As Steve points out, I didn't want to insert an Ohmmeter into a live circuit.? That is poor practice.?
I switched to straight key mode and measured the voltage at Q7's gate.? It did go to 5 V on TX.? The sidetone was still wonky in straight key mode, too.?
The circuit description in the manual indicates that muting is achieved by essentially grounding the wiper of the volume pot through the FET.? I grounded that point using a clip lead, in other words, always muted.? There was no change in the sidetone's performance.?
I did some more general experimenting.? I noted earlier that the problem is present whether I'm connected to my station DL (a 2 KW Drake air-cooled unit) or my antenna (a well-matched dipole -- VSWR about 1.2:1 -- and the same antenna I always use).? But it's much more pronounced on the antenna.? Wondering if there was a problem in the station's coax connections somewhere, I connected the QCX directly to the antenna feedline.? No change.?
I then connected a small commercial-grade 25 W DL directly to the QCX.? The problem cleared up!? Switching back and forth between the small DL and the normal station connections produced repeatable results... for a few minutes.? Then the problem showed up on the small DL!? It was not as pronounced as on the station DL, but obvious nonetheless.?
I continued experimenting for a few more minutes, and I noticed that the problem became significantly worse under all circumstances.? Maybe something is failing, and I need to stress it enough to cause it to give up?? Connect a DL, lock the paddles in dit mode, and let it run for a while??
This is aggravating.?
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73/72,
Dean K5DH
