SWR Meter affected by Audio cabling?

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relistan
 

Posts: 38
Joined: 23 Jun 2022, 12:12

SWR Meter affected by Audio cabling?

Post by relistan »

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.
EI9ITB / KB8SWH
relistan
 

Posts: 38
Joined: 23 Jun 2022, 12:12

Re: SWR Meter affected by Audio cabling?

Post by relistan »

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.
EI9ITB / KB8SWH
John
 

Posts: 49
Joined: 19 Feb 2022, 08:56

Re: SWR Meter affected by Audio cabling?

Post by John »

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.
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