Batboard

I just pulled a GR500 in the office from active service, assuming it had narrowband friendly radios inside it.. Well, I was wrong, the radios in side are not 12.5 able GM300 radios, which shocked me because we purchased the repeater in 2003. I suppose it was built up from existing stock of GM300 radios.

Since the accessory connector is the same, I am wondering if the M1225 can be swapped into this unit as is? I realize fully that the M1225 isn't nearly the radio (and certainly doesn't have the heatsink abilites) but this is basically a backup repeater and whatever radio is in the unit will be used with the minimum/low power setting only. We have an external amp in line to provide needed output power.

Theoretically yes. You should be able to swap in a M1225 for a GM300. YMMV of course.

M1225 has a small heatsink surface area so you will need to be careful what power level that you run it at.

We have done a lot of GR500 conversions from GM300 to CDM750 radios. No major issues.

I have 3 repeaters set up with 4 channel M1225 mobiles. I removed the Maxtracs also. None are heavy duty, nor used often. I have had no issues on them as of yet. One has been online for over a year with no issues. Again these are not high use repeaters but fill in units for a SAR team...

Absolutely. Get a 20W radio and crank it down to about 8W in the alignment and you'll be fine for ~70% duty. I built a repeater for AllStar use that way (driving a 100W TPL amp) and it never flinched at typical long-winded hammy chat.

Be sure to check your output deviation if you're switching from wideband to narrow.. your RICK or whatever controller may need the audio bumped down a bit.

I am doing the same thing, just the the receive side is not passing audio. I have pin 8 on the receiver set right, and also on the TX side too, but no audio passing. Repeater keys up, but no audio. Any ideas? Using M1225 NB mobiles.

Michael