Carl Moreschi N4PY kindly provided these useful suggestions for those of you looking at options for configuring the RSP as a full bandwidth panadapter and wanting to share antennas for TX and RX.
Subject: Re: FW: can I do this without damaging the sdrplay unit
I offer two solutions here with external boxes form either MFJ or DXE.
The one from DXE is a little safer but more expensive.
Solution to share antennas with an SDR panadapter receiver
The DXE-RTR-1A can be used to share antennas between the transceiver
and the SDR receiver. This is a $170 unit that will provide a safe
way to share antennas between the SDR receiver and transceiver.
1) Place the "Main On" switch in the middle "RX ANT" position.
2) Connect the amp key line of the transceiver to the "Transmit Ground" connection.
3) Connect a radio shack Y cable (part #42-2535) between the "Main ANT OUT"
and "RX ANT IN" connections.
4) Connect the third leg of the Y cable to the antenna input
of the SDR receiver.
Here's the MFJ solution. It requires a small mod.
The solution to share antennas is to add an MFJ-1708 T/R switch. This
unit will automatically sense RF from the transmitter and then remove
the panadapter radio from the receive antenna connection. But the MFJ
switch will also remove the transceiver from the transmit connection
while in receive. So the MFJ switch needs two very simple mods. You
must solder a 14 gauge wire between the transmit and antenna SO-239
connections. This will then make the switch operate properly for this
use. Additionally, you should wire the relay to energize from your
radio's amp key line for faster and safer switching.
Also for safety in case something fails I recommend adding two back
to back diodes between the receive SO-239 and ground. These diodes
will act as limiter and further protect the panadapter receiver in
the event of a timing problem. Radio Shack 276-1661 diodes should
Carl Moreschi N4PY
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