Testing and modifying the “POTA PERformer” antenna

What is the POTA PERformer? Greg Mihran KJ6ER has introduced us to an antenna that he calls the “POTA PERformer”. The capitalized PER in its name is an abbreviation for “Portable, Elevated, Resonant”. But what is it really? The POTA PERformer is an adjustable elevated vertical radiating whip with two adjustable elevated radials. In concept there is nothing really new about it, but the unique implementation devised by KJ6ER is quite interesting.

Get up off the ground

Most hams will be aware that a quarter wave vertical antenna, mounted on the ground, requires an extensive system of radials to be efficient. I have successfully used such an arrangement with as little as four radials during a POTA activation out in the Big Blue Sky Shack. But, as they say, even a poor antenna will get you contacts when conditions are right. Some recommend as many as 120 radials although anything over 16 provides very little further improvement. In a portable situation laying out a lot of radials for a short-term temporary station doesn’t make a lot of sense. So what is the alternative?

Less is more

If the base of the antenna is raised above the ground, fewer radials are needed to form an effective counterpoise and make the antenna efficient. How many? KJ6ER has settled on two radials for the POTA PERformer. If the radials are arranged at 90 degrees to each other the antenna has a directional radiating pattern. But using two radials increases the footprint on the ground and that could be an important consideration if, for example, we are operating on a narrow trail. Could we get away with just one radial? I modeled a POTA PERformer using EZNEC and came up with a comparison, shown in the following table.

TABLE: 1 radial versus 2 radials

Now I’ll admit that I am no expert in computer modeling, but the results I obtained seem to differ from what KJ6ER found. In either case, whether two radials or just a single radial are used, we have a directional antenna that can be rapidly deployed in the field.

One radial or two? Now here’s a surprise!

The original POTA PERformer is a multiband antenna. It covers all the bands from 20m up to 6m with a 17ft telescopic stainless steel whip and adjustable length radials. KJ6ER suggests extending the band coverage to 30m and 40m by means of a loading coil at the base of the whip and then … surprise … combining the two radials to create one long radial wire. I suspect the 30m/40m version may lack some of the gain and efficiency of the higher band version due to the losses involved in base loading a vertical radiator. Perhaps a full length vertical wire supported by a pole, or a tree, might be better.

I have always felt there is something incongruous about using a counterpoise that is longer than the radiator. Perhaps that concern is unfounded if we consider that a raised radial wire also radiates.

Customizing the original clever idea

I have tried the POTA PERformer with both a single radial and two radials. Both versions “worked” and I made contacts. It is difficult to interpret which was better, but my own preference – for field expediency – is a single radial. The 20m, 30m and 40m bands are my preferred haunts, only for the reason that two of my QRP radios do not support the higher bands. Even though the POTA PERformer is a great idea with very positive reports from several sources on YouTube and elsewhere, it doesn’t fit well with how I like to operate. Here is why.

Please remain seated

A raised radial wire is a tuned counterpoise. Its length is important. That means band changes involve adjusting the length of the radial(s). One way of doing this is to insert a non-conducting link in the wire and move it between linked sections to set the conducting part of the counterpoise to the correct length for the band of operation. The overall length remains the same but the sections of the wire not being used are isolated from the rest of the antenna. Another way that I have tried is to use a metal measuring tape and unwind it to the correct length. Perhaps using multiple raised radials where each wire is adjusted for a different band would also work. Whatever method is used, getting out of your chair and fiddling with radials and whip lengths is a time consuming distraction. So what’s the alternative; how can you stay in your seat and change bands?

Get on the ground and spread ’em!

Sacrificing a little efficiency is required but it can be done. My own method is to spread out four radials wires in a fan pattern on the ground, facing the direction I want my signal to go. Are four ground radials enough? If the vertical element is ground-mounted then using only four radials results in efficiency loss. But, if the whip is elevated? Who knows, but it works.

Since ground radials are detuned their length is not critical. No adjustment is required whether operating on 20m, 30m or 40m. The only requirement is that there is sufficient copper on the ground to provide a good counterpoise; I use 4x13ft radials. Orienting all the radials in one particular direction does improve the signal in that direction to a small extent. How much efficiency is lost? That is very hard to quantify but the convenience factor is high.

A 17ft whip with an adjustable loading coil (bypassed for 20m) will cover all three of the bands that I need. I have also used a 9ft “tactical” whip whose fixed length sections are held together with bungee cord. This shorter whip uses a separate loading coil for each band and is usually only employed with my QROp rig (a 100 watt radio that is usually set to 20 watts or less). This radio gives the ability to transmit a little more power when needed.

“QRP when possible, QROp when needed” – Ham Radio Outside the Box

Is there any real difference between 5 watts and 20 watts? Maybe not but it does give me a nice warm feeling – especially if I get too close to the antenna while keying up.

To better understand and learn more about the POTA PERformer it is worthwhile downloading and reading Greg KJ6ER’s PDF document. It may inspire you to build one or even devise your own variant to suit your unique operating needs.

Note to Fediverse readers: the formatting of this post may be presented better on the original WordPress site. Visit: https://hamradiooutsidethebox.ca/2025/05/27/testing-the-pota-performer-antenna/

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Reviving a Webster Band Spanner – a 1950s manual screwdriver antenna

About 20 years ago I was approached by a neighbor who, knowing that I am a ham, asked if I might be interested in looking at some of the old ham junque he had accumulated over many years. He was a fine gentleman, in his golden years, who was no longer active in the hobby. Hesitating for less than a microsecond I eagerly agreed. Among the treasures I acquired was a Signal Electric straight key. I believe it was an R48 model first introduced in 1920 when it sold for $2.80. But my prized acquisition was a Webster Band Spanner antenna.

The Band Spanner was produced in the 1950s and 1960s by the Webster company in San Francisco. It is a center-loaded manual screwdriver antenna intended for mobile operation. Unlike modern screwdriver antennas, like the popular Tarheels, that use an electric motor to make band changes, the Band Spanner has to be manually adjusted for each band by sliding the whip up and down.

Two models were produced; the A-61 and the A-62. The A-61 (that I acquired) has an extended length of 93 inches and a collapsed length of 60 inches. The longer A-62 model has an extended length of 117 inches and a collapsed length of 63 inches. Both models support the 75-40-20-15 and 10 meter bands. There is a mark on the whip indicating the mid-point of each band. I suspect the WARC bands could also be tuned although it would be necessary to locate the correct whip length by trial and error. The antenna is rated for “100 watts or more”.

The Band Spanner is constructed from a fiberglass support column with a 24-inch long internal loading coil. At the base of the whip is a circular contactor that connects with the windings of the loading coil. As the whip is raised or lowered, the contactor connects to individual exposed turns of the loading coil inside the support column. This type of continuous adjustment permits exact resonance to be achieved anywhere within a band. It is a very high Q antenna – moving the whip just one click up or down (one turn of the loading coil) makes a significant difference to the tuning.

Would the vibration of a vehicle change the tuning?

You might expect that a bumper-mounted antenna would be subjected to a lot of stress as a vehicle crashed through pot-holes and other rough ground, but there is a very tight connection between the whip and the loading coil. The connection is so tight that it requires some force to adjust the whip length and it is quite possible to skip a turn if too much force is used. The tight connection has a another positive benefit – it makes the connection point self-cleaning. There is also a locking thumb screw at the base of the whip to help secure it in place.

Stationary mobile operation

I am not a mobile HF operator; there are enough distractions already to compromise driving safety, so I prefer to use the Band Spanner as a stationary mobile antenna. For those who do intend to use it as a mobile antenna, there is the H-200 ball mount (shown in picture).

I have tried several ways of mounting the Band Spanner as a temporarily fixed position portable antenna. The manufacturer suggests using a matching section of 21 feet of RG-8/U coax and grounding the shield of the coax to the vehicle body. I did once try using such a matching section with a Band Spanner on a tripod, but it didn’t seem to improve the tuning at all. Most recently I attached my Band Spanner to my “QROp” (5-100 watts) radio set. It is a Yaesu FT-891 mounted inside a mil surplus 50-cal ammo box. The Band Spanner was connected directly to the rear of the rugged steel case. My ham-made L-match tuner was used for fine adjustment of the SWR.

Tuning was fairly easy. I set the radio to 20m and 5 watts power output. I threw a 17ft wire counterpoise on the ground behind the radio. A single wire counterpoise is not really sufficient ground for this antenna so additional inductance had to be added via the L-match. I would usually lay out at least 4 radials for a portable vertical antenna, but I was on a mission. I wanted to find out if the Band Spanner could be employed as the radiating element of a “POTA PERformer” type of antenna. Ham Radio Outside the Box will be exploring the “POTA PERformer” in more detail in an upcoming post. For now we can describe it as simply a raised quarter wave whip with raised tuned radials.

Now comes the surprise

Having tuned the antenna with one ground radial to less than 1.5:1 SWR I thought I was on a roll. Next step, I raised the radial so that it would not be detuned by contact with the ground. I now had the Band Spanner set for the 20m band, finely adjusted by means of the L-match to give a good SWR. I expected some further adjustment might be necessary with a raised 17ft counterpoise, so imagine my dismay when the radio flashed its “high SWR” warning.

The Band Spanner is intended to be used while mounted to a couple of tons of steel vehicle serving as its counterpoise. It is a very short, loaded vertical antenna with very high Q performance. A lesson I learned early in my ham career, but overlooked in this exercise, was that a short-loaded, high Q vertical whip requires a carefully tuned counterpoise – or a good ground. Simply using a raised 17ft wire isn’t good enough. I would have had to precisely trim the raised radial wire to get a good SWR. To make this even more complicated, a precisely trimmed radial wire counterpoise for each band would be required. So the mission objective to examine the Band Spanner’s suitability as a portable POTA PERformer was concluded. In future, the Band Spanner will be used with the best ground system I can erect during a temporary field installation.

Another thought …

A Band Spanner (or even better – a motorized screwdriver antenna) could possibly be used in an HOA situation. If it were ground mounted, with a good system of buried radials, it could potentially be disguised to prevent detection by the HOA hounds.

And finally …

I am not sure of the actual age of my Webster Band Spanner. They were produced in the 1950s and 1960s so I estimate it to be at least 60 and maybe as much as 75 years-old. The bumper mount has entirely lost its plating and is now a dull rust color. The fiberglass support column is equally dull and has lost its identifying markings. But, the antenna still functions as the Webster company intended all those years ago, which is more than can be said for its owner who is of the same vintage!

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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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Matching an EFHW antenna – a third way

There is no doubt about the popularity of the End-Fed Half-Wave antenna. It is used by a very large number of hams, especially during portable operations like POTA, SOTA, WWFF etc. Why is it so popular? The principal reason seems to be ease of deployment. The EFHW requires only a single support and can even be used without any kind of transmission line – i.e. it can be directly connected to a radio without any coax, so zero transmission line losses!

But despite those advantages the EFHW has its critics. There are two principle objections: first the commonly used 49:1 impedance transformer, or UNUN if you prefer, is claimed to be inefficient.

Secondly, the antenna wire is only a half wavelength long on its design band. Although it can be used on its even harmonics the antenna becomes multiple half-wavelengths long. Of course, we know that the impedance of the wire is theoretically replicated every half-wavelength so that shouldn’t be a problem.

It is even possible to get a 1:1 SWR match on other bands by pressing “the magic (Tune) button”. That doesn’t make the antenna any better but it does convince the transceiver that it shouldn’t roll back the power, or even worse, throw an exothermic hissy fit.

The disadvantage of using an EFHW as a broadband antenna is that the radiation pattern may change with each band. It may even break up into multiple lobes, making getting contacts a hit-and-miss affair.

If you are standing on the top of a wind swept mountain with a storm approaching and you need to get your 4 contacts to qualify a SOTA activation, you may not be entirely engrossed in the finer points of antenna physics. I have been an EFHW user for many years and have thousands of QSOs in the log. For a long time I was blissfully unaware of what a terrible antenna I was using while I battled countless pile-ups and enjoyed the thrill of operating my radio out in the Big Blue Sky Shack.

Those were the days my friend

As I read more and more about the theory of the End-Fed Half-Wave antenna I would deploy mine and agonize about efficiency and radiation patterns while reminiscing about the days when ignorance was bliss and I just enjoyed my hobby.

Keep It Sweet and Simple – Use a dipole

Critics often argue that a simple dipole is a good replacement for the EFHW. After all, both antennas are a half wavelength long; the main difference is where they are fed. A center fed dipole has a nominal impedance of 70 ohms, not 50 ohms, so still not perfect. It is usually erected as a “flat-top” which requires three supports. No problem in a quiet corner of the forest where nature benevolently provides ample leafy poles, but in a public park where zealous guardians of arboreal sanctuary patrol the greenwoods you may indeed have a problem.

A dipole can be erected in other ways, for example as a sloper. Now only one support is required but another tiny problemette arises – the feedline has to be kept at 90 degrees to the radiating wire. In either deployment fashion a long feedline is required. Let’s say we are operating a flat-top dipole on 20m. The antenna should be a half wavelength above ground so we need three 33ft/10m supports and 33ft/10m of coax feedline. The center support pole could be omitted but the weight of 33ft of coax plus a 1:1 UNUN at the feedpoint will drag the feedpoint down.

The long and winding (coaxial) road

Unless the operator is sitting right beneath the feedpoint, even more coax is needed to reach the radio. Two issues here, the coax will incur some loss although it is often too small to be significant. Secondly, the SWR will be changed by the coax loss – perhaps for the better, but it may create the illusion of a better SWR than is actually occurring up on the antenna wire.

Don’t leave home without it

You could connect the dipole feedpoint directly to the radio and operate the antenna in a “V” orientation. I did do exactly that during an emergency (I had inadvertently left my antenna at home) and successfully completed a POTA activation using a spare piece of wire. It must be realized that the feedpoint in such an arrangement is a high current point, and hence a point of maximum power radiation. Some of the radiated energy will be cooking the earthworms – and the operator!

So back to the “horribly inefficient, avoid-at-all-costs, snake oil” End-Fed Half-Wave antenna. How can we overcome the problems exaggerated by its naysayers? First, make it a single band at a time antenna. What do I mean by that? Use a separate wire for each band? There is a very simple way to do that. I designed and built a 3-band EFHW for 20m, 30m and 40m. I started with a half wavelength of wire on the 20m band but added a 2mm banana connector at the end. I then attached an extension wire to make the the antenna a half wavelength on the 30m band – again with a 2mm banana connector at the end. Then another extension for the 40m band. Each section of wire is attached with a short piece of thin cord to allow the links to be adjusted for each band.

And now for something completely different

Now for the biggest objection to the EFHW – the matching device. Ham Radio Outside the Box has already discussed two different matching devices, the 49:1 impedance transformer and the L-network. Now we have a third competitor in the race to perfection – the tuned tank circuit. I have to credit two sources for the inspiration to try this method: Steve AA5TB and John M0UKD. Both these gentlemen have built what is essentially a parallel tuned circuit to match the very high impedance at the feedpoint of an End-Fed Half-Wave wire to the 50 ohms expected by a transceiver.

Being an avid experimenter by nature I had to build one myself to see if it would work. I get the most enjoyment out of projects that go from adrenalin inspired enthusiasm to field trials in a half hour or less. As a result the finished product is often inelegant but hopefully functional. And so it was with this project. Having a collection of radio-junque accumulated over decades helps.

The picture shows a little project I threw together in a half hour to test whether AA5TB and M0UKD were promoting a good idea or snake oil. Both were using a variable capacitor to tune the tank circuit but, in my haste, I substituted a coax capacitor to make a matching device that would serve only a single band – I chose 20m.

**RED ALERT** **RED ALERT** **RED ALERT**

The parallel tuned circuit comprises, in addition to a variable capacitance (mine is variable by trimming its length with side cutters), the secondary winding of an impedance transformer. An impedance transformer? Isn’t that the weak link in the common 49:1 UNUN design employed by the unenlightened multitude?

I forged on regardless. A powdered iron toroidal core is used instead of the usual ferrite material. Why? To reduce the inductance to a level that can be resonated by the capacitor. As an experiment I tried winding 14 turns of magnet wire on a FT82-43 core but the inductance was way too high. The alternative is to use a powdered iron core and the only one I had in my junque box was a T200-2 so it would have to do. Another alternative is to wind an air core inductor. I soldered the coax capacitor in parallel with the secondary winding then wound two turns over the center of the secondary to create the primary winding.

Now, armed with my faithful side cutters I boldly went out onto my deck and hooked my new hastily built tank circuit matching unit to a piece of wire that I had previously established to be a true half wavelength on 20m. I attached a short coax between the matching device and my RigExpert AA55 Zoom antenna analyzer, fully expecting a “you gotta be kidding me” message on the display.

Surprise!

The RigExpert displayed a different message: “no snake oil here” craftily encoded by the numeric “1.8:1”. I was cheerily gobsmacked and, encouraged, I adjusted my “variable” capacitor with the side cutters a tiny bite at a time and watched as the SWR dropped inch-by-inch (2.54cm-by-2.54cm?). When the SWR dropped below 1.5:1 I laid down the side cutters and declared the match “good enough”.

Like a bridge over troubled waters

It all seemed too easy. The troubled waters of the End-Fed Half-Wave antenna have now been crossed by three different bridges: the traditional 49:1 UNUN, an L-match and now a tuned tank circuit. If the inefficiency of the traditional 49:1 UNUN arises in the flux leakage between its windings then the tuned tank circuit approach replicates that weakness. Perhaps flux leakage is even worse when using a powdered iron toroid or air core design. In one of AA5TBs projects the tank circuit inductance comprises an air core inductance with an 8-turn secondary and only a single turn primary which I found very surprising.

There are still more ways of matching the high feedpoint impedance of an EFHW antenna that may be explored later on Ham Radio Outside the Box, but for now the simple L-network seems to offer the best hope for a high efficiency matching device. What is your opinion? Let me know in the comments or, if you prefer, send me an email (good on qrz.com). I reply to all email received.

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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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EFHW matching: 49:1 Impedance Transformer or L-Network?

What is the best way to match the very high impedance of an End-Fed Half-Wave antenna to the 50 ohm impedance of a transceiver? There are various ways to do this but this week’s post is going to focus on just two – a 49:1 impedance transformer (or UNUN if you prefer) and an L-network.

We are dealing with QRP devices but the same issues arise with QRO devices. In fact some of the complexities may be exacerbated at higher power – especially core overheating.

49:1 impedance transformer

This is by far the most widely used matching device but many claim it is inefficient. I have used an “Outside the Box” winding method that I have seen described as “Fuchs style”. The primary and secondary windings are entirely separate instead of being twisted together. This method isolates the windings and is said to prevent static from traveling back down the coax to damage the transceiver. But it also requires a separate 0.05WL counterpoise connected to the bottom of the secondary winding.

Pros

• Broadband operation
• Easy to construct
• No calculations needed

Cons

• Lower efficiency claimed
• Can be used on even harmonics but the antenna is only a half-wave on its fundamental frequency
• Potential for losses due to core overheating
• Leakage flux due to poor coupling between windings
• May require capacitance across primary and/or secondary to compensate

L-network

Some claim that an L-network is more efficient than an impedance transformer. While I don’t dispute the claim I would respond “show me the math”. An L-network is usually constructed from a fixed value serial inductor and a fixed value parallel capacitor (although there are other topologies depending on the matching parameters involved). I built one using a slug-tuned variable inductor and a ceramic trimmer capacitor.

Pros

• Higher efficiency claimed
• Easy to construct
• Avoids complex issues with transformer cores and winding coupling

Cons

• Single band only
• Calculations required to establish correct values of L and C

The Ham Radio Outside the Box laboratory (a grand name for my basement workbench) has built many 49:1 impedance transformers for both QRP and QRO operation. The QRP units are deployed in backpack portable operations and the QRO units have seen service both in the field and in the home shack. Both the conventional “twisted” coupling method and separate windings have been used.

Which winding method is best?

One of the issues with 49:1 transformers is “leakage flux” which means not all of the energy in the primary winding is coupled to the secondary. The conventional winding method is to twist the first two turns of the primary and secondary together to improve coupling. The remaining turns are only coupled to the primary by the flux in the core. Furthermore, there is often a “crossover” turn to bring the far end of the secondary out on the opposite side of the core from the primary. This may further reduce the coupling efficiency.

An alternative method is to wind the secondary, without a crossover turn, around the core. The separate primary is then wound around the center of the secondary. Should the secondary be spread around the core, or closely spaced? Opinions vary on this. I now favor keeping the secondary turns closely spaced. The reason? A closely spaced secondary winding should improve inter-winding coupling and reduce leakage flux.

What about the turns ratio?

Should it be 49:1, 64:1 or …? There is an easy answer to that: just divide your antenna impedance by 50 and bingo, there’s your answer. Oh, but what is the impedance of your antenna, 2000 ohms, 2319.647 ohms, 3000 ohms? We don’t actually know and it may vary depending on how the antenna wire is erected (which for portable operators may be different every time). A ratio of 49:1 provides a good enough match to most every value of End-Fed Half-Wave (and multiples) we are likely to experience.

Or just build an L-network!

We have seen that 49:1 impedance transformers have many variables that impact efficiency. Leakage flux has been discussed so it is relevant to note that placing a small capacitor (typically 100pF) across the primary winding is recommended to somehow compensate. Conventional 49:1 transformers are wound as autotransformers, so we have a series inductor between the antenna and the radio, and a parallel capacitor. Doesn’t that sound very similar to one of the topologies of an L-network?

My initial experiments with building L-networks involved a fixed series coil and a parallel capacitance made from a short length of thin coax – like RG-174. I experienced the problem that the calculated values of L and C did not provide the best possible match to 50 ohms. I still needed a “touch-up” tuner to bring the SWR down to a safe level for my QRP Labs QMX transceiver. I realized that a field portable antenna was going to need slightly different component values depending on whether my temporary station was setup on exposed ancient bedrock, or over the moist ground at the edge of one of the Great Lakes. What I needed was an L-match “tuner”, i.e. an L-network with variable inductors and capacitors.

42 years ago …

A long, long time ago (42 years to be precise) I was a penniless SWL foraging for food in the forest – alright that’s an exaggeration, but I had a young family and couldn’t spare the cash to buy a decent shortwave receiver. A friend told me about a design in Practical Wireless magazine for a shortwave converter that would work with a regular domestic AM receiver. I had the components shipped over from the recommended UK suppliers and built the converter. It worked splendidly and I spent many happy hours listening to the busy shortwave bands. Then I became fabulously wealthy (i.e. I could at last afford shoes and to eat every day of the week), bought a real HF radio and the converter was relegated to the back of a closet.

The point of the story is that I was able to scavenge that converter for the components I needed to build an L-match for an End-Fed Half-Wave antenna. The inductor shown in the picture above is wound over an adjustable slug-type ferrite core of unknown mix. The capacitor is a ceramic trimmer with a couple of fixed ceramic capacitors in parallel to bring its value into the range that was needed. The only comment I can make on the efficiency of that unknown core is that it didn’t get hot (or even warm) after an extended period of transmitting at 5 watts. Tuning is quite sharp but I was able to get a 1.5:1 SWR from my Shortened Sloping End-Fed Half-Wave antenna (see last week’s post). I probably could have obtained an even lower SWR by adjusting the length of the high Q top section of the SSEFHW.

QSO’s?

As a recent convert to L-networks I have only made enough QSOs to be countable on fingers and toes. On the other hand, over the years, I have made thousands of QSOs with a 49:1 impedance transformer. Both the devices shown in the pictures above accompany me on every field portable outing so I have options and can compare their performance.

Does it matter, really?

Sometimes I give my head a shake and tell myself to put the physics textbooks back on the shelf and just enjoy the experience of being out in the Big Blue Sky Shack with my radio. At other times, after calling CQ ’til the cows come home and getting no responses, I ponder the question of whether my antenna is doing its job or, as sailors used to say, is idly “swinging the lead”.

What are your experiences with either impedance transformers/UNUNs or L-networks? Your opinions are very welcome either by adding a comment below, or if you prefer, by email (QRZ.com).

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.

I KISSed my Antenna – Here’s Why …

Many years ago I learned about a design technique called KISS. It was an acronym for “Keep It Sweet and Simple”. Somewhere along life’s journey I started seeing the acronym change to the rather offensive “Keep It Simple Stupid” which I entirely dislike. There are many sound reasons for simplifying a design but none of them imply a lack of intelligence on the part of the designer. Designs evolve and, in the process, become very complicated to the point where the probability of failure becomes critical.

A case in point is the Saturn V rocket that first took astronauts to the Moon. If I recall correctly, the Saturn V had something like 10 million components. If each component had been designed so that it had a 1 in 10 million chance of failure, the rocket would probably have failed at every launch. The reason is straightforward – failure probabilities in a complex machine are additive.

Every mistake is a learning opportunity. The designers of early rockets were certainly not stupid, but their rockets exploded on the launchpad, or during the early phases of launch. Even when rocketry had advanced sufficiently to repeatedly land men on the Moon, terrible disasters still happened.

There is a temptation to be so focused on an objective that errors slip into the design. Reviewing my own antennas, many of which have been featured in this blog, and the feedback I have received from some very knowledgeable Ham Radio Outside the Box followers, caused me to stop and re-think my designs. Every antenna discussed here in this blog has worked, meaning I have personally made contacts with each and every one of them. But, at the same time, some of the designs had flaws caused by too narrow a focus on end objectives. So, I made a decision to adopt a KISS approach.

These are my principle objectives based on my personal interest in operating backpack portable out in the Big Blue Sky Shack:

• Rapid deployment – an antenna must be ready to transmit as quickly as possible upon arrival at an operating site.
• Field expedient – An antenna must be specifically designed and constructed for temporary field operation. This necessarily implies that efficiency is not the prime objective. A “compromise” antenna is acceptable if it works well enough to make contacts.
• A small footprint – the entire station should occupy as small a footprint as possible, keeping in mind that many operating sites are in public spaces where other people may be present.
• Ham-made, meaning I don’t buy commercial antennas. I prefer antennas I have constructed myself. It saves money and allows more scope for experimentation.
• Stealthy – the mission objective is to make contacts, not educate curious people passing by. Ham radio equipment may look suspicious to some people; better to look inconspicuous and not be noticed.
• Self-contained – the antenna must not be dependent on anything I didn’t bring with me. This includes trees, vehicles or any other kind of antenna support.
• Everything must fit in, or on, a backpack that is sufficiently lightweight to be hiked into a remote operating site, or transported using a wheeled cart.
• Ancillary equipment, any chairs, tables, shelter, spare cables, spare battery, water and food must be part of the backpack portable package.

Softly, softly, catchee monkey

The “Stealthy” objective may sound unfriendly but it is very practical, especially when working a pile-up as is often the case with POTA. If somebody stops to ask questions I give them a very simple, but polite explanation. Usually they are just curious with no particular interest in ham radio. I was set up in a local park recently and had just completed a POTA activation when an official Ontario Parks vehicle pulled up in front of me. A young park warden got out and came over to ask me what I was doing. She told me she saw my big whip antenna and wondered what it was for and seemed interested when I told her I was contacting people by radio using Morse Code. She asked me how long I had been doing this. I was tempted to reply “oh, only about a half hour” but I overcame my frivolous inner self and replied “25 years”.

And another consideration; CW ops have a stealth advantage over phone ops – our operation is silent if we wear headphones – or ear buds which look less suspicious. If they can’t hear me they are more likely to pass on by. “He must be tracking wildlife, or something, best not to disturb him”.

It’s okay to be an ambassador for the hobby, that’s what Field Day is for. If it’s a quiet day on the bands I might be happy to have a nice conversation with a passer-by, but when the ether is overflowing with chasers and hunters the focus is on the mission’s prime directive.

We gotta get out of this place

There are many reasons for wanting a rapidly deployable portable rig. Out in the great outdoors the weather can change suddenly necessitating a fast teardown of antenna and radio. In a public space – such as a park – other people may gather in close proximity to our operation creating a disturbance or becoming susceptible to tripping over wires or being electrically excited by the high voltage at the end of a wire. In the backcountry there is also the possibility of a representative of the ursus americanus community paying us a visit. For these reasons, among others, having a portable rig that can be set up, or moved, in a couple of minutes is a great advantage.

All these factors led me to build and deploy many of the antennas described in this blog. One in particular has led to a lot of discussion – the Coil-Loaded End-Fed Half-Wave (CLEFHW). This antenna comprises an 18.5ft telescopic stainless steel whip with a small loading coil at the base and a very short (0.05 wavelength) counterpoise.

What is “Electrical Length”

I made the claim that the loading coil changes the physical length from 18.5ft to an electrical length of a half wavelength on the 20m band. The choice of words is very important here. The physical length is measured in feet but the electrical length is measured in wavelengths.

Wikipedia defines electrical length thus:

In electrical engineering, electrical length is a dimensionless parameter equal to the physical length of an electrical conductor such as a cable or wire, divided by the wavelength of alternating current at a given frequency traveling through the conductor. In other words, it is the length of the conductor measured in wavelengths.

The purpose of the design was to eliminate long radial wires laying on the ground. A very short length of coax terminated in a common mode current choke acts as sufficient counterpoise. I wrote once before about a nice lady who stopped by to inquire, in a friendly manner, what I was doing. I was using a different antenna at the time and cautioned her to be careful of the wires on the ground. She responded by entertaining me with a little dance as she attempted to avoid stepping on them. Wires on ground in public spaces – ungood!

Another design objective of the CLEFHW was to be integral with a self-contained backpack kit occupying a ground footprint of only a couple of square feet. The backpack rig is its own operating table, so dump it on the ground, erect self-contained antenna, transmit. If I didn’t have worn out knees I wouldn’t even need a chair, but I did have to add an ingenious collapsible plastic stool to the kit.

Time for confessions

Now it’s mea culpa time … while the CLEFHW has performed successfully in more than one POTA activation and numerous casual QSOs, it does have a couple of design flaws. First, the biggest and baddest. A full-size vertical EFHW has a current maximum point half way up the antenna, far away from the power gobbling greedy green ground. But the CLEFHW cheats; it is not a physical half wavelength long, it is an electrical half wavelength long so the current maximum point remains at the base of the antenna. That results in high radiation around about head height. I checked with the ARRL RF exposure calculator and found that shouldn’t fry too many brain cells while operating at QRP levels. Proximity to ground also increases power loss. I mitigated this loss by raising the base of the antenna to about 1 meter above the terra firma. A few hundred milliwatts may still slip away to warm the worms, but heck, that’s the fun of QRP, so they say.

Another, shall we call it flaw, is the double impedance conversion. An email correspondent whose views I much respect advised me to think of loading coils as impedance matching devices. Using that way of thinking the CLEFHW’s loading coil converts the impedance of the whip to an R+jX value resembling that of a full-length EFHW. The 49:1 impedance transformer then reduces the impedance down close to 50+j0. There is almost certainly some inefficiency in that double transition. But, one of the design parameters already listed calls for Field Expedience above efficiency so I guess there is no free ride here. As somebody else once said: “every antenna is a compromise”.

The big, overriding objective of the CLEFHW design was to work as an integral element of a backpackable, rapid deployment portable ham radio kit. Despite some unusual quirks in its conception it gets the job done. Is it overly complex? Does the bizarre double impedance conversion cause more chaos than a monkey in a china shop? Should I abandon the design based on its assault on sound antenna physics? I seriously considered scrapping the project in favor of a Sweet and Simple tunable whip, but I am uncertain whether that would be an improvement.

The direction in which I am heading at the moment is to replace the 49:1 transformer with an L-match “tuner”, that is capable of dealing with the vagaries of terrain I experience in my itinerant portable operations. Despite widespread opinions describing End-Fed Half-Wave antennas in less than flattering language, the advantages for a portable operator outweigh any negatives so future endeavors will remain on that course.

As always, your feedback is much appreciated.

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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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A Ham with One Voltmeter Always Knows the Battery Voltage

There is a popular old saying about a man with one clock always knowing what time it is, but a man with two clocks is never sure. Well doesn’t that also apply to voltmeters and any other kind of meter in a ham’s kit bag?

The Ham Radio Outside the Box QRP field portable kit is powered by a Talentcell 3000mAh Li-Ion battery. It’s a nice little battery, but it has one rather annoying feature – an on/off switch. I am going to guess that the function of the switch is to prevent battery drain due to the LED capacity gauge on the battery. Problem is, I forget to switch the battery off when I have finished operating. Until recently the battery was buried deep in the bowels of my rapid deployment backpack radio kit – out of sight and out of mind.

To overcome this failing of the operator’s gray matter I connected one of those tiny LED voltmeters found at many hamfests, or online via the usual suspects. If the voltmeter is lit up, the battery is still turned on. It works fine business but how accurate is it? Should I care? It was just a quick and easy way to remind me to fish inside the radio box and turn off the battery when I’m done operating. Perhaps I should have used a simple LED instead.

During a recent outdoor operating session at a local park I found myself obsessing about the battery voltage. When I turn on the radio the tiny voltmeter shows a drop of one decivolt (cute word, means one tenth of a volt). Ok, the radio is drawing current so that’s to be expected. So what’s the problem?

Too much information?

The radio is the mighty but microscopic QMX from QRP Labs although these observations could equally apply to any other QRP radio with a restricted DC supply range. The QMX is a tiny little package that packs a powerful punch. It has proved it’s worth on a lot of POTA activations over the last year. The QMX has a small LCD screen that displays a lot of information – maybe too much in fact. Yes, some of the info displayed can be turned off in the user settings but who wants to keep fiddling with the settings when we could be pounding brass to get more contacts?

The paranoids are chasing me again!

The QMX tells me my frequency, signal strength on send and receive, ALC level, SWR and among other distracting data, the battery voltage. It can also decode and display the incoming CW but I turned that off. Call me paranoid, but if the radio can replace the need for the operator to copy CW, how long before a future firmware update incorporates AI and does the sending for me too?

Now here’s the problem: when this ham had just one voltmeter he was happy in the knowledge that all was well. But now there are two voltmeters – one on the QMX and another one whose job is to remind me to turn off the battery before packing up. The two voltmeters do not agree – which one is right? Are they both right but measuring the supply voltage in different places? Is it important?

There is much discussion in the QMXverse about the sensitivity of the PA transistors to excessive voltage, or high SWR, or both. In the world of big radios 12 volts means well alright, try to keep the DC supply voltage down below maybe 15 volts. Twelve volts, 13.8 volts, what’s the difference? But in QMXville, 12 volts means 12 volts. How strictly must we QMXheads adhere to 12 volts? No guarantees there and no hard and fast rule. Those four eensy-weensy BS170 transistors that pump power into the big, blue sky are as unpredictable as the weather.

Here comes my 19th nervous breakdown

So maybe you can understand why the obsession with the state of the battery. Which voltage is the one that is going to fry the finals – the voltage at the battery terminals, the voltage displayed on the QMX in receive mode, the voltage during transmit?

And … after sending out CQs for a half hour or so, the QMX display tells me the radio is no longer pumping out a full gallon. OMG, will the battery outlast the activation or will it die on me before I get “my ten”?

Don’t worry, be happy

Before “running for the shelter of mother’s little helper” anxiety can be overcome through understanding the discharge curve of a typical Li-Ion battery. But before we delve into that let’s talk about how to wrap our QMX baby in electronic swaddling clothes.

A freshly charged 3S (3 cells in series) Li-Ion battery will have a voltage of 12.6 volts which represents 4.2 volts per cell. The nominal voltage is a little less at 11.1 volts or 3.7 volts per cell. As the battery discharges it will hold its voltage fairly steady in the Goldilocks Zone of 10.8 to 12 volts. Eventually, when the battery is nearly fully discharged, the voltage will drop precipitously and the internal BMS (Battery Management System) will shut it down to prevent damage due to over-discharging.

The only external protection needed is to curtail the excess voltage at the start of the discharge. This can be achieved by series diodes or (as I and others have adopted) a Buck Converter. The job of the buck converter is to limit the voltage to a preset value, for example 12.0 volts. When the battery voltage depletes to lower than the preset value the buck converter has no effect (except perhaps a very small voltage drop across the device). A buck converter is preferred over diodes because the latter will reduce the voltage by 0.6V per diode even in the Goldilocks Zone.

That makes the job of the buck converter very easy. With reference to the discharge diagram above, the buck converter only plays a role during the first 10% of the battery discharge cycle. A Talentcell 3000mAh battery has a nominal capacity of 36Wh. So the excess voltage is only a problem during the first 3.6Wh of operations. In theory that represents about three quarters of an hour of operation at 5 watts, although my own experience is that the battery voltage drops more quickly. I suspect this may be due to improper charging. Although I have been using the charger supplied by Talentcell, I have been leaving the load (i.e. the buck converter) connected. This creates a small “parasitic load” which may confuse the charger.

Is battery voltage regulation really necessary?

Are the radio’s final transistors in jeopardy at 12.6 volts? Some users have reported using an unregulated 12.6 volts with no damage to the radio. Perhaps the magic smoke is waiting for a later time to be released – who can tell? It’s a gamble.

What is the impact of operating the radio at 11.1 instead of 12.0 volts?

When I received my QMX a year ago, it came with a test sheet from the factory. The lab results showed my radio produces 4.8 watts on 20m with a 12 volt DC supply. Since the output power is proportional to the square of the voltage we can calculate the expected output power at any supply voltage. A quick and dirty back-of-an-envelope calculation suggests that at 10.8 volts (at the end of the yellow/orange Goldilocks zone in the diagram) the expected power output will have dropped to 3.9 watts. Let’s round that number to 4 watts.

So, after discharging the battery until it is almost fully depleted we can expect to lose less than 1 watt of output power. Even that could be compensated for by replacing the buck converter with a buck/boost converter. A buck/boost converter will ensure a constant voltage right up to the point where the BMS turns off the lights and says goodnight.

Is it really necessary to become paranoid about battery life, or output power? Before reaching for the “little yellow pill” prescribed by Messrs Jagger and Richards, maybe we should just relax and enjoy playing radio out in the Big Blue Sky Shack. It doesn’t matter if we run out of battery power, or our puny signal gets eaten by the D-layer on its round trip into space because QRP is such fun (isn’t it?).

Addendum: I have recently made a couple of small changes to my kit to overcome the issues identified above. First, I relocated the battery to make the on/off switch more accessible and allow the load to be disconnected during charging. Second, I eliminated the tiny voltmeter since I have convinced myself not to become paranoid about the supply voltage. Third, I have invested in a CC/CV (Constant Current/Constant Voltage) bench power supply to charge the battery. Now I can see the changes in charge voltage and current and verify that the battery is indeed reaching full charge.

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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A Simple Antenna that is Omnidirectional, Directional and NVIS?

Our winter weather may have a few weeks to run yet, but a relatively warm spell gave me the opportunity to get out into the Big Blue Sky Shack to try out another antenna idea. Destination: MacGregor Point Provincial Park on the Ontario shore of mighty Lake Huron. The shore ice still stretched quite a long way out onto the lake in the direction of Michigan, about 100 miles away and a cold wind was blowing in off the lake. Not perfect weather for outdoor operations – but good enough.

Purpose: to find out whether a simple idea could turn a humble vertical whip antenna into something more versatile. Could this be used as a directional antenna to focus a signal into a desired target area? Could it even be used as a cloud burner to shoot a Near Vertical Incidence Skywave (NVIS) signal straight up to the F2 layer for strong local coverage? I decided to find out.

The antenna was actually not quite a simple vertical, but close. It was the Ham Radio Outside the Box Coil-Loaded End-Fed Half-Wave (CLEFHW). Its advantage over a quarter-wave vertical is that no separate counterpoise wire is required – just a short length (about 18 inches) of coax terminated in a 1:1 unun.

This was also the first outing for a new ham-made radio backpack. The radio is a QRP Labs QMX (low band), built into a steel 30cal ammo box along with a Talentcell 3000mAh Li-Ion battery, Drox buck converter (to keep the voltage down to 12 volts – the QMX gets unhappy with excessive supply voltage). The Putikeeg paddle key has strong magnets on its base that lock it into place on the steel ammo box which keeps my keying from getting too erratic!

A second identical ammo box sits below the first one and contains all the spare parts that might be needed during an outdoor ops session (standby battery, spare cables, connectors etc).

Both boxes sit on a custom aluminum frame, secured by 1-inch webbing straps. The whole pack is carried by means of a set of 2-inch webbing shoulder and waist straps. In use the radio and key sit at just the right height when the operator is perched on a camping stool so no table is needed.

Why the military look?

Well, a couple of reasons there. First, I actually like the appearance of military style radio gear. Probably nostalgia because I was first introduced to ham radio in the 1960s and the first “amateur” radio I saw was a converted WW2 surplus No.19 Wireless Set. But second, and more importantly, the military and I have similar objectives – we both need rugged gear that can withstand the rigors of rough handling out in the field. Snow, mud, wind and rain all be damned – comms must continue regardless <smile>.

The canvas parachute bag at the front contains a selection of coax cables, as well as other wire antenna options.

The radio box at the top can be sealed by replacing the detachable lid. It has a rubber gasket to keep out the elements when the radio is not in use.

The radio box can be removed from the pack frame quickly and easily. I keep a wire bail for picnic table operation, although that luxury is a rare occurrence for me.

Orienting the antenna

The whip and loading coil are attached to the pack frame by means of an aluminum bracket with a 3/8×24 to SO-239 adapter. I wish they made a 3/8×24 to BNC adapter; instead I made up a short cable with a PL-259 on one end and a BNC on the other.

The bracket is the secret to the antenna’s versatility. As you can see in the picture, the pack frame has curved shoulders. By mounting the bracket on the straight portion of the pack frame, the whip remains vertical and vertical whip antennas have an omnidirectional radiation pattern.

Now, if the bracket is mounted on the curved shoulder of the pack frame the whip becomes oriented at an angle. As we shall explore in a moment, this creates a major lobe in the radiation pattern in a direction away from where the whip is pointing.

But doesn’t the weight of a leaning 18.5ft whip cause the whole pack to topple? Actually no. It was discovered that the weight of the two steel ammo boxes and contents are sufficient to counteract any potential gravitational instability. In fact during the field trial on the shore of Lake Huron the whole pack remained entirely stable, which is vital for this operator who cannot operate a set of paddles properly unless they are very securely mounted.

It is not necessary to set the antenna bracket too high on the curve of the pack frame because the whip itself is quite flexible which enhances the lean angle.

To operate in NVIS mode all we have to do is raise the bracket a little higher on the curve of the pack frame so that the top section of the whip lays almost horizontal a few feet above the ground. This method has been used on vehicles by the military so I have to credit them as the originator of the idea. It probably won’t perform as well as a low dipole, but it benefits from being self-supporting and quick to deploy.

How did the directional antenna perform?

The Huron shore trial tested the directional properties of the antenna. The wind coming off the lake was a little too cold for a long operating session and besides I had to find a small corner of the operating area that was sheltered and clear of snow and the vast expanse of thick mud created by the early spring thaw. So, the test was focused on checking the performance of the whip oriented as a sloper. A sloper is a simple, well-established way of getting directionality out of an antenna, but is usually achieved with a wire antenna. This unique version of that method gets the same effect with an entirely self-contained whip antenna in a rapid deployment portable radio pack.

A simple antenna such as this could not be expected to rival a Yagi-Uda beam but it does exhibit a very pronounced directional radiation pattern as EZNEC reveals in detail.

The elevation pattern shows a strong low angle lobe in the direction opposite to the lean of the whip. This should produce good DX results when the propagation conditions are favorable.

If we look at the azimuth propagation we can see that it is almost omnidirectional at low angles. The front/back is only about 2dB which is less than half an S-unit.

The real power of this antenna orientation can be seen when we examine the azimuth propagation at higher angles. In the third image we can see the radiation pattern at 60 degrees elevation. The front/back is now at around 13dB which is approximately 2 S-units.

60 degrees elevation is almost in NVIS territory and should provide excellent propagation over quite a wide area.

NB: For simplicity, these results were modeled using a full-length EFHW on 20m. If anybody wishes to model the exact configuration please note that the base loading coil is 6.6 microhenries and the whip is 18.5ft long. I chose not to go this route because the curve of a sloping telescopic whip is unpredictable (especially in the wind).

Could a puny 3.5 watt signal into a compromised whip antenna cut the mustard? On the principle that you can work DX with a wet noodle on the right day, then yes. Propagation conditions were moderate with a K-index of 3 on the day of the trial, but among my other contacts I did work a station in North Dakota (from my QTH is southern Ontario). That’s a distance of a little less than 2000km; not outstanding but encouraging.

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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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Fighting the winter blues with a little radio therapy

The winter takes it all – aka A Brief Break Activity

We haven’t had this much winter snow for several years. Every day seems to bring a fresh snowfall to add to the accumulation on the ground. My poor John Deere snowblower is getting a real workout keeping the driveway clear. I live on the corner of two streets and as the snow plows turn the corner they deposit a fresh wall of the blessed white stuff across the end of my driveway. All the trails and parks I like to visit to play radio in the summer are buried and impassable. Even parking spaces outside the parks are cutoff by walls of hard-packed snow and ice. Since I prefer to operate outdoors instead of inside a vehicle I am having a hard time getting out to scratch my radio itch.

What’s a ham to do?

A few weeks ago I ordered a small ice-fishing shelter from an online company named after a river in Brazil. It’s an uninsulated pop-up style nylon shelter that keeps the wind off my back. Several layers of warm winter clothing and a good pair of mukluks take care of combating the frigid air’s attempt to lure me into hypothermia.

I am not an ice-fishing person but this compact shelter is an ideal way of getting some comfort while playing with my wireless set when the weather isn’t too extreme. I am toying with the idea of taking my shelter down to the Owen Sound harbor and setting up on the ice alongside the other huts. Our harbor is completely frozen over and likely to remain so for several weeks. The port of Owen Sound, Ontario is not a busy place, but every winter the harbor attracts big “Great Laker” ships that come to rest and await the opening of the spring shipping season on the lakes. The last arrival needed the assistance of a Canadian Coast Guard ice breaker to get into the harbor.

It might be fun – if a little overwhelming – to setup my radio-fishing shelter alongside the hull of one of these behemoth vessels. Their steel hulls would probably make an excellent reflector for my signal.

Although we have been getting a motherlode of snow, temperatures have remained quite reasonable, hovering around -5C to -15C most days. A couple of days ago, in between snowfalls and with the thermometer reading a relatively balmy -6C, I set up my radio-fishing shelter on my driveway. I could tell I was on my driveway because I could just see the tips of my driveway markers peeking above the snow banks.

If this was a regular winter season I would have already completed several POTA activations under the shelter of my new nylon home-from-home. In previous winters I have happily snow-shoed my way into a park towing my radio sled, but age and a recently acquired medical condition have limited my physical prowess. So, unfortunately, this was the first time I have had the chance to try it out. I was feeling almost desperate. Day after day was passing by and the feeling of unease was building to intolerable levels. I just had to get out and disturb the ionosphere and if that meant a driveway radio session then so be it.

The radio-fishing shelter is a bit of a pig to set up. It relies on the tension in several poles to keep its shape. There are four sides and a roof section that have to be tensioned by pulling them out via a short strap in the center. I guess I’ll eventually get the hang of it – maybe by summer! The best part of its construction is that there are no poles to assemble; it’s all one piece and with the strength of Hercules it can be erected very quickly.

It is actually quite comfortable inside the shelter. There is ample space for two operators, but since I prefer to operate alone I have room to spread out my gear.

I use a simple camping stool to sit on while operating. A second camping stool acts as a table on which to mount my rig. A lesson I learned during this test setup was to add a small shovel to my portable kit. I had set up on compacted snow several inches deep and the back of my seat began to sink into the snow almost tipping me over.

I own a small folding shovel that packs away into a case only a few inches long. I am going to throw this into my backpack for future deployments.

My fameless DIY radio sled sits outside the shelter and, in addition to carrying all my gear out onto the tundra, acts as a support for the antenna. For this deployment I set up my CLEFHW (Coil-Loaded End-Fed Half-Wave) 20m antenna.

The CLEFHW is a resonant antenna and requires no tuner, so it’s a nice simple way to operate. My driveway – and the rest of my home – sits right in the Niagara Escarpment which is a POTA entity. However, the rules say a valid activation has to be on public property so I restricted myself to hunting.

Operating as a POTA hunter has become difficult these days now that POTA is such a popular activity. The difficulty is increased when pumping out puny peanut power and hoping to get the edge on other hunters with their big indoor rigs and more efficient antennas. Operating QRP takes skill and quite a bit of good luck and patience. Suffice it say that I QSOd, packed up and ran for the warmth of home.

I am looking forward to better weather later this winter when – maybe – I can get out to do an activation. POTA activations are much easier than hunting because the hunters clamor for my attention rather than vice-versa. Only another two months of winter to go so there is hope!

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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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How Can A Lossy Wire on the Ground Work Better Than A Quarter Wave Vertical Antenna?

Let’s get real here! If we lay a wire antenna on the ground, surely It can’t radiate more power than that cool-looking, expensive quarter-wave whip you just spent a small fortune to buy? Well, yes it can – but with a few caveats.

We can use a trick of geometry to support our claim. Our magic wire antenna has a footprint on the ground of only one square foot. The cool, costly ground-mounted whip has a footprint on the ground of only one square inch (ignoring the radial field). Bigger is better yes? Not convinced?

Okay, let’s unravel the geometric trickery while still maintaining our original claim. You might picture one square foot as a small square with equal sides of one foot. Therein lies the trickery. If we take 144 feet of wire of 1/12 inch diameter and tightly wind it into a square with sides of one foot, we’ll have a footprint on the ground of one square foot. Now let’s unwind that wire and stretch it out in a straight line along the ground. It is now 144ft long and 1/12 inch wide which is still one square foot.

Enough of the mathemagical sleight of hand; there is a much more convincing way of proving our point. Everybody knows that an antenna wire laid directly on the ground is lossy and, for once, everybody is right. But, only a few of us know how to take advantage of such a wire and make it a very useful antenna. I have personally enjoyed multiple QSOs with wires on the ground – despite the losses. I too was a skeptic until I actually tried it.

The theory of why it works has been covered in previous posts on this blog. The secret is that the wire has to be at least one wavelength (and preferably multiple wavelengths) long. The radiation pattern is a directional beam with low elevation.

As we can see in the far field plots above, EZNEC predicts an elevation angle of 25 degrees and a beamwidth of 54 degrees. However, the antenna has a loss of 3.9dBi. If we allow for the fact that some signal is also radiated outside the main beam, let’s treat that loss as, say, 5dBi.

Now compare that to our quarter-wave vertical for which we can estimate unity gain with a beamwidth of 360 degrees.

Now a clearer picture is beginning to emerge. If we calculate the RF energy within a beamwidth of 54 degrees for both antennas we can see how they compare. Let’s say our transceiver puts out 100 watts (I can hear QRP diehards loading for bear here). The lossy wire on the ground will only radiate 30 watts. The quarter-wave vertical will radiate all 100 watts but spread over 360 degrees. Within the beamwidth of 54 degrees, the vertical will radiate only 15 watts!

Gadzooks! A reel of wire costs only a few bucks but can radiate twice as much power as a shiny whip costing significantly more? Date check: yes it’s still January, not the first of April. Admittedly, this is a theoretical analysis lacking rigorous procedures for a proper engineering investigation. But, once again, I have personally made QSOs with more than one wire-on-the-ground antenna. Were my signal reports very poor? Absolutely not. This is not a spoof post, trust me.

There is another advantage of this wire-on-the-ground antenna when compared to a quarter-wave whip. Vertical antennas are generally considered to be susceptible to vertically-polarized noise. A wire on the ground is relatively immune to noise because of its inherent signal loss.

I don’t recommend selling your shiny, expensive whip and replacing it with some wire strewn across your backyard. However, imagine the possibilities when operating out in the Big Blue Sky Shack. A long wire can be concealed in a ditch, or in tall grass. Store it on a fly-fishing reel, then when you have finished operating simply reel it back in. It is the ultimate stealth antenna which could also be useful in a HOA situation.

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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