Homemade GMRS Repeater Help

[unioner101]

I am looking for some help. I am a long time Motorola Radio Mod Guy, first time repeater builder. I have a basic understanding of repeaters.
I am trying to build my FIRST repeater, a very simple unit.

The repeater will simply consist of 2 Radius GM300 linked together with a bidirectional cable. I then plan using a ham radio duplexer (is this possible or must a duplexer with cavities be used). I also have taken into consideration power concerns as well as cooling for the housing which I planned on using a plastic file storage box.

Am I missing something? Also what other programming consideration should I take when programming the radio system?

Thanks
Kevin

[transistor747]

Kevin, are you building a cross-band repeater? If not, and your receiver and transmitter are in the same band then you definately will need somthing other than the little ham unit you are describing. Typically those things will deliver one band to a port.. for example, I have one that connects to a dual-band antenna and passes uhf (400-500) to one port and vhf (130-195) to another.
Sam

[Will]

The GM300 radio transmitter is NOT FCC type accepted for use in the GMRS as a repeater transmitter. The frequency stability on the GM300 is only .0005%.