Try the manual power mod, iv taken a low power 900 maxtrac and brought it down to about 250mw before the radio stops tx'ing, it got stabler at about 350mw. I had a range of a stable 350mw to 20w or so. I dont know if the mod can be done to a GM300 as i have never done one to that radio, but iv done many to maxtracs. No major hardware changes, look up the mod in the maxtrac section on repeater-builder.
I used the radioshack 10k 15 turn pot btw... Jeff - KG6UYZ
