Switched UN-UN’s for the Inverted-L

If it weren’t for 80M, I could continue to just use the Balun Designs 1:1 current choke at the base of my Inverted L. One way to make my Inverted L happy is to put a Vacuum Variable Capacitor in series to the vertical – and use the AT2K Tuner in the shack. Tune the capacitor remotely as I did the URAT.

The second option, which is perhaps easier is to switch in one UN-UN or another, and this is so I can use the antenna on 160 or 80 (schematic above).

The Balun Designs 1435t UN-UN is a 1:4 model and would step the 80M 7 ohms j27.4 up to 50 ohms.

The Balun Designs 2132u is a 2:1 UN-UN and would step the 194 ohms j213.4 on 160M down to 50 ohms.

I am going to try this. It might just turn out that all I would then need for 160 and 80M is the SPE 1.3K built in ATU – which has a pretty small range, but these UN-UN’s most likely would make the tuner happy. I would still need the AT2K if I wanted to use the Inverted L on say 30M or some other band.

Speaking of other bands – the 3Y0Z DXpedition will most likely be good into the West Coast on 17 and 15M, and while I am pretty sure I will get them on 40, 30 and 20, I might try them on 17 and 15 using the Inverted L.

The switching circuit you see above is approximate – I might even add two more relays to switch in a 1:1 current choke instead of the 2 UN-UNs only because then I would be able to cover pretty much any band from 160 – 10M.

I could wire the control voltage so that one “line” is a default switched in line and all others are closed. The natural default would be 160M. Then with basically a simple rotary switch – I could control the three different “chains”.

I could even use an Arduino or Raspberry Pi Zero W to control the relays via WiFi if I wanted to get fancy, but because I still have to run a control line for remote power, I will just hard wire it and control it with a rotary switch. The rotary switch simply sends the plus 12v line to activate each pair of relays – I think I will everything to be normally opened, and then when I switch to a position, it switches in the relay pair for each matching transformer. I like instant switching, so, maybe this would even mean I would no longer need the AT2K at all. I can easily test my assumptions and then use an old Ameritron RCS-4V switch box controller that I have in my junk box (where I burned up the remote relay board) that has a rotary switch and leds and just do a little re-wiring.

I’m going to try it and see – it will be a lot of fun.


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