I had the Class D working well enough on 160 at 100w to make a few contacts but now a gremlin has jumped in and I can't seem to find him. Here are the symptoms:
1. Large hum content on output inversely proportionate to freq. Not heard on 80 but unacceptable on 160.
2. Changing nothing but the VFO freq and receiver frequency, I can see and hear it decrease as I move up in 500kc steps.
3. Using a lab supply in place of the modulator produces a clean sig with no hum on both bands.
4. Using the modulator on 80 meters produces a clean sig with no hum.
5. Power level is not a factor. As soon as I start applying HV (10V?) the hum begins.
Any ideas?
js