Hi there, Brian, nice job and happy to hear that your "random" is working well, sure 144ft isn't exactly a "portable" length, but if that's ok for you, fine with me notice though that a shorter length covering the 80m band, with a good counterpoise, could allow to "tune" down to 160m although being short er than 1/4 lambda the antenna won't be so efficient thereBrian - K3ES wrote: ↑Tue Jan 31, 2023 10:35 am I finished my build this month, and used the antenna for Winter Field Day... Er... used Winter Field Day to test the antenna. Particulars are:
- 9:1 unun auto-transformer was built on a FT50-43 core, wrapped with 9 turns of tri-filar (3 twisted strands) 24 AWG magnet wire.
- I connected a 144 ft radiating wire, with the objective to enable tuning for CW on the 10m through 160m bands.
- I used a three 17 ft wires for a counterpoise.
- LDG Z-11Pro II tuner was successful matching 10m, 15m, 20m, 40m, 80m, and 160m bands with 1.5:1 or better SWR.
I am pleased with the results, and am working on a more complete field report, so more to follow. Thanks to all who helped with tips and advice.
73 de Brian - K3ES
Anyhow, if you want to try building an ATU, have a look at this design
https://pa0fri.home.xs4all.nl/ATU/FRIma ... tcheng.htm
it can be built for QRPp using two polyvaricons or one may use a couple of regular air var caps to build a version supporting QRO, the only limitation of that ATU is the fact that it doesn't tune down to 160m, or better said, it could do so by changing the coil, but then it will just tune "up" to the 30m band, not a big issue but worth mentioning, on the other hand, that tuner has two main advantages, first of all it doesn't need any "switched tapped coil" or "roller inductor" so it's easier to build, second the coarse tuning can be performed in RX mode, just by adjusting the two capacitor for "max noise" and then switching to TX and doing the final "fine adjustment", so it will help sparing batteries in portable mode !
If you'll decide to go on and try building one, I suggest following the approach shown here (see the schematic)
the above adds a pair of swithes, one allowing to reverse the input/output to match hi-Z or lo-Z (instead of having to manually swap the connections) and a second one used to bypass the ATU (useful if you have low SWR on some bands so don't need the tuner), other than that, there's nothing particular, just a tapped coil (winding it on a toroid isn't a bad idea) and two variable capacitors
Getting back to your "random", did you consider carrying a fiberglass fishing rod with you ? A 33ft one will allow to lay out the antenna as inverted V or inverted L and once closed may be tied to a backpack and carried around quite easily