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VHF Micor®, MCX100®, Syntor®, and SyntorX® HAM Conversions and General Repairs by W9FIU

You may have noticed that many of the older Motorola two way FM radios are available at reasonable prices at hamfests, surplus auctions, and on-line internet auctions such as eBay, etc. These are excellent radios, very well designed and built, and many of them can be converted for use on the two meter amateur band, as repeaters and also as high quality mobile radios.

Old Micor® repeaters are often available and are readily converted to two meter repeaters. The conversion of Micor® transceivers to two meter repeaters is very popular as shown by the number of articles on this subject. There is at least one web site devoted almost entirely to the subject of converting Micor® transceivers into full duplex repeaters. Micor® transceivers also make an excellent source of parts (receivers, exciters, etc.) for a variety of amateur "projects" including links, packet radio devices, telemetry, etc. The list of things that can be done with the exciters, transmitters and receivers from these radios is limited mostly by ones imagination.

Syntor® radios are also readily available at low cost and can easily be converted to very high quality amateur base or mobile radios. These are not quite so adaptable to repeater service because the Syntor® design unifies the receiver and transmitter into a "transceiver" in which some parts are common to both the transmitter and receiver. This makes it almost impossible to have a single unit transmit and receive simultaneously, as is necessary for a repeater station. It is still possible to build a repeater based on the Syntor®, though two radios are required.

The Syntor® radio is fully synthesized (the synthesizer being the main component that is "shared" between the transmit and receive parts of the Syntor®). The synthesizer makes it possible to operate the Syntor® on a virtually unlimited number of channels without the necessity of buying a multitude of crystals. The frequencies are simply "programmed" into a PROM that plugs into the Syntor® radio circuit board. Normal Syntor® radios can be programmed for 1 to 32 channels this way. It is also easy to make an adapter for the Syntor® which allows one to use an EPROM (or EEPROM) instead of the normal Syntor® PROM. This strategy, along with some fairly simple modifications to the radio allows one to expand the number of channels available almost without limit. It also makes it easy to change the channels that are programmed into the radio. Just erase the EPROM or EEPROM and re-program it with the new frequencies. A suitable adapter which allows up to 256 channel operation is our Syntor® Frequency PROM to EPROM/EEPROM Adapter. Software is also available which can be used to manage a list of desired frequencies and other information and to create an "image" file containing the data to be programmed into the PROM or EPROM. One such program, suitable for use on Windows style computers is our VHF/UHF Syntor® PROM Editor and Hex File Generator program.

THE NEED FOR FREQUENCY CONVERSION:

One thing that is common to converting these radios to amateur radio service is the necessity for "frequency conversion" of the radio. These radios are designed to operate over the VHF frequency range from about 132 MHz to 174 MHz, but do so in "ranges", usually four ranges being required. This is because the various tuning circuits that are part of the receiver and transmitter cannot be designed to cover the entire range and still maintain the desired performance. This means that the VHF Micor® and Syntor® radios are actually built to cover four different "ranges" (often called "splits") of the VHF band. The splits are often different for the receivers (more splits needed) than for the exciters, etc. The table below shows the four splits for Micor® receivers. Notice the last number in the receiver's model number indicates the frequency split.

Similar tables exist for Micor® exciters and also for various parts of the Syntor® Radios.

Most of the parts in a Micor® (or Syntor®) receiver, exciter, etc. are the same in all splits. Some are not, however. Also, some parts that are the same may be wired differently. Frequency conversion of these radios involves a careful scrutiny of the schematics and parts lists of the receiver (or exciter, etc.) to determine which parts are different, etc., then replacing these parts with the correct ones for the desired new split.

The above is the straightforward method but is not always possible anymore. This is because many Micor® and Syntor® parts are no longer readily available, available at affordable prices, or available at all. This does not mean that conversion is now impossible or even prohibitive. Micor® receivers and exciters can still be converted to the amateur band by a combination of strategies, some old, some new. The Micor® receiver's helical resonator front end filter is a good example. This filter provides the receiver with very good front end selectivity which is very important to its performance, especially in repeater service. To "convert" this filter to amateur service one simply has to replace the five helical resonator coils. These used to cost about a dollar each (back in the 1970s) and about three dollars each (in the late 1990s). Last I heard they were about $15.00 each and likely will soon be "no longer available". I have developed a method of converting these filters to the two meter amateur band that does not require replacement of these coils, and which does not result in degradation of the filter's performance. For more details about this conversion see VHF Micor® Front End Filter Conversion to the Two Meter Amateur Band. This article shows how you can perform this conversion yourself and also documents the performance that can be obtained. You can have me do it for you if you prefer. I offer complete conversion services for VHF Micor® and Syntor® radios to the two meter ham band.

REPAIR SERVICES:

I have found that some of the Micor® and Syntor® radios I have studied have some sort of problem, often minor, frequently un-noticed. This should not be unexpected considering that these radios are typically 30 years old. These radios are so well designed and built that often a complete failure of one component results in only fairly minor performance degradation which can easily go un-detected unless the radio is carefully tested. These types of problems still result in poor performance such as poor range, distortion, susceptibility to noise, etc. I am prepared to troubleshoot and repair VHF Micor® and Syntor® radios for users who require the full performance normally required in repeater service and other demanding applications.

I worked for several years in a Motorola Service Shop when these Micor® radios were the newest and best radio that Motorola made. Our shop was the "central shop" for a group of several other Motorola Service Shops scattered over central Illinois and the surrounding area, so I repaired many of these fine radios. In those days one could order any of the repair parts needed from Motorola and we kept a good stock of the most commonly used items. The parts situation today is difficult, but still managable.

I have been a radio amateur (W9FIU) since 1956 and an electronic design engineer since 1966. I am now approaching retirement and looking for ways to keep myself occupied doing something that I enjoy.

I always enjoyed radio repair work, and have all of the test equipment and tools necessary so I decided to offer reasonably priced repair and conversion work on these radios to keep busy, supplement my retirement, and generally keep out of my wife's hair. I have the experience, expertise, equipment and attitude to do a good job.

MICOR FREQUENCY CONVERSION FOR REPEATERS AND GENERAL AMATEUR USE:

I have developed a successful method of converting "H" split (150.8 to 162 MHz) and "HH" split (162 to 174 Mhz) Micor® receiver front ends to the two meter amateur band without the need to replace the front end coils (which are now difficult to obtain and very expensive if you do find them) and without loss of performance. I can perform this conversion alone or with a complete receiver conversion, including conversion of the local oscillator chain, receiver tune-up, frequency setting, any necessary repairs, etc.

The above development makes it possible for me to convert any of the VHF Micor receivers to operate on the two meter ham band. The cost for this service does vary according to the "split" (native frequency range) of the receiver. See the rate examples below for more information.

I also convert Micor® exciter boards to the two meter band, tune them up, set them on frequency, set deviation, etc.

I can work with individual boards or with a complete transceiver, etc. Check with me first before sending anything larger (like a complete Micor® Repeater station, etc.) so that I can make any necessary arrangements.

SYNTOR FREQUENCY CONVERSIONS FOR AMATEUR USE:

I can convert Motorola Syntor® radios that were originally built for the 150.8 MHz to 162 MHz frequency range to operate in the two meter amateur band fairly easily. These radios include a built in frequency synthesizer which can be programmed to any of the two meter FM channels and come in 40 Watt, 65 Watt, and 75/110 Watt flavors. The normal control heads come in 1 frequency, 4 frequency, 8 frequency, 12 frequency, 16 frequency and 32 frequency (2 banks of 16 frequencies) flavors. The number of channels available can readily be expanded to 256 or more channels with some (fairly minor) modifications to the radio. These are very nice radios that include a helical resonator front end filter, single conversion to a monolythic crystal filter I.F., etc. and well worth the conversion to the two meter ham band. These radios and accessories for them are readily available at reasonable cost at hamests, surplus auctions, internet auctions like eBay, etc.

REPAIRS:

I am currently set up to work on VHF Micor® and Syntor® radios This means the "original" Syntor® radios (not Syntor® X, Syntor® XX, Syntor® X9000, etc.) Also their common accessories including the microphone, speaker, and control head. I (currently) don't have manuals for most of the other accessories like scan heads, multiple PL encoders, etc. so until I do (or unless you can provide manuals for

I will consider other jobs if I am confident that I will be able to do a good job for you. I will NOT ATTEMPT to work on any equipment for which I do not have (and which you cannot supply) any necessary documentation. For other than Micor® and Syntor® radios, I mayl also need all interconnect cables and accessories. Be prepared to send service manuals, schematics, etc. as necessary.

RATE EXAMPLES (note: rates are subject to change without notice!):

Special Tuning screws used for Micor receiver 2 Meter front end conversions. These cost $7.50 for a single tuning screw or $30.00 for a set of five (enough to convert one front end filter). Shipping cost via UPS ground within the continental U.S. is typically $11.50 for delivery to a residential address or $9.50 for delivery to a commercial address. The shipping cost is the same for a single screw up to several sets of them.

Receiver and exciter conversion jobs: If possible, before starting these jobs I test the receiver or exciter using a channel element in the unit's "native" range to be sure that the unitis working OK. I do this to attempt to insure that the converted unit will produce full performance without the need for additional repairs. If repairs are indicated, extra charges will apply but I will notify you and wait for your approval before I proceed.

Front end filter conversion: $35.00 for conversion of a Range III ("H" split) (150.8 to 163 MHz) or Range IV ("HH" split) (162 to 174 MHz) Micor Receiver front end filter to the two meter amateur radio range. This includes a set of five special tuning screws plus alignment of the filter to the two meter band.

Micor Range III Receiver conversion: $65.00 for conversion of a Range III ("H" split) (150.8 to 162 Mhz) Micor® receiver to the two meter band. This includes the front end filter conversion, oscillator injection chain conversion, receiver alignment, and setting your channel element "on frequency".

Micor Range IV Receiver conversion: $45.00 for conversion of a Range IV ("HH" split) (162 to 174 MHz) Micor® receiver to the two meter band. This includes the front end filter conversion, receiver alignment, and setting your channel element "on frequency".

Micor Range I Receiver conversion: $35.00 for conversion of a Range I ("L" split) (132 to 142 MHz) Micor® receiver to the two meter band. This includes conversion of the oscillator injection chain, receiver alignment and setting your channel element "on frequency".

Micor Range II Receiver tune-up: $20.00 for testing, tune-up, and frequency setting for Micor® receivers that do not require conversion -- including Range II ("M" split) (142 to 150.8 MHz) receivers and receivers from other ranges that have already been properly converted to this range.

Micor Range I Exciter tune-up: $20.00 for testing, tune-up, frequency and deviation setting for Micor® Range I ("L" split, 132 to 150.8 MHz) exciters.

Micor Range II Exciter conversion and tune-up: $25.00 for similar (including frequency conversion) service for Micor® Range II exciters. Note: VHF Micor® exciters come in two splits (132 to 150.8 MHz and 150.8 to 174 MHz). I have found that many of the "high" split VHF Micor®s will tune down to the two meter band (down to at least 146 Mhz) and produce normal performance without needing component changes. In these cases I don't change parts unless it proves necessary. (This reduces unnecessary wear and tear on the circuit board, etc.) This service includes any necessary component changes, exciter alignment, deviation setting, and setting your channel element "on frequency".

Micor Range III transceiver conversion and tune-up: $80.00 for frequency conversion, tune-up, frequency setting, etc. for a complete "H" split (150.8 to 162 MHz) Micor® transceiver (receiver and exciter).

Micor Range IV transceiver conversion and tune-up: $65.00 for frequency conversion, tune-up, frequency setting, etc. for a complete "HH" split (162 to 174 MHz) Micor® transceiver (receiver and exciter).

Micor Range II transceiver tune-up: $45.00 for tune-up, frequency setting, etc. for a complete "M" split (142 to 150.8 MHz) Micor® transceiver (receiver and exciter).

Micor Range I transceiver conversion and tune-up: $55.00 for conversion, tune-up, frequency setting, etc. for a complete "L" split (132 to 142 MHz) Micor transceiver (receiver and exciter).

Hourly rate for repairs and modifications: $15.00 per hour for repair work done on a T&M (Time and Materials) basis. Any materials used are extra.

WANT TO TRADE or BUY?

I often will trade -- don't be surprised, I have been a Ham for over 50 years.

Sometimes I accept un-converted radios, accessories, etc. for conversion work, repairs, etc. I often then convert and sell (or trade, etc.) these items so I sometimes have already converted radios for sale. If you are interested you can contact me by going to my Home Page and using the "Contact us" link.

PAYMENT and TERMS:

I accept payment for radio conversion and repair work by bank checks, money orders, and company or personal checks. I also accept on-line credit card payments thru the eBay payments system (PayPal). Sorry but I accept only PayPal, bank checks or money orders for parts orders.

If you pay by personal or company check, you should send a payment for the expected cost of your job with your equipment. I will deposit the check when it arrives. If the check "bounces" and you don't make it good (including the fees charged to me by my bank for depositing a "bad" check), then I will simply keep your equipment. I have had terrific luck over the years accepting checks from hams, with only a very few "bad apples" to teach me to protect myself.

If you pay by bank checks, money orders, or on-line credit cards, you can wait until your job is finished to pay if you prefer.

SHIPPING AND HANDLING CHARGES:

I charge the customer the full costs of return shipping. This will include a packaging cost if the received packaging is not adequate for return shipping due to shipping damage, etc.

PARTS AND MATERIALS:

I have a fairly good supply of small parts (resistors, capacitors, diodes, chokes, etc.) which can be used for repairs when the exact Motorola replacement part is not required.

If you supply me with a spare board or radio for parts, I offer to not charge for the extra time needed to remove parts from the spare board used to repair your "good" board, and in exchange keep the remains of the spare board when I am done. Naturally, if you prefer otherwise, I will be accommodating.

MY SHOP:

My shop is fairly well equipped with general test equipment such as oscilloscopes, digital multimeters, frequency counters, r.f. probes, audio signal generators, soldering and de-soldering tools, bench power supplies, etc. It is equipped with specialized radio service equipment such as a Motorola Service Monitor (a synthesized and calibrated signal generator, receiver, deviation meter, etc.), Bird wattmeter, Tektronix spectrum analyzer, SINAD meter, dummy load, cables and controls for Micor® and Syntor® radios, etc.

SCHEDULING:

I do this work as my schedule permits, and in my spare time. You should be prepared to wait if necessary for me to complete your work. If this is a problem for you, be sure to check with me about my schedule before you send me any work.

WARRANTY:

I warranty the work that I do for 90 days. Since the radios are old, I do not offer to warranty anything beyond the work that I performed and materials that I supplied (but not including parts salvaged from other old circuit boards). My warranty does not include any shipping costs in any case.

Note: Micor® and Syntor® are registered trademarks of Motorola, Inc.

If you have any questions or comments, or would like to discuss having me do some work, you may contact me via eMail by using the "About Ries Labs" link on my Home Page (see link just below).