I posted info on my old Motorola Micor UHF repeater on my blog, and people asked questions about how to do it. This is a fairly easy task, though it's far easier to stack two of these radios (one for receive, and one for transmit), but I enjoyed the task of repeating within a single radio.
There's adequate isolation to do this, even when using a receive preamp, with a good set of cavities. These radios are cheap as dirt, often costing less than the crystal required for conversion to the ham bands. The nice thing, being crystal controlled, is you have no phase noise to deal with as with synthesized rigs. They are TOUGH AS NAILS! I've run them hot, it's been hit by lightning, and has operated an horrible physical conditions at one of the repeater sites. Users have locked it up for hours on end while cross-banding HF operations through it. The repeater in my previous blog has been in operation since 1994, so 26 years is nothing to sneeze at. I'll snap some pics of the internals that I've modified, when I go back into it, to help illustrate the process.
As I said, it's much easier to simply tune up a couple, one on the RX frequency and one on the TX frequency, wire a controller, and let'm fly. But, if you want to modify one for full duplex repeat, here's the info. I wrote the compilation of notes I accumulated and included my experiences in Microsoft Word. You can download the file, and if you don't have MS word, there's a host of online converters you can open it with for free.
Go to my website at http://www.WB4IUY.net , mouse over the toolbar across the top of my webpage to [WORKSHOP], and click on "Schematics Manuals". You'll find Motorola Micor in the listings. Have fun!!
Dave WB4IUY
