Amateur radio: working 80

I didn’t do any major stuff over the weekend, just working a couple special event stations that I heard, a couple contacts for the Montana QSO Party, and a few more for Winter Field Day.  However, the big thing is that I found that my magnetic loop with a size optimized for 20 meters still gets out a readable signal on 80 meters on SSB even though the predicted efficiency is only about 2%.  Of course, I’m now confidently running 75 watts into the loop, but if the calculation is right, that’s still only 2 watts of radiated power!

I don’t think that’s quite right, though.  Whether the loops are more efficient than one particular prediction says they are, or via coupling with nearby power lines, metal eaves, house wiring, etc., I bet I’m getting out more than 2 watts.  I even managed to work Connecticut on 80, another QSO over 2000 miles.  The big downside is that the 3:1 SWR bandwith of the loop is down to around 10-15 kHz, depending on how good the peak SWR is for a particular frequency.  Not a big problem for listening, but a big problem for transmitting.

I’m working on a mounting system that will let me get my loops up higher with the center of the loop at 15 feet.  It has to go up and come down fairly easily in a very limited space and I have to be able to do it alone without the threat of damage to myself or the antenna.  Having the 2-pound vacuum variable capacitor with another pound of the motor assembly and project boxes for both at the very top of the PVC mast makes the system very top heavy and unstable.  I could buy a much lighter ceramic vacuum variable, but at $200+ a pop for these specialty items, I’d rather not go that route unless I would need to have both capacitors mounted on loops at the same time.  Hopefully the new system will work well; if so, I’ll probably do a blog post and/or a video about it.


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