The unforgivable happened to me recently: I packed my radio for a weekend away, but I forgot to pack my antenna (and the toolbag). What is a man to do! Redemption came in the form of a roll of cheap twin cord wire.
QRP may be low power, but it still needs an antenna
One of the fun aspects of my Ham Radio life is working low power. I’m not ashamed to admit that I sometimes heat up the antenna wires a bit with my amplifier, but there is a certain charm in skirting around the big bangers with your pee-wee-powered setup and also make a few contacts.
This happens especially when I am physically separated from my shack, for example when my wife insists that we go away “somewhere” for the weekend. So to minimise the separation anxiety I’ve started packing a small portable radio, just in case the symptoms overcome me and I need a dose of RF. My standard go-to antenna is a EFHW wire thrown into the nearest tree, of course.
My travel kit contains QRP stuff because it is easy to throw it into my luggage between my clothes and in so doing hiding it from the prying eyes of the XYL. My favourite bands when mobile are HF, usually 40/20/15/10, and apart from doing a good bit of voice (SSB) I also love the digital modes, maybe FT8, JS8Call or the best thing for me is PSK31. I can sit in a hotel in Richards Bay and work Argentina on 5 watts PSK31! It is really fascinating.
Equipment-wise I am jealous of the hams who can afford a Yaesu FT-818 or ICOM 706, but I get by quite nicely with my Chinese Xiegu X6100 (with a built-in tuner!) and a few pre-cut lengths of wire. With only 5 watts it’s not DX-competition-class equipment, but it gets the job done. And it packs in my luggage which is important.
Power usually comes from the grid if load shedding approves, or my USB Power Bank (see my website). I’m not ready yet to walk into the wild blue yonder with only my backpack and a small battery. One day, when I grow up, I’m going to be brave and get a backpack like the RADAR and SOTA people, people that I admire for their fearless attack on the airwaves, and enjoy the mountains. Until then, I’m just going to play in my little corner.
Finally, I’m a computer junkie, so my laptop and logbook is always next to me. I cannot live without my laptop and a fast internet connection. Maybe that is why I’m not yet on the mountains?
And that is how the fight started
Maybe an All-in-One Radio Carrybag is not such a bad idea.
Until recently I would walk past my shack on the way to the front door to leave for the weekend and grab a radio plus whatever I think I might need, and throw it on top of my clothes. What can go wrong, right?
Until one day, after a lovely drive in the sunshine from Johannesburg to Parys, with perfect weather, and a perfect camping ground with large trees just the right distance away (ever noticed how you look at trees in a completely different way once you go portable?) to hang a wire antenna.
After making sure the XYL is settled in, I grab a cold beer and my radio and start looking for the rest of the “stuff” I need, things like the mic, and an antenna for example. Scratching like a rat in a packet I go through all my bags and pockets and every nook and cranny of the car and boot, but alas, no sign of anything that resembles an antenna could be found.
The cold hand of disaster clutched around my heart. Does that mean that I will be away from my radios for a whole weekend!
Fortunately we arrived at our campsite early. The good news is that I had a few minutes of shopping left before the shops closed for the weekend. The bad news is that I could only find a roll of 20 meters of 1mm2 twin flex wire (ripcord in local parlance), without connectors or crimping lugs or any other Ham hardware. Not one to be chicken, I bought the wire and rushed back to camp.
Somewhere in the dark corners of my memory I remembered some articles from yonks ago that mentioned flex or ripcord being useful (references). It was too late to read anything, and I immediately hoisted a dipole in the air by splitting half of the ripcord into two legs, with the remaining 10 meters acting as a feedline. From the outside this looked like a grand setup and I eventually wired up something that resemble a station.
Receiving was actually ok, I could hear many stations on most of the popular spots. The Xiegu X6100 tuner also didn’t sound completely unhappy.
Transmitting was attempted cautiously at first, but after all the tuner is supposed to protect the radio, right? It seemed to be able to tune up into a safe zone. A few contacts were made over the rest of the weekend.
I have no idea what I did, or why it works. Or even if it worked well. Or if I will be able to repeat my lucky shot at another venue with different circumstances. But a disaster was averted and I am a convert to Ripcord for now. Or am I??
Science to the rescue
Once in a while I meet somebody who explains a difficult concept in a few easy to understand words. One such person is Vince Harrison ZS6BTY, who was able to lift the foggy veil (note I didn’t mention my foggy brain) of the EZNEC model. His scientific approach to the problem of antennas made a lot of sense.
I asked Vincent to model my rescue antenna and why it might have worked. Vince gladly obliged and we exchanged quite a few emails on the subject.
Unfortunately the news is not all good news. I think I was lucky that day, in that I managed to get a working length by accident. Much more good luck than good measurements.
But, as Vincent points out, under certain circumstances the losses are low enough to make a really useful antenna on certain bands. I’ll try to give some hints on those lengths.
Rules of a Temporary Antenna (or, How long is a piece of string?)
Right, so we know I was lucky that one time. But if I want to repeat my luck, what would be some of the things I can do to improve my chances of success? Armed with half a knowledge is better than none, right?
So here are some of my observations, as Rules of Thumb.
Rule of Thumb 1: Any antenna is still better than no antenna. All the nay-sayers will tell you that ripcord is inferior for whatever scary reason they can invent. Maybe they are right, but the fact is that on that day, that is all I could find. And I made some contacts on my “inferior” antenna. Understand the limitations of your set-up and enjoy practising your skill – your next turn of the dial can turn up a diamond. I remember an occasion where I was working USB from Hibberdene on a very small vertical antenna and nobody answered. Disappointed, I was ready to switch off, when Gerald ZS5GS boomed back and gave me a very nice contact.
Rule of Thumb 2: Don’t act immediately upon all the advice you get. Your own circumstances are unique, and so will your solution be. Try something, anything, everything. Experiment. Look at all the options. Listen to everybody, for buried in their words may a gem of an idea, but finally make up your own mind. I find that writing down measurements helps me a lot. When somebody asks me, I can go back to my notes and say with confidence what I measured. Just keep on going at the problem.
Rule of Thumb 3: Relax your standards. To scrape miniscule signals out of thin air you need a very good antenna, I know. But when you are on holiday and you are just making some contacts for fun, relax your standards a little bit. I know that there will always be a bigger and better antenna, but let’s remember our objective here: We are having fun! Just remember your objective is not to win the next DXCC, but to have a nice contact.
Rule of Thumb 4: Almost any wire will work. It pretty much doesn’t matter what kind of copper wire you use in an antenna. Thick or thin, insulated or bare, stranded or solid, they will all perform fairly well. Any effects due to these varying characteristics will be “second order”. The old formula for cutting a half wave dipole, 468 / frequency (in Mhz), may be a bit different for various combinations, but this formula is only an approximation anyway. You can lose 1/2 of your power in a poor antenna system efficiency and only be down an S unit or so. I hear lots of S9 QRP stations. They would still make fine QSOs at S8. I am not advocating antenna inefficiency, but you can live with it. It is better than no antenna at all.
Rule of Thumb 5: Always consider using a tuner. Yes, I know that the ATU may introduce a small loss, but you will reclaim that loss ten times over with your improved output on today’s solid state radios. Modern radios kick in the protection very quickly if the SWR isn’t good.
Rule of Thumb 6: Whatever antenna you choose, if it is fed with coaxial cable you should use a choke balun. This will prevent the feed line from becoming part of the antenna which can cause all sorts of problems. There are many designs to choose from. Under certain circumstances Ripcord can be a good feedline.The impedance varies a bit but usually settles around 110 ohms which is a great value, but hardly the issue. The feedline itself may have some losses especially on the higher frequencies and also depending on the type of dipole on the top. But again, being on the air with some slight losses is still better than nothing on the air.
Rule of Thumb 7: Most of what is written on the internet for Hams was written for the American market where bigger is better. The chokes are bigger, the cables are thicker, and the Texas stories are cuter. Don’t believe everything you read on the internet. Our situation is not the same and our solutions are sometimes better. Local is lekker after all.
We are not alone in the Ham universe
After my near disaster I found out that using speaker is actually quite common and a lot of POTA and SOTA activations are done like this. For example:
Thomas Witherspoon published this article: Field Report: Let’s build a super simple antenna on-site and activate this park! https://qrper.com/2021/06/field-report-lets-build-a-super-simple-antenna-on-site-and-activate-this-park/
Frank Bremer PA0FBK in the Netherlands wrote: “I looked for another simple portable system and found following combination: A dipole of 2x16m (splitted) loudspeaker wire of 0.35mm square (is about 0.65mm dia) and a 10m symmetric feeder line of the same (not splitted) loudspeaker wire, this antenna is tuned by a mini tuner with the Z-match principle. The (not splitted) loudspeaker feeder line behaves as a balanced line with about 120 ohm impedance, the loss is somewhat larger as 300 ohm line, but you will not notice this when using max. 10m of this line. This antenna system is tunable from 6m to 180m (minimum and maximum frequency depend strongly on the used tuning capacitors!), I use it portable with a 5m fibre-glass telescopic fishing-rod in the middle and 10m thin kite-line at each dipole end to ground. The result is an inverted V antenna, the centre at 5m and the ends at about 1.5m above the ground. For transport the complete antenna with feeder line is wound on a small kite-line reel (15cm dia). The telescope fishing-rod is about 1m long, so it is possible to carry the complete HF station by bike, hi” https://www.qsl.net/pa0fbk/hampage_uk.htm
And finally. The most important lesson to learn from that weekend is to pack a radio bag with all the required goodies well before the time, so that nothing gets left at home again.
And that is my story for today. As always, comments on WhatsApp or Telegram to +27 82 573 5580 are always welcome.
73 de Leon Uys ZR6N (AG5RH when I visit the kids in Texas)