A Scrap Wire Antenna for 10m and 20m
I usually have obligations on Wednesday nights, but this last week I was under the weather and found myself at home on Wednesday with nothing in particular to do. Of course, when you've got nothing else you have to do, you're supposed to make antennas out of items you have lying around, and so I got to work.
There's a bit of wire that has been bugging me, sitting around the shack. It was a green-clad wire reclaimed from an old extension cord, stranded, decent gauge, and very flexible. I had used the black and white wires from that same bit of cord to make removeable extensions on a dipole, so that I could use it on either 30m or 20m. But this bit wasn't doing anything. This was the main component of this particular build. The total parts include:
- A bit of reclaimed extension cord wire (approximately 80in?)
- A 4ft long 3/4in wood dowel
- 14 small zip ties
- An SO-239 connector
- About 6in of metal plumbing strap
- Solder, two screws, an aligator clip, and a 68in counterpoise scrap wire
Note: I should mention the motivation (beyond finding ways to spend time): my 30m dipole is currently down, and so I've only got the EFHW up in the air for HF. I have two stations, and would prefer to be able to cover two bands for JS8 when I'm in the mood, rather than swapping bands. And so, I had hoped to build some little antenna that I could put inside my shack for QRP on a band that wouldn't mess with my 40m main station (not in the mood to find a spot outdoors).
I didn't design this antenna, I simply built in and then figured out what it could be used for. Here's how the build went:
- Zip-tied one end of the green wire to the top of the dowel
- Every ~4in down for a total of 39in, I zip-tied the wire to the dowel in a straight line
- At the 39in mark, I double-zip-tied the wire and started wrapping in tight coils
- I wrapped approximately 20 tight coils, then double-zip-tied again, with a couple inches of wire left
- I soldered an SO-239 connector, and screwed that connector to the dowel
- I soldered an aligator clip to the scrap counterpoise wire, and clipped it to the SO-239 connector
- I screwed the plumbing tape to the top
After putting it together, I hooked up the nano-VNA and found that SWR was quite low (2 point something) right where 10m JS8 happens. So, I hung it in the corner and hooked it up to the G90 running at 10w-15w. It tuned up very quickly on 10m, and I was shocked at the distance I was able to get two-way contact on FT8, and via HB on JS8. I had a QRZ confirmed contact to Germany, with this thing hanging in the corner. Images of PSKReporter are below, you can ignore the 40m reception reports that are mixed in there.
I played with 30m, but that wouldn't tune up (maybe with a different counterpoise?). Then I tried 20m, and it tuned up with some effort. I'm able to run 3w-5w into it on 20m without any issues. Reception is very poor, compared to my EFHW, but hey, it works! Plus, the poor reception means my 10w 40m station isn't creating issues being so close to this one. I can now fire up the G90 without taking my main station down, and fiddle on 10m or 20m. The cost was a small amount of time and effort, and some scraps that were already around the shack.
