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Motorola GM350

The Motorola GM350 is a PMR radio which can easily be used in the amateur bands. Versions are available for low-band VHF (4m), VHF (2m) and UHF (70cm), and can often be picked up for as little as £20. More information on the radios can be found here.

Accessory Port

On the rear of the radio is found the antenna socket (BNC), the power socket, and the accessory port. The accessory port has sixteen pins, explained below¹⁾:

Pin diagram:

2 4 6 8 10 12 14 16
1 3 5 7  9 11 13 15

Pin	Purpose	Description
1	EXT SPKR -	-ve connection for an external speaker
2	EXT MIC AUDIO	an alternative microphone signal input (note only one microphone should be used at a time)
3	MIC PTT	radio PTT
4	PRG O/P	re-assignable output (from within config s/w)
5	FLAT TX AUDIO	for injecting unfiltered audio into the radio
6	PROG I/O 6	used for programming or tuning the radio - accesses the radio's SCI serial bus
7	GROUND	ground for both analogue and digital signals
8	PROG I/O 8	re-assignable digital i/o (from within config s/w)
9	PROG INPUT 9	re-assignable digital input (from within config s/w)
10	IGNITION CONTROL	connected to the ignition line of a vehicle, this will automatically turn the radio on when the ignition is turned on
11	RX AUDIO	analogue output for taking audio out to a TNC, etc. Note this needs configured from within the software
12	PROG I/O 12	re-assignable digital i/o (from within config s/w)
13	SW A+ SENSE	unsure what this is for!
14	PROG I/O 14	re-assignable digital i/o (from within config s/w)
15	RSSI	received signal strength indicator (analogue voltage)
16	EXT SPKR +	+ve connection for an external speaker

¹⁾

This information is taken from the user manual - see https://obrazki.elektroda.pl/8715300300_1347271923.gif and http://batlabs.com/gm350.html

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Motorola GM350

Accessory Port