#antennas — Public Fediverse posts

This Tiny Gadget Lets Sports Fans Watch Free OTA Games on Their Phones Without Paying for Streaming

https://fed.brid.gy/r/https://cordcuttersnews.com/this-tiny-gadget-lets-sports-fans-watch-free-ota-games-on-their-phones-without-paying-for-streaming/

This Tiny Gadget Lets Sports Fans Watch Free OTA Games on Their Phones Without Paying for Streaming

https://fed.brid.gy/r/https://cordcuttersnews.com/this-tiny-gadget-lets-sports-fans-watch-free-ota-games-on-their-phones-without-paying-for-streaming/

No loading coils, no top-hats, no transformers, no ununs, no baluns, no tuners, no radials – just the perfect antenna?

Just imagine, if you could get rid of all those lossy loading coils, impedance transformers, ununs, baluns, tuners and ground radial trip wires. What do you have left? Could it be the most perfect, the ultimate, 100% efficient, dream antenna? Yes, yes; it’s a dream! But back in the real world …

I spent most of the day recently, sweltering under a hot sun (suck it up John, the snow will be back before you know it) deploying all my recent experimental antennas, comparing results. It’s a lot of fun to experiment with various combinations of wire, whips, cores and coils, seeking “the one”, the best one, the antenna that will outperform expectations and fill the log book with DX galore.

Conditions that day were far less than perfect. Some stations I called faded away before the QSO was complete. Others couldn’t hear my 5000 mW signal at all. QSOs came along every few minutes of calling but most involved a struggle to squeeze enough microamps through my antenna to exchange signal reports and QTH. Every one of the antennas I tried bore the same result – until, out of desperation, I erected an antenna I had been keeping as an emergency backup. Suddenly the bands seemed alive; could this be “the one”?

We live on a Goldilocks planet

The Earth might be what astronomers call a “Goldilocks” planet – a planet with a breathable atmosphere, that is just the right distance from a star to maintain temperatures compatible with human life. Such planets are rare in the universe. Of course, there are areas on our planet that don’t meet the Goldilocks criteria and I’m sure Canada must be one of those areas. On a snowy, freezing cold day in February ain’t nothin’ gonna convince me I live on a Goldilocks planet.

But Goldilocks has a flaw – it doesn’t conduct electricity very well. I am sure you are wondering why this narrative has drifted off the topic of ham radio and into astronomy. Explanation coming. Maybe there would be all kinds of downsides to a planet that did have good electrical conductivity, but building antennas would not be one of them.

As a consequence we have to go to a lot of trouble to compensate for the Earth’s poor conductivity. One of my CW buddies has a full-size quarter-wave top-band vertical. It’s a monster of a vertical antenna and requires hundreds of ground radials to work. I am more of a field portable operator who likes to work with simple wire antennas. Something that can be deployed rapidly out in the field and taken down again just as quickly. I have used plenty of antennas that have ground radials and sometimes even had pleasing success with them. But, throwing just a few wires on the ground is inefficient, and when you are a QRP operator you don’t have watts to spare.

So, to sum up, sorry Goldilocks, but you can’t be part of my antenna; I need wire in the air, not on the ground. Before you reach for the comments section to remind me that the ground is always part of an antenna, yes you are correct. In fact even the ground thousands of kilometers away affects our antennas. Our signals, of course, bounce their way around the planet between the Earth and its ionosphere. And even a good antenna, on a day when the propagation gods are displeased, may be disappointing.

“The One”

How about a simple wire antenna that is one half wavelength long, fed in the center. You could call it a Center-Fed Half Wave (CFHW) but a simpler way to describe it is with the word “dipole”. I have never been a fan of dipoles in the past. First, they occupy a lot of space. A flat top dipole requires three supports which takes longer to erect. Feeding dipoles in the center implies a long length of coax which may lead to losses.

During a field deployment there are a couple of ways to mitigate these issues. If a dipole is erected as an Inverted V the horizontal space is reduced and only a single support is required. The radiation pattern changes from bi-directional to omni-directional, but maybe that’s sometimes a good thing. The ends of the dipole can be attached to the top of trekking poles, or simply pegged into the ground via a length of cord.

The long coax issue can be overcome using a sleeve dipole. A sleeve dipole comprises one quarter wavelength of coax and one quarter wavelength of wire. It is physically fed at one end, but the electrical feedpoint is in the center where the coax inner conductor is joined to the wire. The coax acts as part of the feedline while the outer surface of the coax braid forms a quarter wave element due to the skin effect.

There is a variant of the sleeve dipole called the Off-Center Fed Sleeve Dipole (OCFSD) which has been discussed here on Ham Radio Outside the Box in the past. The one I built supports multiple bands, but requires a 4:1 unun at the electrical feedpoint and a tuner in the shack. But, this post is all about keeping a simple wire antenna sweet and simple – no ununs, baluns, tuners etc allowed.

Another idea is to feed the dipole in the center using Open Wire Line (“OWL”). Now it becomes what is known as a “doublet”. OWL has very low loss, even over long runs. A doublet can support multiple bands with the aid of a tuner. But, again, this post is all about keeping a simple wire antenna sweet and simple – no ununs, baluns, tuners etc allowed.

Doesn’t a simple coax fed dipole require a balun at the feedpoint?

Technically, yes it does. If the dipole is perfectly symmetrical it is a balanced antenna. Feeding it with coax creates an interface between a balanced antenna and an unbalanced coax feedline. There is a possibility of common mode currents flowing back down the outer surface of the coax braid causing problems at the radio end.

Here we can get away with cheating a little. QRP operators have the advantage that any common mode current caused by lack of balance in the antenna, or by pickup of signal in the feedline will be very small and probably dissipate before reaching the radio. This little hack will probably not work at higher power.

But don’t you have to erect a dipole a half wavelength above ground?

No. Nein, nicht, non. For low angle radiation aimed at DX then, yes, erecting the feedpoint up high is definitely an advantage. But those of us activating or hunting any of the now numerous xOTA programs don’t have to follow that rule. I have had success with a 20m dipole with the apex at only 16ft. The angle of radiation is very high, but there is enough signal at lower angles to make intra-continental contacts. Similarly, my 40m dipole is targeted toward contacts in the eastern half of North America.

So simple dipoles it is then, or …

My antenna attention span can best be defined using quantum physics, i.e the science of things that are infinitesimally small. But for now I will be using simple wire dipoles for my field operations. Am I being too strict in my definition of “the one” antenna? Many a good contact has been made with miserably compromised whips, wands and wires. Perhaps my next venture will be a revisit with the Off-Center Fed Sleeve Dipole to explore how it compares with a pure, unadulterated dipole. Stay tuned.

Trust me I am a X-spurt

No really, but with the explanation that “X” is an unknown quantity and, according to the American Dictionary of the English Language, “spurt” is “a sudden forcible gush or jet” or, put another way: a short burst of energy. I have also heard “spurt” defined as “a drip under pressure”. So you can place whatever value you wish on my “X-spurtise”; it is based on endless tinkering and experimentation. I often venture down blind alleys and produce results that are worth the product of one-squared and infinity to the power of minus one. Occasionally I may also accidentally stumble on a good idea; I’ll let you be the judge.

Gallery

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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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I ordered a bunch of antenna books from #ARRL and was hoping for more information and advice above 1ghz.

I'm looking at RF cables for making #meshtastic #antennas, but I also want to use them with my decade-old #SDR that goes up to 6Ghz. And I have interest in higher frequencies.

To set expectations, I remember 900mhz radios were sold by radio shack when it existed. 2.4 ghz was commonplace 20 years ago. Cellphones and wrist watches now use 5ghz wifi, and cruise control for cars uses 77ghz.

But the highest freq in the books are the UHF to Microwave chapter. It spends a lot of time on UHF and VHF, and the diagrams mostly go from 1-100Mhz. A few tables show losses at 1 ghz, and a single graph shows 10ghz.

I'd love to see separate chapters (or books) dedicated to microwave and mmwave, maybe with some hints about thz. Especially if it has the practical wisdom the HF bands get.

E.g. What's the best way to connect to a 5ghz yagi?

I'm not the person to write them, unfortunately, but I'd love to read them.

@kilroy_was_here I never understood why people use wrenches and sockets and the like to get wires into trees. It seems to me that they would inevitably get stuck up there sooner or later. Here's how I do it: https://www.kb6nu.com/from-the-mouths-of-babes/ #hamradio #antennas

QRP Labs QMX Gets a Serious CW Upgrade: What Firmware 1.04.004 Changes

A small firmware update with some meaningful improvements for QRP and CW operators.

A firmware update may not sound exciting, but for CW operators using the QRP Labs QMX, version 1.04.004 brings several changes worth paying attention to.

The QRP Labs QMX has become an interesting little radio for operators who enjoy QRP, CW, digital modes, portable operating, and experimenting with software-defined radio technology.

One of the advantages of a modern software-defined transceiver is that the radio sitting on your desk today doesn’t necessarily have to be the same radio you bought months ago. Firmware can correct problems, refine operating characteristics, and even add capabilities without replacing any hardware.

That’s exactly what QRP Labs continues to do with the QMX.

Firmware version 1.04.004, released July 23, 2026, includes several changes that should be particularly interesting to CW operators.

Better Control Over CW Transmit Shaping

Perhaps the most interesting part of the update is additional control over the QMX’s CW shaping.

CW isn’t simply a matter of switching an RF carrier instantly on and off. The way the transmitter brings the signal up to full power and then reduces it again can affect how the transmitted CW sounds.

Transitions that are too abrupt can contribute to unwanted key clicks and unnecessarily widen the transmitted signal.

With firmware 1.04.004, QRP Labs provides additional control over the CW shaping envelope and rise and fall times.

For the everyday operator, the important point is simple:

You have more control over how your CW signal is generated.

That’s especially welcome on a radio likely to be used by operators who care about clean CW signals.

CW Key-Down Spike Addressed

Another important change involves a CW key-down spike.

A brief power spike at the beginning of a transmission may only last a very short time, but correcting that behavior helps make the transmitter’s output more predictable and controlled.

For a QRP transceiver, where operators are deliberately working with only a handful of watts, good control of the transmitted signal is particularly desirable.

The firmware addresses this issue as part of QRP Labs’ continuing refinement of the QMX.

Semi-QSK Improvements

The update also contains a correction related to Semi-QSK operation.

QSK, or break-in CW, allows a CW operator to transition rapidly between transmitting and receiving. It’s one of those features that may not mean much to someone primarily operating SSB, but experienced CW operators quickly notice when transmit/receive switching doesn’t feel right.

Good break-in behavior can make CW operation feel much more natural.

The Semi-QSK changes therefore aren’t simply another obscure item buried in a firmware changelog. For operators who spend a lot of time behind a paddle, improvements in this area can have a noticeable effect on the operating experience.

New CAT Commands

Firmware 1.04.004 also expands computer control of the QMX through additional CAT commands.

New commands include support associated with GPS information and SWR protection.

CAT—or Computer Aided Transceiver control—is increasingly important because modern amateur-radio stations often combine the radio with logging programs, digital-mode software, station automation, and other computer-controlled equipment.

The additional commands provide developers and experimenters with more ways to integrate the QMX into a computer-controlled station.

For operators who enjoy experimenting with software and station automation, this may ultimately prove to be one of the more interesting parts of the update.

Changes to SWR Protection

SWR protection is particularly important in a small QRP transceiver.

Portable operators regularly change antennas, feed lines, bands, and operating locations. Inevitably, sooner or later, someone presses the key when the antenna isn’t quite what they thought it was.

Having the radio monitor conditions and protect its output stage provides another layer of protection for the transmitter.

The new CAT capabilities associated with SWR protection could also provide interesting possibilities for external software and station monitoring.

A 12-Watt Meter Scale Option

There’s another interesting addition for experimenters.

Firmware 1.04.004 includes a 12-watt power-meter scale option intended for configurations where the QMX power amplifier has been modified.

Most QMX operators probably won’t need this setting.

But its inclusion says something interesting about QRP Labs and its customer base. This is equipment designed for a community where experimentation and modification are still very much encouraged.

That’s something I’ve always appreciated about the QRP side of amateur radio.

SMPS Bias Pre-Warming

The update also introduces SMPS bias pre-warming.

The QMX uses sophisticated power-management techniques inside a remarkably small package. Changes such as bias pre-warming are aimed at improving the way those internal systems behave as the radio transitions into operation.

It’s one of those behind-the-scenes refinements that may never receive the attention of a new menu item or flashy feature.

But these small engineering changes can contribute to making a mature radio more polished.

Why This Update Matters

None of these changes individually turns the QMX into a completely different transceiver.

• Cleaner CW behavior
• Better transmit control
• Improved Semi-QSK operation
• More flexible CW shaping
• Expanded CAT control
• Better protection and monitoring
• Support for experimentation and modified hardware

And that’s actually the point.

Good firmware development isn’t always about adding a spectacular new feature.

Sometimes it’s about improving the details:

Meta description: QRP Labs QMX firmware 1.04.004 adds CW shaping controls, Semi-QSK improvements, CAT commands, SWR features and other refinements for QRP operators.

Put those improvements together and you have a radio that’s continuing to mature after it has already reached operators’ shacks.

The QMX and the Modern QRP Radio

The QMX represents an interesting change in what we expect from inexpensive QRP equipment.

Years ago, buying a small QRP transceiver generally meant that its capabilities were essentially frozen the day it left the factory.

Modern SDR-based radios have changed that.

Today, manufacturers can continue refining receiver behavior, transmit characteristics, digital interfaces, CAT commands, keying behavior, and other features through firmware.

Your radio can literally operate differently after an update.

For experimenters, that’s exciting.

It also means amateur-radio operators should start treating firmware updates much like we treat adjustments and maintenance elsewhere in the station.

Should You Install Firmware 1.04.004?

If you’re operating a QMX—particularly if you’re an active CW operator—this is an update worth investigating.

The improvements to CW shaping, keying behavior, Semi-QSK operation, and CAT control are more than cosmetic changes.

As always, read the QRP Labs release notes and firmware installation instructions before updating your radio. Confirm that you’re installing the correct firmware for your hardware and preserve any settings or configuration information recommended by QRP Labs.

There’s rarely a prize for being the first person to install new firmware.

There is considerable value, however, in understanding what the update changes before pressing the button.

Final Thoughts

The QRP Labs QMX is a good example of where amateur-radio equipment is heading.

It’s small. It’s software driven. It’s affordable compared with many full-size transceivers, and it’s designed for the sort of operator who isn’t afraid to experiment.

Firmware 1.04.004 doesn’t reinvent the QMX.

Instead, it tackles exactly the kind of details serious CW and QRP operators tend to appreciate.

And for a little QRP radio, that’s probably more important than adding another flashy feature to the menu.

73,
KE2YK

(reposting public, rather than quiet)

#HamRadio question: What types of #RF cable to buy and from where.

Low power < 1 watt
700 M to 5Ghz typical
DC to 6G sometimes.
Low loss is nice
50 Ω

Specific uses
1) making #antennas with matching or stubs.
Indoor and outdoor.
900 mhz #yagi
900 mhz folded #dipole

2) connecting antennas on patio to indoor radio.

( 900 mhz, UV / weather resistant outdoor, fire resistant indoor. Possibly flat cable at door. Lightning arr.)

3) connecting boards together indoors (filters, amps, SDR, etc)

What I think that requires:

5 feet of moderately stiff cable for making antennas, #LMR 240/400 or equiv?

10-20 feet of low-loss outdoor cable (not buried)

1-2 feet of thin / flat cable to pass around door.

10-20 feet low-loss indoor cable. Fire resistant?

10 feet thinner flexible indoor cable to interconnect boards.

Tools for cutting & crimping. SMA, RPSma, but ideally also other types (TNC, N, maybe BNC, maybe ufl)

An Outside the Box look at the 48 inch base loaded vertical antenna

It’s not the smartest idea really is it? A quarter wavelength vertical whip for the 20 meter band should be around 5 meters (17ft) tall. Why build a vertically challenged whip that is less than a sixteenth of a wavelength long and expect it to work? And … with a QRP transceiver too!

Yes, indeed it’s not the smartest idea in the world, but Elecraft and others sell such an antenna and many hams use them. So is there another angle to this idea? Am I missing something? I watched another of G3OJV’s videos recently in which Peter Waters (of the UK’s Waters and Stanton amateur radio store) put a different perspective on the idea, so I decided to try it.

G3OJV’s idea is to force the counterpoise to do most of the radiating. Huh? If the counterpoise is raised above ground it will radiate – in fact, if the radiating element is only 48 inches (about 1.2 meters) tall, the counterpoise will do most of the radiating. I decided to model the idea using EZNEC to find out how to configure such an antenna so that it would actually have a chance of working. The model yielded some very interesting surprises.

But there’s a hidden gotcha!

The radiation pattern looks fantastic, and the gain is equally impressive at 4 dBi. It’s no wonder these little critters sell so well, but wait, let’s take a closer look. The NEC-2 engine I use for antenna modeling is notoriously unreliable for antennas that are close to the ground. I had set the Ground Type to Real | MININEC. Now suppose we take another look using Ground Type: Real | High Accuracy. Whoa, now we lose 6.4 dB; the actual gain figure is now predicted to be minus 2.4 dBi.

There are two ways to look at this result. First, the optimistic view: -2.4dB is less than half an S-unit at the receiving end – the receiving station probably won’t even notice the difference. Second, the pessimistic view: if our transmitter is pumping out a mighty five watts of RF, the amount of RF actually leaving the antenna drops to less than 3 watts (ignoring any losses in the feedline). On a good day when the propagation is favorable we are still going to make contacts. But, if the propagation is unfavorable, or we are trying to break a pile-up, our self-imposed handicap is going to be a problem. And, all of this assumes that NEC-2 is not being optimistic in its calculations.

But wait, there’s more bad news

I only modeled the far field propagation of an unloaded 48 inch whip worked against a 17 ft (5 m) single raised counterpoise. Of course, a base-loading coil is also required to match the impedance of the short whip. We’ll get back to that in a moment.

Let’s go ahead and waste more of our radiated power

Typically, very short whips are used for portable operations, and the temptation is to simply throw the counterpoise wire on the ground. Now EZNEC Pro/2+ set for high accuracy ground shows a gain of -3.31 dBi and our actual radiated power drops even further to a little over 2 watts. We are on our way to QRPp! (QRPp refers to radiated power of 1 watt or less). Remember, these little baby whips work best when we force the counterpoise to do most of the radiating. If we lay the counterpoise down on the ground the whole strategy is defeated (but the earthworms will be grateful for the warmth).

About that loading coil

The usual method of constructing a loading coil is to wind wire around an air-core former, or some other non-conducting material. Sometimes the wire used is copper, sometimes it is stainless steel. Now we have to take into account the DC resistance of the wire. Copper is good, silver or gold is better; stainless steel is ungood. You don’t need to be a rich ham to use silver or gold (although it might be a good hedge against inflation if you wind all your coils with solid gold wire); due to the skin effect gold-plated wire would work very well. Even copper-plated stainless steel would be better than unplated stainless steel.

The website 66pacific.com calculates that a loading coil of 9.1 microhenries is required to match a 48 inch whip at 14.150 MHz. That would require 30 turns on a 1 inch diameter air-core former. The length of wire required will be about 95 inches (2.4 m). The same coil can be wound around a powdered iron toroidal core with considerably less wire. Less wire means less resistance loss. Are we nit-picking here? Yes, the resistance losses are fairly small, but remember, we are already down to 2 watts out of our original 5 so every watt counts.

The long and winding coax that leads to your transceiver

Our best bet is to use a very short whip mounted directly on the antenna connector of our transceiver, otherwise coax loss can also become an issue. But make sure your antenna connector is mechanically capable of supporting the weight of a loading coil and whip. Some radios have a BNC antenna connector directly mounted on the transceiver’s circuit board which is an obvious weak point. Further stress is added if the counterpoise directly connects to the shell of the BNC.

I built a 48 inch whip antenna; how well did it work?

I own a collection of old ham stick antennas. Hamsticks have two parts, a helically wound loading coil section and a stainless steel whip. I grabbed one of the whips which happened to be the magic length of 48 inches and mounted it on a tripod with the feedpoint about 4 feet above ground. I then added a loading coil wound with 16 gauge enameled copper wire around a small type 2 toroidal core. My counterpoise was a single radial wire, 17 ft long sloping down from the feedpoint to a few inches above ground at the far end. EZNEC predicted that mounting the far end close to the ground improves the performance.

I fired RF at the antenna, through a few short feet of RG-58 coax, from my mighty mini QMX transceiver at nominally five watts and monitored the SWR on the QMX – all was good. Time to go hunting.

I considered it risky to attempt a POTA activation with an experimental antenna so the trial was to be a backyard hunting session. Well, knock me down with a feather, I actually made a contact with my microwhip. Propagation conditions that day were forecast to be good on 20m and I could hear several POTA stations on the air. I selected a station in Florida which is over 2000 km from my QTH in Ontario, Canada. I could hear the Florida station fairly well so, with a good deal of trepidation, I called him on CW with 5 watts into my test antenna. He came back to me right away, and after a couple of attempts to copy my callsign, we signed off and I put the contact in the log with his RST report to me of 229.

Wow, is this antenna a “keeper”?

No.

There is a popular expression in the QRP world: “QRP – when you want to send the very least”. My interpretation is: when you want to send the very least – get a 48 inch whip!

What is your experience?

If you are still wondering (really?) what my opinion of these vertically challenged antennas could possibly be, then let me say there are better options for ultra-portable lightweight antennas. Even a slightly longer whip would be better. I also built a version with a 9 ft whip – the extra length makes a lot of difference. Adding a top (capacitance) hat improves performance even further.

But, I am sure there are Ham Radio Outside the Box readers with entirely different experiences. For example, if you are an FT8 operator, the lower signal to noise performance – even over CW – may help to squeeze contacts out of a highly compromised antenna. SOTA operators working from the top of a mountain out in the Rockies may experience very short whips very differently. Perhaps if I were to take my 48 inch whip out to one of Ontario’s soaring peaks which sometimes scrape the clouds at 500 m (1640 ft) above sea level I might have a different experience. But then again I might go to the same high point with a real antenna!

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.

About 30dB of common mode attention should be fine for the 80m vertical antenna. With a little force, I get two turns of RG58 into these Würth ferrites. Also, please disregard the adapter mess :-) #hamradio #antennas

TechTip #3 Radials and counterpoises

TechTips on Ham Radio Outside Outside the Box are occasional short posts on specific technical topics. But beware, along with regular posts here on this blog, the content is not a definitive technical treatise and should not be read as such. I write about my own opinions and experiences; your opinions and experiences may be quite different. I welcome constructive feedback either in the comments or, if you prefer, by direct email.

“All lies and jest …

Still a man hears what he wants to hear and disregards the rest”. Paul Simon and Art Garfunkel sang those words in their song “The Boxer”. The words reflect how hams often react when our long-held, cherished beliefs are challenged. “My antenna just works, I don’t care about all that technical stuff” is a view I have heard – especially when the antenna cost hundreds of dollars. And nothing creates more exothermic debate than the subject of radials. Or is that counterpoises?

Definitive definitions

On Ham Radio Outside the Box, when the word “counterpoise” is used, it refers to the “other half of an antenna”. The “other half” could be 120 buried radials, or it could be a “magic carpet” (Faraday cloth). It could be a ground rod driven vertically into the ground. It could even be the ubiquitous (and apparently blessed by angels) 17 feet of wire laid on the ground. That magic length of 17 feet has been proved by thousands of QSOs so why care about all that technical stuff? Eh?

When you read the word “radial” here on Ham Radio Outside the Box it refers to a length of wire. A counterpoise may comprise one or one hundred and twenty radials. Radials could be buried in a shallow grave inches below the surface or they might be raised above ground. Buried radials – or even radial wires laid on the ground – are detuned by the ground and can be any length. Longer radials work better on the lower bands.

“Crickets are singin’ and lightning bugs are floatin on the breeze”

It’s been a while since I went “Fishing in the Dark” (for contacts on the radio) but I do spend a lot more of my on-air time out in the Big Blue Sky Shack, usually on a sunny afternoon – even if it’s only out in the backyard. If we venture out to a park to spend a couple of hours playing radio, we really aren’t going to waste that time laying out 120 radials. If an antenna needs ground radials I lay out between 4 and 8 of them. I know my antenna’s efficiency will be compromised, and I acknowledge the physics, but field expediency is the prime directive. Heck, I usually operate QRP in the field too; maybe I should try “QLF” (sending CW with my left foot) too. Some of my code buddies claim I’ve already mastered QLF!

Floatin’ on the breeze

Compromising efficiency is not mandatory. If we raise the antenna (a vertical whip) above ground. Now just a couple of tuned radials is as efficient as a rat’s nest of wires on the ground. A couple of radials? Why not just one radial? I was asked that question recently by a Ham Radio Outside the Box reader. I had to put on my physics graduate gown and mortarboard while I thought about that.

I started with the idea of a vertical dipole – that’s a quarter wave of wire on top of another quarter wave of wire with the feedpoint in the middle. Now let’s bend that dipole a little. Now it looks like a vertical radiator with a quarter wave high flying counterpoise. If we keep that configuration well above ground it should still be as efficient as a dipole.

I got wires in low places

How low can we go? My theory (which is open to debate) is based on interaction between that raised radial and the ground. The current in the radial wire induces an out of phase image in the ground. In the near field the image wave and the wave in the radial wire tend to partially or fully cancel each other.

The amplitude of the image wave in the ground varies based on two things. (1) the amplitude of the current in the radial, and (2) how close the radial is positioned with respect to ground. A high radial has almost no interaction with the ground, whereas a low radial will have a much greater interaction.

Now, let’s consider this: we can reduce the amplitude of the current wave in the counterpoise if the current is shared between more than one radial. Two radials each carry half the current; four radials each carry a quarter of the current. The lower the current, the lower the canceling effect of the image in the ground.

So we can conclude that it is fine and dandy to use low radials if there are a lot of them. On the other hand, a single radial should be kept well clear of the ground. Does that make sense, or didn’t I wake enough brain cells with my morning espresso today?

But wait, there’s more …

If the objective is to reduce the interaction with the ground, and the amplitude of the current wave in the radial wire(s) is a factor, there is another way – reduce transmitter power. See, QRP ain’t so bad after all!

Incidentally, the image wave in the ground travels more slowly than the current wave in the radial. If the length of the radial wire is one full wavelength, or more, the two waves eventually are in phase and the current is reinforced instead of being canceled. That is how Grasswire antennas work.

Murphy’s opinion

Electrically, a single raised radial will be efficient, subject to the conditions discussed. According to Murphy’s Law, if you use a single raised radial, you better anchor that antenna down good or the tension in that radial wire is gonna pull your antenna over. Murphy says two radials, 180 degrees apart, will keep it up.

Поставил свой личный рекорд - две навайбкоденных тулы для себя за день.

Предыстория: я в какой-то момент решил, что хочу побаловаться не только с LoRa антеннами, но и с LTE для дачи, продал свой NanoVNA-H4 и взял себе NanoVNA-F V3, который работает до 6 GHz.
Но в какой-то момент обнаружил, что в него нельзя вставить флешку и он не делает скриншоты фреймбуфера как это делал более простой и старый вариант.

Впрочем, это меня не остановило и я быстренько с Codex нафигачил две штуки:

• vnacg - генератор графиков в стиле NanoVNA по S1P/S2P входному файлу (их пишет NanoVNA), только в большом разрешении, без ограничения по маркерам и ещё пачкой других фишечек, которые делают демонстрацию замера именно в качестве графика ещё удобнее.
• vna-android - крайне примитивная, но полезная в поле штука, которая запускается на телефоне и по USB забирает фреймбуфер с NanoVNA, грубо говоря делая скриншоты извне.

Обе тулы работают только с NanoVNA-F V3, но если вдруг будет нужно, то добавить поддержку других моделей не должно быть большой проблемой.

Теперь я могу и прямо в поле пошарить скриншот, и сгенерить красивый детальный графичек уже дома.

#dev #agents #vibecoded #log #generated #Go #Kotlin #tools #NanoVNA #radio #DIY #automatization #Codex #pic #antennas #LTE

Как сказал ChatGPT, с которым я просчитывал геометрию этих антенн после того как я её собрал "на глаз" без подстроек и показал ему первый замер:

Человечество иногда случайно сгибает медь правильно.

#quotes #ChatGPT #fun #DIY #antennas #log

Поотпаивал кабели с медной оплёткой от валяющихся без дела мештастиковых антенн.

Как будто бы для такого широкого диапазона как B3 (маркеры тут не на краях, а на серединах uplink и downlink) вышло вполне неплохо.

#antennas #LTE #pic #log #DIY

• Купил 15 метров антенного кабеля чтобы делать LTE антенну на дачу и на запас
• Отрезал полметра для одной половины антенны
• Зачистил для пайки к фидеру
• Это кабель с аллюминиевой обмоткой

SOOOOOOQUAAAAAA 🤦

И возвращать уже не буду потому что, блядь, полметра отрезал...

Ну будет у меня 15 метров кабеля под двусторонний обжим 🤷

#FAIL #log #hardware #DIY #antennas #radio

A 5-Band, Lazy-L, Linear-Loaded, Ladder Line Antenna (aka the “5B6L”)

About a year ago I mentioned an antenna devised by Peter Waters G3OJV that used a 13 feet (4 m) vertical wire to create a multiband antenna. I used Peter’s idea to create “A Simple, Low Profile, Multiband Antenna for POTA“. The antenna was designed to work on 20m, 17m, 15m, 12m and 10m with the aid of a tuner. But, I discovered a small problem on the 17m band. If we do the elementary calculation for the length of a quarter-wave radiator at the bottom end of the band (18.068 MHz) we find that it works out to be 12.95 ft – just a whisker short of the 13 ft recommended by G3OJV. So why is that a problem?

The problem arises because the antenna uses a 4:1 unun at the feedpoint. Since the 13 ft length is already almost resonant on 17 meters, the 4:1 unun makes the job of the tuner much harder. That did indeed prove to be the case when I tested my derivative in the field. So, I made a small change when designing the new 5B6L antenna – I increased the length to 14 feet (4.2672 meters) – well … not quite true, but that is the underlying principal behind the linear-loaded equivalent.

Here are the calculated lengths of a quarter-wave radiator at the mid-point of each of the five bands of interest:

A 14ft radiator slips nicely in between the 20m and 17m quarter wavelengths and becomes a “random length” on all 5 bands. Nice. But this is a linear-loaded antenna made from ladder line. Linear-loading shortens the required length by around 30%. Fourteen feet, shortened by 30% works out to 9.8 feet (~3 meters). After field adjustments I settled on a length of 9.75 ft (a little less than 3 meters).

Lose the radials!

I wanted this antenna to be what could be loosely described as a random length dipole – two equal lengths of ladder line (each shorted at one end) so that was how it was constructed. Now we have the benefit of versatility. It could be erected as a traditional dipole although with two very short arms it would be tricky to get it up in the air. It could also be erected as a vertical dipole on a support pole about 7 meters (23 feet) tall like my Spiderbeam. But that would make it difficult to orient the coax feedline so that it comes away from the antenna at 90 degrees, as is required to prevent the feedline picking up some of the radiated signal. Perhaps a sloper would work; now that is a very viable solution.

How ‘Bout a Lazy-L?

One of the YouTube channels I follow is “Jim’s Cool Stuff“. In one of his videos Jim suggested using a “Lazy-L” orientation of a vertical simple wire radiator and single raised radial wire. Why? The purpose is to increase the take-off angle. A vertical antenna usually has a very low take-off angle which is great for chasing DX, but what about shorter-range contacts? From my location in Southern Ontario, Canada it is only a short hop down to the north-eastern states in the USA. The US northeast has a very large concentration of amateur radio operators many of which participate in popular activities like POTA. A vertical antenna is likely to send my signal whistling over their heads, or at the very least, be received at a reduced level.

A Lazy-L configuration optimizes radiation to favor short to mid-range contacts by raising the take-off angle to achieve much shorter hops. Does it work? Yes indeed, during test operations I have been able to make contacts, just over the shallow puddle they call Lake Erie, into Pennsylvania, and across Lake Ontario into the state of New York, with quite respectable signal reports for my QRP CW signal.

But what about DX?

Stations on the west coast of the US or western Canada could be considered almost DX – each is thousands of kilometers away. No problem! I said this antenna has versatility. The Lazy-L configuration can be re-oriented to a straightforward regular vertical with a raised counterpoise very easily. In fact the angle at which the radiating element leans can be adjusted to find an optimum at which near-DX and short hop stations all fall within its radiation pattern.

How to Build a 5B6L

The following describes construction of a 5-Band, Linear-Loaded, Ladder Line antenna that can be operated on 20m, 17m, 15m, 12m and 10m with the use of a tuner. Materials needed are:

• Ladder Line. I recommend stranded conductors because this makes the ladder line more flexible than solid copper conductors. Use of the 5B6L as a field portable antenna may stress solid conductors and lead to failures.
• a 4:1 unun. This item can be purchased or you can build your own using twin lead speaker wire (or similar) wound around a type-43 ferrite toroid

Instructions

• Cut two lengths of ladder line each 10 feet (3 meters) long. These may need to be trimmed during testing.
• Connect the two conductors of each piece of ladder line together at one end only.
• At the other end of each piece of ladder line, cut off the end of one of the conductors.
• Strip the insulation from the other conductor – this will be connected to the 4:1 unun.
• Connect each piece of ladder line to the unun.

Erection of the antenna

Attach a coax feedline to the 4:1 unun. A tuner may be inserted at this end if desired. For practical purposes, unless a very long coax is used, the SWR losses in the coax will not be significant so a tuner at the radio end can be used.

Set up your choice of pole, or other support, attach one end of the antenna to the top of the pole. The other end of the sloping radiating element (the feedpoint) should be supported on a short stick.

The other half of the antenna serves as a raised counterpoise and its far end can be supported by, for example, a trekking pole.

The slope angle can be adjusted by simply moving the counterpoise support sticks. See what works best for you. The whole antenna can be quite stealthy. I erected mine on only a 10 feet high pole. Efficiency may be improved by using a taller support but I prefer stealth when operating in public spaces. Tall antennas arouse suspicion!

The end is nigh!

A generous friend donated a lot of ladder line some time ago and I have used all but a few feet of it. Maybe it’s time to experiment with something different. So my next project – take a deep breath – is something I have been writing about in unflattering terms recently – a short, base loaded whip! What? Have I been enjoying too much Scottish champagne? Well, I thought it would be an interesting challenge to see how efficient I could make a short-ish whip antenna with a base-loading coil. A prototype has been constructed and has made contacts in backyard tests (with my helping fingers tapping on the key ). When the design has been completed you will be able to read about here on Ham Radio Outside the Box. 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!

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.

📡 Ah, yes, the granddaddy of all #antennas that no one asked for! Finn spent a decade constructing this colossal contraption in his backyard—because nothing screams midlife crisis like a 32x17 #Yagi monstrosity. 🤦‍♂️ Now he can talk to the moon while the rest of us are stuck debating if we should upgrade our Wi-Fi routers. 🌙📶
https://la0by.darc.de/LA8YB_EME_MBA.htm #midlifecrisis #backyardprojects #hamradio #antenna #HackerNews #ngated

Entropy’s Rotoscope Issue I [page 5/19]

https://kamiokan.de/entropysrotoscope/issue1

RSS: https://kamiokan.de/entropysrotoscope/rss.xml

Support me on ko-fi: https://ko-fi.com/j_g00da

CC0 / Public Domain

Next page tomorrow.

#unix_surrealism #comic #art #entropysrotoscope #kamiokande #snails #antennas

A short 2-band ladder line antenna for portable ops

Introducing the 2B2L antenna

Wouldn’t it be nice to have a short, fairly efficient, rapidly deployable, low visual impact, vertical antenna that can be operated on both the 20 meter and 40 meter bands? The 2B2L (2 Band Linear Loaded) antenna comes very close to a perfect match for those specifications.

The 2B2L is the brainchild of Tim KQ4TQ who pitched the idea to me in an email recently. Seeing the potential in Tim’s idea, I hastily built a prototype and erected it in my backyard for testing. The 2B2L is based on the “Simple Ladder Line Antenna for Portable Ops” discussed a couple of weeks ago here on Ham Radio Outside the Box. But here is the genius in the 2 band version: by adding a loading coil and a tail section – also made from ladder line – to the top of the original single band (20m) version, we can add the 40m band. The whole antenna towers up to the dizzying height of just 15 feet!

But, just a moment; before the grey-haired, white-coated men with a physics diploma hanging on the wall pick up their quill pens to denounce the 2B2L, a confession is in order. Yes, admittedly, the 2B2L is not perfect; field portable antennas rarely are perfect. Those of us who like to operate out in the Big Blue Sky Shack must necessarily accept some compromises. Those of us who like to operate QRP accept even more compromises. So where’s the gotcha?

The loading coil for the 40m extension is the weak link. It serves two purposes: (1) it acts as an RF choke for the lower 20m band section; it’s high impedance effectively terminates the lower section of the antenna so that the top section does not affect operation on 20 meters; (2) it acts as a loading coil for the 40 meter top section which is considerably shortened as a result. But is it actually all bad? Yes, it has some loss due to the i^2R effect, but consider this: the whole antenna is radiating on 40 meters and the coil is near the top where the current is lower. If I am thinking with half a brain here please correct me in the comments. I did once think I was wrong, but I was mistaken!

Can an antenna that is only 15 feet tall really be efficient on 20m and 40m? The secret to how it can claim enough efficiency to actually make contacts out in the field lies in its use of linear loaded elements. Two sections of ladder line, each shorted at the top, provide the linear loading which shortens the required length by about 30%. Linear loading is considered one of the most efficient ways of shortening an antenna.

Also, the 2B2L is mounted quite close to the ground which inevitably diverts some RF to warming the earthworms. Mine is fed about 12 inches (~30 cm) above ground. It could also be raised higher and used with tuned, raised radials, but on 40 meters the radials would each be around 33 feet long. I chose to use short ground radials instead.

Where to buy a 2B2L?

Sorry folks, this is another real hobbyist’s project – you gotta build it yourself. You’re going to need some ladder line from whatever source you go to for ham radio supplies. Mine was a generous gift from my friend and CW buddy Mary VE3MVM. You will also need a coil. I had an air core coil lying in the drawer from a previous project. I built it using a a short section of PVC tubing about 2 inches (5 cm) in diameter. You will need an inductance meter, or a NanoVNA, to measure the inductance. As a purely rough guide, my coil has 35 turns of 20 awg stranded insulated wire. Here is the materials list:

• 11.5 feet (3.5 meters) of ladder line for the 20 meter radiating element
• 38 inches (0.97 meters) of ladder line for the 40 meter extension
• 35 microhenry coil

Setting up the 2B2L antenna

The 2B2L can be erected on a pole about 16 feet (or about 5 meters) tall. It is fed at the bottom via coax to a transceiver. The 2B2L requires radials. I tried a set of 8 radials, each 7 feet (2 meters) long. That worked but 4 radials, each 13 feet long provided a better return path on 40 meters.

In keeping with recent practise here on Ham Radio Outside the Box, the radials are tuned with a GTU (Ground Tuning Unit). The GTU has to be separately adjusted for each of the two bands. This ensures that the antenna system is working as efficiently as possible – without a tuner! An antenna analyzer connected via a short coax showed an SWR well below 1.5 could be obtained on both bands.

Does it QSO?

No, it just sits there grinning at the sky, but I have QSO’d using the 2B2L. My best contact so far has been a 2000 kilometer QSO with a station in Colorado on 20 meters by QRP CW. 40 meters is most active in the early morning and in the evening when I am inactive, but I am going to have to make the effort to go 40 meter QSO hunting real soon. 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!

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.

A Simple Ladder Line Antenna for Portable Ops

For the last several weeks I have been experimenting with ideas for low impact field antennas that optimize stealth, rapid deployment and small footprint while maintaining efficiency. It’s a trade-off between size, portability and efficiency. The antenna that is very small, highly portable and very efficient hasn’t been invented yet – and never will be invented because it would defy the laws of physics.

Some hams may hold the belief that a short, base-loaded whip defies physics because (1) it can be tuned to 1:1 SWR, and (2) it can be used to make contacts. On the right day, under favorable propagation conditions even a wet noodle makes a “great antenna”. I have personally made contacts with a dummy load (across a room during a technical presentation). A 1:1 SWR ensures a transceiver won’t release the “magic smoke”; it does not make a poor antenna work any better.

Oh yes, I’m the great pretender …

The Platters (love those songs) could have been singing about ham radio tuners. Internal tuners, or any tuner located at the radio end of a feedline is a great pretender. It pretends the antenna is doing well when really its only job is to convert the impedance of the antenna, and feedline, into something that won’t vaporize those little 3-legged fuses that we like to call PA transistors in the transceiver.

For this reason I prefer to avoid using a “tuner” at the radio end of the feedline. A tuner has a role to play when using a multiband antenna (such as a random wire), but a monoband antenna can be adjusted to resonance (or close to resonance) thereby avoiding any need for an impedance transformation at the radio end of a short feedline. For example, a simple resonant whip mounted on a pole a couple of meters above ground, with two or more resonant radial wires does not require a tuner. But there’s a gotcha.

High wire act – danger, danger!

I was playing radio in a provincial park once when my wobbly whip attracted the attention of a patrolling park warden. Her job included preventing mad boffins with dubious aerial erections from endangering other park users. I was able to persuade her that my activities were unlikely to trigger the arrival of emergency services and all was well. That experience convinced me of the value of operating stealthily by staying under the radar of anybody who may look on my activities with suspicion. Lesson learned – low antennas equal low attention.

The Dancing Queen

I have told the tale of the dancing lady several times on Ham Radio Outside the Box. My unusual activity attracted her attraction and she approached to inquire what I was doing. When I advised her to be careful of the long radial wires on the ground she broke into an impromptu and erratic dance routine. Lesson learned – long radials are where angels fear to tread.

When the twilight is gone, and no songbirds are singing …

My wife and I have been putting out bird feeders in our back yard for quite some time. The feeders have attracted many different kinds of birds, prompting us to learn more about their behavior and habitat. One of the important things we learned is that trees are birds’ safe place. It is where they shelter and nest. Lesson learned – avoid invading their space by firing projectiles and dragging long wires through it.

Park wardens licking their pencils ready to write out an infraction ticket, dancing queens dodging wiggly wires, and fishing weights landing in bird nests … by all the ancient Norse gods, what’s a poor ham to do? Those were the design parameters I had to work with. Could it be done? Could I design antenna that will fit into those restrictions? The Devil was dangling a short base-loaded whip in front of my eyes but I banished him. No, that is not the solution!

So what is the solution?

There are inevitably many solutions to this puzzling conundrum and each may work in some fashion. One contender is something I have come up with and called a “Ladder Line Antenna”. Ladder Line (sometimes referred to as “Window Line”) is usually used as a feedline but it doesn’t have to be so. Ladder Line is simply two conductors separated by plastic with a series of rectangular holes. It resembles a ladder, or looked at differently, it could be seen as a series of windows.

Why use Ladder Line as the antenna’s radiator? Because, to reduce the overall height of the antenna by around 30% the antenna is linear-loaded. Linear loading is the technique of folding back the radiating element and can be achieved by shorting the two ladder line conductors at the top. The far end of the folded side of the radiator is left unconnected. The radiator is connected to the coax center conductor.

The overall length of the Ladder Line radiating element for my 20m band antenna is approximately eleven and a half feet (three and a half meters). It was trimmed while measuring its electrical length with an antenna analyzer.

Banishing the Dancing Queen

Understanding that long radials for this antenna are strictly verboten creates a bit of a problem. Usually, a set of ground mounted radial wires are employed with a vertical antenna and a tuner is used at the radio end of the feedline to match the impedance.

No matter how many radials are laid down they will not be resonant. And, the use of a tuner has been ruled to be equally verboten. But there is a solution and that is to use a GTU (Ground Tuning Unit) to increase the current in the radial system, making it appear resonant. To keep the Dancing Queen at bay I shortened the radial wire length to 7 feet (a little over 2 meters) and used eight radials. The radiating element has already been adjusted for resonance so now is the overall antenna resonant? Well not quite.

You can’t cheat physics. Eight short radials, even when “tuned” with a GTU are not resonant. My experiments with a square meter of Faraday cloth proved that principle. There remains a small reactive component to the antenna impedance as can be seen in this image of the antenna analyzer reading when connected by a very short length of coax.

The reactive component, in this case 5.43 ohms of capacitive reactance, could have been reduced further by careful adjustment of the GTU. Unfortunately, the GTU is difficult to adjust precisely and hand capacitance also affects the adjustment. Another challenge for brainy boffins to overcome. The impossible done at once, miracles take a little longer!

Is a linear loaded antenna efficient?

L.B. Cebik W4RNL(SK) published a series of articles on shortening HF dipoles. He established that dipoles remain quite efficient down to 10% of their full length. However, below 70% the complex impedance becomes increasingly difficult to match. My simple ladder line antenna is shortened to approximately 70% of its original length.

The real world test

Following several sessions out in my backyard, hunting POTA stations, I figured the antenna was ready for the real test. Could it work well enough for a QRP CW POTA activation?

I had two activations planned, each in separate locations. During the first activation, propagation conditions were a little difficult with a lot of signal fading (QSB). Stations would disappear into the noise then, seconds later, come back bending the needle on the signal strength meter. It took an hour to log 13 stations, but with the furthest being 1876 km away it showed the short, low profile antenna had good potential.

The second activation a few days later showed even better results.

Propagation conditions were better this time around and contacts were made in Arizona, nearly 3000 km away from my QTH on the Canadian shoreline of Lake Huron, Colorado (2200 km) and several others close to 2000 km. It was also interesting to note that some of the contacts made were less than 1000km away. This means the antenna is capable of radiating signals at a broad range of take-off angles.

Overall I am very pleased with this simple, low profile antenna. It can be supported on a very lightweight 13 ft high pole that mounts on a small stake in the ground in summer, or a compact tripod when the ground is frozen in winter. The eight 7 feet long radials take the longest to deploy and occupy a circular footprint of 14 feet. An alternative I am working on involves a single raised linear loaded radial to replace the ground radials. This will reduce the footprint to two dimensions and make the antenna suitable for deployment on a narrow trail. I am also working on a multi-band version of this antenna. More details to follow in a future post; 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!

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.

So I'm new to the world of #antennas and radio calibrations and from what I understand the #meshtastic ranges are supposed to run in the 915 megahertz range for the US, not 868. Though I also see 906MHz as the auto calculated range in the app, so is this just the floor for this antenna and it does support 915MHz?

TechTip#1 – a continuous loop of cordage

This is the first in an occasional series of short posts here on Ham Radio Outside the Box. The purpose of these TechTips is to share useful techniques I have learned over the years. I hope you will find them helpful.

TechTip#1 is an idea I picked up from a bushcraft video for creating a continuous loop of cordage. Of course, it is very easy to create a loop of cordage by simply tying the ends together with a knot. But that can be untidy and inconvenient, especially if the knot gets in the way of a neat join between two components of, for example, an antenna system.

How to use a continuous loop?

I use them a lot when erecting portable antennas. For example, if a cow hitch is formed at one end of the loop and a knot is tied at the end of a radial wire, the cow hitch can grip the wire end very securely – as long as tension is maintained in the loop. A second cow hitch can be formed at the other end of the loop to attach it to a tent stake. To release the wire simply pull out the tent stake, which relieves the tension and the wire is free.

Creating a continuous loop is surprisingly easy to do in just 3 simple steps.

STEP 1

Cut a length of thin cordage about 18 inches (46 cm) long. I use Atwood 1/16 inch (1.6 mm) Utility Rope, but any similar cordage, such as Bank Line, will do.

STEP 2

This is a very important step! Make sure both ends of the cordage are freshly cut, then melt the ends with a barbeque lighter, or similar. While the ends are still very hot press them gently together to form a bond. Be careful with this step because melted cordage can be quite painful if it gets on your hands. Being an amateur masochist I wait a couple of seconds then roll the join between two fingers to smooth the finished bond.

STEP 3

When the join has cooled – after just a few seconds – grab the loop either side of the join and pull like hell to test it. I was skeptical at first, but I can pull as hard as I like without breaking the bond. The Atwood cordage I use has a breaking strain of 110 lb (50 kg) and I suspect the join has the same strength.

If you have any similar amateur radio tips to share please send them to me via email, with photos if available and your tip will be featured here in a future Ham Radio Outside the Box TechTip.

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.

A road trip with the VP2E antenna … and wolves

My wife and I recently took a short early summer vacation in the Haliburton Highlands area of Ontario. The area is just south-west of Algonquin Park (Ontario’s first and by far the largest provincial park, most of which is accessible only by canoe with sometimes very long and challenging portages … and with a very large population of black bears and wolves).

I had hoped to be able to get a lot of radio time during the trip, but various obstacles, including a major solar storm, intervened to disrupt my plans. I did take one opportunity to put my mighty QMX QRP rig on the air, along with my full-wavelength, low apex, VP2E antenna built for 20m. Conditions were starting to deteriorate but I put a few CW QSOs in the log before shutting down the hilltop field station.

The QTH for the radio activity was a small park overlooking Haliburton Village. We had the park all to ourselves for most of our visit, which was a blessing since the VP2E occupies quite a large footprint. The propagation forecast did not look good because of an incoming Coronal Mass Ejection. A planned POTA activation the next day had to be canceled because the CME arrived and made QRP operation a little too challenging.

A learning opportunity

Even though poor propagation conditions limited actual time on the air, the activity did result in a couple of ideas for future radio road trips. First, I noticed I was getting better signal reports from stations thousands of kilometers away – generally to the west and south-west. Contacts along the upper eastern US seaboard were generally more difficult. This result suggests my signal may have had a lower take-off angle than modeling predicts. I have come up with a potential solution for this, thanks to the excellent website at portable-antennas.com. Details later in this post.

My wife and I stayed at a lakeside resort style hotel with more rules and restrictions than you could shake a stick at. Although ham radio was not mentioned specifically, I made the decision not to try to set up a 60ft long wire antenna in the limited space available between our room and the shore of picturesque Kashagawigamog Lake. Lesson learned: take an alternative compact antenna on the next road trip. That idea has stimulated a quest to find options for a low impact, discreet antenna that could be used in situations like this. Reader suggestions are welcome.

Who’s afraid of the big black wolf?

The bands may have been disappointing but our visit to the Haliburton Wolf Center certainly was not. A pack of five wolves is maintained inside a 7 acre enclosure. The wolves can be viewed through one-way glass to ensure they are not intimidated by the presence of humans. The wolves are not socialized and their environment is maintained as close to nature as possible. They are fed every 5-10 days with already dead animals such as beaver, tossed into their pen from a platform. Larger roadkill carcasses – such as moose – are lowered into the pen by crane.

It was very interesting to be able to view these magnificent animals from a safe location. I have camped in the backcountry of nearby Algonquin Park several times and (thankfully) never come into contact with any of the population of several hundred wolves. Algonquin Park is also home to several thousand black bears and, unfortunately, I did once experience a visit to my tiny lakeside campsite by a very large bear in the middle of the night.

Improvements to the VP2E antenna

My VP2E (Vertically Polarized 2-Element) antenna has given good service in many field operations, but over the years, fiddling with wire lengths to optimize SWR and changing the feed arrangement have resulted in a less than optimal configuration that needed correction. Fortunately the VP2E is very forgiving and despite my sometimes clumsy adjustments it just keeps on working.

Followers of this blog may remember I recently installed an air wound Common Mode Current Choke (CMCC) at the VP2E feedpoint. I used this choke during the Haliburton road trip. It worked fine business but it is a little too bulky when packing out for field operations. When we returned from the trip I decided to replace it with another new CMCC. This one is 15 bifilar turns on a FT82-43 toroidal core. It is so compact that it mounts directly on the inelegant feedpoint insulator. Kudos for innovation, brickbats for style!

Another advantage of the new compact CMCC: it gives 33dB common mode current attenuation across the whole 20m band.

What other VP2E improvements?

Why is it that antenna designers assume everybody wants to work DX? I know many operators enjoy DXing, collecting countries and communicating with hams in the land of far-far-away. I usually have a different objective. Most of my field operating time is spent participating in activities like POTA and SOTA.

When I take a look at a map of, for example, POTA activators in North America, a clear picture emerges. What do I see? The vast majority of the activity is in the eastern part of the United States, and mostly in the northeast. It is disappointing to see that POTA operators in Canada are a rare breed!

And where is most of the POTA activity to be found? On the 20m band. The distance between my QTH in southern Ontario and North Carolina is about 750 miles (1200 km). If Florida is included (I often make contacts there too) the distance extends to around 1250 miles (2000 km). A side note: I once drove my family from Toronto to St Petersburg in Florida for a vacation. RF might take a few microseconds to complete the journey, but it took a heck of a lot longer to get there by road. I never repeated that drive; that’s what airplanes are for!

Now, if I want to target the US northeast, it is not the smartest plan to use an antenna designed for DX. It might be a better idea to use the 40m band instead, but that’s not usually where the activity is to be found. So 20m it is, and my antenna needs to have a higher take-off angle to avoid sending my signal sailing right over the heads of operators in my target area. But … not too high a take-off angle that my signal enters the NVIS zone. The ionosphere will not cooperate by refracting 20m signals back to the planet’s surface, the way it does for the lower bands. Instead, high angle signals on the higher bands tend to become outer space explorers.

Here is where portable-antennas.com becomes very useful. The site includes a design feature for the VP2E antenna with which we can experiment with the various dimensions of the antenna and determine the effect on its performance.

I selected a very low apex height of just over 3 meters which nicely matches the height of one of my fiberglass support poles.

Looking at the elevation plot we can see the main lobe at a take-off angle of just over 50 degrees. The -3dB points include a useful component below 30 degrees, but part of the signal is poised to boldly go where where no man has gone before (although Spacex may change that before long). I specified a “good” ground type in my model because my home QTH is in between two huge lakes (Georgian Bay and Lake Huron) with plenty of surface water and high dissolved solids levels. As I travel to other areas where sandy soil or exposed bedrock are present, the antenna will inevitably behave differently. Hey, amateur radio is all about experimentation eh?

As the apex of the VP2E is lowered the model shows the antenna’s directionality improves. This could be a very useful feature. How many other simple wire antennas have the directional property of a beam antenna? Well, apart from the Grasswire (discussed several times in this blog) I can think of none.

I usually point my antennas at Texas and expect to cover the whole of CONUS. Now, while evaluating this new configuration of the VP2E, Washington D.C. may be a better target. I hope that last sentence won’t be misinterpreted by the security bots at the NSA!

The VP2E can be rotated very easily by simply picking up the wire ends and swinging them around. Maximum signal is radiated from “the long end” of the antenna (the VP2E is an off-center fed, full wave wire, so “the long end ” refers to the longest wire end away from the feedpoint).

Note: the VP2E with lower apex is an experiment. Experiments never fail; they only provide data for follow-on experiments with revised parameters. My 10ft pole has extensions for 13ft and 16ft that can be deployed if necessary.

What’s next John?

Now that summer is finally here (that brief period between snow storms here in Ontario) I will be spending more time in the great outdoors trying various antennas. That means Ham Radio Outside the Box will be publishing about every two weeks – unless there is something that needs to be urgently communicated to this blog’s burgeoning list of followers. In that vein, a sincere thank you to all the new followers who have signed up in recent weeks. I have some very interesting ideas to share over the coming weeks so please 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!

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.

I’ll be camping in West Virginia in EM97 this week. Going to try to work the #MagicBand with this “thrift store” ham stick dipole and a QMX+.

Is #WestVirginia rare in others’ logs? I hadn’t been able to get it in my last 1.5 years as a Technician.

#HolidayStyle #HamRadio #AmateurRadio #6m #6meters #EM97 #antennas #hamstick #MFJ #QRP

Another one for the radio geeks. Sure, the view across the river is beautiful, but there are antennas on the side.
#AmateurRadio #HamRadio #antennas

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”.

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!

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.

#hamchallenge week 3: Understand how your antenna works. 🧵

Let's check out the lowband vertical antenna I built before #CQWW in November. It is 16.5m long, built with an 18m Spiderbeam mast minus the top element. About 18m of wire are coiled up on it (for stability), and it is tuned at the feed point with a CG3000 automatic tuner. There are 12 ground radials with an average length of 10m below it. When I built it and laid out the radials, I noticed that the feed point impedance stayed at about 37 Ohm at the resonant frequency of ~ 4.1 MHz any more after 12 radials, so I left it like that. HC03 @hamchallenge #hamradio #antennas

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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).

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.

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

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

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)

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

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

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!

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 #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!

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

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

Shark’s Teeth and Canadian Jam – a tall story

I recently purchased a Spiderbeam mast from a vendor in the United States. The list price was US$78 – a great price for a high quality product. But the story didn’t end there – not by a long shot. The cost for shipping via courier was an additional US$44. I expected there would be more to pay once the product crossed the border into Canada and that expectation couldn’t be more true. There was plenty more to pay! I received an email from the courier telling me I owed them a further CDN$90 and that to expedite delivery would I like to send them the loot in advance. I paid the ransom and received another email saying thanks for the cash, now your delivery is going to be delayed by three days!

I began to feel that I was being treated like a sucker; I was charged brokerage fees, handling fees, processing fees and, of course, taxes owed to the Canadian government. Then along came the credit card bill from the bank advising me of their extortionate exchange rate to convert US dollars into Canadian dollars. In the end my US$78 mast cost well over CDN$250! I am going to take very good care of this most precious piece of ham radio gear.

What did I buy with that small fortune?

I chose the Spiderbeam 7m (23ft) mast, primarily because it collapses down to a very manageable 28 inches and, although heavier than most, is still light enough to backpack into a field operating location. Is 7m tall enough? Well I thought about that for a while and decided it would be quite sufficient for my needs. Spiderbeam masts are built from heavier gauge fiberglass tubing than other similar products. Many telescoping fiberglass poles – especially those intended for fishing – are very flexible. When deployed for ham radio purposes they tend to bend which reduces their effective height. Spiderbeam masts remain fairly straight – a 7m mast supports a wire at 7m; it doesn’t bow down under the weight of the wire.

Crash prevention

Many years ago I invested in an MFJ 31ft telescoping fiberglass pole. One day, while testing an antenna in my yard, a gust of wind blew the mast over. It crashed against the wall of my house destroying several sections near the top of the mast. Fortunately I was able to restore it to a shortened length of 29ft by replacing the broken sections with those scavenged from a Crappie fishing pole. It has served me well since but it is heavy and collapses to a length of around four feet.

My new Spiderbeam mast is going to be very well protected – it cost far too much to replace if it became damaged. So here is a short account of what I have done to protect it during transit and while in use out in the Big Blue Sky Shack.

First, in transit, I pack it inside a length of 2-inch (50mm) PVC plumbing pipe. That all goes inside an expanding document tube which, in turn, goes inside a carry bag previously used for a camping chair. The bag is also used for packing tent pegs and guy lines.

What is the plumbing pipe for?

Well I guess I could just set the Spiderbeam mast down on the ground and guy it in place. However, by slipping it inside the plumbing pipe it can be easily removed for adjusting the antenna wire when needed.

Shark’s teeth?

Experience has taught that tall masts have a tendency to slip at the bottom. It is simple physics; 23 feet of mast supported 2 feet from the base provides enough leverage to topple the mast in windy conditions, or when a long wire under tension is attached at the top.

In the past I have dug a small divot to hold the base in place – effective but with a tendency to generate disapproval from park wardens. Now, to protect my precious Spiderbeam from catastrophic collapse I cut a set of “shark’s teeth” at the base of the support tube. It works and, if I ever encounter a growling bear on the trail, I can show it my shark’s teeth to intimidate it into retreat.

The top of the support tube has a small section of enhanced diameter created by slipping several strong rubber bands covered in electrical tape. It’s purpose is to prevent the guy lines from slipping – simple and effective. The guy lines made from 550 paracord are secured using Canadian Jam knots. I have no idea why Canada is credited with this particular style of knot, but it is a very secure way of tightening a guy line around the support tube. Canadian Jam knots are also very easy to release when it is time to pack up the station.

At the other end of the guy line I use modified taut line hitches to create an adjustable loop around lightweight “aircraft grade” aluminum tent pegs. The modified taut line hitch involves a couple of extra wraps of cord to make it more secure. I have found standard taut line hitches tend to loosen a little when tied on paracord.

Finally, at the top of the pole, I attached a small loop of very thin, but strong, cord. I took a few inches of cord, formed a loop and tied a simple knot at the end. The knot was fat enough to fit tightly in the top, hollow section of the Spiderbeam mast. It was secured with hot melt glue and is very secure. I don’t think it could be dislodged even if I wanted to remove it.

The loop can be wrapped around an antenna wire, then slipped over the top of the mast as seen in the picture. To remove the wire I simply lift the wire above the top section of mast to release it quickly and easily.

So far, all is well. The small fortune I have invested from my meager retirement savings into this excellent Spiderbeam mast is going to be very well protected!

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 #Portable #Spiderbeam

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