Foundations of Amateur Radio

Recently I discovered that the antenna that I had connected to my WSPR or Weak Signal Propagation Reporter beacon was not a 40m antenna, instead, it turns out to be a 15m antenna. The how and why of that mix-up isn't particularly helpful, so instead I set out to remedy the situation.

Step one was simple, go into the garage and pull out the antennas and check if I had forgotten about an 80m antenna. As it happens, I'd forgotten about a 17 megacycles antenna. At the moment I couldn't tell you if it was intended for Maritime or Amateur use, but it doesn't really matter, since I'm not permitted to use those frequencies for transmit and I was on a mission.

Oh, I also discovered that you can dislodge two shelves with stuff on them by moving an antenna. Fun.

So, 7 MHz, or 40m it is.

The antenna mount is clamped with G-clamps to the side of a steel roofed framework that's bolted to the house. It's been there for about eight years or so. From time-to-time I change over the antenna depending on my mood.

Today I wanted to move the mount and after taking it down decided that it could do with a little maintenance, least of which due to the fact that the feed-point connector had detached itself. I also needed to remove the ground wire, which turns out to be a bit of a palaver, since my socket wrench adaptor has gone walkabout and the 10 mm socket that fits into the next size is too large. Eventually I found an imperial socket with a matching wrench to undo the thing.

Then I set about moving the mount to a new location, tucked inside a tree, so plenty of branches to poke me in the eye, or the belly, depending on which was handy at the time, and discovered that the steel beam was thicker, to the point that my G-clamps were 2 mm too small.

So, I spent some quality time comparing hardware store offerings, finally found a bigger G-clamp for a reasonable price, but in the process discovered customer reviews and photos showing that the clamps fail if you hand-tighten them. Me being the "if you can move it, it's not tight" kind of person, figured that this would not work. Found F-clamps at a different hardware store and went on my merry way to get one. The hardware store was undergoing maintenance, so hammer drills and stuff everywhere, more fun.

After getting back home I discovered that the new location was great in theory, but in practice it turns out to be less than spectacular, since the beam has a slight curve in it, making for a poor clamping surface and no place to put two clamps.

Back to the original location.

Using the new clamps, fighting for space, I realised that I could re-use the old clamps, so swapped them over.

Then I got to the point of connecting the feed-point and discovered that my 40m antenna is missing the mounting thread and the all-thread inside the old antenna wouldn't budge, neither would any of the threads in the other two antennas.

So, at this point, three hours in, I came to the realisation that this was going to be a 15m antenna or no antenna.

So, 15m it is.

There is one actual change.

I discovered that the feed-point connector is actually an SO-239 socket and the connector to it was a standard banana plug which in turn was connected to a BNC connector, with the shield connected to ground.

I realised that I could use a BNC to PL-259 adaptor instead to connect the RG6 coax to my antenna.

This means that the coax is now directly connected to the feed-point, rather than through a weird cobbled together BNC-to-wire-split-thinga-ma-bob-contraption. It looks very pretty.

Measuring the result also shows some changes.

On both 40m and 15m the SWR is still the same, on 10m it's a little worse and on 2m it's significantly better.

All in all, I think this is a perfect example of 17 steps backwards and 18 steps forward.

I suppose it could be worse.

I'll let you know how the beacon goes.

Now, I should probably log this. Something like: "QTH HF antenna mount maintenance, nothing changed, 15m antenna, PL-259 to BNC adaptor to replace homebrew wire splitter. 3 hours."

I'm Onno VK6FLAB