"Joel Kolstad" wrote in message
...
At work we have these "do-hickeys" that look like a regular "tee"
connector.


We called these an "isolated T" when I worked in 2 way radio and used them
to check for receiver desense in a repeater. The through ports were placed
in the line to the antenna, while the isolated port was connected to a
signal generator on the receiver frequency. We would disable the repeat
function, turn the generator amplitude up until we got some value of
quieting in the receiver, and then re-enable the repeat function. If the
duplexer was mistuned (or was a cheap notch only type), or you had a dirty
transmitter, you would hear the noise level in the received signal rise.
The isolated port was needed so you did not transmit into the generator and
cause the magic smoke contained therein to issue forth.

Some repeaters were very quiet (Motorola for one). Others (brands will not
be mentioned but they had horns on them) often showed several dB of desense.
I spent many an hour trying to finesse a sow's ear into a silk purse by
tuning for minimum desense. Ahhhhhhhhh those were the days.....


Bob WB0POQ