23cm groundplane antenna

I thought it would be a useful experiment to make up a 23cm groundplane antenna. There is a useful guide at https://vk1nam.wordpress.com/2017/06/24/23cm-14-wave-ground-plane-antenna/

Using some 2mm copper wire from a supplier on eBay plus a N-type female socket the construction was fairly simple. Using the dimensions given above plus a bit for fiddle room I soldered the vertical element to the centre conductor of the socket. For the radials, given it was copper wire I decided to press my jewellers anvil to work and flattened the end of each element sufficiently to drill a 2.5mm hole. Using 2.5mm bolts each was secured to the respective mounting hole in the socket, and then the excess thread was cut off with a Dremel.

Bringing it all indoors – the heavy stuff like drills and hammers live in the workshop – I calibrated my NanoVNA and gave the new antenna a go. It was a bit off but then each element was too long. Trimming each gave a fairly flat SWR where I wanted it. Well, almost, but near enough to stop cutting bits off!

But does it work? Yes, I can open up GB3WC from the shack holding the antenna up inside the window. It’s about two S-points down on the Yagi, or anyway two of whatever the divisions are on the signal strength meter on the FT2D. Surprisingly I can get into the repeater with the antenna on the desk, albeit only coming alway up the signal strength bar and very hissy. It was the same when sitting the antenna in an old bottle as a support – at that altitude there are a lot of houses and trees between us and the repeater.

For a bit of copper wire and a socket it was a fun little thing to make. I actually planned to make a collinear and may still,  but this was nice and simple and quick.

23cm first FM experiment

Since my last post about the SG-Labs 23cm transverter I realised I have several handhelds all of which have low power settings. Time to try some FM and get a better frequency readout. 144MHz did indeed produce 1296MHz (and some small change) on the frequency counter. Time to get adventurous – GB3WC in Wakefield is about 15 miles away and pretty much line of sight and so would make a good test.

With the transverter in repeater mode with a -6MHz shift (jumpers 1 and 3 on) and the FT2D programmed for 145.375MHz simplex (WC transmits on 1297.375MHz) – the transverter does the shifting – and the necessary 82.5Hz tone I can open GB3WC and receive it at S9+ on my 8 element 23cm Yagi. In the true spirit of let’s get this new shiny box working this test entailed the use of a microphone stand, some wire and some clamps. But it works.

Only a quick test today as the battery was nearly out on the Yaesu and it’s kind of hard to talk into it where it is. Somewhere I have a headset for it which will make life easier until I figure out how to site it properly. The tricky thing with the transverter is to get it back to simplex means taking the lid off and altering the jumpers, not particularly easy if it’s up in the loft where things are easier to leave in place.


I’ve always been interested in microwaves and 23cm is one band up from where I currently have kit (well, ok, apart from the QO100 setup) so I got an SG Labs 23cm transverter from eBay. I thought I may as well have a play before The Powers That Be trash the band as seems threatened. Nice little box. Of course, it gives me a problem now and having just spent an hour cobbling stuff together I am a way away from being able to actually use it.

But I wanted to make sure it worked, not that I suspected otherwise but it’s a new (to me) shiny box and I want to play with it. So, how to feed it… I grabbed the TR-9130 that had been relegated to the workshop since I got a 144MHz transverter and let it acclimatise overnight. Apparently this puts out 5W on its minimum setting which is borderline for the SG Labs kit. Fumble around for my attenuators – but those are F-types.

And of course I had no patch leads to hand… but I did have some useful crimp PL259s to quickly make a lead up.

Running the VHF set through a SWR/power meter into a dummy load confirmed the 5W, of actually more like 6 but SSB should be fine if I don’t shout. I have a short 23cm Yagi so seemed all set for a test. But… something missing… ah yes, what do I receive it on? Ugh.

Ok, run up CubicSDR on the Mac and use the SDRplay box with one of the baby antennas that came with the Pluto. The desk is now covered in bits of kit and wires. Can’t find the signal in CubicSDR. I have a handheld scanner which goes up to 1300… but impractical to slowly run through the band hoping, and anyway it does not do SSB. Setting the TR-9130 to FM caused the transverter to whinge via it’s red LED showing far too much input.

Ah, the frequency meter then, that goes to 2.7GHz. Finally I can see output in the form of a fleeting count on the counter. Getting a BNC cable and the baby Pluto antenna so the antenna is close to the Yagi and I could get a more accurate reading of 1296. Good. Now I can tune to it in CubicSDR and finally see a signal, which saves me from figuring out how to do it all properly in CubicSDR!

And that’s as far as I can get. I need an attenuator so I can run it via the 144MHz transverter which puts out up to 10W, or so I can use FM on the TR-9130 – ok make that two different attenuators. Not that I will get very far with an 8 element Yagi on the desk but in theory, and perhaps using a handheld I should be able to open up GB3WC from here as it’s pretty much line sight.

Lots of faffing around then for an incomplete result… but then, isn’t that what it’s all about?



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