Batboard

Just when you think "that cant be done" you run across something that blows it out of the water. I had a customer tell us they blew their transmitter and its a maxtrac. They also informed me they were on 800Mhz. well im thinking they probably are on UHF and all that. I get out there, and sure enough its a pair of 800Mhz maxtracs, one of them happily recieving at 806.xxxxMhz going thru a rick to another maxtrac transmitting at 851.xxxx. How the hell did they get the maxtrac to RX the inputs of 800?

While i did not open their receiver, upon visual inspection it appears to be your standard run of the mill 15w trunked w/ conventional maxtrac. No SP or anything. They said they got this repeater from the local MSS who apparantly does not want to support it anymore.

The easiest way to do that would have been to replace the radio's RF board with an RF board from an 800 Desktrac repeater receiver. This RF board was available as a replacement part.

The next alternative would be to replace the existing RF board's front end filters with ones intended for the Desktrac repeater receiver - either obtained from Motorola parts or a third party supplier - the same process as converting one of these to the 900 ham band.

The sleezy way would be to remove the filters and install jumpers - perhaps tolerable IF the repeater has a good duplexer with bandpass filtering [NOT a notch only mobile duplexer]

You will just have to open it up to see what they did.

If you do the 902 receive mod to an 800 maxtrac, it will also receive 90.2 Megs below your programmed 902 freq. (double IF).
There is some good discussion at repeater-builder.com on the "converting an 800 to 902 receive" page.
I just checked one I have and it is receiving at 822 megs, I havn't had a chance to check the sensitivity though....