Hytera Mt680 Tetra Mobile Terminal Owners Manual R4 0 New Jun 2026

| Problem | Possible Cause | Solution | | :--- | :--- | :--- | | | Blown fuse or loose connection. | Check the vehicle fuse box and radio power cables. | | No audio received | Volume too low or mute enabled. | Adjust volume knob; check if headset is plugged in (diverting audio). | | Cannot transmit (No TX) | Out of coverage area. | Check signal bars on LCD. Move to a better location. | | "Service Restricted" | SIM card issue or not registered. | Check SIM card insertion; verify network subscription. | | GPS not working | GPS disabled or weak signal. | Ensure GPS is enabled in Menu > Settings > GPS. Move to open sky. |

The manual is ruthless here: For UHF (380-430 MHz) models, the antenna requires a ground plane of at least 30 cm radius. The R4.0 new version includes a troubleshooting flow chart for "High VSWR" errors, noting that modern thin-film antennas often fail this spec. hytera mt680 tetra mobile terminal owners manual r4 0 new