Reduce chassis heating in the receive mode, remove the
following components: R66, R67, R68, Q32, D42, and D44 in the main unit.
To restore high-frequency receiver audio response, replace C-103 on the
main unit with a .0022 uf mylar capacitor (that's 2200 pf).
To restore LOW-frequency receiver audio response, replace C-106 with
a .22 uf mylar capacitor.
To eliminate the distortion in the transmit audio, install a 4.7k ohm
microphone case, in series with the white lead coming
from microphone element. Once the resistor is installed, set the DTMF level
pot to the middle of its range (this pot is the only one inside the
microphone case). To complete the mod, set R88 inside the radio to the
desired "mike" level.
To improve the receiver sensitivity, power output, SWR at the radio, and
reliability, remove the RG-58 pigtail and the UHF connector extending from
the rear of the radio. Install a BNC chassis mount, screw-in connector
(UG-1094/U) in the hole left in the back of the radio. The new connector
will screw in as if the modification was done at the factory.
-pin voltage regulator] on the transmitter power amp shield
behind the space reserved for the optional voice synthesiser. Thermal
compound is recommended. Hook the input of the 7808 to the point where R67
and R68 used to connect. Hook the output of the 7808, in series with a
1N4001 diode, to J14-1. The cathode of the diode goes to the connector goes
to the connector, and the anode goes to the 7808.