how to eliminate air-born RF


any ideas on how to eliminate airborn RF. I have disconnected all equipment from themselves and the ac outlet. Even shut off the main circuit breaker in the service panel. Have disconnected all video cabling and antenna wires. after all this, when I place my head behind my rack, which just holds my amps, I can here a humming noise similar to the ground like hum you hear from an electric guitar/amp combo or similar to a bad tonearm phono ground loop. With system wired up and operational, this humming is easily heard at idle on, with gain on preamp down. Again, this is occuring with nothing physical wired together or to the ac outlets and with all ac power shut off in the house. PLEASE HELP!!!
mooncrikit

Showing 1 response by billshenefelt

I am getting dit dat from a ham operater keying somewhere.  I just ordered some material that is supposed to shield from RF.  I have a
SOTA sapphire turntable and Hana low output moving coil on a unipivot  Ultracraft tonearm.  It is a function of where the cartridge is located above the turntable.  It is highest when not above the turntable platter but outboard of the record perimeter the noise  has some varation in volume and stereo channel it is on depending on the location over the turntable.  It does not disappear at high volume but is still apparent over mostly the outer edge of the platter but over the outer inch or two of record grooves.
I have tried different tonearm pipes(the tonearm has changable "pipes" not changable headshells), and tonearm bases.  It is present on a Hana low output moving coil and also on a moving magnet Grado mounted on a second tonearm pipe. Different tone arm cables make a minimal difference in the amount of the noise.   I even tried adding ferrite chokes over my tonearm cables 

Any thoughts?