Thanks for all the feedback and suggestions.? I haven't had time to work through everything yet, but here is what I have learned:
- I get similar hum on a SLA battery.? The voltage is a bit low (it's an old, mostly dead battery) but it definitely sounds similar.
- I took a pass at getting better grounding around the board with no results.? More to do here.
- I checked the antenna connection.? The connector is keyed correctly, from what I can tell, with brown going to the signal trace on the board and black going to ground.? Brown is going to the center of my BNC.
- The audio is extremely quiet even on side tone when I key down into the dummy load.? Through the 8 ohm speaker or head phones with the audio gain all the way up, it is just barely a whisper volume.
- Key down into a dummy load @ 12.1V, I'm getting around 4 watts on 40m.? Not sure if this is relevant or not, but another data point.
I do have a small amplified speaker so I can certainly use that, but it sounds like my experience is at least somewhat different than most so I'm interested in pursuing the differences, more for the learning experience than anything else.
Hoping to have some time this weekend to follow up further and do some more measurements.
Thanks,
73 Ben KN4COI
