RF Sensing TR Switch
MFJ 1708 RF Sensing TR Switches can automate your nostalgia! Do you still enjoy using the vintage tube-type transmitters and receivers of your youth? In those days, it was a real chore to switch your antenna from receiver to transmitter and back… and it still is!
These neat little MFJ automatic T/R switches sense transmitted RF and switches your antenna from receive to transmit using a relay. They also short your receiver's antenna input to ground… protecting your receiver from transmitted RF.
Optionally, a control-line input from your transmitter will let your key/keyer or PTT line switch control antenna switching. An adjustable time delay circuit provides delayed switching, if necessary. This delay prevents your antenna from switching between dots and dashes or between syllable and words.
These switches provide an auxiliary contact closure to ground during receive (opened in transmit) for an illuminated "On-the-Air" sign or other use.
MFJ 1708s work on all modes; CW, AM, SSB, FM, and digital modes. They can handle up to 200W SSB PEP. Their compact size is only 4.0 in.-W by 2.625-H by 1.5-deep. SO-239 coax connectors are used for antenna, transmitter, and receiver. They use convenient RCA connectors for the control input and the auxiliary contact closure to ground. These switches require 12 VDC station power or 110 VAC with optional MFJ-1312D power supply (not included).
Dust off the old S-Line, C-Line twins or the old National, Hammarlund or Hallicrafters and get on the air with the vintage gear you love.