Repeater Tech


Motorola radios
GE FM Radios
6 meter duplexer

"W4XE Repeater Tech page "




Mastr II

Micor vs Mastr II

Shown above are two of the most popular radios that are modified for amateur radio repeater service, the Motorola MICOR and the GE Mastr II. Both of these mobile radios are plentiful on the surplus market. They are both well designed and feature rugged quality construction. They are relatively inexpensive ($25-$125) and they make excellent repeaters. After conversion, their specifications compare to other commercial repeaters on the market. There are a number of excellent websites devoted to the conversion of these mobile radios into amateur repeaters.

This one is one of the best places to start:

Rather than duplicate the excellent information that is already out there on the web, I've tried to augment this with new material. The information on the following pages will help you put those finishing touches on your new conversion.

Shown above is a side by side comparison of both radios. The Micor is a little taller, where as the Mastr II is a tad longer, but thinner. Both radios have relative advantages of one over the other. The Micor is renowned for it's dual squelch operation. The UHF Micor only requres ONE crystal for repeater operation. The Mastr II provides a slightly cleaner modification and has a drop-in NHRC controller for repeater operation. However, in the end they both will provide years of excellent service. There are a number of surplus dealers on the web offering these radios. See my favorite links for details.

I've also built repeaters out of the GE MVP and GE EXEC II mobiles and base stations. These are both close relatives of the GE Master II. These are crystal based units. They can both be modified for full duplex repeater operation.

There are a number of smaller under dash mobile radios that are useful to make repeaters out of. Most are synthesized which provides a very nice frequency agile remote base. For these they do not full duplex so you'll need one radio as the receiver and one radio as the transmitter. If you need a remote base these type radios will serve the purpose well. I started using GE Phoenix SX type radios a number of years ago. These are excellent synthesized units with great audio. I've also started looking at GE MVS and GE MONOGRAM units as well. The GE  MONOGRAM is actually a MAXON SM-4150 or SM-4550 mobile.

Uniden has made a desktop repeater that several hams have used for low duty cycle repeaters. Uniden also makes under dash mobiles (FMU) that are suitable for remote base use.

Motorola has the Maxtrac / Radius / GM-300 series of radios that make very nice repeaters or remote base radios. I am using some of these and will document their use in the future. 

Follow the links to the left to see more details on conversion of these radios.

See New! GE MVS and GE Monogram on the GE page


DISCLAIMER - - Any information on this website is for informational use only! Use of this information to modify any equipment is at your own risk. The author is not held responsible.


A nice history of GE and Motorola old time radios...

A work in progress...


Ralph W4XE






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This site was last updated 01/02/07