I have done many of these in the past. With a Phelps Dodge Miniplexer they
made great full duplex ham phones in the 70s and 80s. Somewhere in my
garage, I have a 558 built up as an emergency repeater.
Its as simple as eliminating the switching transistor that turns off voltage
to the receiver during transmit. Replace it with a jumper. The purple wire
also needs to be cut. That mutes the audio stage if memory serves. Then
you need to dike the rg-188 off of the pin diode deck that goes to the
receiver helical resonator deck on the underside. Drill a small hole
between the fins of the heatsink and pass it out of the casting. Attach the
connector of your choice. Getting the pin diodes out of the transmit path
is optional.
All of this would be much easier with a manual if you are not familar with
the radio. I do it by memory mostly, if I forget where something is, I
sniff it out with a meter or scope. My point is, it is a very easy radio to
duplex. Even a 558 with the varactor tripler and antenna relay works very
well in duplex.
There may be some frequency combinations that are violations for this radio,
but with low in, high out I have never run across this problem.
td
wb6mie
I was given a mint condition EF Johnson 559 UHF mobile which I wish to
convert into a repeater. I have prior repeater building experience,
mostly with GE MVPs and Exec lls. Any and all info would be greatly
appreciated
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