Remove 1.0 µfd 50V capacitor C76 (circled in red) to eliminate delayed squelch during reception of weak signals.
Motorola GM300 radios start adding delay to the squelch drop out time as received signal strength becomes less. Normally this is desirable to prevent squelch chatter when receiving weak signals. For link radio use however, as little squelch
delay as possible is desired. To remove the squelch delay feature, in the GM300 radio, remove C76 (circled in red in above photo).