Re: RFI from uBitx TX after AGC and other mods installed

Don, ND6T

I am a bit overwhelmed, perhaps. Alan, are you referring to the AGC board, not the "Click eliminator"? I'm not finding where Kees posted any photos of mounting the click eliminator. That would be the board that I would expect to cause the problem (if the receive audio gate was always on). The AGC board (the one that plugs into the receive RF trace) would have the devil's own time passing microphone audio into the speaker.
Mark, your observations may really help Alan and I understand what's going on. I doubt that you caused any problem on the board by running the +5 volts to ground. The Raduino regulator would have been stressed but seem to remember the 7805 has a  thermal foldback feature for short duration faults. You may, however, try removing that +5 ground lead, I don't know where you ran that from but it shouldn't be necessary and inserts another unknown variable into the mix for me.
The volume control connection, however, is essential. The high side should NOT be connected to the wiper. Aside from swapped leads, about the only thing that I can think of is improper grounding. If anyone is using a plastic panel or case they need to go to extra lengths to provide short and solid ground returns. This is especially important where large signals or currents are present. The antenna RF connector needs to have its own additional ground back to the BITX board connection, not relying upon the panel or chassis. Same goes with the speaker and headphone jacks. The AGC and RF manual gain control should have the best grounding possible with connections to the BITX ground plane.
Aside from that, I'm out of ideas for now. What did you find Mark? -Don

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