ARTICLE FROM JULY 1996
I have to admit I am in the summer doldrums. For the last month ham radio has had to take a back seat to earning a living and other personal things. Not all of us have been dead in the water although!
KE0BX brought up a Mitrek to be converted into the new 145.45 repeater for Centerville Iowa. KD0YU is working steadily on the ICN interfacing equipment and me, well I've been struggling with the dead Micor hub repeater chassis.
Michael, KE0BX, was very pleased to find out just how easy it is to convert a Mitrek to a repeater. Based on his questions (he asks good ones) I decided to discuss the Mitreks a little more this month. The sudden abundance of Motorola Mitrek RF drawers at Hamfest this past year has been a godsend for SEITS. The Mitrek series radios are excellent for packet on both two meters and 70cm. They are the best 9600 baud radio we have found. In the 75 and 100 watt chassis models they make excellent repeaters.
I have paid as low as $5.00 for a 60 watt VHF radio to as high as $100 for a 100 watt UHF radio. This is for the RF "drawer" only, not the accessories. If your going Mitrek shopping you need two things. First a drawer key and second a copy of the Mitrek Identification sheet published last month.
All Mitreks have a lock on the front that secured them to a base mounting plate for installation in the trunk of a car. The lock also kept the cover plates locked on as well. When you see a likely looking flat bluish gray aluminum box at the next hamfest look closer! If it has fins on the back, a lock, big plug on the front and Motorola name plate it might be a Mitrek.
Check the FCC ID and transmitter number on the name plate against the ID sheet. If it looks good, stick your key (there's only one!) in the front slot and turn it. The handle should fold down releasing the mounting plate. Pressing a metal button under the handle should release the top and bottom cover plates.
At this point check out the inside of your prize. First look for the chassis ID number. It is stamped in ink right on the top edge of the die cast body of the radios case next to the handle on the top. This is right under the top cover plate. Check this number against the ID chart to make sure the radio is one of the useful models.
If so, check to see if the radio has a PL board and channel elements. PL and DPL boards cost $35 each surplus. Sometimes they are worth more than the radio. In other words, a dud radio for $10 is a great bargain if it has a working PL or DPL board in it!
Mitreks use plug in modules called "channel elements" for frequency control. One for the transmitter and one for the receiver. You need there to install your new crystals in. These sell for $3 to $10 each surplus. If it does not have any, try to talk the seller out of them!
The last item you need is the front panel plug. Normally this is part of what Motorola called the "accessories." That is a ugly mess of cable lugs, fuses, a control head, microphone, speaker and other junk. Most of this stuff is almost worthless. One reason you might want to keep a complete accessory kit is to use it for testing your radio and servicing it. Other than that, the original stuff is pretty useless.
Most of the time when offered the "accessories" I just cut the front panel plug off and leave the rest behind in the dumpster. Surplus this pile of crap sells for around $35. Sometimes you can buy the plug alone for $5. You DO NEED the plug so try to get one!
Least you worry, the plug for the older Mocom series radio will also work. And new ones are still available from Motorola. Many Motorola shops still have used ones in their junk boxes.
The next thing you need is a service manual. The Motorola manuals are wonderful. If only "real" ham equipment manuals were so good! Surplus the manuals sell for $10. Rarely you can find these at hamfests. A better source is C.W. Wolf Communications. 1113 Central Ave. Billings, Montana 59102 Phone: 406-252-9220. They have a $25 minimum order.
Wolf also sells radios (not cheap like hamfests) and all the other items you may need like channel elements, other manuals or other accessories like PL boards you might need for your radio(s).
For tuning you will need an old fashioned VOM or some other meter that you can switch between 50uA to 1 mA. Motorola gives you two funny looking female plugs where a fancy test set was intended to be plugged in for tuning. Since no one has one of these, an ordinary micoamp meter works just as well. I found a nice 25-0-25 zero center meter at a hamfest years ago that works perfect for tuning Motorola radios. I added a range switch to it so I could keep the needle on scale when the radio "came alive."
Handy Hint: The lead of a 2 watt resistor works perfect as a probe to connect your meter to test plugs.
At this point the last thing you need is a bench full of test gear to tune up your radio and one other little item. Read on in this issue!
David Metz, WA0AUQ
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