wishes go out to all in the hope that you will enjoy whatever religious or secular festival you celebrate at this time of year. Stay out of the cold!

https://hamradiooutsidethebox.ca/2025/11/04/a-simple-fix-for-my-broken-telescopic-whip/

https://hamradiooutsidethebox.ca/2025/08/29/two-resonant-simple-wire-antennas-for-pota/

https://hamradiooutsidethebox.ca/2025/09/23/a-simple-low-profile-multiband-antenna-for-pota/

https://hamradiooutsidethebox.ca/2025/08/05/rapid-deployment-field-expedient-random-wire-antenna-ideas/

https://hamradiooutsidethebox.ca/2025/07/23/does-an-antenna-top-hat-really-work/

https://hamradiooutsidethebox.ca/2025/07/11/an-outside-the-box-version-of-the-delta-loop-antenna/

https://hamradiooutsidethebox.ca/2025/05/21/reviving-a-webster-band-spanner-a-1950s-manual-screwdriver-antenna/

https://hamradiooutsidethebox.ca/2022/08/15/vertical-antenna-redesigned/

https://hamradiooutsidethebox.ca/2022/07/30/no-antenna-no-problem/

https://hamradiooutsidethebox.ca/2022/06/21/80m-band-antenna-fits-into-just-1-square-foot/

https://hamradiooutsidethebox.ca/2021/12/17/an-easy-t2lt-portable-antenna/

https://hamradiooutsidethebox.ca/2021/11/08/a-portable-vertical-antenna/

https://hamradiooutsidethebox.ca/2021/09/13/a-most-unusual-antenna/

https://hamradiooutsidethebox.ca/2025/05/14/matching-an-efhw-antenna-a-third-way/

https://hamradiooutsidethebox.ca/2025/04/23/ssefhw-another-shortened-end-fed-half-wave-antenna-for-20m/

https://hamradiooutsidethebox.ca/2025/03/19/a-simple-antenna-that-is-omnidirectional-directional-and-nvis/

https://hamradiooutsidethebox.ca/2025/03/05/a-quick-and-easy-qrp-emergency-field-antenna/

https://hamradiooutsidethebox.ca/2025/01/16/a-top-loaded-end-fed-half-wave-antenna-for-20m/

https://hamradiooutsidethebox.ca/2024/12/12/a-clefhw-antenna/

https://hamradiooutsidethebox.ca/2024/11/13/antenna-height-matters-true-or-false/

https://hamradiooutsidethebox.ca/2024/10/09/the-titanic-40m-field-expedient-backpack-portable-antenna/

https://hamradiooutsidethebox.ca/2024/08/16/how-does-the-speaker-wire-no-counterpoise-antenna-work/

https://hamradiooutsidethebox.ca/2024/07/18/a-neat-trick-with-a-20m-efhw-wire-antenna/

https://hamradiooutsidethebox.ca/2024/03/13/an-improved-self-supporting-low-footprint-field-expedient-antenna-for-20m/

https://hamradiooutsidethebox.ca/2024/03/06/antennas-a-riddle-wrapped-in-a-mystery-inside-an-enigma/

https://hamradiooutsidethebox.ca/2024/02/14/a-most-unusual-vertical-antenna-for-20m/

https://hamradiooutsidethebox.ca/2023/12/06/a-simpler-field-expedient-rybakov-antenna-for-winter/

https://hamradiooutsidethebox.ca/2023/11/05/an-upside-down-antenna/

https://hamradiooutsidethebox.ca/2023/10/19/using-a-municipal-flagpole-for-an-antenna-fine-business/

https://hamradiooutsidethebox.ca/2023/02/15/the-vp2e-a-strange-but-proven-antenna/

https://hamradiooutsidethebox.ca/2023/02/09/what-in-heavens-name-is-a-rybakov-antenna/

https://hamradiooutsidethebox.ca/2023/01/14/a-magic-ground-mobile-antenna/

https://hamradiooutsidethebox.ca/2025/01/23/an-off-center-fed-sleeve-dipole/

https://hamradiooutsidethebox.ca/2024/07/12/cutting-my-losses/

https://hamradiooutsidethebox.ca/2023/10/24/an-itsy-bitsy-teeny-weeny-upside-down-hf-whip/

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#amateurRadio2 #antennas #counterpoise #cw #outdoorOps #portable #pota

What really determines the efficiency of an antenna?

Is it Standing Wave Ratio (SWR)?

It is common knowledge that when an antenna has high SWR some of our transmitted power is wasted instead of being transmitted. But is this really true? The trouble with “common knowledge” is that it spreads without further scrutiny. “It must be true because that’s what everybody thinks”. But let’s consider another perspective.

What happens to our signal when it meets an antenna with high SWR? Some of the signal is radiated while the rest is reflected back down the transmission line to its source – the transceiver. What happens to the reflected signal when it reaches the transceiver? It is re-reflected back towards the antenna and the cycle repeats.

So does all the signal eventually get radiated? No. Energy is lost (RED ALERT from the physics department: Energy can neither be created nor destroyed, only converted from one form to another). Ok, my apologies to the physics department, some of the energy is converted to heat as our signal passes along the transmission line and through any ununs, baluns, impedance transformers or other devices en route. Further energy is converted to heat due to the resistance of the wires and the impedance of the transmission line itself.

Thus, on every trip between the transceiver and the antenna, some of our transmitted RF is converted to heat. If the antenna has a high SWR some of our signal travels back and forth between the transceiver and the antenna multiple times and becomes further attenuated on each trip. Therefore, if we can reduce the loss of RF (due to conversion to heat) as it passes through any devices along the journey between the source (transceiver) and load (antenna) we will improve the efficiency of our antenna system.

How can we do that?

One simple way to achieve that is to correct for the high SWR right at the antenna. A remote tuner can do that. A loading coil will compensate for the high capacitive reactance of a short antenna, but loading coils can be inefficient because of wire resistance. This is especially true in the case of base-loading coils on a quarter-wave vertical antenna. The current is highest at the base of the antenna so more RF energy will be lost to heat (P=I^2*R) than with a center-loading or top-loading coil.

So the real culprit is not SWR, but the insertion loss of ununs, baluns, impedance transformers, loading coils, transmatches and any other “energy conversion” devices, including the transmission line itself, through which our signal has to pass.

Insertion loss of Ham Radio Outside the Box’s 4:1 ununs

In the previous post I reported on my build of field test versions of a 4:1 unun and a 4:1 balun to compare how each would handle the task assigned to them. Now the job I set myself was to transform what might be called the “Ugly Sisters” builds into something with the good looks of Cinderella. And Cinderella had to be an unun tough enough to withstand rough treatment out in the Big Blue Sky Shack through all four Canadian seasons (Late Winter, Brief Summer, Early Winter, Deep Winter).

QRP 4:1 unun

I built two versions of a 4:1 unun; one for QRP and another for what I like to call QROp. “QROp” is an unofficial label I have adopted to mean about 20 watts or so. Twenty watts will give a 1 S-unit advantage over 5 watts – maybe just enough for our signal to poke its nose above the noise floor when propagation conditions are not so good.

QROp unun

There are 2 main differences between the QRP and the QROp versions: The QRP unun uses a BNC connector and a 4:1 transformer wound on a tiny FT82-43 toroid. The QROp version uses an SO-239 connector and a 4:1 transformer wound on an FT140-43 toroid.

If we look at the tables below, we can see that the QRP version may have a little too much insertion loss. When we are trying to do as much as we can with as little as possible every milliwatt is wanted. As the wonderful friendly folks on the big Canadian island of Newfoundland like to say: “A little’s a lot if it’s all you’ve got”.

Insertion Loss effects of the Ham Radio Outside the Box QRP unun

BandQRP (5 watts) UNUN Insertion Loss (dB)RF Power Lost (watts)% RF Power Lost10m0.390.438.612m0.370.418.215m0.350.397.817m0.340.387.614m0.330.377.430m0.320.367.240m0.350.397.880m0.730.7715.4

Insertion Loss effects of the Ham Radio Outside the Box QROp unun

BandQROp (20 watts) UNUN Insertion Loss (dB)RF Power Lost (watts)% RF Power Lost10m0.241.085.4012m0.231.035.1515m0.220.994.9517m0.210.944.7014m0.200.904.5030m0.200.904.5040m0.200.904.5080m0.220.994.95

A little extra heat in winter

You would think Canadians wouldn’t mind a little extra heat in winter. It’s true, but not when the source of that heat is our precious transmitted RF. In case you were wondering, the amount of RF converted to heat by inefficient devices is mostly undetectable. If it can be easily detected the “magic smoke” can’t be far behind. When it’s 253 Kelvins outside you just ain’t gonna notice when the temperature rises to 254 Kelvins (note: the physics department advised me to use Kelvins to avoid confusion between degrees Fahrenheit and degrees Celsius).

Oh no! There’s more?

Yes indeed. An unun does not attenuate Common Mode Current (CMC). For that we need a Common Mode Current Choke (CMCC). CMC is the current on the outer surface of a coax braid. Differential mode current is carried on the core and inner surface of the coax braid. Does a CMCC also have insertion loss? Yes, but how much? Let’s take a look.

Insertion Loss of a QRP (5 watts) Common Mode Current Choke (CMCC)

BandQRP (5 watts) CMCC Insertion Loss (dB)RF Power Lost (watts)% RF Power Lost10m0.250.285.612m0.220.255.015m0.210.244.817m0.190.214.214m0.170.193.830m0.150.173.440m0.140.163.280m0.130.153.0 QRP CMCC

Insertion Loss of a QROp (20 watts) Common Mode Current Choke (CMCC)

BandQRP (5 watts) CMCC Insertion Loss (dB)RF Power Lost (watts)% RF Power Lost10m0.180.814.0512m0.160.723.6015m0.150.683.4017m0.130.592.9514m0.110.502.5030m0.100.462.3040m0.090.412.0580m0.080.371.85 QROp CMCC

The (not so) grand total of RF going up the chimney

BandTotal QRP (5W) % RF power lost to heatTotal QROp (20W) % RF power lost to heat10m14.29.0912m13.28.7515m12.68.3517m11.87.6514m11.27.0030m10.66.8040m10.06.5580m18.46.80

The white bearded man in the red suit and his flying reindeer might be grateful for a few watts of heat going up the chimney at this time of year, but those of us in the frozen barren tundra of the northern states and provinces, as well as licensed ham dwellers in other cold lands, may not see things the same way.

What can we conclude?

If we only consider the insertion loss – in this example – of the 4:1 voltage unun and the Common Mode Current Choke and ignore resistive losses in the transmission line, and possibly insertion loss in a transmatch (“tuner”), we can determine the potential efficiency of our antenna system.

• For our QRP devices the efficiency varies between 81.6% and 90% across the bands
• For our QRO devices the efficiency varies between 90.9% and 93.5% across the bands

This conclusion is based on the assumption that there is no loss in the antenna itself. We are treating the antenna, the transmission line, unun and CMCC as the “antenna system”. I have made no allowance for SWR losses for the reasons stated in the introduction to this post.

What a load of old codswallop!

I am an expert in the sense that “X” is an unknown quantity and “spurt” is a drip under pressure. I may be completely wrong; I may have fallen off my horse and bumped my head on a rock. I may have come to a fork in the road and taken it as Yogi Berra once famously said. If you would like to correct me on any wrong assumptions please do so. I receive a lot of direct emails from readers and, while they are most welcome, if you write a comment to this post instead it may trigger an interesting technical discussion here.

A big thank you to all the new and many existing subscribers to Ham Radio Outside the Box. It is people like you who make writing these posts so worthwhile. I appreciate every one of you.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#amateurRadio2 #antennas #cw #outdoorOps #unun

POTA PERformer radials – can we make a compromise?

There has only been one light snowfall in southern Ontario so far this season – just a few centimeters that melted away within a couple of days. In anticipation of upcoming heavier snowfalls and a semi-permanent white blanket that will last until spring, I bravely shrugged off the chilly outside air and set up my Ham Radio Outside the Box version of the POTA PERformer antenna out in the backyard to experiment with radial lengths.

The cunningly repaired broken shortened whip with a capacitive top hat, to compensate for its inductive reactance on the 20m band, sat atop my custom spike mount that, despite falling temperatures, could still be pushed into the ground about 25cm (10 inches). Two radials were attached each of which sloped down to a fiberglass stake about a foot (30cm) above ground. The radials are approximately 5m (17ft) long for the 20m band with links to shorten the wires for the 17m and 15m bands.

Now, to find a shortcut

The objective for the day’s tests was to investigate whether compromises could be made in the radial lengths. Why? Later in the winter, when the snow lies deep and crisp and even, it can become a real chore to wade through accumulations of the infernal white stuff to adjust the radial lengths for band changes. I have adopted 2mm banana plugs for the links – a great idea in the summer, but maybe I neglected to consider what will happen when even a few snow flakes freeze on those tiny connectors in the winter!

So, how to minimize pedestrian excursions through the challenges of winter operating conditions to accommodate band changes? The POTA PERformer is an efficient antenna but it was designed in California where the climate is just a little milder than in Ontario. Should I go back to using a random wire antenna – like the Rybakov – until spring comes around again?

I could perhaps use “fan radials” i.e. separate radials for each band. That would probably work but setting them up might still involve wading through deep snow. In the past I have used ground radials laid on the snow – a multiband arrangement that requires no adjustment for band changes, but is less efficient.

Back to the backyard tests; what did I find out?

• First, my approximately 16.5ft (~5m) raised radial wires provided an acceptable SWR (less than 2:1) on 20m and 17m (with the whip length shortened for 17m).
• Second, the same wires – with the links adjusted for 15m and the whip shortened again – gave an acceptable SWR on 15m, 12m and 10m.

So, is this a result? Maybe not. There is a potential for lost efficiency when the radiating element is shorter than the counterpoise. Let me explain.

Let’s assume we are using a field portable version of the POTA PERformer in which the feedpoint remains quite close to the ground – maybe 1 to 1.5 meters. The two radial wires slope away from the feedpoint to an end point even lower to the ground. Now, if we examine the current distribution on a halfwave dipole, we can see that the maximum current, and therefore the point at which maximum RF is radiated, is located in the center of the dipole.

We would like the high current point to lie within the radiating element, not the counterpoise. For the purposes of this discussion we are going to refer to the two radial wires as “the counterpoise”.

Going back to my backyard tests, I found that:

• a 20m counterpoise “worked” on the 17m band.

• a 15m counterpoise also “worked” on the 12m and 10m bands.

In each of these cases the radiating element was shorter than the counterpoise.

Referring to the accompanying diagrams we can see that the high current point, in each case, lies within the counterpoise.

Does this finding matter?

Changing the radiating element versus counterpoise balance creates an antenna that looks very much like an Off Center Fed Dipole (OCFD).

If an OCFD is mounted high enough above ground it doesn’t matter at all although two things need to be considered here:

1. Changing the radiating element versus counterpoise lengths changes the impedance at the feedpoint.
2. The overall length of the dipole might change unexpectedly. This can be seen with Greg KJ6ER’s Challenger antenna which is a vertical OCFD halfwave dipole that is shortened by laying part of the counterpoise wire on the ground.

A relatively small change in the ratio between the radiating element versus counterpoise lengths changes the feedpoint impedance, but this can be compensated by adjusting the whip length to still obtain a usable SWR.

However, we cannot compensate for the proximity to ground of the counterpoise in the POTA PERformer. If the current maximum occurs at the feedpoint (1 to 1.5 meters above ground) very little power is lost. But, if the current maximum occurs below the feedpoint we are going to keep the earthworms warm in winter.

Not the best plan

So we can conclude that using a 20m counterpoise on 17m risks losing some of our RF energy to the ground. The same applies for using a 15m counterpoise on 12m and 10m. The following diagram summarizes this.

The way forward

“Fan radials” may still be a solution but they require some careful experimentation. There is interaction between the wires for each band due to mutual capacitance. This is compounded when multiple bands are involved. To make matters worse, when used out in the Big Blue Sky Shack where the wind doth blow through the wires and changes the interaction, who knows what wild swings in SWR may occur? The radio I have dubbed my “very clever poodle” (QMX: see last post) will not take kindly to that.

A final thought

I have watched several videos in which a very short whip is mounted on a picnic table and used with a single long counterpoise wire draped down to and across the ground. Sometimes the “Magic (Tune) Button” assists in finding an SWR that keeps the radio smiling. Contacts get made, so what’s the problem? I hope the above discussion answers that question.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#amateurRadio2 #antennas #counterpoise #ground #outdoorOps #pota #qmx

A simple outside the box fix for a broken telescopic whip

“If it ain’t broke, don’t fix it”

Or conversely, if it is “broke” you have two choices. Order a replacement from the other side of the planet, and wait for the slow boat from China to navigate thousand of nautical miles across the stormy waters of international seas. Or, alternatively, and my preferred solution, is to see if it can be fixed. So when I managed to break the 18.5ft telescopic whip I had ordered from China a year or so ago, I was faced with that choice.

Hair of the dog

There is an old supposed remedy for the after effects of over indulgence in adult beverages. It is called the “hair of the dog that bit you”, often simplified to “hair of the dog”. The idea is that, in the morning, if you drink some more of the beverage that caused the problem you will recover. I rate that high on the skepticism index.

The dog that bit my antenna was another product from the same oriental source as the whip. It was a “top hat” designed for the PAC-12 antenna. This set of electric antlers proved too heavy for the whip that was never designed to carry them. The tip of the whip swayed rather wildly in the wind, before collapsing on the ground and decapitating itself in the process. The top hat survived but the top two sections of the whip parted company from the rest, never to be reconnected again.

What remained was 15 feet and 9 inches of whip that sat in a dark corner of the shack until, one day, a random firing of neurons in my brain came up with an idea. I call the idea “hair of the dog”; i.e. I wondered if I re-attached the top hat, the same one that caused the problem in the first place, to the shortened whip would it at least get me back on 20-meters?

The shortened wounded whip was a little too short to be resonant on the 20m band. Could the addition of a top (capacitance) hat lower the resonant frequency sufficiently to fix the problem? I embarked on an impromptu mission to find out.

Unextended top hat and whip

Top loading a vertical whip is a very efficient way of convincing an electrically short antenna to resonate on a lower frequency. In effect, it increases the electrical length of the antenna. I have been chided by sagacious readers for using the term “electrical length”. The term may be technically incorrect but it makes it easier to understand what happens when an antenna is loaded. Is my top-loaded shortened whip as efficient as a full-length unloaded whip? I’ll leave that for the experts to comment upon.

There are advantages to a top-loaded vertical whip for field portable operators like myself. For a start, a shorter whip is less conspicuous. While activating a park back in the spring of this year, a uniformed Ontario Parks warden pulled up in her official pickup truck to see what I was up to. Ontario Parks wardens have the same authority as police officers when it comes to park rules and regulations. They can impose on-the-spot fines for infractions of a sometimes vague set of rules like “disturbing trees”. She told me that my long whip antenna had caught her eye. When I told her I was using Morse Code to contact other amateur radio operators and read out the list of all the states I had contacted, she was genuinely interested. We struck up a good rapport, especially when discussing which trail the resident park bear preferred. Although that encounter with officialdom went well I prefer to operate under the radar – nothing to see hear, move right along please.

Custom, ham-made (by me) support pole.

As I write this we are well into fall. The winter months still lie ahead of us – 7 months of dreary, snowy, icy weather. So I took advantage of cool temperatures and still unfrozen ground to test my top-loaded shortened whip. I mounted the whip on my recently constructed support that uses PVC plumbing bits and part of a fiberglass driveway marker driven into the ground. For lucky readers in the southern states and other milder climates, a driveway marker is a thin pole used to identify the edges of a driveway when the snow comes. I use 5ft markers, and during last winter’s unusually heavy snowfall, they disappeared deep beneath the snow banks left by the snow plows on their daily runs. I gotta move to sunny Florida, snakes and gators be damned!

It might be considered folly to adopt a hair of the dog approach to fixing the whip but, of course, the lower sections of a telescopic whip are thicker than those at the top. Thicker sections are less likely to experience the wild, wind-induced, oscillatory motion that caused the initial problem. In fact, I had to shorten the whip by another two sections to bring resonance within the 20-meter band, thereby enhancing the physical rigidity even further.

For this initial backyard test I used a set of four 13ft radials that lie mostly on the ground. I know this isn’t the most efficient way of providing the “other half” of an antenna. I have now improved on that by extending the support pole to 43 inches (109cm) and replaced the ground radials with two sloping, above ground radials with links for 15m, 17m and 20m.

Very soon our ground will be frozen hard – like concrete – and then other support options will be required. However, this top-loaded short whip is going to be traveling with me on my winter POTA activations. It works fine business on 20m but, even with the whip extended to its full 15 feet 9 inches, the top hat can’t get it to work on 30-meters. Shortening the whip further (and collapsing the top hat’s “antlers”) allows the higher bands to be used, which is useful while band conditions create openings there.

When I broke the whip I started to look into finding a replacement. The Chameleon 25ft whip sounded interesting but then I watched a video in which one of these whips waved at the heavens during windy conditions. I could foresee another catastrophic collapse in my future if I went that route. I wondered whether a park warden might consider a very tall waving whip a hazard to other park users and wave an infraction notice at me in response. No, there had to be a safer solution and I think this top-loaded formerly broken whip fits the bill quite nicely.

Meanwhile, back in the shack …

Work continues on renovating my rigs to return to QRP operations when band conditions permit. I have been using my Yaesu FT-891 throughout the summer. I like to think of the FT-891 as a QRP rig with optional QRO capability. The trouble is, it is too easy to tweak the power just a little to give my signal a little more muscle. My QRP Labs QMX is a great little radio but it isn’t built for hostile environments – like Ontario winters. Unfortunately I chose the low band QMX when ordering so I am limited to 80m, 60m, 40m, 30m and 20m – no access to the higher bands which have been quite active lately. I do have another option – a rugged, pugnacious but rather old little rig that covers all bands. It was built back in the era when there were fewer options for QRPers and lacks some of the features we now take for granted. There is a way to add on the missing features; I’ll publish the details in an upcoming post.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#Antennas #CW #MorseCode #OutdoorOps #Portable #POTA #QMX

Which is best – An EFFICIENT antenna or an EFFECTIVE antenna?

What’s the difference? An EFFICIENT antenna is one that converts as much transmitted energy as possible into radiated RF energy. “Efficient” is not clearly defined but is often understood to mean more than 90%. An EFFECTIVE antenna is undefined. The term is subjective and could refer to a favorite antenna that “gets the job done”. If an antenna brings in the QSOs it could be described as “effective”.

This antenna in Toronto which stands at 553.3 meters (1,815.3 feet) seems to be quite effective.

Even an efficient antenna won’t guarantee we will make QSOs. It is quite possible that an inefficient but effective antenna will bring in more QSOs than an efficient antenna. How can this be so?

To answer that question we have to examine the factors that affect the effectiveness of an antenna. These factors are unrelated to whether an antenna is actually efficient (although efficiency certainly helps).

Propagation Conditions: When our friendly neighborhood star gets hyperactive and hurls, for example, CMEs (Coronal Mass Ejections) in our direction things can get quite difficult for radio communications. We have witnessed this frequently during the recent maximum of the 11-year solar cycle.

As an aside, many ancient civilizations worshiped the Sun as a god. In the absence of our advanced technologies perhaps they could be forgiven for doing so. In terms of volume, the Sun is a million times larger than the Earth (source: Encyclopedia Britannica). It sustains all life on Earth and at some point in the distant future it will destroy the Earth when it runs out of the fuel that keeps its immense internal fusion reactor working. At that point it will swell into a red giant encompassing the orbits of all the inner planets.

But back to the Sun’s effect on radio communication, it controls which bands are active at any given time. It controls whether the ionosphere has the ability to refract RF back to the Earth’s surface, and to what degree. It doesn’t matter what kind of antenna we are using when a solar storm creates an HF blackout. For that reason it makes sense for amateur radio operators to pay attention to propagation conditions when planning to operate. Ham Radio Outside the Box discussed what all the propagation parameters mean in an earlier post. Personally, I pay particular attention to the Solar Flux Index, Sunspot Number, K-index, Bz (Interplanetary Magnetic Field) and the Solar Wind Speed.

How many stations are on the air?

There are times when the “band is dead”, meaning if we scan the band we don’t hear any activity. Sometimes, all it takes is for one station to call CQ and the band joins the “undead”. At other times there just ain’t nobody listenin’; for example, Superbowl Sunday may not be the absolutely best time to get on the air. On the other hand, during ARRL Field Day in June the bands are usually a tad busy. I once made the mistake of waiting until Field Day was over before starting a POTA activation. Of course most Field Day stations had gone off-air by then so I ended up with a busted activation. Field Day contacts are valid POTA QSOs too so I probably could have completed the activation in short order if I had jumped on the air a few minutes earlier.

During the week many hams are at work and the bands are quieter. Those of us who, being of a certain age, are unencumbered by employment may still be disturbing the peace and quiet of the ionosphere.

So if we want to test whether our new antenna is a good’un it probably makes sense to get on the air when there are plenty of other hams pounding brass by the light of brightly glowing tubes (or “valves” as they are called in the land of the Pilgrim Fathers).

Location, location, location

As Bobby Darin might have sung if he had been a ham:

“Somewhere, beyond the sea; Somewhere waiting for me; Another ham on golden sands; Is watching the bands for me”

If you are a ham on golden sands – for example on the Atlantic or Pacific coast you can take advantage of the “Salt Water Effect” which makes even a wet noodle look like a great antenna. From my location in Southern Ontario Canada I would have to travel 1000km north to find salt water inside my own province, but that would be on the frozen shore of James Bay. Alternatively, at about half that distance, and across the US border, is New York City. I have tried operating on the beach beside the world’s largest underwater salt mine on Lake Huron but it didn’t do it for me.

If we can’t go down to the sea to CQ another alternative is to get high – as in up a mountain. Once again, I struck out. The highest peak in Ontario soars to a mind numbing, breathtaking … well actually it doesn’t even make it to 3000 feet (about 900 meters). Height helps!

What kind of antenna is the other guy using?

I remember having a great QSO with a ham in France from my backyard in Ontario. I was testing a wire antenna for NVIS that was only about 12 feet above ground. I was blown away by how clearly he could hear me. When I told him about my antenna he had the good grace to compliment me on how well it was working. A low antenna, designed for NVIS can sometimes still put out a -6dB signal (down 1 S-unit) at a low radiation angle and snag some DX. After the QSO I checked him out on QRZ.com and saw what kind of antenna he was using – it was a multi-element Yagi up about 70 feet on a tower. Now that was what I would call an “effective antenna”! It was doing the heavy lifting during the QSO, not my puny wire.

So the lesson here is, if you are operating QRP with one of those trendy 4ft base-loaded whips, and you are getting great DX contacts, it may not be your modest compromised miracle antenna that is getting the job done, it could instead be the DX operating from a powerful super station.

So could an inefficient, but effective, antenna beat out an efficient antenna? Perhaps; it is possible if the inefficient, but effective, antenna is up a mountain – or a saltwater beach for example.

What’s to be done?

Let’s get back to what makes an antenna “effective”. The millions of us who live within the interior of the great north American continent don’t have to imagine what it is like to operate far away from salt water and mountain peaks; we live it every day. Some among us have further limitations such as living in an HOA where the guardians of the establishment will descend like a swarm of screaming demons upon any ham who erects an antenna higher than a blade of grass. The custodians of many public spaces bring fire and brimstone upon anyone who dares disturb their trees, so throwing a weighted object up into the green canopy and pulling a nice long, efficient wire antenna up and over a branch is out of the question. But there is a solution.

Imagine you have to live with all these limitations and maybe even more. The best antenna you can get on the air is only 30 percent efficient. The bands are in turmoil due to a minor solar storm. If you are a QRP diehard your signal will at best be limited to a couple of watts. If you get lucky you may still make some contacts; if you don’t – well that’s the fun of QRP. A day in the park flattening your battery calling CQ with no responses is better than a day at home doing chores, or so they say.

Here at Ham Radio Outside the Box our motto is: “QRP when possible, QRO when required”. Or, to put it another way, a day in the park flattening your battery calling CQ at a blistering 30 watts and making QSOs is better than a day at the park flattening your battery calling CQ at 2 watts with no responses. That’s the fun of what I like to call QROp.

What are your experiences? Do you have a favorite antenna that gets the job done?

Coming up in a future post … A return to QRP and why I am reluctant to take my QRP-Labs QMX to the field.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #Antennas #OutdoorOps #QMX

A Road Trip with the POTA Tripod Antenna – with surprises!

A spell of warm, sunny weather and a chance to get out to see the fall colors in early October prompted my wife and I to go on a road trip up to Ontario’s Muskoka region and on to the fabulous Algonquin Park. The park is Canada’s largest and oldest and is the home to thousands of black bears, as well as moose, deer and wolves. Sadly, all the wildlife hid from us on this trip.

Propagation conditions remained uncertain at best, so the third passenger on the truck journey north was my Yaesu FT-891 QROp rig set to an unusually high 35 watts. And the antenna of choice was the 13ft tall vertical based on a tripod that has been the subject of recent posts. Once again, this antenna got the job done, and even revealed some surprises.

Inside Algonquin Park, at Mew Lake campground, I set up to check band conditions. As usual, I started by hunting other activators to see what kind of signal reports I would receive. Bad propagation numbers do not always result in difficulty making contacts. I had considered just leaving the radio in the truck and enjoying the sunshine on the quiet beach by the lake, but after settling into my camp chair I grew restless and within a few minutes I was calling activators and making QSOs.

There are two ways to perform an activation

Calling CQ is the best way; it makes an activator the target for eager hunters and often results in pile-ups. If you know how to handle a pile-up you can complete an activation in short order. But, when conditions are not so good, calling CQ repeatedly and getting no responses can be disheartening. Once I have spotted myself on the POTA website I like to complete at least a basic 10 QSO activation even if it takes a while. Trouble is, when time is limited, other priorities may take precedence and that can result in a busted activation and disappointment. Of course, it is still fun to get on the air out in the Big Blue Sky Shack, but there is another way to have fun and do an activation.

On several occasions I have taken a more relaxed approach and simply hunted other activators until I have completed 10 or more QSOs. This method is a little more difficult because it is necessary to compete with other hunters for each QSO. The advantage, as I see it, is there is no compulsion to complete the minimum 10 QSOs if conditions are bad. I can stop at any point and just consider it a fun day in the park. If I make my 10 contacts I file my logs with POTA and every QSO is automatically a “P2P” (Park-to-Park).

“Hunted activations” are my backup method when time is limited and conditions are bad. On that day in Algonquin Park I chose this method and ended up short of the required minimum of 10 contacts for a valid activation. We had two more days in this mini fall vacation and better conditions were ahead of us, but that day the park had other attractions we wanted to see.

Our overnight accommodation was a “bricks and mortar tent” with breakfast included. Many years ago I canoed into the backcountry inside Algonquin Park every summer and slept in a tent at the edge of several of the park’s many lakes. It was refreshing to get away from the crowds and enjoy the solitude of nature out in the wilderness. In almost complete darkness, at 2:00 AM one night, that solitude was interrupted by a very close encounter with a very large black bear. Fortunately the bear didn’t have me on his supper menu that night. After ransacking the campsite and attempting to claw the food bag down from a tree, it moved on in search of easier meals.

“CB or Ham?” inquired the lady with the Whippet

Activating Arrowhead Provincial Park in the October sunshine surrounded by beautiful fall colors.

Leaving the safe, solid, bear-proof accommodation in a nearby town the next morning we entered one of our favorites among Ontario’s parks where we would spend the entire day, with plenty of time for radio. The QTH for the day was Arrowhead Lake Provincial Park (CA-0140), a park I have activated before so I already knew the best location for setting up the radio.

The operating site was at the far end of the lake beside the dog beach. The accompanying picture shows my relaxed operating position. We spent several hours at the dog beach and that included meeting and greeting several dogs (we love dogs).

A couple of ladies came by and one of them asked me: “CB or Ham?”. It is nice when I don’t have to explain ham radio to a visitor. She seemed genuinely surprised though when I explained that I was using Morse Code to contact other hams all over North America. And her pet Whippet was very excited to meet a CW operator in person.

Band conditions had improved since the previous day and the contacts were much easier to obtain. I started out hunting other activators as usual and the contacts just kept adding to my log despite the K-index sitting at an uncomfortable high of 4. The activation wasn’t as fast as if I had called CQ, but time was not pressing so I earned a complete activation, with QSOs to spare, over a period of an hour and a half. Eventually, as the area grew busier, I decided to pack up and head back to the “tent”.

POTA activation at CA-0140 Arrowhead Provincial Park – October 2025

Smoke on the Wahta

The next day we had to head back home, but the route took us via another of my favorite parks – Torrance Barrens Nature Reserve (CA-1669). The “Barrens” is a couple of hours relaxed drive south of Algonquin and the trip took us through the Wahta Mohawk First Nation reserve where tax-free bargains can be found on gasoline and smoking products. My wife and I are not smokers but we are always amused by a sign along the road advertising “Smoke on the Wahta”. Readers who grew up in the same era that we did may recognize the reference to a popular song from the 1970s.

Activating The Barrens

The Barrens is located at the south end of Muskoka and is a popular haunt for astronomers. The topography is characterized by the exposed ancient rock at the southern end of the Canadian Shield.

Exposed 2 Billion years old rock covers much of Torrance Barrens Serene natural beauty elsewhere at Torrance Barrens. Antenna worked fine – despite my failure to deploy the tripod’s top section!

I set up my station on the bare rock near a small lake and once again started hunting other activators to test band conditions. After only four QSOs I switched to CQ mode. Things were going well and in just 27 minutes I completed 15 QSOs. Then suddenly, as I was finishing a QSO with KC5F in North Carolina, my radio shut down. I powered the radio back up again and managed to finish the contact before the radio shut down once again. I checked the voltage of my Bioenno Lithium Iron Phosphate battery and saw the reason why – the voltage was 11.5 volts. I hadn’t recharged it during the trip and it had given up on me. Lithium batteries maintain a fairly constant voltage until they are almost fully discharged. Neglecting to keep them well charged comes with surprises – like a forced QRT.

But that wasn’t the only surprise of the day. As I was packing up my station I noticed that I hadn’t fully erected the antenna. The top tube section of the tripod, which forms part of the radiating element, was not extended. Despite this error the antenna performed very well. I was pleasantly surprised and pleased with the results for the day.

POTA activation at CA-1669 Torrance Barrens Conservation Reserve – October 2025.
Good results despite improperly erected whip and a battery that ran out of charge!

A final word about the radials

I had originally intended to use the linked, tuned radials from my wire version of the POTA PERformer antenna, but there was a problem. Those two raised radials contain links for 17m and 15m. The link for 17m is at 13ft along the 17ft radial wires and the link for the 15m band is at 11ft. Now here’s the rub (as Shakespeare would have said), the radiating element is also 13ft long. Since there is a 4:1 impedance transformer in the feedline the impedance on 17m was out of the tuning range of my LDG Z-11 Pro antenna matching unit.

The solution was to use a set of four 13ft radials laid partly on the ground. Now the LDG Z-11 can easily find a match on all the bands from 20m to 10m. Is 4 radials enough? The feedpoint of the antenna is raised about 3ft/1m above ground so maybe less ground plane is required. Setting antenna physics aside, the prime rule for temporary field expedient antennas is to use the antenna you have and just get on the air.

Winter is fast approaching

Up here in the Great White North life contains 3 absolute certainties: death, taxes and snow! The time for relaxed operating in the sunshine beside a lake is nearly over; now it’s time to get back to planning antennas for operating while shivering in my truck!

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No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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Construction of the Simple Low Profile Multiband POTA Antenna

Following on from the previous post, there seems to be some interest in how the Simple, Low Profile, Multiband POTA antenna was actually built. Although the antenna is described as “simple”, that term relates more to how it is deployed and its appearance than its actual construction.

The construction does not involve any special tools or techniques, but it does involve some care to transform a photographer’s lighting tripod into a ham radio antenna. This is especially true since only the top two of the three vertical tube sections of the tripod are used as part of the antenna radiating element. The base tube section, to which the legs are attached, is only used as a support structure for the rest of the antenna. Thus the problem emerges of how to electrically isolate the top two tube sections from the bottom tube.

Where can you purchase such a tripod?

I was able to buy one from my local Habitat for Humanity charity store but a very similar product is available from Amazon. Simply search your local Amazon online store for “Amazon Basics Aluminum Light Photography Tripod Stand with Case”. It is a very inexpensive product – even here in Canada!

Where can you purchase the whip?

The whip can be purchased at hfportable.com (“Home of the Buddipole”). Search for the “Long Telescopic Whip”. I already owned one of these that I acquired several years ago and mine measures 9 feet 4 inches fully extended. The product on the Buddipole website describes it as being “nearly 10 feet long”. As an alternative you could use any 17ft telescoping whip extended to 9 feet. The tripod tubes form the other 4ft of the radiating element. Peter G3OJV advises against using a longer radiating element. Apparently 13 feet is the magic length for this antenna.

Adhesive copper tape

After completing the basic build I realized adding copper tape to the contact areas would be a good idea. There is a choice of copper tapes available from your friendly mom-and-pop Amazon store. I purchased 15mm tape which came on a 20m roll (20 meters, that’s interesting; I wonder what else I could use it for?)

Conductive grease

The tripod tubes nest inside one another allowing the tripod to be collapsed for transport and storage. This means contact will be made and broken at every deployment. Therefore I recommend conductive grease to lubricate, prevent oxidation and assist high conductivity where the tubes connect to each other.

Challenge #1: Joining the lower radiating tube to the bottom support tube

There are three tubes in the tripod. The top two tubes, along with the whip, form the radiating element. They must be electrically isolated from the bottom tube. Although the tubes are coated with a thin layer of black paint, continuous use may create scratches leading to unwanted conductivity. A short length of shrink tubing over the bottom of the second tube fixed that issue. Note in the picture the copper adhesive tape applied over a bare section of the tube (after paint was removed with a Dremel tool). This is where the feedpoint is connected.

Coax is attached by means of 3/8×24 CB mirror mount fixed onto the copper tape feedpoint area. This was described in the previous post. The mirror mount is fastened with two bolts with wing nuts so that it can be moved when the antenna is taken down.

Bottom end of center tube showing the insulating section of shrink wrap and the copper tape connection area for the feedpoint.

There is a possibility that a very small capacitive coupling between the overlapping sections of tube will occur although no adverse effects of any such coupling have been observed.

The lower tube section is electrically isolated from the legs by means of plastic fixtures, so there is no ground connection. The lower tube section is therefore just electrically floating.

If any RF is getting across the junction of the two lower tubes due to capacitive coupling it is likely to be so small as to be inconsequential.

Challenge #2: A good electrical connection between the upper tubes

Isolating the top two sections of tube from the base section was relatively straightforward. Now the problem of how to ensure a very good electrical connection between the top two sections had to be dealt with.

The tubes are concentric, but are a loose fit to enable the intended light fixtures on top of the tripod to be raised and lowered easily. But the loose fit became a problem when the need arose to electrically connect two sections. Not just connect, but ensure a very low resistance connection was made. It would be highly undesirable if the connection were intermittent or had a high resistance. “High resistance” in this context could be as little as an ohm or two since the RF current this close to the feedpoint is quite high.

So here is how the problem was tackled. As can be seen in the accompanying image, two broad slits were sawn in the top end of the center tube section. The plastic clamps that secure tube sections together compress these slits.

Center tube (left) with slits. Top tube (right) with copper tape bulge

Now it was only necessary to use layers of copper tape to create a slight bulge at the bottom end of the top section of tube, where it mates with the center section. When the antenna is erected the copper tape bulge in the top tube engages with the compressed slits in the center tube and form a secure electrical connection.

Challenge 3: Connecting the whip

The whip is attached to the top end of the top tube of the tripod. It would have been very simple to use a CB mirror mount, but I wanted the entire assembly to appear as one continuous length of tube.

To achieve this it was necessary to fix a 3/8×24 coupling nut inside the top end of the top tripod tube. I guess I got lucky here because one of the coupling nuts in my junque drawer turned out to be a nice snug fit inside the tube. But a snug fit isn’t good enough for an electrical connection so a tiny hole was drilled through the tube and coupling nut. A small nut and bolt was then added to ensure a tight fitting. For good measure, the outside surface of the coupling nut was coated with conductive grease to reduce the electrical resistance and prevent corrosion during use outdoors in the Big Blue Sky Shack.

I hope this post will encourage others to build their own version. As was shown in the last post, the antenna does a creditable job and is so easy to transport to a park (or mountaintop) and super fast to set up. I am happy to respond to any further inquiries; just leave a comment below or send me an email (qrz.com has my correct email address).

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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#1 #2 #AmateurRadio #Antennas #OutdoorOps #Portable #POTA

A Simple, Low Profile, Multiband Antenna for POTA

Sometimes it is necessary to set up for a POTA activation in an area where other park users like to go. In this situation we can either entertain distracting inquiries from people passing by who may just be curious about our activity, or blend into the environment and not be noticed. I prefer the latter. So when I learned of a field antenna that could be mistaken for an innocent fishing pole I was immediately interested. But, of course, this is Ham Radio Outside the Box so I just had to re-invent the idea to create my own variant. I was influenced by three ideas I had read, or seen, online.

Influencer #1

The spark that ignited the creation of this new antenna came from Peter Waters G3OJV who recently published a YouTube video with the title: “Invisible HF Vertical Ham Radio Antenna”. Peter used a 13ft vertical wire worked against a set of ground radials to cover the 20m, 17m, 15m, 12m and 10m bands. A 13ft vertical antenna is, perhaps coincidentally, comparable to a half-size Rybakov. A full-size Rybakov comprises a vertical wire 24-29ft long that can be tuned to all the bands from 40m and up. Just like the Rybakov, Peter’s antenna employs a 4:1 impedance transformer and requires a tuner.

Influencer #2

I liked Peter’s idea very much, but I immediately considered that a ground-mounted vertical antenna requires an extensive system of radials to be efficient. Laying out lots of radials is not very convenient for temporary, portable antennas. I still recall the “dancing lady” who stopped by one of my activations. When she was advised to be careful of the wires on the ground, she performed an entertaining little dance routine to avoid stepping on them. Greg, KJ6ER popularized the idea of using a raised vertical to reduce the number of radials to just two. Greg’s now famous POTA PERformer antenna uses this technique and it works very well.

Influencer #3

My third influencer was actually two hams. Jim Heath W6LG posted a video about using a photographer’s lighting tripod to build a portable antenna. Jim’s idea was expanded upon by Frank K4FMH with his “Eiffeltenna”. Frank and Jim both proposed using a telescoping whip mounted on the steel tubing of the tripod to create the radiating vertical element of the antenna. But both had the same idea of working the radiating element against a ground plane of radial wires or Faraday cloth.

Could I combine these three ideas to create a shortened portable antenna with a raised feedpoint and just two raised radial wires that could be used on multiple bands? Of course, the answer is most definitely yes. I built the antenna, took it out to the field to test it and was pleasantly surprised by how well it worked.

Antenna feedpoint at top of bottom tripod tube section. NB: the insulating washer had to be inserted so that the coax braid is isolated from the mirror mount – the opposite of its usual orientation. Whip mount on top tripod tube section

The key component was a lighting tripod purchased at a charity store for less than the cost of a Happy Meal at the Golden Arches. The whip is from Buddipole and extends to 112 inches (2.85 meters). The tripod has two extending steel tubes mounted in a lower fixed section. The challenge was to create a feedpoint at the top of the fixed section, about 3ft (1m) above ground, while ensuring isolation from the bottom tripod tube section and reliable connectivity between the top two sections when fully extended. The total length of the top two tube sections plus the whip totaled 13ft – perfect!

In order to mount the whip to the top tripod tube section, a coupling nut was slipped into the top tube and secured by drilling a hole through the tube and coupling nut so that a small nut and bolt could be inserted. The coupling nut is a very snug fit already so there is a good electrical connection. The Buddipole whip and top tripod tube are just about the same diameter and color making the appearance of a continuous length to enhance the “fishing pole” illusion.

The whole antenna (less radials) packed and ready to go

There was also a key design requirement that the tripod had to be collapsible for carrying to an operating site. This complicated the design, but for every problem there is a solution. I used a Dremel tool to remove the paint where an electrical connection was required. That created a bare steel-to-steel connection which may corrode over time. I may further improve the connectivity by applying copper tape to the points where the tubes meet.

Antenna base showing the radial connections and Guanella 4:1 unun

I took the antenna out to the field to see whether it could perform well enough to complete a POTA activation. I chose nearby CA-0281 – MacGregor Point Provincial Park for the trial. MacGregor Point lies on the Ontario shore of Lake Huron about a hundred miles (160km) across the lake from the State of Michigan. The Great Lakes are freshwater bodies that do not enhance propagation in the way that saltwater does, but at least there were no topographical features to impede my signal to the west and southwest.

Propagation conditions were not so good with a lot of QSB so I didn’t expect a great result. My radio was my trail-hardened Yaesu FT-891 at 30 watts CW.

Before calling CQ I decided to try hunting some stations to see where my signal could reach. This was so successful that I was able to secure a “basic 10” QSO’s by hunting alone. The results were impressive enough to give the antenna a strong thumbs up.

Radials oriented southwest. 20m band, 30W CW signal reached Utah and New Mexico
despite poor propagation conditions.

Finally, did the “fishing pole” disguise work? The park was quiet, but two park wardens stopped nearby to empty a bear-proof trash bin (MacGregor Point has just one resident black bear that I have only seen once). The wardens did not show any interest in my activity, neither did several other passers-by. My cunning cloaking device apparently worked fine business.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#1 #2 #3 #AmateurRadio #Antennas #CW #OutdoorOps #Portable #POTA

What happens when you press the magic TUNE button?

What happens when you press the magic TUNE button on your radio, or external automatic tuner? You will likely hear the rapid clicking sound of relays trying different combinations of capacitors and inductors as it looks for the lowest SWR to present to the radio.

But, a “tuner” does NOT actually tune your antenna. It simply provides an impedance match between your antenna system and your transceiver. It used to be more accurately called a “transmatch” but that term is seldom used these days.

The transceiver may “see” a perfect match coming from the “tuner”, but that low SWR exists only between the “tuner” and the radio. The SWR between the antenna system and the “tuner” might, in fact, be as high as 10:1! Like many other tuners, my LDG Z-11 Pro can resolve impedance mismatches up to 10:1.

Is that bad? And what happens to the signal after it passes through the “tuner”?

Greater minds than mine have discussed those questions at great length. Here is my understanding of what happens. Let’s say the antenna is an electrically short, non-resonant whip. It has a high capacitive reactance and will present a high SWR if it were to be directly connected to a transceiver. Instead, the antenna is connected to a “tuner” which transforms the impedance and provides a match close to the 50+j0 ohms preferred by the transceiver.

** But the SWR at the ANTENNA remains unchanged! **

Will the antenna still radiate a signal?

As is often said in antenna related forums, “RF gotta go somewhere”. However, because the antenna has a high SWR, only part of the signal is radiated and the rest is reflected back down the coax toward the shack. It is often thought that the reflected signal is converted into heat in the tuner (or transceiver). While that might be expected according to the Laws of Thermodynamics, it is only partially true. Actually most of the signal is re-reflected back toward the antenna where more signal is radiated with the remainder reflected, once again, back to its source. These back and forth reflections continue until there is no signal left to be radiated.

So all the signal eventually gets radiated then?

Once again, the Laws of Thermodynamics apply. Let’s assume the antenna is connected to the shack via a length of coax, and the tuner is in the shack. It could be an internal antenna tuner built into the transceiver, or an external tuner. As the signal passes along the coax toward the antenna it is attenuated due to the ohmic losses in the cable. At each reflection a little more of the signal is converted into heat in the coax. So, no, all the signal is not eventually radiated.

The transceiver reports a low SWR, but that only extends as far as the “tuner”. Between the tuner and the antenna signal losses are incurred due to the impedance mismatch. The amount of loss depends on the degree of impedance mismatch in the antenna system.

So now what? Non-resonant antennas are bad?

No, non-resonant antennas are not bad at all. If the big issue is lossy coax, but we use a very short coax – or no coax at all – the loss may be insignificant. In a field portable situation it is often possible to directly connect an antenna to the “tuner” or transceiver, eliminating the coax completely. If the antenna is non-resonant and a long transmission line is required, the coax may be replaced with ladder line, window line or open-wire line which has very low loss.

Another alternative is to use a remote antenna tuner. The signal will still be attenuated as it travels along the coax from the transceiver out toward the antenna, but the remote tuner will reduce the number of reflections necessary to radiate as much signal as possible.

Coax affects SWR

It is important to note that long lengths of coax affect the SWR seen by the radio. Some signal is lost in the coax, and that is also true for common mode current reflected back from the antenna. This means the SWR seen by the radio may appear to be better than it really is at the antenna.

A non-resonant high SWR antenna used with a tuner incurs insertion loss in the tuner and resistive loss from multiple reflections back and forth along the coax. These losses are not necessarily a concern and should be weighed against the convenience of being able to use the tuner to match multiple bands. A resonant antenna may incur less loss due to no tuner being required and low SWR at the antenna but it is a single band antenna.

There are situations in which only an inefficient, non-resonant antenna is available. In that case the inefficiency may be combatted by increasing the power transmitted. Paraphrasing the FCC’s Part 97.313 rules: An amateur station should use as much transmitter power as is necessary to carry out the desired communications. Clearly, if you are a die-hard QRPer and you only have an inefficient, non-resonant antenna to work with … well that’s the fun of QRP isn’t it?

This is a very complex topic and I can’t pretend to be an expert, so this post is intended to present the way I understand it. You may disagree, or have other explanations or opinions. If so, please share what you know in the comments.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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#AmateurRadio #Antennas #OutdoorOps

Two Resonant Simple Wire Antennas for POTA

One antenna that has garnered a significant following among POTA operators is the POTA PERformer designed by Greg Mihran KJ6ER. In essence it is a raised quarter wavelength vertical with 2 above ground radials. A simple idea that Greg has engineered into a rapid deployment, highly efficient, multiband, portable antenna. Greg has backed up his design with a detailed analysis supporting the claimed high performance characteristics. Many operators, including myself, have built and used the POTA PERformer and can verify that it is indeed a very good antenna.

NB: I have already covered the POTA PERformer in a recent post and concluded that just a single raised radial was sufficient. However, after reading Greg KJ6ER’s analysis in more detail I am now convinced that using 2 radials raises the antenna’s efficiency.

There are three innovative antenna designs in KJ6ER’s kit bag. The other two are both half-wave designs. The POTA Challenger is an off-center fed half-wave that supports 20m and up; the Dominator is an end-fed half-wave that supports 17m and up. I have not tried to build a Dominator (yet) since most of my own POTA operations are on 20m, but the Challenger caught my attention so much that I had to build my own version.

When I first looked at the design I was completely bewildered. It comprises a 25ft telescopic vertical whip with a wire counterpoise, part of which lies directly on the ground. Does that look like a typical half-wave antenna, I thought to myself? I had never seen anything like it before so my skepticism was aroused. After exchanging a couple of emails with Greg I was encouraged to go right ahead and build one in the hope that actually using it to fire RF up to the edge of space and back would bring about a better understanding of this strange new electromagnetic beast.

Well, I did build my own version of the Challenger, massaged the design a few times and came up an antenna that got me some very encouraging signal reports from the land of far, far away. Of course, this blog is called “Ham Radio Outside the Box” so, just like Frank Sinatra, I “did it my way”. To learn more please read on.

The Ham Radio Outside the Box version of KJ6ER’s Challenger

First, I would like to wholeheartedly endorse the work of Greg Mihran, KJ6ER. One might have expected him to be selling commercial versions of his antennas, but instead, he has published detailed build instructions and readily responds to emails from fellow hams. That is the true spirit of our hobby; hams helping hams.

Ham Radio Outside the Box interpretation
of KJ6ER’s Challenger antenna

It wouldn’t be fair to even refer to my own version as a “Challenger”. Instead I will just say that it is inspired by KJ6ER’s Challenger. It follows the same ideas but implemented in a different way. I don’t own a 25ft telescoping whip and didn’t really want to have to buy one, so I decided to incorporate a wire radiating element, supported by my 7-meter Spiderbeam telescoping fiberglass pole.

Then, whereas the Challenger is a multiband (one band at a time) antenna supporting every HF band from 20m and up, I looked at my own POTA activations and realized that I rarely stray from the 20m band. Maybe a monoband antenna is all I need. That keeps the design sweet and simple. I like sweet and simple when I am out in the Big Blue Sky Shack. I did wake up one morning with an urgent need to rush down to my basement shack and sketch out an idea for a multiband version that still uses wire elements. More information on that idea later in this post.

Spiderbeam with wire radiator loosely coiled around it.

I took the dimensions of the radiating element and counterpoise wires directly from KJ6ER’s document. Of course, a wire – in this case teflon covered 20awg multi strand wire from BNTECHGO almost certainly has a slightly different velocity factor from a tapered stainless steel telescoping whip as I discovered when the antenna was erected. It was necessary to shorten both wires a little to bring the antenna into resonance in the CW portion of the band.

Another gotcha is the height of the feedpoint. It has a quite dramatic effect on the tuning. The first iteration of the Ham Radio Outside the Box version used a taller pole. The wires were trimmed to obtain a 1.07 SWR, but when I substituted the shorter pole and re-erected the antenna with the feedpoint only 12 inches above the ground, the SWR shot up into the stratosphere.

NB: KJ6ER built a “backpack” version of his Challenger in which the feedpoint is lowered to 12-inches above ground. I found this height allows me to use my 7m Spiderbeam pole and also makes it easier to orient the counterpoise so that it makes good contact with the ground.

After further adjustments of the wire length a low SWR was restored. I ended up with 22ft/6.7m for the radiating element length and 5.5ft/1.7m for the counterpoise. If you were to reproduce this design your own dimensions might be different; an antenna analyzer is a very useful tool to have.

A multiband version?

The original Challenger uses a telescopic whip so switching bands is quick and easy by simply adjusting the length of the whip. The counterpoise length must also be adjusted, but this is accomplished by means of a linked wire.

I have not built a multiband version of the Ham Radio Outside the Box interpretation of the Challenger but I have entertained two ideas for how to accomplish this goal. First, simply using links in the radiating element wire might be the simplest and easiest way to do it. There is a second possible way and that is to employ parallel radiating element wires in the manner employed by the DX Commander vertical antenna. If you are not familiar with the DX Commander, do a web search on the name and you will see what I mean.

I am so impressed with the portability, efficiency and small footprint of this antenna that it is going to replace some of the other SWAs (Simple Wire Antennas) in my field operations kit bag.

Same Pole, Different Wire

Ham Radio Outside the Box POTA PERformer wire variant supported on a Spiderbeam pole

The title of this post is “Two Resonant Simple Wire Antennas for POTA” so what is the second one? I had built my first version of the POTA PERformer using an MFJ-1979 telescoping 17ft/5m whip mounted on a tripod. If I wanted to do a field outing carrying both this and my own Challenger variant I would have to carry my Spiderbeam pole and the tripod. Since I often stray far from my truck when operating out in the Big Blue Sky Shack I need to economize on the amount of gear I have to carry. Maybe I could build a wire version of the POTA PERformer that could be supported by the 7m Spiderbeam pole.

I realized I already had such a beast – a super light QRP version I built many years ago. Now I needed to copy that idea and build it for QRP or QROp (20-30 watts). So, the new SWA Ham Radio Outside the Box version of the POTA PERformer was born, and again it is a monoband 20m antenna.

As we can see from these images, the simple wire version of the POTA PERformer adapts very well to being supported by the compact, lightweight Spiderbeam pole.

The vertical radiating wire is attached to a standard 3/8x24tpi to SO-239 adapter. The two radial wires connect to the adapter via a 2mm banana connector so they can be separated for storage. The female 2mm connector is crimped and soldered to a 3/8 inch ring connector.

The image also shows the ham-brewed-by-me common mode current choke made from an FT240-43 ferrite toroid core wound with several turns of RG-58 and tested with a nanoVNA to ensure it is doing its job.

Now I only have to carry the Spiderbeam pole and two small freezer bags containing the wire elements for both the PERformer and Challenger variants and I have choices when I get to my operating site. Which to choose? I highly recommend reading KJ6ER’s documents, linked below, especially Greg’s “Antenna Primer”. Greg explains everything you need to know so much better than I ever could.

Cloud Drive File Links (KJ6ER):

• YouTube™ Interview with Michael Martens, KB9VBR –
  youtube.com/watch?v=cClmWBYzNaE
• ARRL™ QST 2024 Antenna Design Competition –
  bit.ly/AntennaDesignCompetition
• ARRL™ QST September 2025 PERformer Article (First Page) –
  bit.ly/QSTSeptember2025FirstPage
• KJ6ER Antennas Primer –
  bit.ly/KJ6ERAntennasPrimer
• PERformer 40M-6M Quarterwave Vertical –
  bit.ly/KJ6ERPERformer
• PERformer 40M-6M Quarterwave (Assembled, Etsy) –
  bit.ly/KJ6ERPERformerKit
• Challenger 20M-6M OCF Halfwave Vertical –
  bit.ly/KJ6ERChallenger
• Dominator 17M-10M EF Halfwave Vertical –
  bit.ly/KJ6ERDominator
• Dominator 17M-10M EF Halfwave 2-Element Vertical Beam –
  bit.ly/KJ6ERDominatorBeam

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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#AmateurRadio #Antennas #CW #OutdoorOps #POTA

How many truly field expedient ham radios are available? Maybe only 2!

Only two? If you were to ask the military you might get a different answer. Indeed many hams actually use ex-military portable radios, such as the PRC series. Those radios are in a class of their own, but they are often heavy, designed to be carried into the field by fit, strong, young soldiers. But what are the choices for those of us who still like to backpack our ham gear into the back country, despite being well past our “best before” date?

I anticipate many readers might think differently, but this post is about my own criteria for assessing the field worthiness of a portable amateur radio transceiver. I am sure you are proud of your favorite radio. It has probably served you well over many xOTA activations. If, after reading this post, you feel your rig is up to the challenge then please nominate it for inclusion in the exclusive list of truly field expedient amateur radio transceivers by leaving a comment.

What makes a radio field expedient?

There are lots of radios – especially QRP rigs – that are lightweight and easy to carry in a small pouch. Does that make them field expedient? Perhaps, but are they hardened against environmental factors that may be encountered in the field? Lightweight and easy to carry in a small pouch are useful features but not always enough to guarantee success in the field. In this post I will outline my personal experiences which may be very different to your own. I don’t treat my field radio equipment with kid gloves. It gets bounced along rocky trails, subjected to extremes of temperature, moisture, bugs, sand and dust. A really good field radio will resist adverse environmental conditions. If it can’t handle that task out-of-the-box it must be covered in layers of protection to compensate.

Humps excluding Marilyns?

The Parks on the Air (POTA) program has brought about a huge increase in the number of hams taking their equipment out into the field to operate. POTA joins a broad array of similar activities like Summits on the Air (SOTA), World Wide Flora and Fauna (WWFF) and – mostly in Europe – Beaches on the Air (BOTA), Bunkers on the Air (also BOTA) and the very strangely named HuMPs Excluding Marilyns Awards (HEMA) program. Although this list is not exhaustive – there are other outdoor programs not listed – it illustrates the breadth and expanse of programs enticing hams to step outside their comfy shacks to assault the ionosphere.

Hit the road Jack

Just as there are many outdoor ham radio programs available to challenge us, there are also many different ways to tackle those challenges. My greatest admiration is reserved for those who climb mountains carrying their radio gear in a backpack, climbing steeply for many kilometers, ascending lofty snow-capped peaks before reaching the activation zone. In contrast, there are many who prefer to operate from inside a vehicle in a parking lot. There are certain advantages to operating this way. Your car or truck is your own private space where your park activation is less likely to be interrupted by other curious park users. It also provides shelter during inclement weather. I operate this way myself – but only during the winter when snow blizzards, ice-storms and temperatures cold enough to freeze your breath make the surface of the planet inhospitable.

During the warmer months my own preference is to enjoy the great outdoors in what I like to call the “Big Blue Sky Shack”. It is in this environment that I have encountered the conditions that truly sort out the rugged radios from the rest. My home turf is the small city of Owen Sound at the foot of the Bruce Peninsula in southern Ontario, Canada. The Bruce Peninsula extends 100km from my home up into Lake Huron along the Niagara Escarpment. Along the western side of the peninsula Lake Huron is bounded by sandy low lying land with many islands. The eastern side of the peninsula is dramatically different with tall cliffs plunging down into Georgian Bay – a 15,000 square kilometer extension of Lake Huron. The terrain on the peninsula varies between soft sand and hard ancient bedrock.

Lake Huron shore Ontario Canada

Winds crossing Lake Huron from the state of Michigan on the other side, 160km (100 miles) away, pick up a lot of moisture from the lake which is deposited onto the narrow peninsula in the form of rain or snow. Waves hitting the shoreline can be quite high – maybe not high enough for surfing, but enough to create spray along beaches.

Colpoys Lookout POTA: CA-6007 looking out over Georgian Bay
at the entrance to Colpoys Bay

In winter we usually experience continuous snow coverage between December and April, and in summer temperatures can often reach into the 30s Celsius – as much as 50 degrees higher than in the depths of winter.

February 2025 Owen Sound Ontario Canada

Honestly, just what gets me out of my nice air-conditioned in summer, heated in winter home-based shack? A love of the great outdoors! To enjoy the fresh air, to smell the scent of Canada’s 300 billion trees; maple, birch, spruce and pines. Unfortunately my radios have an inconveniently different point of view. They like a nice stable temperature, dry atmosphere and are highly averse to the ingress of sand and small flying, biting critters like mosquitoes and the dreaded no-see-ums. I once disabled my CW paddles by liberally spraying a cloud of bug repellent in response to an all out attack by these dreaded winged pestilences. If only radio equipment manufacturers would take these things into consideration then both I and my radios could get equal enjoyment out in the Big Blue Sky Shack. Really, why on Earth would CW key manufacturers not routinely protect their products from being sprayed with oily bug repellent? I jest of course.

Yaesu FT-817 non-ND. A classic radio from 2001.

Operating outdoors was an early passion of mine, before many of the programs we now enjoy even existed. I had purchased Yaesu’s FT-817 as soon as it was released. This was the early FT-817 before the revised FT-817ND was released. I still own that radio and have often thought about selling it, but whenever I lift it off the shelf and look into that tiny pug-like face I realize how much I would miss it. The FT-817 was built for the outdoors. It’s case just exudes ruggedness even though it still has shortcomings that limit its usefulness as a portable, field expedient radio. For example, it has provision for internal batteries – a set of AA NiCads, but its current draw is so high that the battery life is way too short for serious portable operations.

Yaesu FT-897 circa 2004 and still in service at my home QTH

I then graduated to another Yaesu rig that also exudes ruggedness. I worked for a while in a ham radio store and every day I was exposed to many different radios that I could operate whenever I wished. But one radio caught my eye and each and every day the desire to own it grew stronger. It was the Yaesu FT-897, a 100 watt radio with all the band coverage of the FT-817 plus Digital Signal Processing (DSP). The case has that same bullet proof aura as the FT-817. It can support two internal battery packs so that when one is fully discharged a flick of a switch changes to the other pack. Both of these Yaesu radios have a rubber shrouded microphone plug that seals out unwanted stuff like sand, moisture, bugs – and bug spray! The FT-897 also sports a rugged 1/4 inch headphone jack which I really like.

What’s at the back Jack?

But … and it’s a big but … turn both of these radios around to see the rear panel and you will find 3.5mm (1/8 inch) jacks and mini-DIN connectors. What’s so wrong with that? Maybe nothing if your operating style involves working from your vehicle. But take that radio onto a beach (as I often do) and witness the magnetic attraction these miniature connectors have for sand particles. I have a strong dislike for 3.5mm plugs and jacks – especially the jacks. They are usually enclosed within a tiny sealed plastic box. If even a couple of grains of sand get inside contact integrity can be compromised. And besides, are these things designed for hundreds or thousands of insertions? I think not; they are designed to be cheap to produce. Cheap, fragile connectors may be appropriate on a mobile phone that is likely to be replaced every couple of years, but not for a field expedient portable radio. I have owned a couple of handheld radios from a certain manufacturer based in Japan (not Yaesu) that had particularly fragile 3.5mm jacks that failed very quickly. It was those radios that prompted my crusade against these pernicious connectors.

Ok, so we have radios with fragile connectors; what can we do about it?

I came up with one easy solution that doesn’t cost a penny. Simply leave these reliability-challenged connectors connected. Don’t unplug those headphones, microphones, CW keys and whatever other peripheral paraphernalia uses them. To achieve that you have to create an enclosure that secures all your external devices so that you don’t need to disconnect and pack them away separately each time you operate.

I built two of my field radios into steel ammo cases so that everything can be left connected between operating sessions. My little QRP Labs QMX radio is just bristling with connectors that are vulnerable to hostile environments. Inside its cozy 30 caliber ammo case it can remain totally oblivious to the hazards surrounding it out in the field. I pop off the heavy-duty steel lid that protects it in transit, connect an antenna, switch on the battery, lift out the connected earbuds and I am QRV.

My other main field radio is a QRP/QRO-optional Yaesu FT-891 built into a 50-cal ammo case. The FT-891 has several vulnerabilities and protecting it has become an ongoing project. The radio is a little too big to fit entirely within its (literally) bullet-proof steel box with the ammo case lid attached. The detachable head is mounted to an aluminum front panel and protected by thick steel U-bolts. All the vulnerable connectors remain safely connected inside the steel case. The only external connections required are for the battery, headphone and CW key.

5-pin DIN connector and tough, thick coily cord for connecting CW paddles. The colored buttons are for CW memory recall (homebrew FH-2 remote keypad).

The battery is connected by Powerpole connectors; the headphone is a Heil Traveler with a beefy inline connector and the key connects via a jack on the front panel. The original 3.5mm jack on the aluminum front panel has been replaced; first with a cheap 1/4 inch jack which proved equally unreliable, then with a 5-pin DIN connector. I had considered buying a very rugged 3-pin XLR plug and jack but I already had the DIN jack as well as an old CB mic cord with a 5-pin DIN plug. We shall see whether they can withstand the rigors of the environment on the beaches and cliffs of the Bruce Peninsula.

Now, going back to the title of this post: “How many truly field expedient ham radios are available? Maybe only 2!”. Well, which two radios did I have in mind when I wrote that? Imagine designing and building a commercial radio with a strong, rugged, water resistant case and military grade connectors. You could take such a radio out into almost any environment and be confident that it will remain reliable and get the job done. Does such a radio exist? You have to look beyond the islands of Japan; beyond China. I have highlighted the dangers of sand getting into vulnerable connectors, so would it surprise you if a company in a very sandy country came up with such a radio? I am not sure which country actually manufactures these radios but one of its biggest distributors is in Dubai. If you would like to know more visit Lab599.com. They produce two radios that are truly field expedient and environmentally protected. Only one of the radios is currently featured on the website but a newer handheld HF transceiver has also been released.

Why I am taking up gardening

I want to grow roses; lots and lots of red roses. I can’t afford to go out and buy enough red roses to convince senior management (she prefers to be called “She-Who-Must-Be-Obeyed”) to let me buy a Lab599 TX-500 🙂

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #OutdoorOps #Portable #POTA #QMX

Rapid Deployment Field Expedient Random Wire Antenna Ideas

The image shows amateur radio station VA3KOT/P inside its stealth enclosure – an old airline pilot briefcase made from stout, strong leather.

This is an almost complete station:

• Yaesu FT-891 QRP/QRO-optional in its field hardened steel 50-cal ammo box enclosure
• Bioenno 12Ah LiFePO4 battery
• 9.5ft tactical collapsible whip
• Adjustable loading coil for the whip
• PAC-12 capacitance hat for the whip
• LDG Z-11 Pro auto tuner (I like to think of it as a super fast L-match with a good memory)
• CWMorse aluminum paddles
• Heil Traveler headset (the microphone is feeling neglected due to not having been used for a very long time)
• Ham-made (by me) Guanella 4:1 balun
• Selection of coax cables
• Set of ground radials
• Random wire antennas (we’ll talk about those shortly)
• Operating table (yes, operating table too; see image below)

What’s missing? Just a chair. I have a selection of lightweight folding and collapsible camping chairs to support my delicate derriere.

Oh yes, the table; these pilot cases (NB: I am not a pilot) are so strong that, if stood on end, they make an excellent support for the radio.

When everything is packed inside the pilot’s case then it is a little on the heavy side (not to be confused with the Heaviside which is a layer of the ionosphere). The weight is manageable if it is only being carried a short distance, but I have a small folding cart for transporting it further away from my vehicle.

So what about a rapid deployment, field expedient antenna?

Rule 1: It has to fit inside the briefcase. Rule 2: If an antenna doesn’t fit inside the briefcase refer to rule 1.

I have 2 choices that meet Rule 1; a “tactical” (meaning it is painted green and looks like it might not be out of place on a Humvee) collapsible whip. It can be mounted directly on a 3/8x24tpi bracket fixed to the rear of the ammo box. It is usually deployed with a loading coil and capacitance “top” hat.

Rear connections. Note the bracket for mounting the tactical whip on the left. The antenna wire and radials are plugged into the magnetically attached 4:1 balun. The CW paddles are secured to a steel bracket which is also magnetically attached to the ammo box – a steel box is very handy for attaching accessories with small rare earth magnets.

Second choice is a simple wire antenna. I am currently in favor of random wires due to their inherent multi-band flexibility. Although I have never been a fan of auto tuners, for several reasons, their speed in finding and memorizing a match for multiple bands is very valuable for the kind of hit-and-run style activations that I enjoy. The LDG Z-11 Pro is an L-match which means it is perhaps more efficient than a typical C-L-C type of manual tuner.

Don’t risk disappointment

I have read a lot of blogs and watched a lot of videos in which an operator buys a commercial wire antenna and deploys it in the field without investigating whether the antenna is actually going to work in the manner they expect. We don’t all have the time or inclination to model an antenna to find out how best to use it, but it can lead to disappointment if we don’t do the homework first.

‘Tis a gift to be simple, ’tis a gift to be free

It is very simple to make a “Simple Wire Antenna” (SWA) and it can even be free if you can scrounge some leftover wire. Climb an old telephone pole and pull down disused POTS (Plain Old Telephone Service) wire if your neighborhood has switched to fiber lines. Okay, I’m kidding, don’t do that; some poles also carry high voltage electric cables.

I have had great success recently with a sloper wire 27 feet (8.23m) long supported from a tree, or my Spiderbeam 23ft (7m) pole, and worked against four 13ft (4m) ground radials. The LDG tuner easily finds a good match of 1.5:1 or less on my main bands of interest: 20m, 30m and 40m. Out in the field there is no lossy coax transmission line involved – apart from very short sections to plumb in the Guanella 4:1 balun and tuner. This wire is a little short for 40m but presents no problem for the tuner. I have received some very good signal reports using this wire.

Then I wondered, if the wire was longer, could the antenna work even better? EZNEC helped me decide. I modeled three random wires: 27ft (8.23m), 41ft (12.5m) and 84 ft (25.6m). To make it a fair comparison, the same band (20m) was compared and the three wires were modeled in exactly the same sloper configuration. The results were very revealing.

Model 1: 27ft random wire sloper

The elevation plot shows a good directional signal with a small amount of gain at an elevation of 35 degrees.

The azimuth plot shows a wide angle of radiation with ~5dB of Front-to-Back signal strength.

The 27ft sloper has been a solid, reliable performer with strong signal reports being typical.

.

Model 2: 41ft random wire sloper

It would be tempting to throw a 41ft wire up into a tree and run it as a sloper down to the ground, but the results might be very disappointing.

Although the gain is increased, the elevation angle of maximum radiation has also increased to 75 degrees and the directionality has all but disappeared.

This would make the antenna a cloud warmer and much of the signal would disappear into space. Your CQs might perhaps be answered by extra-galactic radio operators a few thousand years in the future. How patient are you?

Model 3: 84 ft random wire sloper

If you have a much better throwing technique than mine, you might be able to get your throw weight up 62 feet in a tree to pull up an 84ft random wire sloper. But, if you look at these charts you may not want to do it.

Your signal now goes straight up into outer space. In most parts of the world 20m is not an NVIS band so almost your entire signal is wasted. As an aside, I recently experimented with a “V” wire antenna with 29ft arms supported at the ends by trees. I QSOd on it but I received a very disappointing 449 RST report for my 30 watts of signal. When I modeled the antenna afterwards I realized why – the radiation pattern was very similar to this 84ft sloper!

Why does this happen?

What causes the increase in radiation elevation? A big clue emerges when we examine the current distribution on the antenna wire. Remember, high current points along the wire are responsible for the majority of the RF energy radiated.

Current distribution in a 27ft wire Current distribution in a 41ft wire Current distribution in an 84ft wire

As we can see from the three charts, a 27ft wire has just a single high current point.

Along a 41ft wire a second high current point begins to emerge and the interactions raise the radiation angle.

When we look at the 84ft wire we can see that there are two full current maxima and the emergence of a third. Once again, these interact to raise the radiation angle.

Was this a fair comparison?

I think it was fair. None of the three wires is overly difficult to erect as a sloper. Some hams get a lot satisfaction from shooting wires high into trees on the assumption that higher and longer is better. In fact, on the lower bands an 84ft sloper might perform quite well. With the popularity of POTA, and the solar cycle at its peak, a lot of activity is to be found on 20m which is why I chose this band for the comparison.

What if …

Maybe, if we orient an 84ft wire differently, we can get it to be the outstanding performer we would expect on the higher bands. I have QSOd on several occasions with an end-fed 84ft wire hung about 5ft above ground supported by a long hedge, or low branches of small trees. Even at QRP power levels I got good results despite the antenna having no gain.

So let’s follow the old adage of getting as much wire as possible, up as high as possible, but with the proviso that it must abide by the limitations of being rapidly deployable and field expedient. How about an Inverted-L?

In fact, to make it RDFE (Rapidly Deployable, Field Expedient) I am going to call it a Lazy Inverted-L. The feed end of the wire connects to the rig (sitting on the pilot’s briefcase) at a height of 2 feet. The wire then goes to the top of my Spiderbeam 23ft (7m) pole about 3 feet (1m) away with the remainder sloping down to the far end supported 3ft (1m) high on a trekking pole. It might not be the best setup but remember it must be “RDFE”.

Model 4: 84ft Inverted-L antenna

The results are quite encouraging. First, the antenna has a decent amount of gain for a SWA. Second, the elevation angle has two useful components: a forward lobe at 35 degrees elevation with a -3dB point down to 15 degrees for a chance of getting some DX action.

There are two more lobes behind with a higher radiation angle that could yield short range contacts.

Where’s the gotcha?

The azimuth for maximum radiation changes from band to band. That would mean re-orienting the wire for band changes. Fortunately the RDFE, Lazy Inverted-L orientation makes that a fairly easy task.

Imperial or Metric?

I have tried to use both Imperial and Metric dimensions in this post. I was brought up using Imperial measurements, earned my Physics degree which was taught entirely in metric units and now tend to mix them up. Canada is officially metric but supermarkets still mark the prices of meat and produce in dollars per pound. Why? Because it sounds cheaper I guess! Okay fellow hams, what’s your favorite HF band? Mine is 65.6168ft. Yes, that’s 20m.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#1 #AmateurRadio #Antennas #CW #OutdoorOps #Portable #POTA

Does an antenna top hat really work?

Antenna “Top Hat” aka Capacitance Hat

There are several ways to shorten a vertical whip antenna, for example, a loading coil, linear loading (folding back all or part of the radiating element) and one that has intrigued me for quite a while – a capacitance hat, also known as a top hat.

A top hat (shown in this image) is a series of conductors erected horizontally, and connected to, the radiating element of a vertical whip antenna.

Top hats provide capacitance with respect to ground and are used for two main reasons:

1. To shorten the required physical length of a vertical antenna
2. To raise the maximum current point higher up the antenna

One significant disadvantage of using a top hat is that it adds weight to the top of the antenna. That may not be a problem for a fixed installation where a thick, rigid vertical element can be used. But for field expedient portable operations using, for example, a telescoping whip it can be a very bad idea indeed. Let me explain why.

I recently purchased a top hat designed for a PAC-12 antenna from AliExpress. I attached it to the top of my 18.5ft whip obtained from the same source. The top of the whip waved around in the air and clearly was not going to be a practical arrangement. These Chinese whips are made much lighter than similar products from other sources (e.g. MFJ-1979 which I also own) and consequently are not as strong. To be fair, the manufacturer would probably advise against abusing their lightweight whips in the manner of my little experiment. I guess I overstressed the thin top sections of the whip which subsequently parted company from the lower sections. I attempted a repair which wasn’t successful, so I am now the owner of a shorter whip which may see service in a future antenna experiment.

AliExpress top hat for a PAC-12 antenna. NB: I drilled a through hole in the hub to fit it on my tactical whip.

I own another whip – a “tactical”, military style whip that is 9.5ft long. It is made from several sections of fairly rigid tube held together by shock cord. Although the sections taper toward the top, the uppermost section is still quite strong. When the top hat was attached to this whip, the whip bowed very slightly but appeared to be quite able to support the weight.

“Tactical” 9.5ft military style whip

The AliExpress top hat arrived in a surprisingly small package. It comprises a central hub secured to the whip by a small hex screw and four tiny telescoping whips that expand to 12 inches long. When fully assembled the top hat has a diameter of about 24 inches.

How did it perform?

I was a little skeptical about this arrangement. Could a small capacitance hat compensate for the short (9.5 feet) length of my whip on the 20m band? It was a shot in the dark and the short answer is no it could not. But that isn’t to say the top hat totally failed in its mission. In fact, it did make a difference as will be explained in a minute.

A small top hat alone cannot easily compensate for a very short antenna. There are ways to improve the top hat – such as adding a perimeter wire linking the tips of all the horizontal conductors, or even making the horizontal conductors longer. For rapid deployment in the field the perimeter wire is tricky to implement. The stock AliExpress top hat can be assembled and installed in about a minute; adding a perimeter wire makes the assembly more complicated – especially when backpacking the whole station into the bush.

Making the top hat’s horizontal conductors longer introduces another complication. These conductors carry a very small current; if they are made much longer the current will increase (e.g. as in a Marconi T-Antenna) and they will radiate.

A much simpler, but less efficient, idea is to combine the top hat with a loading coil, and that is the route I took. I revived an old ham-made adjustable loading coil I had built for another project a few years ago. The loading coil had to be placed at the bottom of the whip for mechanical stability. Since this is also the maximum current point the coil will introduce i^2R loss, but compromises have to be made.

VA3KOT’s trail-hardened FT-891 rig with ham-made adjustable loading coil and 9.5ft top-hat loaded whip

The end result was a base loaded 9.5ft whip with a 24-inch capacitance hat at the top of the whip. The adjustable coil enabled the antenna to work on 20m, 30m and 40m by simply adjusting the coil slider. Four 13ft radials were laid orthogonally on the ground at the base of the whip as a counterpoise.

Step One

First, the top hat was left to one side and the coil slider was adjusted to find a match on each of the three bands of interest. I used my RigExpert antenna analyzer to measure the results, then when a match on each band was found, my trail-hardened Yaesu FT-891 was deployed and verified the results.

Step Two

The top hat was then installed and the tests repeated. Now the coil setting for each band was quite significantly different. The required inductance was reduced which means the i^2R loss was also reduced – that was encouraging. So the shortening effect of the top hat was verified, but what about the point of maximum current; was that raised too?

I attempted to model the antenna using EZNEC. I have to admit that I have only a very limited knowledge of antenna modeling, so I cheated a little. I modeled a full-size quarter-wave whip for 20m and looked at the antenna currents. Then I added the top hat to the model and looked at the antenna currents again. Would the top hat raise the maximum current sufficiently to get it above the loading coil and thereby reduce losses in the coil? The following chart shows the results.

Bingo! (but no big prize)

As we can see by looking at the chart, the top hat does indeed raise the maximum current point. The model divided the whip into 50 segments and the current maximum is raised from segment 1 with no top hat, to segment 10 with a top hat. That means the point of maximum radiated energy is raised to a point 20% up from the bottom of the whip. Hallelujah.

But just a cotton-pickin’ minute, the actual maximum current changes very little between the first and tenth segment so did we actually achieve anything useful? Well yes we did actually. If we look at segment 50 on the chart we can see that without the top hat the current drops to zero at the top of the whip. On the other hand, with the top hat installed, there is still significant RF current all the way up the whip – so the entire whip is contributing to radiation!

Did the maximum current point clear the loading coil?

I won’t win a Nobel prize for this bit of non-science, but here is my analysis. If the whip is 9.5ft long, the loading coil is compensating for most of the other 7.5ft of a nominal 17ft whip. 20% of 17ft is 3.4ft so that falls well within the loading coil. Hence no, the current maximum will still be in the loading coil. If any reader can convert the above into real science I would welcome your input.

This was interesting experiment and convinced me that top hats really do improve a vertical whip antenna. Will this arrangement actually be used in my field portable operations? Yes, for sure; the top hat has the effect of “decompromising” (to some extent) a compromise antenna. When the prime mission is to carry a rapid deployment, field expedient portable antenna into the bush, remote from roads and parking lots, this antenna has earned in its place in my backpack.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

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#AmateurRadio #Antennas #Counterpoise #Ground #OutdoorOps #Portable

An Outside the Box version of the Delta Loop antenna

I have written about delta loop antennas before – notably in April 2023 in a post entitled “Delta Loopy Ideas“. A few weeks ago I received an email from Alan WA3EKL who suggested I should take another look at delta loops and offered a lot of helpful advice, tips and suggestions for making this type of antenna a success. Alan’s suggestions have been a tremendous help in designing this latest iteration of my rapid deployment, field expedient, portable delta loop antenna for the 20m band.

Before we go on to describe what is definitely an “outside the box” variant of the delta loop I should comment that I remain welded to the idea that delta loops can be tricky to set up. There are so many variables to consider:

• orientation (apex up, down or sideways)
• feedpoint (at the apex, at a corner, a quarter wave from the apex or somewhere in between) giving horizontal or vertical polarization
• loop length (1005/wavelength or some other length, bare or insulated wire)
• equilateral triangle (or not)
• height of wire above ground
• Matching device (quarter-wavelength 75 ohm coax / impedance transformer / L-network / tuner)

On the positive side you can simplify all the variables and just throw up an “inside the box” version. You will make contacts – but will the standard, don’t-bend-the-rules version of a delta loop be as efficient as possible?

My personal quest has been to find an antenna that is efficient enough to let me carry on working QRP during the Sun’s current spate of hissy fits. With that in mind I wanted to experiment with the variables to see if every last picowatt of RF energy could be transferred from my humble, so-small-its-hard-to-see-without-a-lens QRP-Labs QMX transceiver to the ionosphere via whatever variant of the delta loop became necessary. I have a muscle radio that could get the job done, but there is an engineering and physics challenge built into this quest. Part of the challenge of QRP is to use brains over brawn.

So let’s examine those design variables and see what emerges from the mist. First up:

1. Orientation (apex up, down or sideways)

There are arguments to be made for and against each way of orienting the loop – and let’s emphasize that we are discussing only vertical orientations here. This is not meant to be a treatise on the basic theory of delta loops, so let me just state that only one orientation fills my needs. The use case we will discuss here is a rapid deployment, field expedient, portable antenna. The antenna must be lightweight, pack into a very small space and will remain erected for perhaps only an hour – just long enough to complete a POTA activation.

The orientation that fills this need is an apex up triangle supported by a telescoping fiberglass pole (a 7m Spiderbeam) at the center. Each end of the bottom section of the loop is supported by a modified trekking pole stuck in the ground.

The Spiderbeam pole could be omitted if a tree limb is available for the center support. A fence or bush could replace the trekking poles. I prefer to be self-sufficient out in the Big Blue Sky Shack and not depend on whatever might be available at the end of the trail. Trekking poles can also be used for their intended purpose en route to the operating site.

2. Feedpoint

2:1 impedance transformer at feedpoint

A delta loop can be fed at the apex, at a corner, a quarter wave from the apex or somewhere in between. I chose to feed my loop at a corner for convenience. The choice of feedpoint affects whether the radiated signal is vertically or horizontally polarized. Frankly, I don’t care; the radiated signal is going to be fired up to the periphery of the “Final Frontier” where it will be kicked around by the ionosphere’s D-layer, then refracted back down to Earth with who-knows-what polarization. We might be more concerned at, say, a Field Day site where it might be desirable to chose vertical or horizontal polarization to avoid interference in the near field with other stations.

3. Loop length

Far end of antenna supported on a trekking pole

Those who don’t wish to rock the boat of antenna orthodoxy will just cut their wire using the formula 1005/wavelength. Should the wire be bare or insulated? Does it matter? Some sources say absolutely not. Other sources suggest the effect of insulation is finite, but insignificant.

I decided to consult the stone tablets to get an official view of the effect of wire insulation. First I consulted the EZNEC manual in which EZNEC creator Roy Lewallen W7EL suggests the difference between bare and insulated wire is very small – perhaps 2-3%. EZNEC allows users to specify wire insulation in its calculations. If we consider that a 20m delta loop has a nominal wire length of 71.5ft, even a 2% impact could change the wire length by almost 18 inches. Significant? Perhaps not, but when I explain how I derived the wire length of my Outside the Box delta loop you may understand how my thinking was swayed on this issue.

Bottom wire section center secured to pole with a Canadian Jam Knot

One source may not be enough to establish a rule, so I also consulted the excellent website portable-antennas.com from Rob DM1CM. Modeling a delta loop on that site was a simple exercise of selecting various drop-down selection boxes – fast and easy. Portable Antennas.com also allows wire insulation to be calculated into the loop design. After plugging in the numbers for my loop the model gave a correction factor of 0.9754 when insulated wire is used. Based on a 71.5ft loop length that would suggest a shortening of 1.76 feet even using just a 2% shortening factor.

How did I determine my loop length? I made the decision to choose the loop length by trimming the wire until I obtained resonance in the CW QRP portion of the 20m band. I set my RigExpert AA55 Zoom antenna analyzer to plot an R,X (Resistance and Reactance) chart. The wire was then trimmed until the RigExpert showed an X value of zero. The wire length? I laid the wire out on the lawn I had neatly cut the day before and measured the length – it turned out to be just 68 feet. If the shortening factor of the wire insulation is taken into account the corrected length would be between 69.36 and 70.1 feet. Is that significant? Perhaps; if the resonant frequency were changed by 2% it might no longer lie in the desired part of the band.

4. Equilateral triangle? Height above ground

Ideally a loop antenna should enclose as much area as possible (source: well, I read it somewhere). My design was influenced by two factors – the height of the Spiderbeam pole (7m, 23ft) and the recommended height of the bottom section of wire above ground (source: Alan WA3EKL recommended between 4 and 6 feet; I chose 4 feet). So the Outside the Box variant of a delta loop is not an equilateral triangle. The bottom section of the wire (the hypotenuse) is longer than the other two sides. Less efficient than an equilateral triangle? Piff!

5. The matching device

Alan WA3EKL suggested a quarter-wavelength section of 75 ohm coax to match the impedance of the loop to 50 ohms, but cautioned against the use of foam dielectric coax whose velocity factor can change over time which affects its electrical length. The only 75 ohm coax I had available is RG-6 which has foam dielectric so I ruled that out.

I recently watched an interesting YouTube video by Michael KB9VBR, who was discussing his way of matching a delta loop antenna. Michael used an impedance transformer with an impedance ratio of 2.5:1 (8:5 turns ratio). That seemed like a convenient and field expedient way of matching the delta loop impedance of 100-120 ohms to 50 ohms so I built one. Out in the antenna test range (my backyard) it was discovered that a 2:1 ratio worked best (turns ratio 7:5).

The final result

My Outside the Box delta loop antenna is resonant at 14168 KHz (slightly higher than planned, but not a problem). The minimum SWR is 1.03:1 at 14175 KHz. At the lower band edge at 14000 KHz, the SWR is 1.15:1 and at the upper band edge of 14350 KHz, the SWR is 1.11:1. And, yes, I have made contacts with it. I bent the rules but the end result is worthy of making the trip to the field this summer.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #Antennas #CW #OutdoorOps #Portable #POTA #QMX

An improved tank circuit EFHW coupler

About a month ago Ham Radio Outside the Box posted about “a third way” to match the high impedance at the feedpoint of an End-Fed Half-Wave antenna. A link to the original article is at the bottom of this post. A “30-minute special” was built to prove the concept actually works. It did work fine business (as we say on-air), but that initial implementation had a serious limitation – it was limited to a single band due to the use of a fixed capacitance (a trimmed short length of coax). How could we adapt the basic design to cover multiple bands? Read on to hear about a new improved EFHW coupler that does indeed cover multiple bands.

A QRO(p) coupler

Searching through the vaults containing a vast reserve of assorted electronic components at Ham Radio Outside the Box laboratories (my basement) I unearthed an air-spaced variable capacitor. These now rare items were common in the days of TRF (Tuned Radio Frequency) receivers. For a long time now Superheterodyne circuits have seen the gradual demise of air-spaced variable capacitors.

What’s behind the big knob?

When you look a radio in the face you will usually see that one of the knobs is larger than the rest. That would be what we used to call the “Tuning” knob; nowadays it is more likely to be labeled “VFO”. That would be our first clue as to whether the component behind the front panel is an air-spaced variable capacitor or one of those new-fangled devices called a “Rotary Encoder”. If you turn the knob until you hit an end stop it is a variable capacitor; if it turns freely it is a rotary encoder. For somebody like myself who first gained an interest in radio when capacitors were called “condensers” that is important and useful when deciding whether to purchase an old radio at a yard sale with a view to scavenging its parts.

The component I found in the underground vaults is an even rarer device – it has a slow-motion gear drive. That is a valuable feature when tuning a high-Q tank circuit. I re-used the T200-2 powdered iron core and coil windings from the original single-band coupler. Consumer grade AM radio sets often used a thin cord stretched around an elaborate system of pulleys to achieve the same fine adjustment in tuning, but a mechanical gear system is more robust and reliable.

The capacitance range of the “tuning condenser” was measured using my “Almost All Digital Electronics L/C Meter IIB” and those values, along with the fixed value of the toroidal inductor, were plugged into a LibreOffice spreadsheet to find the range of resonant frequencies available with this coupler. My target was 20m, 30m and 40m – the bands I use most frequently. Good luck struck again, my junque box variable capacitor was able to cover those three bands so I got to work building the new coupler.

Construction

There are only two main components – an inductor and a variable capacitor so putting the coupler together didn’t take very long. For expedience I re-used an old Hammond aluminum enclosure from a long forgotten project. I would have preferred a plastic enclosure but I didn’t have a suitable plastic box available. Now that the device has been proven to work I plan to purchase a domestic electrical box from the hardware store. Hammond aluminum project boxes are sturdy and well made, but they have what I perceive to be a design flaw – sloping walls – which makes them unsuitable for projects like this one. Another consideration is that the kind of variable capacitor employed in this project should be electrically isolated from its enclosure because the body of the capacitor is connected to its static plates. We want to prevent stray capacitance or unwanted conductive paths.

This project was built for my “QROp” rig which is a Yaesu FT-891 capable of 100 watts but which I rarely use above 20 watts. I have even used it as a QRP rig by dialing the HF Power setting down to 5 watts. The disadvantage of operating the FT-891 as a QRP rig is the high current consumption. There is very little practical difference in signal strength between 5 watts and 20 watts, but 20 watts might just edge my signal above the noise during poor band conditions. So I am now working on a QRP version.

Working QRP usually involves lightweight station equipment although that isn’t always the case – refer to my post: “My radio is tiny. So why is my POTA backpack so heavy?“. No matter how small your transceiver is, all the ancillary equipment (like a chair, drinking water etc) adds weight to your pack. Lightweight radio gear doesn’t really allow use of heavy variable capacitors. A QRP version of this coupler will replace the heavy, bulky, air-spaced variable capacitor with polyvaricons which are very small and very lightweight.

Incidentally, why are these miniature variable capacitors called “polyvaricons”? Is the name a contraction of “polymer variable condenser“? Condenser? Surely that should be “polyvaricaps”. Now this old codger feels at home!

Polyvaricons scavenged from secondhand AM/FM radios

Tip: Polyvaricons are available from various QRP parts suppliers but there is another source that is very convenient and cheaper. I went to a local charity shop recently and bought a couple of budget AM/FM radios for pocket change. The checkout clerk told me I had 7 days to check that the radios actually work and I could return them if they didn’t.

I replied that I guarantee they won’t work in about an hour from now as I am going to tear them apart to use their components!

Polyvaricons usually have several sets of plates some of which are high capacitance and some are low capacitance. To make fine adjustments of the capacitance in a QRP version of this project I plan to exploit this feature. Combined with replacing a bulky SO-239 with BNC connectors, all in a small lightweight plastic project box should reduce the size and weight and make a QRP version suitable for backpacking.

Why not use an L-match?

I believe an L-match, discussed in previous posts, is a more efficient coupler for End-Fed Half-Wave antennas. Unlike the tuned tank circuit design, an L-match does not involve the use of a transformer which introduces potential losses. So why have I gone ahead with a tuned tank circuit coupler instead?

I have corresponded with readers who use L-matches as couplers for EFHW antennas. One thing stands out about L-match couplers – each band requires a separate coupler with a fixed capacitance and fixed inductance. This is not conducive to rapid band changes in the field. An alternative is an L-match tuner employing a variable capacitor and variable inductor. I have built one of these but I am of the opinion that this introduces potential losses due to the switched inductance. Even a variable capacitance introduces the potential for losses because of the way contact is made with the moving vanes.

There is a way to configure variable capacitors to overcome this problem. Builders of small magnetic loops often employ it because even a tiny ohmic resistance can impact loop efficiency. In regard to inductance changes, perhaps plug-in inductors could be used just like in the old days when capacitors were condensers.

This whole series of posts here on Ham Radio Outside the Box documents the pursuit of a highly efficient replacement for the broadband impedance transformer commonly used with EFHW antennas. What is your opinion? I invite your comments on this topic.

Re-read the original post:

https://hamradiooutsidethebox.ca/2025/05/14/matching-an-efhw-antenna-a-third-way/

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#AmateurRadio #Antennas #OutdoorOps #POTA

My radio is tiny. So why is my POTA backpack so heavy?

We have mountains in Ontario. We call them mountains, but they are really just small hills. So I have never had to actually hike for miles up steep slopes carrying a backpack with all my radio gear, plus anything else I might need for a mountaintop activation. To all those who operate in this fashion, you have my sincere admiration.

VA3KOT’s POTA kit packed and ready to go.

Get your kicks on fourteen zero six

At the other end of the scale we have what has been called PLOTA (Parking Lots On The Air) activators. These operators perform their activations while sitting in their vehicles. It is tempting to think they probably grab their morning coffee at the a drive-thru en route to the activation. I confess that I have done this too, but only when the temperature drops down to double digits with a minus sign in front. I imagine that, in southern states, when it gets hot enough to cook eggs on the sidewalk, operating in air-conditioned comfort is almost a necessity. If this style of operating works for you, or is necessary in your environment, then you are doing your part to keep outdoor radio operations alive and thriving.

Mr Blue Sky

In between hiking up an inhospitable mountain, exposed to the elements, and being welded to a car seat is another option. Maybe this is the true expression of operating outdoors – leaving your vehicle and carrying your station into the back country, or even a local park. This is my personal choice. It combines a love of the great outdoors with a love of radio – what I have dubbed operating in the Big Blue Sky Shack.

There are options even within that. Do you carry your gear from your vehicle to the nearest picnic table, or do you backpack everything you need (seat and table included) down a trail, blatting the bugs that are intent on drinking your blood, admiring the wildlife while avoiding large mammals intent on eating you, to find a clearing in the trees where you can set up.

Oh Yuck!

Let me tell you a story about picnic tables that may discourage you from regarding them as a comfortable, convenient place to operate. I used to be an RV camper; it was fun but for several reasons I eventually sold my trailer. During one camping trip a neighboring camper was packing up his giant fifth wheel. I watched as he laid his sewage hose out to dry on a picnic table. For those who have never owned an RV (or caravan as it is known in many parts of the world), a sewage hose is used for emptying the contents of the “black tank” at the “dump station” on the way out of the campground. But I am sure you always use a plastic table cloth, don’t you? Well consider this, your table cloth is going to pick up millions of bacteria from the picnic table surface and transfer them to your food. Yuck!

Little boxes

Going back to the supremely fit, energetic types who climb real mountains to operate. They tend to carry extremely lightweight radios; often the whole station packs away into a tough, rugged plastic case that slips into the pocket of a backpack. I have often thought of emulating this idea. But instead, not being quite as fit as I could be, and with age-related physical limitations, I have chosen a different approach. My backpack station is a little on the heavy side (not to be confused with the Heaviside which is a layer of the ionosphere that makes our hobby possible).

Say, friend, I got a heavy load

At the heart of it all is a QRP-Labs QMX transceiver. This tiny device is so light it almost defies gravity – but it is not a complete portable radio station. So I built a backpack frame that can carry everything I need – and it is surprising what that includes when you can’t pop back to your vehicle to grab something else. Here is a list of what I carry:

• Transceiver – QRP-Labs QMX (low band version)
• Talentcell 6500 mAh LiFePo4 battery
• Drok buck converter to regulate the voltage fed to the transceiver
• Putikeeg CW paddle key
• Earbuds
• Ham made line isolator (common mode current choke)
• Selection of RG-316 coax cables
• Rite in the Rain log book, pencils
• UTC wristwatch
• Reading glasses
• Selection of wire antennas and radials
• 18.5ft telescoping stainless steel whip
• Lightweight tripod for supporting the whip on rocky ground
• Spiderbeam 7m telescoping fiberglass pole
• Telescoping plastic seat
• Multitool
• Small tarp
• Selection of cordage

Modified lighting tripod – a bargain purchase at a charity store. Shoulder strap was added later.

Of course there are even more things that must be carried such as water, bug spray, snacks etc. Those little hardened plastic boxes with a tiny radio, key and wire antenna are impressive to behold, but they are not a complete and independent station incorporating everything needed for personal comfort and survival far from shelter and the means of egress.

Experience has taught me not to rely on commercial backpacks to carry all my gear. Most are intended to carry the typical range of items needed by a hiker. I bought a rugged, military style, cotton canvas backpack from a local supplier and was disappointed when I tried to use it to carry my radio equipment. There was no padding, no frame; it was very uncomfortable to carry. Clearly it was made for lighter, softer loads than mine.

Another alternative is real backpacks made for the military. They are built tough but are also very tough on the budget. I just couldn’t justify spending many times more on a backpack than the radio equipment inside it.

Custom antenna bracket secured with a quarter inch nut and bolt – and Gorilla tape! Note the radial attachment point.

Just in case

The solution involved a little bit of work in my garage workshop using many items I had already hoarded ready for future project ideas. I had to purchase two 30-cal steel ammo cases, but they were very inexpensive. One was sold for storing hunting ammunition, but the other was a bona-fide military surplus case with markings indicating it was intended for storing 200 cartridges of 7.62mm rounds and other items. I plan to repaint it sometime before it gets me into trouble. Why steel ammo cases? They are built tough for protecting delicate equipment, they are cheap, and they provide sufficient heft to create a firm operating platform.

Vertically stacked cases are the right height for field operations while the operator is seated on a camping stool.

Both steel cases are stacked vertically on a modified aluminum backpack frame. The bottom case holds antennas, cables etc. The top case holds radio, battery, key etc. Everything is pre-assembled inside the radio case – just pop the lid, insert the earbuds, turn on, tune in and go.

Telescoping plastic stool from Amazon

My Putikeeg CW key has very strong magnets on its base and holds very securely to the steel case. I use it in vertical fashion, with the paddles peeking up above the rim of the steel case. The assembly sits at a very comfortable height for operating the radio without the need for a table. My seat is a lightweight, plastic, telescoping thing with a padded cushion on top. It is an ingenious design with many latches holding it up. I was very cautious about trusting my posterior atop this perch at first, but it supports my weight just fine. The pictures tell a lot more than many more words can convey.

Whatever style of outdoor operating you prefer you are helping keep amateur radio alive. This post describes the way I operate and is not meant to be judgemental about any other style. There is room enough in our hobby for whatever way you like to operate. In fact, I invite you to comment or send me a description of your outdoor radio equipment – even if it is mounted on a set of four wheels 😉

All tuned up on fourteen zero six. The antenna connects to the BNC on the right. The Putikeeg paddles are secured by strong magnets. Earbuds are on the right. Beneath the radio are the 6500 mAh LFP battery, Drok buck voltage regulator and a line isolator.

My POTA gear is constantly evolving so what you see and read here may not be what you see if we meet on a trail sometime. I like to experiment and try out different ideas. Some call me nuts; maybe they are right but I’m having fun.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

#CW #OutdoorOps #Portable #POTA #QMX