[CQ-Contest] SO2R Hardware Question

[Richard Ferch]

What I believe John wants is quite simple, and relatively straightforward
to implement, but as far as I can see it has little to do with SO2R.

As I understood it, he wants to be able to listen to two receivers at the
same time, both connected to the same antenna. Presumably he doesn't have a
dual-receiver rig, but he wants to approximate the same capability using a
second transceiver as a second receiver.

One aspect of dual receive is audio routing. The easiest solution to this
is to use stereo headphones with one receiver routed to each earpiece - a
stereo to dual mono adapter will do that, or you can make things fancier
with an audio switching setup where you can choose either or both receivers
as audio sources.

The more significant aspect is protecting the second receiver against the
first transceiver's transmitted signal.

Some transceivers (Elecraft K3, Icom 7600, Yaesu FTDX5000, etc.) provide a
built-in capability to do this, namely RX Ant Out and In connectors. The RX
Ant Out connector is actually a connection to the main transmit antenna
through the transceiver's T/R switch. Connect a splitter (or coax tee)
between the RX Ant Out and RX Ant In connectors and feed the second
receiver from the other branch of the splitter. You can use an SDR as a
panadapter/spectrum display this way.

With transceivers that do not provide this capability you should be able to
do something similar with an external relay, controlled from the first
transceiver's PTT Out connection (the one used to control an amplifier),
that will switch the second receiver's antenna connection out of line
whenever the first transceiver is transmitting. This harks back to the days
of separate receivers and transmitters. Depending on the degree of
isolation required and achieved, you might need some additional front-end
protection for the second receiver. The transmitter also has to have a
sufficient transmit delay, i.e. PTT has to be asserted a sufficiently long
time before output begins, to avoid hot switching.

I believe there may be electronic receiver protector devices available that
can perform a similar function.

This, at least, is how I understood his original question.

73,
Rich VE3KI