Ramsey RFS-1 Radio frequency switch
This is the unit you need when adding a preamp or power amp in line with an existing antenna. It senses the RF power and closes an on-board DPDT relay which can be used to automatically switch in your added power amp or preamp. The relay is good up to UHF -100W! Many folks use one of these ‘lifesavers’ in front of their expensive test equipment. Runs on 10 to 15 VDC. Senses power as low as 50 mW. Size: 1½” x ½” x 4”.
Can switch up to 100 watts of RF power or 1 Amp DC