(tr)uSDX Forum

I am not sure what is happening precisely, as I don't yet have an external SWR meter for this thing. But when I check SWR on 20m without headphones attached, I get an SWR of 1.06 on the (tr)usdx display. As soon as I attach my headphones and headphone amp, this jumps to 3.6! That seems most likely to me to be a measurement error, with the ground of the ATmega being affected by the longer wires attached to the headphones, maybe. When testing without the amp, and with a long lead attached to the headphone jack, I get SWR of 2.06.

Anyone else seen this? Any idea if it's an actual problem and not just a measurement issue? I can totally deal with unplugging headphones to check SWR. But don't want to burn up FETs, either.

Hmm, actually the conclusion I have come to is that the SWR meter is just all over the place, regardless of what changes I make. I guess I'll have to get an external one.

That sounds an awful lot like RF coming down the outside of your coax due to an unbalanced coax cable running to a balanced antenna. That can cause all sorts of glitches and wandering readings to occur.