Motorola Gm3688 Service Manual Top – Updated

3. Alignment and Tuning Procedures

GM3688s can drift out of frequency over time. The service manual provides the exact steps to align the VCO (Voltage Controlled Oscillator), adjust the TX power levels (High/Low), and fine-tune the squelch. Warning: This requires specialized equipment like a service monitor and the Motorola RSS/CPS software.

MDC1200 Signaling: Supports PTT ID encode/decode, radio check, and selective radio inhibit.

Technical Specifications

The manual details several advanced features that made this radio a staple in the transportation and manufacturing industries:

Accessories: Utilize the 16-pin external port for expansion, such as connecting external alarms or public address systems.

• Sensitivity: 0.25 μV (typical) at 12 dB SINAD
• Intermodulation Rejection: 65 dB (typical)
• Spurious Response: -80 dB (typical)