Building a vertical antenna with traps

Last week I bought a few cheap aluminium pipes and decided to build a discrete vertical antenna for my post stamp backyard. The goal was to make something that looks a little bit more professional than a cobweb of wires, and at the same time support the 10, 15 and 20 meter bands. If that wasn’t challenging enough, I didn’t want the antenna much taller than 3 meters in height.

In order to accomplish the above in such a short antenna, I added two traps for 15 and 20 meters. These traps were made with stubs of RG58 coax that was wound around a 30 mm PVC plumbing pipe. I did three turns for the 15 meters, five for the 20 meters, and I did the loop trick where the screen on one end loops back to the center lead on the other end.

I’ll happily admit that, apart from a tape measure, the traps were not metered or measured in any other way before, nor during, the build. I thought “this looks like it might work” and decided to go for it. Fine-tuning could be done later.

The radials are just three 120 cm elevated telescopic rods, and a 20 meter long wire that runs across the hedge. They are definitely subject to change shortly.

Right now the antenna is mounted on a camera stand, fairly close to the ground. My goal is to put it up in the tree to the right, which is maybe 15-20 meters tall, but the realistic install height may be around 10 meters for the base of the antenna. Before I start climbing I need to be sure the antenna is working fine.

The current version of the antenna is working fairly well, and it even brought two surprise bands with it on the way. The SWR is as follows, no ATU:

Band
20m
17m
15m
12m
10m

SWR
1.6
1.2
<1.1
1.6
1.5

The antenna is also quite broadband. The measurements above are for the entire band, from start to end.

I’m going to try and tune this antenna a little further, and see if I can lower the SWR on the 20 meters (and maybe 12) a bit more, but knowing a trap antenna is far from ideal, this may be as good as it gets.

Hopefully, by adding a little height to the equation, this antenna will improve further and suffice for the higher bands once the spring sets in for real. 10 meters is still on fire from time to time, I picked up VK3 on FT8 yesterday morning, using this antenna.

40m Hamstick, trampoline groundplane

My kids have a big trampoline in the backyard, and its built from a massive metal frame. In the beginning I joked about turning it into a magnetic loop antenna, but have settled with using it as a ground plane/counterweight for some antenna experiments. I’ve done 17m and 20m verticals with this one without problems!

This time I wanted to try a set of Hamsticks I’ve had around for a while, and I started out with the one for 40m. The bracket was secured with an old hose clamp and exhaust clamp.

Now, these antennas are known to be narrow banded, so my goal for this experiment was tuning it to the FT8 frequency and leave it there. The tuning process may require some patience and just the right tongue angle, especially at this height. However, after a couple of attempts and with a little help from my NanoVNA, I got as close to 7.074 MHz as I could. The NanoVNA claimed an SWR=1.15 which is way better than anticipated, and the FT-950 in my shack agreed. No tuner, neither internal nor external, was used.

Time to run some tests!

I ran a couple of FT8 QSOs really quick with 50W, and received reasonably good reports from a couple of stations, so this looks promising.

I also have Hamsticks for 30m and 60m, so this is fun to play with and I might eventually try them all on this setup. They’re not as visually intrusive as many other antennas either, so fingers crossed – maybe the XYL will let me have this one up for a while.

Here’s a picture of the complete setup. With the trees, branches, and twigs, maybe nobody will care if it’s there.

I’ll keep testing this antenna the next few days, if you catch me on 40m (or maybe 30/60m?) there’s a fair chance it’s happening with this trampoline/Hamstick antenna!

Update: I’ve worked the antenna for about an hour, and I’m quite satisfied with the results. I was heard from JW (-10dB) and all the way down to VK7 (-14dB). Unfortunately I had work the next day and couldn’t wait for the grayline to hit the yanks – maybe I’ll try again later, one early morning.

Update 2: Finetuned the antenna a bit more, and I’m now down to SWR=1.1. Working Europe is no problem, and with the help of the greyline I’ve had QSOs with Australia, Indonesia, China, Brazil, USA, and Canada. All FT4/FT8, but I’m still slightly overwhelmed.

WAE CW in QRSS…S.

This weekend I attended the WAE CW contest as LC1R, partially because I wanted the CW practice, and a little for testing a new antenna I designed and built a couple of days ago.

The contest was a poor choice for antenna testing, and this is clearly reflected in the participation. Contest QSOs could only be made outside Europe, and my experimental antenna setup wasn’t exactly carved out to be an extreme DX antenna. Despite the challenges I managed to log a whopping 30 – yes, thirty – QSOs, having logged Japan, AS Russia, USA, and Canada.

Keep in mind I’m a CW rookie. I spent most of the time listening to workable stations, making sure I got the call right and sort of could predict the next serial number. I pushed myself to 18WPM, but since most stations had an insane WPM so I had to use software to assist me, or I wouldn’t stand a chance.

Let’s slowly transition into the the antenna topic, which is somehow interesting. I call this antenna the “I don’t care just get me on the air”: it’s not optimal, by no means claimed to be good, no math or any science to back it up. To be honest it was made for a laugh, but it works and it’s simple in terms of use, and setting up.

The antenna is about 5 meters of wire soldered to a SO-239 connector, with the shield connected to a battery clamp. No balun or impedance matching at all. This can be hooked to whatever you have as a counterpoise/radial; be it the car, a park fence, auto barrier, rain gutters — anything might work. In my case, I used the frame of my kid’s trampoline and the SWR is barely registered on the FT-950. A couple of tests running FT8 (60W) and pskreporter.info shows acceptable results.

Colour me surprised. I might keep this one for later “slash portable” activity.