I worked Rick, N6DQ on 14.178 SSB last nite in a group. He was running his SDR into an amplifier at 500 watts and his HiFi SSB was very clean without a trace of RFI ! Rick sounded exceptional, but a little "bright" for my taste. But the high frequencies show up the RFI 1st in my experience, and there was none on Rick's signal! How did he do it? He grounded together the Dell computer chassis to the SDR box and tied that to the station ground. He cut the Hosa cables down to 6" and velcroed the grounded breakout box to the SDR box. Also he used a separate Astron PS with short power leads.
My SDR is still having occational RFI issues, the inline isolators, beads and toroids did not solve the problem completely. If the gain is up just a little - back comes the RFI shadow! I'm starting to think one of those mini cpu cards in a shielded box bolted to the SDR cabinet might be better then ripping apart my computer desk and all the rest. Will it ever end?
IMHO, this demonstrates the flaw with using a soundcard in a near RF field! If the RF is getting in some other way then the audio cables - even optical coupling may not guarantee freedom from RFI! The A/D & D/A must be RF shielded and a computer is not the ideal location for that!
The 870 is back online and the SDR offline, until I can come up with a solution to this MESS.
BTW, no RFI is evident using the TS-870 driving a 1kw amplifier.
