[AMRadio] Receiver Muting

JAMES HANLON knjhanlon at msn.com
Fri Jan 10 17:17:57 EST 2014

I run a bunch of receivers and transmitters together, two groups of twelve to be exact, and I use the extra RF gain control in series with the existing RF gain control to ground technique with the receivers.  I've built up a break-in keying system out of simple, discrete RTL logic gates and several mercury wetted relays.  The relays are very fast, they do not "bounce" on contact closure or opening, and they are very low resistance when closed.  They will handle currents up to several amps when closed, and they don't mind switching at least 300 volts, so they handle cathode-keyed rigs very nicely.  I sequence them with the RTL logic system so that the first thing that happens upon key closure is that my antenna is transferred from the receiver to the transmitter and a transfer relay in the receiver with its swinger grounded opens across the added RF Gain (monitor level) control and closes across the receiver antenna terminals, thus setting the receiver up to become a good monitor for my transmitted signal.  The next thing that happens is that I get a relay key closure for the oscillator and low powered stages in my transmitter.  After that I get a relay key closure for the amplifier stage of my transmitter.  When I open the key, the relays open up in the reverse sequence.  The whole thing follows my keying to well over 30 wpm which is about as fast as I ever go.  I can control the monitor volume level by adjusting the extra RF Gain pot, so I can make it the same level as the incoming signal.  
If anyone is interested I can supply details on the break-in keying system.  I wrote it up for Electric Radio magazine several years ago.  My friend, Mac, WQ8U, duplicated it for his rig, so it can be done.
Jim, W8KGI

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