[Yaesu] tx/rx relay/monitor

[W5HTW@att.net]

A lot of us used to use one set of contacts on TR relays to insert additional
resistance in the RF gain control on the old tube type receivers.  It allowed
the receiver to be used as a CW monitor.  Actually, the relay, in 'receive'
position, shorted out the auxilliary resistor, returning RF gain to normal,
full operation. This works fine with headphones even on AM or SSB.  In one
setup I had the relay available to me had only two poles, so I used one set to
transfer antenna and the other set to key an additional DPDT relay which
inserted/removed the extra RF gain resistor and grounded the receiver antenna,
but did not mute the receiver.  

In my current AM/CW setup, am using a keyer with built-in monitor
(Hallicrafters HA-1) so don't have to monitor with the receiver.  I use a
triple pole double throw relay in a homemade TR setup that switches antenna,
mutes the receiver and the third set grounds the receiver antenna.  But this
is with an old tube type receiver, which is far more tolerant of abuse.  I did
try defeating the receiver muting (by changing the Standby/Receive switch on
the receiver to "Receive." but the overload even with the antenna shorted to
ground was quite apparent.  Doubt it would work with the newer receivers due
to the amount of RF getting into the radio.  

If the Yaesu receiver you are using has the "light bulb" RF protection, like a
few of the older ones, you may not would do any damage, but not sure you could
use it for a monitor unless you found a way to automatically reduce RF gain
AND to protect the antenna input.  

73
Ed
  
--
Ed Brooks, W5HTW
http://w5htw.home.att.net/index.html
Active since June 1956 Extra since
Jan 1970