Hi Don - I tried a small RG174 cable and unfortunately it didn't solve the RFI problem. Still getting a very strong garbled RFI when I transmit SSB and the audio cable is connected. Grounded at both the pot end and the AGC board, with the center of the coax going to the hot side of the pot (not the wiper).
Same problem with TX into a dummy load or antenna.
Not sure what to try next unless I move the AGC board towards the front of the enclosure and redo the cabling. I guess it's hard to know where the RF is coming from so I know the best way to route the cables to avoid it?
Any other thoughts? Is anyone successfully using the AGC kit mounted at the tap point of the RF trace and Sunil's enclosure? Maybe a photo showing cabling for a successful install would help.