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!!!