#qmx — Public Fediverse posts

There is a “small” problem with the QRP Labs QMX transceiver – and an easy fix

Why was it born so beautiful, why was it born so small?

I have to admit to a love/hate relationship with my microscopic, yet bursting with features, QMX transceiver. This marvel of technology is densely packed into a shirt pocket-sized sturdy aluminum case. Just how did the R&D department at Turkey’s QRP Labs manage to squeeze so much into so little? And the big question is why?

Way over yonder where Europe joins Asia lies a radio electronics laboratory in which the entire research and development department goes by the name Hans. My imagination conjures up a picture of something akin to Santa’s toy factory at the North Pole (where, incidentally, there is no land – just constantly shifting sea ice; sorry kids).

And why did I buy this marvelous, lilliputian, bite-sized box of electronic Turkish delight? I guess it was the cute factor – the same reason I bought my Yaesu FT-817 back when it was first released. I have thought about selling that FT-817 many times but that cute puppy dog front panel keeps looking up at me and I change my mind every time. My QMX is cute in a different way in that it’s very small size was the “flash the cash” factor that put my name at the bottom of a very long wait list. After a long 6-month delay I received my micro miracle and haven’t stopped using it ever since.

He’ll be coming up the mountain when he comes

I don’t need to haul my radios up mountains. The nearest mountain to where I live – naively called “Kemble Mountain” – is just a local high point along the Niagara Escarpment. I could ride a bicycle up it’s south face in five minutes. So, no mountains, no need for ultra-light radio equipment. I can carry my outdoor portable wireless sets in a backpack when operating on a trail. So once again: why did I buy a sub-miniature radio? Oh yes, it’s cute; like a little puppy. Now I have my QMX, I really like the little thing so it’s definitely a keeper.

But I like BIG radios

Let’s look at it this way: the QMX is BIG on features, now all I gotta do is fix its physical size. I think I have a solution – strap it to a brick; well actually a Lithium Iron Phosphate brick.

I have rebuilt my QMX-based portable wireless communication set so many times and yet here I go again. As you can see from the picture above, the “brick” is an Eco Worthy 8 Ah Lithium Iron Phosphate battery. Its main function is to anchor the QMX to the surface of the planet – a task it performs admirably well. Oh, yes, it also powers the QMX.

What??? An 8 Ah battery could supply power to half a dozen QMX radios! Yes, but I refer you to its primary function. In fact the high capacity battery is very useful when I venture forth on a multi-day radio road trip. I charge the battery at home with a Sky Toppower PS3010H constant current, constant voltage bench power supply (available on Amazon).

Charging details: I programmed the PS3010H to charge the battery at a constant current of 1.0 amp up to a terminal voltage of 14.2 volts and then to automagically switch to constant voltage until the charging current drops to zero. The battery is then good for several days of operating.

By the way, all those R&D boffins, collectively known as Hans, fixed one of the most annoying features of the early QMX models, and that was the need to keep the supply voltage closely regulated to 12.00000000 volts. This was achieved by using series diodes in the supply line, or a buck converter. I chose the latter, and I have kept “Buck” in circuit despite the clever firmware fix that eliminated the need. I’m the kinda guy who wears a belt and suspenders to keep his pants up. Or maybe just think of it as a backup or redundancy system. If a future firmware release breaks the fix I won’t have to watch as the QMX’s delicate BS170 final transistors make a smoky ascent to the heavens.

And while I’m up on my soapbox …

The dastardly diminutive dimensions of the QMX are not my only gripe. Small size dictates small connections to the outside world. Ok, I have griped about this before, but I don’t like tiny connectors – those one-eighth of an inch (3.5 mm) jacks for hooking up earphones and paddle keys are a failure point waiting to happen – especially when subjected to the rigors of operating in the field. But, there is an easy solution; simply keep all accessories plugged in and there should not be a problem. Take a look at the picture below.

There is another benefit of this everything-connected-ready-to-go solution: it is literally ready to go. My QMX-on-a-brick kit is transported inside a rugged, waterproof European military respirator bag. I don’t even need to remove the rig from the bag to operate, simply hook up an antenna and start firing RF up to the Heaviside layer. No need to stop for several days, the battery is good for it.

There is something else I should mention …

If the QMX hadn’t been designed to be quite so small there is one other missed opportunity that could have been considered. When ordering a QMX transceiver there is a band selection decision to be made. I chose the low band version and that gives me 80m, 60m, 40m, 30m and 20m. Sometimes I wish I had chosen a version supporting the higher bands. Now imagine, if the original design had placed all the band specific components on a separate circuit board, we could possibly have popped open the case and switched circuit boards to gain access to more bands.

So, paraphrasing a song popular in some parts of the world, I ask again: “why was it born so beautiful, why was it born so small?”

Footnote:

It is easy to gripe but, in all seriousness, QRP-Labs founder and head honcho, Hans Summers has produced so many wonderful products for ham radio enthusiasts – and at very affordable prices too. As a well known British knight of the realm, who gathers no moss, once wrote: “You can’t always get what you want, but if you try sometime you find you get what you need”.

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.

#QMX and #QMX+ lovers, have a look at https://qmx.nu

#HamRadio #OpenSource

Dismal morning on the #AmateurRadio #HamRadio #HFbands with #WSJTx but did make #Winlink #rms connection with @qrplabs #QMX

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.

Whoo boy, the new QST rips the #QMX+ on its six meter performance and says it “should not be used to transmit anywhere on that band” because of its spurious emissions. That’s not even all they complained about.

That will put a wet blanket on your magic July propagation. I may have to fire up groups.io to see the response.

#QRPLabs #6m #6meters #AmateurRadio #HamRadio #ARRL #QST

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.

#QRP Power Supply: 12.0V / 9.0V LDO Regulator (V2): A discrete Very Low Dropout (VLDO) linear regulator for QRP radios such as the QRP Labs #QMX, designed for clean power, strict voltage control, and low RF noise.
https://github.com/radio-uncensored/qrp-vldo-regulator

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.

All set for a field day, the aim is to test a home-brewed vertical coil (have an EFHW as backup) with the QMX and zbitx v1, test-driving a Gigaparts POTA20 mast, and the portable ESP32 powered HAM Clock I’ve been working on with the local club. In case, all goes well, might attempt a POTA.

#fieldoperations #qrp #qmx #zbitx #amateurradio #hamradio #pota #esp

Erstes CW „QSO“ als DL9ET/MM \o/ #qmx

Martinique and Portugal in the 10 meter log today, from North Carolina. Loving having my QMX+ back in the shack.

#QMX #10m #FM05 #FT8 #EFHW

Since my #QMX broke and wsjt-x doesnt support specific #WSPR timeslots Iv build my own “TX daemon" for this. It runs in the terminal and uses the #TCI protocol.

https://github.com/tompatulpan/wspr-tci

#HamRadio #Opensource

I am very happy about my first successful #qrp #pota activation (AU-1411 - D’Aguilar National Park) today with the #qmx radio. I must have wound all the toroids correctly and put everything together the right way (phew). Amazing what this little thing can do. K6ARK's mic design worked a treat and VK4KC's Mutt 56:1 EFHW performed very well, as always. Thanks for all the contacts! #hamradio

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.

Yay, it worked first time! #QRPLabs #QMX #QRP #HamRadio #AmateurRadio #AmateurFunk

Made a start on my #QRPLabs #QMX #AmateurRadio Transceiver today. Glad I have an #Optivisor, as it’s very compact! #QRP #HamRadio #AmateurFunk

#SSB on the #QRPLabs #QMX+ 5W HF transceiver is just so unnecessarily painful. The built-in microphone doesn't work. Standard microphones don't work.

The very specific microphone capsule required goes for 21 € inc. shipping from Digikey. A finished microphone assembly by G7UFO is 41,85 € inc. shipping. The whole QMX+ kit is only 125 USD, on comparison.

I have revision 4 of the PCB. Really would have expected it to have been fixed to take any microphone by now, or come with the microphone.

Je suis très content que mon couvercle du transceiver QMX fasse son bout de chemin sur internet.
Je l'avais mis en 2024 en Creative Commons - Attribution - Non-Commercial license.
Et franchement c'est vraiment super cool de voir le projet évoluer et s'améliorer au fur et à mesure des partages vidéos sur YouTube tout autour du monde.
QMX cover and desk stand for hamradio POTA SOTA by F4EGX
https://www.thingiverse.com/thing:6599009
#hamradio #QMX labs #qrp

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

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

And it’s true

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

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

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

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

Back to the future

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

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

Filters can get you into trouble

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

Tis a gift to be simple

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

It get’s worse

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

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

Big eyes, small wallet

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

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

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

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

Help support HamRadioOutsidetheBox

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

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

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

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

Low pass filters wound and soldered. Getting there… #QMX #kitbuild #hamradio

@geobomatic @NuclearSquid Plutôt que de faire un clavier à 4 rangées qui serait trop proche des classiques existants, je pousse l’idée de faire un clavier ultra-simple :
– quasiment ortholinéaire
– TOUTES les touches alphanumériques ISO en accès direct (donc 7 colonnes sous la main droite)
– un seul layer pour les flèches, le pavé numérique, les touches F1‑12, etc.
– monobloc splittable

… bref, un successeur au #TypeMatrix, polyvalent gaming et dactylographie.

3/3

#QuackMatrix #QMx

On est vraiment désolé pour ce retard, et on espère qu’il ne vous impactera pas trop.

Si on avait fait ça professionnellement, ça aurait été bouclé fin décembre plutôt que mi-janvier. Mais voilà, nous sommes des amateurs qui bossons bénévolement sur notre temps libre, et notre électronicien (@NuclearSquid) avait bêtement des partiels à réviser et à valider… On a donc fait le choix de lui foutre la paix, et d’attendre la fin de ses examens pour l’embêter. Il a consacré un temps complètement fou sur le projet (sans parler d’#Ergol !), et on fait en sorte qu’il ne parte pas en burn-out.

Les protos nécessaires à la mise au point ont un coût, mais la générosité des Ergonautes qui ont passé commande nous permet de l’absorber. Le plus important à nos yeux, c’est qu’on ait une base électronique solide, non seulement pour ce #QuackenFlex en cours, mais aussi pour le projet #QuackMatrix / #QMx qui est dans nos cartons.

KD5ZZU’s very elegant build of “Old Barebones” – a Z-match tuner

Back in October 2024 I wrote a post with the title “Old Barebones” – A QRP Z-match Builder Project. The project’s purpose was to construct a simplified version of the Norcal Z-match tuner (which I also owned) to use with my QRP Labs QMX transceiver. The Norcal tuner included some features that I simply did not need – such as balanced transmission line terminals, a simple LED SWR indicator and three switches (Balanced line/BNC, Tune/Operate, High/Low impedance). The schematic was copied from the Norcal tuner – a superb design that I didn’t think I could improve. The end result was a very simple device with three BNC connectors, a toroidal inductor and two polyvaricons, all packaged in a small Amazonian plastic enclosure. Alright, it is an ugly device mainly due to the inelegant knobs I chose to use. But it works very well indeed and has become my main QRP portable antenna matching unit. Heck, it cost me a big fat nothing to build thanks to my extensive junque box stocked from years spent hoarding miscellaneous bits and pieces. When I have finished twiddling the knobs I can always put my hat over it to hide its lack of elegance.

Then, out of the blue, I received an email from Mallory KD5ZZU who expressed an interest in building her own version of “Old Barebones”. Mallory queried whether the design would work on the high bands. I had only tested mine on 20m, 30m and 40m, so I hooked it up to my home 80m EFHW and my portable 13ft tripod vertical antennas to test whether a low SWR could be achieved with Old Barebones on 17m, 15m 12m and 10m. Fortunately Old Barebones did a splendid job on both antennas so Mallory took the plunge and built her own version.

Note: My 80m EFHW (End-Fed Half Wave) is used primarily on 80m but is also useful on 40m and 20m. Using a tuner to obtain a low SWR on the higher bands protects the radio from high SWR but does not imply that the antenna is useful on those bands.

Mallory experienced a hitch in the construction though. Her first build did not function as expected and she asked for ideas on what to look for to resolve the problem. It turned out to be the connections to the polyvaricons that were the problem. Polyvaricons often have several sets of vanes and multiple connection points. I had used a capacitance meter to identify the correct connections in my original build. Realizing this may be the problem, Mallory quickly identified the correct connections and got her tuner working. She wrote that she was able to achieve a nice low SWR on all bands from 20m to 10m with her 71ft EFRW and 9:1 unun. A great result.

But Mallory doesn’t need to cover her version of Old Barebones with a hat to disguise its appearance. It is a beautiful design built into a custom 3D printed case with 3D printed knobs and looks terrific.

If anyone else is interested in building this simple construction project Mallory has kindly provided links to an online source for the parts and the 3D print files:

• Polyvaricons: https://a.co/d/hOYgP2f
• Toroids: https://a.co/d/7mItRXw
• Magnet wire: https://a.co/d/ffqdHo9
• BNC posts: https://a.co/d/5mwLEVI

Here is a link to the 3D print design of the knobs:  https://www.thingiverse.com/thing:3035549/files

Here is a link to the file to 3D print; it’s a print profile (modification) from the original designer of a customizable enclosure box: https://makerworld.com/en/models/2002942-custom-enclosure-box#profileId-2400746

A note on the use of Old Barebones

I designed Old Barebones for use with my QRP Labs QMX transceiver which has a convenient “Tune SWR” feature that reduces the output power to 25% to reduce the stress of high SWR on its delicate finals during the tuning process. I have also used Old Barebones with my Yaesu FT-817 but I manually reduce the power to 1 watt or less during tuning. If using Old Barebones with any radio that does not have an SWR indicator I recommend incorporating an SWR indicator in the tuner circuit similar to the original Norcal BLT design.

Polyvaricons?

The word “polyvaricon” is presumably a contraction of “Polymer Variable Condenser” meaning a plastic enclosed variable capacitor using a plastic dielectric. It is believed to be the trademark of a Japanese company that manufactures these devices. But shouldn’t it be called a “polyvaricap”. I remember back in the dawn of my existence that capacitors were called “condensors” but that term disappeared a long time ago. Strange old world.

What is a Z-match?

“Antenna tuners” are often named after their topology. For example, an L-match comprises a series inductor or capacitor and a complementary parallel capacitor or inductor. The combination of inductor and capacitor forms an “L” shape. However, there is no immediately apparent “Z” shape to the components in a Z-match, so I presume the “Z” refers to impedance. Let me know in the comments if I am wrong.

Pros and Cons of the Z-match

From the GQRP organization in the UK:

Advantages of the Z-Match

• Matches balanced loads without the use of lossy baluns.
• Being a parallel resonant circuit, the Z-match can provide some band-pass filtering for your receiver and harmonic attenuation for your transmitter.
• A well-designed Z-match tuner has a high Q and is more efficient (less lossy) than other types of tuners.
• The fixed inductor simplifies construction (no switches or rollers needed).

Disadvantages of the Z-Match

• Tuning is usually very narrow and can be a bit touchy sometimes to tune up

Thanks again to Mallory KD5ZZU for sharing her build with Ham Radio Outside the Box and congratulations Mallory for turning my original inelegant build into something with class!

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 #OldBarebonesZMatch #QMX

The ultimate rebuild of an ancient Yaesu FT-817.

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

What’s a poor Ham to do?

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

The Paranoid Android

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

Where are the features?

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

Failure is not an option

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

I get by with a little help from my friends

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

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

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

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

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

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

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

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

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

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