Using HRD's DM780 waterfall as a cheap ham's spectrum analyzer, I see the below RFI pattern on all HF bands through 6m with my Yaesu FT-897d mode set to AM. The signal strength ranges from S6 to about +5db on 30 and 40m. This RFI practically eliminates QSOs except for strong JT65 signals that can cut through this noise
It appears to be narrow-band modulation spikes at a 60Hz rate. The RFI disappears when I disconnect my radio antenna.The narrow-band pattern leads me to believe it is NOT power-line arcing which I have had trouble with in past.
Any ideas how to track this down?