Brent, I don't have an 850, but this is the mod I used on my 940. I
assume the antenna TX/RX wiring is probably identical.
1. Install 2 audio plugs in the back panel. You may have one ( as the
940 did ) which is not in use.
2. Disconnect the little coax cable which runs to the 1st RF at the
TX/RX relay, and connect it to one of the 2 audio plugs. Be sure to ground
3. Connect a similar cable FROM the 2nd audio plug and solder it to the
position where the other cable was removed.
To settle your nerves, take a sip from a cool one, and then connect
a short length of double male cable to the 2 audio plugs. The receiver
will now operate EXACTLY as before.
4. To utilize the circuit, (depending on how many extra antennas you wish
to use as RX only ) you will need a 3 position switch box ( such as those
sold by Radio Shack to switch antenna/VCR/ect ) In this instance, I'm
going to only describe 1 extra RX antenna, but to add more, you just add
5. Disconnect the short cable from the 2 plugs. Run a cable FROM THE PLUG
leading to the 1st RF to the COMMON position of the switch box. Run a cable
from the "A" switch connection ( or however it's labeled ) to the
remaining plug which was installed. At this point, with the switch in
the "A" position, you are receiving from your regular transmit antenna.
6. Connect the coax from the RX ONLY antenna to the other input of the
When the box is switched to the "B" position, your RX ONLY antenna is
connected. If you want to add more RX antennas, it is only a matter of
cascading more switch boxes ( or for that matter, finding a switch box
with more than 3 positions---which I have been unable to do. )
Summary: When the switch box is in position "A", everything performs as
before. When in the "B" position, ONLY the RX antenna is used for receive.
It is IMPOSSIBLE using this configuration to transmit on the RX ONLY
antenna. No extra relays are needed, no additional wiring...works like a
charm, costs about $5, and all that's needed to restore the whole works
is just connecting that short cable across the two plugs.
Hope this will be of use to you and the other guys. I have my setup
controlling 3 seperate RX antennas...2 Bev's and a B I G loop.
Name: ed sleight
Time: 11:49:14 AM
This message was sent by Chameleon