radios:gm350
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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.
Physical information
The radio measures 168 × 44 × 180 mm (6.61 × 1.73 × 7.09 in) and weighs 1.7kg (3.8lbs).1) It has a threaded hole on each side for mounting. Variants include a 128 channel version with a LCD screen, and a 4 channel version with push-button channel selection.
Requirements
The radio will accept a DC voltage between 10.8 and 15.6 volts. It requires an antenna with an impedance of 50 ohms.2)
Microphone Pinout
| Pin | Purpose | Description |
|---|---|---|
| 1 | unused | |
| 2 | unused | |
| 3 | Microphone Hook | This port reads ‘0’ when the microphone is on-hook and ‘1’ when the microphone is off-hook. |
| 4 | Ground | |
| 5 | Microphone Audio | This microphone signal input is common with the microphone signal input on the accessory connector (Acc. pin 2) - note only one microphone should be used at a time. |
| 6 | Microphone PTT | When taken to Ground (pin 4) this pin activates the radio's PTT. |
| 7 | BUS+ | This line carries the data for the single line serial comms system used in the radio. |
| 8 | Handset | This line provides buffered audio for a handset. |
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 below3):
Pin diagram:
2 4 6 8 10 12 14 16 1 3 5 7 9 11 13 15
| Pin | Purpose | Description | NinoTNC pin |
|---|---|---|---|
| 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 |
3)
This information is taken from the user manual - see https://obrazki.elektroda.pl/8715300300_1347271923.gif and http://batlabs.com/gm350.html
radios/gm350.1721949603.txt.gz · Last modified: 2024/07/25 23:20 by gm5aug