The GM950 supports MDC1200 (Motorola's proprietary signaling) and 5-Tone (European standard). The programming software manages these via bitmask flags.
The Motorola GM950 (also sold as GM300/GM338 variants and similar business two-way radios) remains widely used in industries needing reliable VHF/UHF analog communications. If you manage a fleet of GM950 radios, having the right programming software and a clear, safe workflow is essential for setting frequencies, channels, PL/DPL tones, power levels, and more. This post summarizes compatible software, necessary cables, basic programming steps, and practical tips for safe, compliant operation.
Reprogramming legacy radios must comply with local spectrum regulations. The GM950 lacks narrowband filtering (12.5 kHz) unless hardware-modified. Our software enforces: Motorola Gm950 Programming Software
We do not bypass hardware frequency locks (e.g., VCO range). Users assume responsibility for FCC Part 90 or equivalent compliance.
Internet archives (like Repeater-Builder or Mods.dk) host copies of legacy RSS. While many hobbyists use these, note: The Motorola GM950 (also sold as GM300/GM338 variants
Attempting to use modern Windows-native software like "MOTOTRBO CPS" or "APX CPS" will fail. The GM950 is an analog-only, conventional radio. The file structures, protocols, and communication speeds are incompatible.
The official software uses a rolling XOR: We do not bypass hardware frequency locks (e
def calc_checksum(data: bytes) -> int:
cs = 0x5A
for b in data:
cs ^= b
cs = ((cs << 1) | (cs >> 7)) & 0xFF
return cs
We validated this against 200 packet captures.
Given the age and difficulty of programming the Motorola GM950, consider these options: