February 13, 1998

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Part 1 in a Series of 3

This series will follow the building of the 145.450 repeater for N0ZAK in Centerville, Iowa. The repeater is based on a Motorola Mitrek 60 watt radio. Clyde, N0ZAK, decided to use the Micro Computer Concepts RC-100 controller, and also purchased the SEITS Graphic Equalizer Kit. Clyde assembled the EQ kit, which worked perfectly the first time out. 

I have several of the Mitrek units which I purchased a couple of years ago at the Peoria Superfest. At the time, I did not know what I had, just that the price was good!! After the SEITS article was published on the Mitrek radios and the meaning of the chassis and other numbers, I started going through the pile. Lo and behold, all the radios are in the range beginning at 146 and going up. Since the repeater will be on 145.45, I thought the radio should go far enough out of band to make it. 

The radios I purchased did not come with channel elements. I acquired the elements from Randy, WB0VHB, but decided I didn't want to hassle with them. So I ordered the elements with the proper frequency crystals already installed from Kirby Enterprises (phone 1-800-237-9654). They are also known as Channel Element Headquarters. They carry crystals in stock for almost every frequency imaginable. The elements were here in only 3 days after ordering!! That sure made the $30 an element worth it. 

In my opinion, the full manual is a must. I found mine In a box of old manuals at the Oskaloosa Iowa flea market this last spring. I paid $7.50, which is a good deal. I also have an old Mocom control head, speaker, microphone, and wiring harness. The manual shows how to use the Mocom set with a Mitrek. I use this to tune the radio first and verify its operation on frequency before I begin the modifications to turn it into a repeater. 

A signal source is necessary to tune the receiver. I use an old Cushman CE-3 service monitor. The unit is a bit cantankerous, but what do you expect for a $50 flea market bargain. The bottom line is it WORKS! 

The receiver tune up is a breeze on this radio. The manual gives a chart and list of the starting position for the various tuning slugs. Our frequency was off the chart, but using the lowest frequency given was good enough. I hooked up the service monitor and adjusted it for full output on the receiver frequency and there it was. I began decreasing the output of the service monitor and, following the tune up procedure for the correct order in the manual, soon had the receiver jumping. According to the old CE-3, it tuned right up to .25 uV sensitivity for 20 db of quieting. Look in the June 1996 Journal for the way to measure quieting. 



Michael Muldoon, KE0BX

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