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© 2000 SouthEast Iowa Technical Society
ge mastr II duplexing 2
Mastr II VHF/UHF Mobile Full Duplex Mods
Notes from the Northwest Repeater Association
PO Box 230788
Portland, OR 97281
1 June 93
Obtain a pair of GE ICOMs on a commercial frequency in the range the radio
was originally operating. Follow the tune-up procedures in the GE manual
(see above) and check to see if the radio meets specs before attemptimg
If your radio is an "E" model (thick case):
Check to see what is located below the main radio chassis. Remove the
second exciter or receiver front end and take out all extra wiring, splitters,
etc. These are not needed to make a basic repeater. Again, check to see
if the radio is still operating properly before proceeding.
On the bottom of the control board, cut the trace between H95 and H96.
This will disable the RX audio mute circuit.
On the top of the control board, cut the trace going into pin 7 of J904
(the Rcvr/Audio Squelch board). This will disable the PL RX mute circuit
Put a jumper between J903-11 and J903-12. This puts 10V on the receiver
to keep it on all the time.
If you are using the GE factory PL deck, several modifications are necessary
to keep the RX decoder from being disabled when the radio goes into transmit.
First, cut the top lead of CR1009 which is mounted vertically on the PL
deck. Next, cut the trace on the bottom of the board that goes from PTT
to pin 7 of U1001.
Install a small fan on the top of the radio directly over the PA compartment
to pull air out of the radio. Fan cooling on the rear heatsinks may also
be required if you are running the radio close to its rated power.
The factory control head can be used but you are probably going to want
to shorten the cable. If you build you own control box, the cable can be
used to bring out all of the connections. CAS is used for the COR line
and if you are using the factory PL deck, RX mute will give a decoded PL
signal. Pullup resistors may be required depending on the controller you
are trying to interface to.
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