Keying an amp without a relay

[tunedandloaded]

How does one go about keying an amplifer with a radio that doesn't have a amp relay output?

 

[IMD262]

Ham Radio Outlet | MFJ MFJ-1709 | FOOT SWITCH

 

[W5LZ]

There are probably several ways of doing that. The two that come to mind is by using an existing "keing" circuit if there is one. The other is by "RF" keying. Which is basically a circuit that when it detects RF present (the transmitter's output), it turns on the amplifier. That RF keying is usually done because there's no keying relay in the radio. And then there's always the option of putting a keying relay in that radio.
- 'Doc

 

[VA3ES]

RF Sensed T-R Relay Kit

From Ramsey Electronics:

"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: 11/2" x 1/2" x 4"."
$19.95​

RF Sensed T-R Relay Kit

 

[Beetle]

Ham Radio Outlet | MFJ MFJ-1709 | FOOT SWITCH

Heil makes a footswitch also. What I like about the Heil FS-2 is that it has two separate microswitches, set so that one actuates just a few milliseconds before the other. That way, you key the amplifier first, and then the transmitter. Much easier on amplifiers that way.