la3rk

At least one source identified and reduced. My station pc is powered via the 12 volt supply. Even when off it supplies 5v via usb. The internal voltage controller sent significant noise back on the 12 v bus and was picked up by the outside antenna. Probably following the coax outside, my choke was not sufficiently effective below 2 mhz.

Found by sniffing with a ferrite rod antenna while watching the spectrogram.

There is also some noise on my mains ground, my mains filter had a straight through earth wire.

My SNR ratio is improving, now seeing numbers around 25 dB (P90 level minus mean level, 0 to 30 MHz)

73 de Olaf - LA3RK