Motorola GM300 @ 9600 baud ??

Motorola GM300 @ 9600 baud ??

Post by colinlow » Sun, 26 Dec 1999 04:00:00

I have a Motorola GM300 and would like to use it on 9600 packet radio.

Here is the mod that I found on the internet......

The Maxtrac/Radius Series are 9600 baud packet capable. They do need a minor
modification though. For RX, its no big deal, just take RX audio from PIN 11
of the Accessory Connector and swing JU551 to the (A) position (Flat RX
Unmuted). For TX audio, you will have to run a jumper to the junction of
R223,C228,R222 on the RF board to inject the data (if applicable you may
need to set the deiation pot in the radio to maximum). You might want to put
a pot on your TX line somewhat like the setup Motorola uses (voltage
divider) to adjust the deviation. It would be wise to do some measurements
to make sure you have the deviation correct. You might also want run the RX
and TX pins to the unused pins on the front mic connector after the mods are

OK I have opened up the radio and found Jumper JU551 and moved it to the new
"A" position.

I now need to find the junction of R223,C228,R222 on the RF board to inject
the TX data.

Please can you let me know were the juncion of R223,C228,R222 is. The PCB is
not marked and I don't have a diagram for the radio............Can you help

73 de Colin (For Motorola GP300 and GM300
mods etc.....