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W4ZT
UHF Repeater
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The General Electric Mastr II (yes that's correct spelling but most folks call it Master 2) radio is one of the most popular conversion radios available to the amateur community. If you do a search on "amateur repeater" on the web you will find hundreds of GE MastrII repeaters. I give all the credit to Darryl, N4OME, for introducing me to the Mastr II (and creating the monster). I found the Mastr II to be easy to convert and easy to work on. I have done several things with mine that are not documented in any of the conversions I have found on line and I will document them here as time permits. You can read about my Modifications.
The pictures below are but a few of the radio as it sits in service. It's constantly going through change right now and is likely to see a few more modifications before it's declared stable.
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The UHF repeater: Controller on the bottom, MastrII radio above that with the heat sink sticking out, and the duplexer above that. The fans are hanging down out of the view. |
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The UHF repeater: Controller on the bottom, MastrII radio above that with fans hanging in front of it, and the duplexer above that with the fan bracket hanging on the knobs. |
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The side of the heatsink drilled and tapped, ready to mount the White-Rodgers thermal switch #3F01 111 available from Grainger for less than $10. This switch senses the heat sink temperature and closes at 110 F and opens at 90 F. The controller runs the fans all the time the transmitter is keyed and the thermal switch keeps them running until the heatsink cools down. |
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The heat sink is thick at this point and handles the drilling and tapping well. Just so happens this end gets hotter too. |
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Another view of the drilled heatsink. A small amount of heat sink compound was put on the end of the thermal switch where it touches the heat sink. |
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The thermal switch and fans are mounted and wired. |
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The RECEIVER antenna connection. Note the protective ear has been removed. |
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The TRANSMITTER antenna connection. The protective ear has been removed here too. |
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The front of the Mastr II radio sitting in the rack. |
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The Motorola T1504A duplexer above the Mastr II radio. |
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The antenna connection to the duplexer with desense tee in place. |
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The 2C ICOMs in the exciter and receiver. |
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The duplexer and radio all connected. |
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View showing the heat sink of the Mastr II radio sticking out of the rack, the fans hanging in front of it from a piece of aluminum channel hanging over the duplexer knobs. You can also see the thermal switch (round yellow lable) mounted to the heat sink. |