Modifing
the Mastr II Systems Board
for
full duplex.
By Kevin Custer W3KKC
Concept:
To modify the "Systems Board" to allow a GE Mastr II Mobile radio operate
full duplex. Information is provided for both the Common and Special
Systems Board.
Common Systems Board
Above is the solder side of the common system board
which is located at the front of the radio.
P901 is the control/power cable connector.
-
The H6-H73 jumper assures that channel one is always selected.
-
H89-H90 applies A+ to the radio circuits.
-
H79-H81 forces the RX oscillator to always be on.
-
Cut the trace between H95-H96, this prevents muting of the receiver during transmit.
Special Systems Board
Above is the solder side of the special system
board which is located at the front of the radio.
P901 is the control/power cable connector.
-
H79-H81 forces the RX oscillator to always be on.
-
Cut the trace between H95-H96, this prevents muting
of the receiver during transmit.
-
The other jumper straps F1 channel select to A- enabling
both RX and TX F1 positions.
Option: You
can jumper H89-H90 as in the the common Systems Board
outline, or you can supply A+ to the radio circuits via a fuse (preferred
method) by connecting A+ to control head pin 24 (Ignition Sense).
Tie pin 24 to the large TX A+ lead (red) through a 3 to 5 amp fuse.
Also tie control head pin 29 (A+) to the large TX A+ lead (red) through
a 3 to 5 amp fuse.