If this is a repeat visit you can jump down to the articles.

Overview:

On this web page we are going to attempt to provide an overview of several series of radios. As it was related to me, the Maxtrac history can be traced back to the Motorola GMBH of Germany model called the MC‑Micro (anybody have external and internal photos of an MC‑Micro mobile?). When Moto USA marketing decided to sell through retail channels they needed as simple-to-install dash mount radio (think "as easy as a CB radio") so the USA engineering staff "americanized" the German MC‑Micro design (sometimes referred to as the German Maxtrac).

At the time these radios were on the current sales sheets, the MaxTrac was a "Motorola direct sales channel" product and the Radius models were retail "dealer channel" products. Also at that time, trunking products were more or less reserved for direct sales, so initially the Radius line did not have trunked models. Internally the early Maxtrac and similar Radius models were pretty much the same. The later GM300 series was a update or redesign to fix some of the problems (like adding a thermistor to the PA deck, and an attenuator (switchable on a per-channel basis) to the receiver to cut the intermod). The result is the M10, M120, M130 and the GM300.

By the way, the Motorola GMBH MC-Micro radio was also the first repeater-in-a-box (also called the MC-Micro), which interestingly enough, was available as a factory 220MHz unit. The exciter was a MC-Micro RF board with the receiver components missing, and the receiver was another RF board with the exciter components missing. The MC-Micro Repeater was later marketed in the USA as the R100.

Because MaxTrac was the first series marketed in the US, and because the later GM300 series radios are so similar the term "MaxTrac" (or "Maxtrac family") has been used by some people to refer to just the Maxtrac series mentioned below while others use the term to apply to all three series of radios collectively. So don't be surprised if someone points to a Radius or a GM300 radio and refers to it as a MaxTrac.

The table below is in technical groupings, not marketing grouping. Technically, there was a lot of crossover, for example, the M120 and M130 are derived from the GM300. On this web page we are only concerned with the technical ancestry so we can intelligently work on and program the radios.

Note that the hyphenated model names (i.e. "M-10", "M-100" or "GM-300") are improper, it's "M10" "M100" or "GM300". Very few Moto model names have an embedded dash / hyphen.

The Maxtrac is a synthesized dash mount mobile radio that was originally designed to be a "second tier" or commercial / business radio (a "first tier" radio is a public safety grade radio). When 800 MHz channels were allocated to business Moto took the existing MaxTrac chassis and designed an RF board to plug into it... and then had to live with the problems that were created in using an audio / logic board that couldn't handle some problems that 800 MHz and trunking created. When 900 MHz came along the designers came up with a 900 MHz RF board, but they also redesigned the audio / logic board to work with it. They didn't have enough circuit board real estate for the audio compander circuitry so they were forced to redesign one of the two front panel boards as well.

One of the differences is that the MaxTrac and Radius series radios control the RF power output with a timer that counts seconds of PTT key-down time, where the GM300 series actually measures the PA deck temperature with a thermistor (but note that there are "Radius" named radios in the GM300 line).
A second difference is that the front end has a local/distant attenuator to cut the intermod, and the channel data had a data bit (that was set in RSS) to switch it in and out.
A third difference is in the data sheets and RSS only... Moto Marketing reduced the maximum channel count from 32 in the Maxtrac/Radius to 16 in the GM300 in an effort to force the folks who needed more than 16 channels into a "first tier" radio like the Spectra. But they didn't tell the radio itself that - the average GM300 does 32 channels just fine (but you have to patch the RSS, and there is an article on that below).

As an aside, all three product lines are based on a single-synthesizer design, which uses a single VCO. Due to this fact none of these radios will operate full duplex (this is why the DeskTrac tabletop base station and the GR series repeaters used two separate radio chassis). The exception is the R1225 full duplex radio (and the GR1225 repeater that was built from it).

The low band, high band and UHF MaxTrac logic boards are identical and interchangeable within their own product lines, but all of the boards and firmware used in the 900 MHz radios are unique to that radio with the exception of the display board. In other words, the 900 MHz radio design is very unique and you can't mix parts between it and any other band.

From an email to repeater-builder:

Another unique Maxtrac that doesn't mix parts well is the famous (or infamous, take your pick) Ontario Hydro low band Maxtrac. (Ontario Hydro is the electrical power utility for the province of Ontario, in Canada). The model number is ACD51MJA9HA5AK, where the AC signifies Canadian manufacture, the rest is a regular model number. Really, it should have been either an "-SP" or an "X" model (see the page at the repeater-builder web site on breaking down a radio model number).

The Ontario Hydro Maxtrac is / was a special 42-50 MHz radio with a standard 42-50 MHz RF board and power amplifier mated with a very interesting logic board derived from the standard HLN9313A unit.

The stock Maxtrac/Radius/GM300 logic board uses a 2 kilobyte 24-pin EEPROM in a 24-pin socket, soldered into a 28-pin PC board layout (leaving the top four pins of the 28-pin circuitry unused). Obviously the designer of the HLN9313 planned on someday needing expanded EEPROM so he/she included it from the beginning. The Ontario Hydro radios use an 8-kilobyte 28-pin EEPROM in a 28-pin socket, soldered into the same 28-pin PC board layout location in the PC board and then a few jumpers are moved around. The firmware is a special chip labeled VLN5443A. All of this is described in manual 6802950A44-A.

A standard HLN9313A logic board The 24-pin EEPROM chip is in place

The special 99-channel logic board made from a HLN9313A A 28-pin EEPROM chip fills all the pins

The RSS is also special - VVN4167A for 5.25 inch floppies or VVN4168A for 3.5 inch floppies. Several people have tried swapping an Ontario Hydro logic board into a high band or UHF radio and they claim that it does not work. Apparently when the RSS was modified for 99 channels it was stripped down to the 42-50 MHz range only. It would take someone with an advanced debugging package that could "look" into the Maxtrac RSS and see where the problems/limitations are before high band and UHF could be added back in.

Several stock 42-50 MHz Maxtracs have been upgraded to the Ontario Hydro configuration - all it takes is a 42-50 MHz radio with the standard HLN9313A logic board (the only one with the 16-pin accessory connector), the special firmware, the special RSS, a 28-pin socket, the larger EEPROM chip, and some time to swap the sockets, chips and move some on-board jumpers. The problem is locating the special firmware and special RSS.

Programming and the Radio Service Software (RSS):

No matter which band radio you have, the synthesizer is controlled by the radio's internal microprocessor whose operation is controlled by the codeplug which is generated with the Radio Service Software (RSS) and loaded into the radio through the Radio Interface Box (RIB). To do any reprogramming of the radios you need the correct RSS, a RIB, the appropriate cables, and an old, slow PC.

The MaxTrac was designed in the days when the bleeding edge software development computers were 33, 50 or 66 MHz 486-based machines and the average user had a 16 or 20 MHz 386. The MaxTrac and Radius RSS runs only on older computers as it uses software timing loops to create critical delays (the last revisions of the RSS are less sensitive to this than the earlier ones). You must have an appropriate older computer booted into pure MS-DOS or PC-DOS (version 5 or later) and this does NOT mean a DOS window in any version of Windows!!! If RSS or the RIB is a new topic to you I suggest that you see the Motorola RSS and RIB page at this web site. There are more details including some "old computer" notes there.

The MaxTrac, Radius and GM300 series are programmable radios as opposed to crystal based. Their internal processor runs a program that is contained in either the CPU chip or in a Programmable Read-Only Memory (PROM) chip. If you are gong to be doing any upgrading, or you are converting a trunking radio to conventional, you will need a PROM-based radio (which leaves out the HLN9123 low-end 5-pin logic board) and a 27C256 PROM chip programmed with the correct progam (referred to as firmware). Most of the later radios will have this, but not all! And if you take a logic board from a cheap 800 MHz eBay radio it is most likely going to have trunking firmware, so you will need a replacement chip anyway.

Speaking of trunking, if you find a firmware chip that has the name "Scholer-Johnson", "Scholer-Johnson Inc.", "SJI", "CVT-2-400", "ver. 2.14", or any combination thereof then you have one of the radios that was converted to LTR trunking (usually 800MHz, but occasionally seen on UHF or even high band). To convert it back to a regular radio you need the stock conventional firmware, and then you blank and reinitialize the logic board. Occasionally you find the stock firmware in a antistatic bag stuck inside the radio but that is extremely rare. If you want to use the radio on an LTR system then you need the Scholer-authored RSS to talk to it (and you will need that anyway to read and save the tuning data before you blank the board).

The latest MaxTrac conventional firmware (version 5.34) is available from Motorola, part number HLN5569A and it supports 32 channels in a low band, high band or UHF radio. The 900 MHz conventional radio uses a different logic board, and uses different firmware - it's FVN4019A version 30.03 (or later). Either is about $25. More notes on firmware, including a list of 10 different part numbers, is in the "Introduction to..." article linked below.

The MaxTrac-specific RSS is part number RVN4019 (on 5.25 inch floppy disks), or RVN4020 (on 3.5 inch floppies). Later versions were offered on 3.5 inch disks only. Version R07.00.02a, dated 25-Jun-97 (the current version at the time of this writing) was used in preparation of these articles.

The Radius M100, M206, M208, M214, M216, and VR100 radios use a different RSS, model HVN9173 commonly called RADMBL.

The Radius M10, M120, M130 and GM300 mobiles and the GR300, GR400 and GR500 desktop repeaters use RSS HVN8177. As of this writing the current version is R05.00.00 released in late 1995. The RSS is only available on 3.5 inch diskettes.

A DeskTrac is a tabletop station containing one or two MaxTrac mobile radios and uses RVN4079 which also has the MaxTrac software as part of it (either RVN4019 or RVN4020). Note that the Desktrac case was also used with one or two Spectra radio(s) inside, so lift the lid to make sure what you have.

To do any logic board swapping in a MaxTrac you will need the MaxTrac Lab RSS, a totally different package.

It's interesting but Moto's RSS software can do things the radio can't - make sure you don't have the same function (i.e. PL decode out, COS out, etc.) programmed for more than one pin on the accessory connector at the same time. While the RSS will let you do it (the programmer forgot to check for that), the radio doesn't work right if you do... And the symptoms are not what you would expect... So in your programming procedure add a step right before you write to the radio: go through the I/O pins, one by one, and make sure that no function is duplicated. The radio will do strange things if any are.

On any radio that is new to you do NOT assume that any accessory connector pin programming is present, or if it is there, is correct for your radio environment.

Likewise, don't forget to archive your original codeplug. When you acquire your MaxTrac or Radius radio remember to make a copy of the original (i.e. commercial frequencies) code plug and archive it. If you screw something up you will want to be able to backstep to something that is known to be good. It's better to have a backup and never need it than to need it and not have it. If you have access to MaxTrac Lab software make a second backup using that as the Lab backup copies a lot more data to the saved file. And remember, a floppy disk is NOT a good long term archival medium. Personally I use two different CDRWs, and the media is from different manufacturers. More details are on the RSS / RIB pages at this web site.

Limitations:

Above all, remember that the MaxTrac, M-series and GM300 are MOBILE radios, made with minimal heat sinks, and while they can be used quite readily as a low-to-medium performance repeater receiver, or as a link receiver, you can NOT use it as a repeater transmitter or link transmitter without due consideration to the normal mobile radio limitations on RF power and duty cycle.

Remember that the beauty of a repeater is that it is a device that allows one-to-many communications rather than a cellphone which is limited to one-to-one. As such, while any individual user may only transmit for 10 to 30 or even 60 seconds the repeater is transmitting for the duration of the transmissions of all of the users continuously one after the other.

As a 10% to 15% duty cycle radio the MaxTrac and the Radius is designed to transmit for no more than 10 to 15 seconds out of each 100 seconds. This is not to say that you can't transmit for three minutes, but the transmitter is going to get hot, and the longer it talks the hotter the mobile radio gets. These radios were designed for a 10% to 15% transmit duty cycle, and the internal power control is the only thing preventing the radio from burning itself up.

The MaxTrac and Radius radios have power control circuitry that turns the transmitter power down if you talk too long (all it does is measure PTT time), where the GM300 series radios actually measure the PA deck temperature with a thermistor (hence they "know" if there is a fan present or not).

The MaxTrac and Radius power control timer can create a situation where the transmitter goes into power shutdown on its own, which can happen in the middle of a conversation. This WILL happen in a long transmit situation. The radio might not be hot (due to the fans), but the microprocessor "knows" it has to be, and steps the transmitter power down to zero. It'll recover for a few minutes after it's unkeyed, then do it all over again until it has adequate time to rest. You really don't want your repeater fading out during something important like a search and rescue operation, or even a 911 autopatch call. The article on Manual Power Control (below) shows how to address this problem by bypassing the shutdown control. Just make sure you have a suitable external temperature control system in place (fans, etc).

In short, with very, very few exceptions, a mobile radio used as a link or repeater transmitter is a recipe for failure, especially if the system includes EchoLink or IRLP... as I said above, the repeater is transmitting for the entire conversation of all the users, with a linked system the user pool now includes everybody on the local system plus everybody on the far end node, or if connected to a reflector then everybody on every node hooked to the reflector.

I've seen a photo of a 110w Spectra trunk mount mobile where the power control failed and let the transmiter run at full blast for as long as PTT was held down. Then one day the driver sat on the microphone for an hour during a road trip. The radio PA burned itself up and was not repairable.

The "Executive Summary": If you are going to put up a repeater (or a point-to-point link that will have a similar duty cycle), don't use a low-end low duty cycle mobile radio (from any manufacturer) as the transmitter.

These radios were designed for a range of RF power - for example, the D44 series is a 40 watt radio, and is designed to run from 25 to 40 watts, which means not more than 40, but also not less than 25. If you run outide that range, it will be inefficient and run hot.   Yes, strange as it may sound, a D44 run at 15 watts runs hotter than when run at 30 watts.

Even this DeskTrac tabletop base (which also came in a repeater version with two radios inside) has the MOBILE limitations.

FACTOID: If you want to use one of these radios to drive an external power amplifier, the exciter output is anywhere from 20 to 220 milliWatts, depending on the operating band. The schematic diagrams show signal levels of +13dBm to +17dBm for various VHF/UHF/800 MHz radios, but +23.5dBm for the 900 MHz models. These power levels have been confirmed by actual measurement. The exciter output mates with a male Taiko-Denki connector. These require a unique crimping tool to be installed properly, and they are designed to fit only a few types of coaxial cable. We've been told that TenTec Corporation (the same folks who make HF gear) down in Tennessee will make RG174 cables with T-D connectors professionally crimped on one end for very reasonable prices (under $10).

Initial Checkout, Repair and Hardware Oddities:

The radios that have a 16-pin accessory connector DO NOT have the internal speaker connected by default - it takes a jumper plug to enable it. More details (including a photo) below and in the Interfacing articles.

To open the radios you will need to remove the two screws from the control panel (T15) and the four flat-head screws from the sides (T10). Pull the control panel outwards from the front of the radio and off of the top and bottom covers, then pry the covers off. They are identical and split in the middle of each side. Sometimes they're hard to get apart, but nothing else holds them together. Usually you can get them going by using a flat blade screwdriver and starting in the front where the edge is exposed over the metal chassis. If you need to remove the logic board you will need a T8 screwdriver to remove the small flat-head screws that hold the logic board's heatsink to the side of the chassis. The threaded holes for the mobile bracket are metric threaded - 5MM point 8 thread.

If you acquire a radio and don't know it's history, as you do the initial bench check you will want to check it for frequency accuracy. Program it for an even-megahertz channel (i.e. 31.000, 40.000, 47.000, 155.000, 455.000, etc.) and test both the receiver and the transmitter. If it's off, and it is shock/vibration sensitive you will find that in many cases if you clean the pins and jack between the boards very well the problem goes away. Once the pins are clean a drop of a product called "Stabilant-22" (also known as "Tweek") on each pin helps a lot. The 15 mL bottle size is carried by Motorola Parts as part number 1180369E78.

This is very rare these days, but does show up once in a while... the entire radio is waaaay off frequency (both transmitter and receiver) and cleaning the pins doesn't help. The RSS contains a "warp" adjustment to bring the reference oscillator (the main frequency determining circuit in the radio) back on channel, but Motorola had a bad batch of the 14.4 MHz reference oscillator crystals that drifted beyond the ability of the warp adjustment. The story that I heard from two independent sources is that the offshore crystal manufacturer tried to cut one too many corners and didn't fill the crystal cases with dry nitrogen during manufacture, but nobody knows for sure (or if they do, they aren't talking). The crystals passed receiving inspection, were assembled into radios and shipped to customers. Within a year or two they had drifted to the point of being almost unusable. Any surplus MaxTrac is old enough now that any bad crystal has probably already been changed out by the time it is in an amateur radio operators hands, but you occasionally find one that has been a shelf spare all its life. While a crystal house like International, Bomar or JAN is one source for a replacement, Motorola Parts is cheaper in this case (and you won't have to wait for it, it's in stock). The part number for the 14.4 MHz crystal is 48-80174D05 (when you get it don't be surprised if it's labeled "14400.00", "14400", or "14.4"). The part number is the same in the MaxTrac, Radius and GM300 series and it will set you back around US$14. In the GM300 manual Moto says this crystal is not field replaceable but it obviously was in the days of the mass swapout under warranty (supposedly Moto was shipping out thousands of crystals per month for many months). There is a paper tag glued to the side of the factory crystal with an 8-digit number that contains the temperature coefficient information (see this photo), and naturally a new crystal will be different than the old one, but the old data should be a good starting point. See the paragraph titled "Reference Oscillator Coarse Adjustment Procedure" on the GM300 info page.

If the transmitter is on frequency then the main crystal is OK. If just the receiver is off frequency then you will need to check the frequency of the second oscillator crystal (44.645 MHz, part number 4880008K02). Some M10, M120, M130 and GM300s used a 44.845 MHz crystal (4880908W04) so look before you order the replacement. There is also a 10.245 MHz crystal (but that one rarely causes problems... if it does it's part number 48-80908W01). Again, the "real" Moto part is probably the cheapest (and you won't have to wait for it, it's in stock).

You will need T8, T10 and T15 Torx bits to open and work on the radios. Torx head fasteners are getting more and more common in the automotive world and most tool stores, even Home Depot, Wal-Mart and Harbor Freight now carry the screwdrivers and bits. Note that the T8 is less common in the prepackaged kits... I've seen several bubble-packed kits that started at T10 and went up in size so you may need to hunt a little for a set that includes the T8 size. Personally I avoid the sets with a single handle and changeable bits - it seems that you spend as much time changing bits (or looking for dropped bits on the floor) as working on the radio. And after a while the bits get loose in the handle and won't stay put.

Note that the base station and mobile microphones for the MaxTrac and several other radios (including the DeskTrac) look absolutely identical, but may or may not be interchangeable because they can be wired differently inside (the differences involve only the first two pins, see the table below). So yes, any RJ-45 mic can be plugged into any MaxTrac series radio, but if the first two pins are wired different it may not work. Before you purchase microphones that have a RJ-style plug on the mic cord you need to verify that the wiring is compatible. There is a table of known good microphone part numbers below (if you have one that works but isn't on the list please let us know), and addtional parts information is in the parts catalog PDFs below. Note that there are lots of errors in these catalogs, so always check with Motorola's Parts ID group before placing your orders. Since pin 1 and pin 2 on the microphone jacks are unused we take advantage of that in the interfacing article). Both pins ARE wired on the DeskTrac, and one is wired to power, so be careful.

Replacing the Microphone Connector in the radio:

Occasionally you will find a radio with a bad microphone jack - perhaps from wear, or perhaps from corrosion problems (green mold). Sometimes it's not obvious until the RIB does not make contact or is making intermittent contact. Don't attempt to clean it, you are just wasting your time. The genuine Moto mike jack for all of the MaxTrac / Radius / GM300 series is part number 09-80132M01, available for about US$4 (at the time of this writing - early 2006) from Motorola Parts. Do not try and unsolder all 8 pins and remove the old jack!! You don't want to risk lifting the copper traces on the board (been there, done that, wasn't pretty). Use a large pair of diagonal cutters and chop apart the old jacks plastic body (you are replacing the jack because it's dead anyway) and bend the 8 pins straight up away from the board, lifting out the pieces of the plastic body as you go. Once the eight individual pins are free from the plastic body then unsolder each pin one at a time (from the bottom of the board) and lift it out (with a pair of needle nose pliers) from the top of the board. When all eight pins are removed clean out the holes with a solder sucker or a round wooden toothpick. Now mount and solder the new jack.

Replacing the Antenna Connector in the radio:

Sometimes the chassis mount coax connector needs replacing... I've seen several with damaged threads, and one that was really mangled. Often the little "teeth", that keep the plug from rotating when tight, get worn off. The part number listed in the service manual for the mini-UHF connector is/was 2889309U01, and most manuals show that number. The part has been renumbered in the last service manual (only the last digit changed) to 2889309U03, and will set you back about $2.15 (early 2007 pricing), however the Motorola web site shows a part number 0980131M01. Either way, at under $3 it's not worth futzing with any problem connector.

However, due to the way the radio was put together, it's a lot more work than you would expect, so don't proceed unless you have to.

The antenna connector itself is rather easy to replace, but you must remove the circuit board from the power amplifier to extract it. That also means you must unsolder and remove the DC power connector from the circuit board first. This is a lot more difficult than it initially seems. The connector leads are thick and the circuit board holes are just big enough for them. The holes also have copper sleeves inside that connect both sides of the circuit board together. These sleeves often come out when extracting the power connector, requiring further work to fix the new damage.

Use a soldering gun to heat each lead, then remove as much solder as possible from the joint. Remove the power connector's mounting screws (T10), then pull on the connector as you alternately and quickly heat each lead at the circuit board. Eventually you can wiggle it out and do a better cleaning job on the leads and holes.

Once the DC power connector has been extracted, you can remove the screws holding the circuit board and RF components to the heat-sink. The mini-UHF antenna connector can be unsoldered from the board, or you can remove its mounting nut and remove it with the circuit board. The new connector is easily replaced. It's probably better to install it into the heat-sink first, then reinstall the circuit board, then solder the center pin of the antenna jack, and finally install the DC connector.

Should you decide to replace the power connector (since it's already out) the new one is part number 0980255E01.

Accessory Connector Notes:

Depending on the radio model it will have either a 5-pin or 16 pin accessory connector. Most hams look for the 16-pin radios because they are easier to interface to other equipment. That's fine as it leaves the 5-pin radios for me, and adding a single resistor, a single transistor, and a DB9 pigtail cable is easy (see the article below). And 9 pins are plenty to do everything I need to (including feeding power into a receive-only radio).

The radios with a 5-pin accessory connector have the internal speaker on full-time, where the ones with a 16-pin connector enabled it with a jumper on the accessory connector. This jumper can be implemented in one of several different ways:
1) an official MaxTrac jumper plug inserted in the back of the radio,
2) a PC two-pin option jumper inserted in the back of the radio,
3) a soldered jumper wire inside the radio bridging the two pins together.
4) and I've seen one where the person bent the two pins together (so they were touching) and soldered them together. It required replacing the accessory connector before you could insert an accessory plug into the back of the radio.

To enable the internal speaker you will want to tie pins 15 and 16 together or connect an external speaker to pins 1 and 16. Note that one side of the speaker in the Maxtrac series and both sides of the speaker in the later series radios is/are hot, and grounding a hot wire (even momentarily) will let the lifetime supply of magic smoke out. The Maxtrac series uses two inexpensive individual transistors as an audio output stage, the later series uses an expensive audio power module.

Above shows where to put the PC jumper - the rightmost two vertical pins.

YOU CAN NOT USE THE ABOVE JUMPER TECHNIQUE ON MOST FACTORY-PROGRAMMED RADIOS.

You will find that most radios are programmed for the alert / alarm function when they land on the surplus market. The alert pin is grounded when normal (i.e. not in alert mode) and removing the jumper (i.e. lifting the alert pin off ground) causes the radio to transmit the alarm signal. The speaker jumper shown above is only usable on radios that have the alert fuction disabled in the programming of the radio codeplug. More details on the Interfacing pages. By the way, in the photo above, the exposed power pin is the positive pin.

Note that the GTX radio uses the same 16-pin accessory connector, and it also needs a speaker enable jumper plug... but the connector has a very different pinout which is covered on the GTX pages elsewhere on this web site. DO NOT plug a GTX optioned jumper plug into a MaxTrac, Radius or GM300 YOU WILL DAMAGE THE RADIO as covered in this warning article - you will kill the audio output capacitor and 9 times out of 10 the shorted cap will kill the MaxTrac speaker amplifier transistors or the GM300 audio output module (which is expensive). Expect that any other radio that uses the same 16-pin plug assembly will also have a different pinout.

The plastic 16-pin accessory connector shell (the piece that plugs into the radio) is DigiKey's part 104422-1-ND. At the time of this writing DigiKey's price is about a US$1.50 each, or about US$1.25 for quantity 25. AMP makes a wide variety of contacts for this shell with varying wire sizes and plating types. The one most appropriate for 22 AWG wire is DigiKey part number A3007-ND (AMP 1-87309-3) at about 14 cents each (or about US$12.50 per hundred). And these pins are gold plated! Mouser part numbers are 571-1044221 for the connector (under US$2.00) and 571-1873093 for the pins (about US$0.20).

The pins snap into the connector body, and once in are designed to not come out. To remove one you need the pin extraction tool, Moto part number 6680947W01, which can be purchased by itself for about $2, but it is more economical to buy the HLN9242A 16-pin Accessory Kit, which includes this tool along with nine pre-terminated wires, a connector body, and 16 extra socket contacts. At the time of this writing the HLN9242A kit costs about US$7.

There's an instruction sheet that explains how to remove the pins in the GM300 article listed below. Scroll down to the Accessory Jack section and click on the image that's there. It shows the extraction tool, and where to insert it.

HINT: If you are just getting started I suggest you buy a HLN9242A kit as you get a connector body, 16 loose pins, 9 pre-ended wires, and a pin removal tool. Then when you need more plug bodies or pins just order them from DigiKey or Mouser (part numbers are on the interfacing pages).

Replacing the Accessory Connector in the radio:

Occasionally you run across a radio that needs a new 16-pin accessory connector. Maybe one pin is bent, or even broken off. The part number for the 16 pin right angle accessory connector is 2804503J01, at around US$5.25 (early 2007 pricing). Like the microphone jack, do not try and unsolder and remove all 16 pins of the old jack!! Use a large pair of diagonal cutters and chop apart the old connector. Once all of the individual pins are free then unsolder each pin one at a time from the bottom and lift each individual pin out of the top of the board with a pair of needle nose pliers. When all are removed clean out the holes with a solder sucker or a round wooden toothpick. Now mount and solder the new connector.

Another source for a replacement accessory connector is an old PC computer motherboard or disk controller card. Many had right angle pin assemblies of 36, 40, or more pins that can be cut down to 16 pins. The fun part is salvaging it - i.e. removing it from the PC board without destroying it.

Speakers:

If the internal speaker is not loud enough, the standard Moto mobile speaker with a 5-pin plug is part number HSN4019B, or the same speaker with a 16-pin plug is HSN9326A, or you can take an old Motrac, Motran, Micor, Mastr-Pro or Mastr-II vintage swapmeet speaker and change the plug (just make sure that both sides of the speaker are internally floating off of ground). There are also amplified speakers (used in fire trucks, and other noisy environments) that are part of Motos "Power-Voice" line that include the HSN1000B.

From an email from Jeff Kincaid W6JK:

The MaxTrac family radios have a built-in front panel speaker and sometimes you will find a radio that has the jumper wire that connects the physical speaker to the logic board missing (the radio was obviously used only with an external speaker). A leftover lead from a PC case that has a 2-pin push-on connector on one end will fit the speaker connector on the audio/logic board and substitute temporarily - look in your PC parts box for a leftover front panel red or green LED, or the wiring from a reset button. Just push the two-pin female plug onto the MaxTrac logic board and cut the wires to length then solder the wires to the speaker. At this point you will find that the case half won't go on because the plastic body of the PC connector is too tall... been there... The quick and dirty solution is to remove the pins from the PC plug body, put heat-shrink on them individually and push each one onto the logic board pins. Note that they will vibrate loose in mobile service but this will get you by in a base station environment or until you can locate the proper connector... some PC sound cards use the actual connector Motorola used and you may find one in someones junk box or at a PC repair shop.

Mailing Lists:

The MaxTrac / Radius / GM300 radios can be discussed in detail on the Motorola-Radius group at YahooGroups...
Another interesting group is Motorola-User, also at Yahoogroups. Don't waste your time with the "motorola-Radios" group (yes, with a lower case Motorola) as it's totally overrun with spam, and all the moderators and the owner have abandoned it.

There are two more YahooGroups just for the amateur 900 MHz band (any make and model of radio - as long as they are 900 MHz):

The first is http://groups.yahoo.com/group/AR902Mhz.   From the description text: "This listserv is used to further experimentation and utilization of the 902-928 MHz amateur radio spectrum using voice and data communications. Please limit your posts to information relating to these subjects ONLY. Want and For-Sale ads allowed. Do not post EBAY links. Do NOT list non-900 MHz applicable items."

The second is http://groups.yahoo.com/group/900mhz.   From the description text: "For those interested in utilizing the 900 MHz amateur radio band. This group is here to discuss modification of commercial radio gear to amateur radio use, repeater construction for 900 MHz, and other related topics relating to the 900 MHz amateur radio band."

Microphones:     If anybody wants to contribute additional schematic scans we will post them.

• HMN1035 series Palm Microphone, full size (uses Hang-Up Clip HLN4606A)
• HMN1056D Compact Palm Microphone (uses Hang-Up Clip HLN9073B). The "D" series of this mic (and maybe some of the earlier ones) is glued or solvent-welded together during manufacture and you can't open it without destroying one side or the other. See the photos of the interior of a 1056D in the "Microphone Hang-up Mechanisms" article below for more details. The microphone cord plugs into the microphone itself with a telephone style plug.
• HMN3596A palm microphone (black)
• HMN4016A Noise Cancelling mobile microphone
• HMN1037B non-backlit DTMF Microphone, for 100/300 models only
• HMN3013A non-backlit DTMF Microphone, for 820/840 Series
• TDN8305B or TDN8310 Backlit DTMF Microphone
• TMN6169A Backlit DTMF with Autodial Last Number Redial
• HMN1038 (beige) or HMN3000B (black) base station (desktop) microphone, with PL defeating "Monitor" button
• HMN3031B base station (desktop) microphone (used on carrier squelch radios, does not have a PL defeat)

The larger 1035 microphone sounds much better than the 1056 microphone, so if you have a choice pick the 1035. The replacement mic cord for the HMN1056 is part number HLN9449A for a 7 foot cord or HLN9560A for a 10.5 foot cord. With either one you can adapt other mics (like a David Clark aircraft headset).
Note that most but not every RJ-45 style microphone will work in a MaxTrac... Moto used the same plug but with other pinouts on other radios.

If you have an old junker microphone that you have dedicated to the test bench/workbench it might be worth mounting a toggle switch in the case... wire it so that flipped one way pin 3 is open (the radio is in carrier squelch), the other way it's in PL mode (pin 3 is shorted to pin 4).

MaxTrac / Radius / GM300 / DeskTrac Microphone Jack Pinout When looking at the front of the MaxTrac radio the mic jack is vertical, with pin 1 is at the top, nearest to the volume control, with the locking clip to the right. The DeskTrac has a horizontal mic jack with the locking clip at the bottom, and the pins numbered from left to right. Six of the pin functions are the same but the numbers are sdrawkcab. MaxTrac Pin Description DeskTrac Pin 1 On the low band, high band, UHF and 800 radios both pin 1 and pin 2 are unused, but fed to the logic board. On 900 MHz radios these pins are unused but never leave the front panel board. See Note 1. On a stock DeskTrac this pin has +5vDC on it. See Note 2. 8 2 Same situation as pin 1. On a DeskTrac schematic this pin is labeled "HD". 7 3 The receiver is in carrier squelch when this pin is floating, and when it is grounded (if the channel has PL or DPL programmed) the receiver must have the proper PL or DPL to unsquelch it. The method of grounding this pin varies with which model of microphone is used. See note 3. 6 4 Ground 5 5 Microphone audio and preamp DC bias voltage. 4 6 PTT (ground to transmit). 3 7 The Moto schematic names this pin "SCI+". It's the bidirectional programming data lead which is used by the RIB for programming the radio, so leave this pin taped off in the microphone. Some microphone cords do not have a conductor in the cable for this pin. The special plug that was used to put a trunking MaxTrac into test mode simply grounded this pin with a pin 7 to pin 4 jumper. 2 8 In palm microphones this pin is unused, as it carries audio out intended for a handset earpiece. On the early series radios the audio level coming from the radio on this pin is a fixed level (not affected by the volume control) which works well as a source of repeat audio (i.e. de-emphasized). On the later series radios the audio level at this pin is affected by the volume control, and if you are going to use it as a repeater or link receiver you may want to cut a trace and add a jumper to make it a fixed level. 1

Table Notes:
1: On the low band, high band, UHF and 800 MHz MaxTrac radios, the microphone jack pins 1 & 2 run through the internal cable to spare pins on the logic board where they sit unused. On the 900 MHz board (with HearClear), these pins are not attached to anything on the board (solder pads only) as the two connections from the logic board are used to provide +9.6V and enable/disable signals for the HearClear hybrid module located on the microphone jack / volume control circuit board. In the 900 MHz radio there is one unused lead in the cable between the logic board and the microphone jack / volume control circuit board and could be wired to pin 1 or 2 of the microphone jack and used for other purposes, such as providing a COR signal to the outside world. On low band, high band, UHF or 800 MHz radios this lead was used to provide the headset audio to pin 8 of the microphone jack through a 560 ohm resistor located on the logic board. On 900 MHz radios the headset audio is optained at the output of the HearClear hybrid module (which is already on the microphone jack / volume control circuit board, so they put the 560 ohm resistor there and freed up a signal pin on the logic board.

2: CAUTION Some surplus DeskTracs have been found with a modification which replaces the +5vDC with +12vDC.   I've been told of, but not seen, similarly modified MaxTracs. Don't count on this pin being unused in a new-to-you MaxTrac / Radius / GM300 or at +5vDC in a DeskTrac until you verify it. Best as we can figure this mod was done for one of two reasons:
a) to power a low-drain outboard device.   One of the DeskTracks seen with this mod was known to have been used with an external telephone interconnect unit at one time (if you are not familiar with the term "telephone interconnect" just replace that term with "commercial 2-way radio autopatch").
b) to allow the use of a Maratrac programming cable (which is identical to that of a MaxTrac except for one extra wire in it to power the RIB from the +12V pin). This makes for easier programming as the tech does not need to crawl around on the floor hunting for a convenient place to plug in the RIBs wall-wart power transformer.

3: On the HMN1056 microphone the button is hot, and the ring is ground, on the HMN3596, the ring is hot, the button is ground. See the "Microphone Hang-up Mechanisms" article below for more details.

Manuals and Documentation:       If anybody wants to contribute additional part numbers (or even manual scans) we will post them.

There are some additional manual part numbers listed in the GR-series repeater section below.

	MaxTrac 100 and 300 User Manual   6880901Z04   389KB PDF file   Donated by A. Nony Mous
	Radius M10 User Manual   6880903Z05   1.34MB PDF file   Donated by A. Nony Mous
	User's "cheat sheet" for the Radius M10, M120 and M130   6880902Z96. Save your money, if you have an IQ higher than that of egg white, you don't need this.
	Radius M100, M208 and M216 User Manual   (early)   6880901Z47   770KB PDF file   Donated by A. Nony Mous While the title page says M100 and M200, there is no M200 model... it instead covers the M100, M208 and M216. The later book is 6880900Z45
	M120 User Manual   6880902Z97   1.33MB PDF file   Donated by A. Nony Mous
	M130 User Manual   6880903Z64   1.29MB PDF file   Donated by A. Nony Mous
	GM300 User Manual   6880902Z09   1.37MB PDF file   Donated by A. Nony Mous
	GM300 Accessories Brochure   743 KB PDF file   Donated by A. Nony Mous
	GM300 Programming Manual   6880902Z36, about $30 This is just the RSS manual, it does NOT include the RSS itself.
	M10 Service Manual   6880903Z03, about $28
	M120 Service Manual   6880902Z98, was about $29 (but has been canceled)
	M130 Service Manual   6880903Z65, about $30
	Radius M100, M208, and M216 Service Manual   6880101W58, about $45
	MaxTrac service manual   6880102W84, was about $30 (No Longer Available) This is the low band, high band, UHF, and 800 MHz MaxTrac service manual. You want this on your shelf... it's chock full of good stuff. You occasionally see these on eBay and the other auction sites.   Until then... Part one has the manual index, model charts, assembly breakdown tables, performance spec tables, options, general information, block diagrams and the front panels Part 1   Pages 001-058   4.3mb Part 2 has all of the Logic boards Part 2   Pages 059-081   15.4mb Part 3 has all of the RF boards Part 3   Pages 082-125   41.4mb And part 4 has the PA deck info, Radio Disassembly/Assembly procedures and the exploded parts lists Part 4   Pages 126-163   17.1mb Originally this book arrived as a shrink-wrapped pile of 3-hole punched pages - you had to provide your own thick 3-ring binder. The shrink-wrapped stack was slightly over 2 inches tall - I used a 3.5" (ring diameter) binder to hold this W84 manual, a 900 MHz Trunked manual, and a DeskTrac manual.
	GM300 Service Manual   6880902Z32, was about $13 (No Longer Available as of June 2007) This service manual covers all models of the GM300 radio (not all of the GM300 series radios, just the GM300 itself). This is another one you want on your shelf... You occasionally see these on eBay and the other auction sites.   Until then... The GM300 service manual pages 001 thru 030   14.4MB PDF The GM300 service manual pages 031 thru 072   14.5MB PDF The GM300 service manual pages 073 thru 077   9.9MB PDF The GM300 service manual pages 078 thru 085   8.4MB PDF The GM300 service manual pages 086 thru 144   15.1MB PDF Total download is 62mb.

The 900 MHz MaxTrac conventional radio service manual is part number 6802980G40

The 900 MHz MaxTrac trunked radio service manual is part number 6802977G10

Both of the above 900 MHz MaxTrac manuals are NLA (No Longer Available) from Moto but show up on eBay from time to time. Both radios use exactly the same boards and parts. The only difference is the firmware: The trunking version supported trunking and some conventional channels, where the conventional firmware did full conventional only.

The conventional manual has about 4 pages describing the operation. The trunking manual has these pages plus another few on the test modes the trunking radio has, plus a little bit on troubleshooting in the trunking environment. Basically, if you have the trunking manual, that's all you'll need for either radio. I still don't know why Motorola didn't just include the 20-30 pages of the 900 MHz trunking manual in the big MaxTrac W84 manual and be done with it. It certainly wasn't worth TWO separate manuals (that were 99% identical) to cover the same 900 MHz hardware.

The 900 MHz manuals deal with the 12w radios. An addendum that came with it deals with the 30w PA deck. By the way, the 30w model is rated for 30w on 896-902 MHz (i.e. the repeater input range) but only 20w on the talk-around / simplex 935-941 MHz range.

The DeskTrac manual is part number 6802993G65. This covers all of the LxxSUM70D0A, 70D0B, or 7000_T DeskTrac tabletop stations (where "xx"=51, 43, 53, 24, 44, 54, 35, and 45, and the "_" is any letter). I have a -A version of this manual in my file cabinet and it does not list any 900 MHz models. There may be a later one out there, or a separate manual specific to the 900 MHz units that I am unaware of. If you do any servicing of the Logic or RF boards in the DeskTrac you will want the W84 manual as well as the DeskTrac manual manual since it does not go into as much detail as the W84 book does. And note that some "DeskTrac" stations had one or two Spectra chassis instead of MaxTrac chassis inside, so before you go ordering a manual you will want to lift the lid and look which radio you have inside...

As shown in the table above, the DeskTrac manual has one major weirdness. The MaxTrac manual numbers the microphone jack pins from top to bottom, and the DeskTrac manual numbers them from left to right. Six of the pins have the same assignments, but the numbers are sdrawkcab. And the MaxTrac does not use pins 1 and 2, the DeskTrac does, and one pin in the DeskTrac has +5vDC on it.

Other info:

The locking MaxTrac / Spectra mobile mounting bracket is HLN-4426A. The standard 2135 key will open it (unless the lock has been changed). More key info is on the radio keys page. The non-locking HLN5189A trunnion bracket is also listed for the MaxTrac 820-840 series.

All MaxTrac, Radius and GM300 models draw about 5 milliamps when turned off (standby current for the microprocessor) and about 400 milliamps in receive (squelched) mode (the GR series repeaters have two radios plus the control unit so they draw additional idle current). Each of the front panel LEDs or segments draws about 11 milliamps, so the receive current draw varies as you change channels.
Under worst case conditions (full volume blaring squelch noise) the receiver can draw as much as 1.6 amps.
The transmitter can draw as high as 17 amps depending on RF power level and frequency band.

Base Station / Control Station Kits:

In the business radio world the base station that talks into the repeater is called a "Control Station". Motorola made two "Control Station Kits", one for low power (1- 25 watts) situations, and the other for high power (25-60 watts) situations.

This table lists the kit contents:

Item Low Power Kit HLN5292BR High Power Kit HLN3199C Base Station Tray HLN5292BR HLN5292BR Desk Microphone HMN3000B HMN3000B Power Supply HPN4002B HPN4001B Power Supply Cable HKN4139A HKN9455A

It's interesting, but both power supplies look like Astron clones.

Remote Mount:

If you have a small car or otherwise have limited space you can split the MaxTrac / Radius / GM300 in half and mount just the control panel up front and have the rest of it under the seat or in the trunk. A company named Valley Industrial has a product called the "Quick-Mount QM1" with details at 800-260-6025 or at http://www.quickmount.com/quickmount/qm1/qm1.htm. Moto themselves used to have a split kit but they discontinued it. Valley Industrial saw a need and filled it.

GR-series Repeaters:

Motorola sells low-end consumer grade repeaters called the GR300, GR400 and GR500 that are intended for low duty cycle situations / applications like schools, shopping mall security, sports arena management, etc. They replaced the R100 repeater (that was based on the German version of the MaxTrac) after it was discontinued. The GR series units usually have two GM300 series radios in them, a controller and a power supply all in a metal box. Some have a mobile duplexer in the very bottom.

Surplus GR units have been seen with almost any two MaxTracs or Radius radios that have 16-pin accessory connections. Moto made the GRs with a variety of controllers (including the Instrument Associates I50R, TRA100R, and the Zetron ZR320, ZR330 and ZR340), but the most common is a very basic controller called a "RICK", model number HLN3333B (it's so basic that it does not even have an identifier). The GR300 power supply is the HPN9041 or HPN8393, both of which are made by Astron for Moto, and are unusual in that they come with a 120v / 240v switch. The schematic of the supply is on the Astron page at this repeater site. The GR500 power supply is the HPN9005 and is made by StarWerks, Inc. at 847-397-3600.

There is no clean and elegant way to make a RICK-based repeater have a legal IDer in the amateur radio service short of replacing the RICK with another controller. The NHRC-4 or the ICS Basic are both good inexpensive units. An alternative method that has been used with some success is to purchase an ID-O-Matic kit from NØXAS (at www.hamgadgets.com) and patch it into the RICK transmitter audio.

The GR300 manuals listed below only cover the GR unit itself. You still need the manual(s) that cover the radio(s) themselves.     (prices listed are mid-2006)

• GR300 Basic Service Manual 6880902Z73, about $17
• GR300 Detailed Service Manual 6880902Z68, about $23
• GR300 and GR500 Repeater Stations and Controllers Service Manual 6880903Z42.
  This manual has information on the RICK, Instrument Associaltes and Zetron controllers mentioned above.
• RICK (HLN3333B) Instruction Manual 6880901Z79, about $5
  (this is the book on the later RICK that has surface mount parts, does anyone have the manual number on the early RICK ?)
  
  

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This page originally posted 05-Jan-2005

Credits and Acknowledgements:
MaxTrac, Radius, GM300, Spectra, GT, GTX, GR300, GR400, GR500, Hear Clear, Radio Service Software, RSS and several other names are trademarks of Motorola Inc.
Torx is a trademark of the Camcar Division of Textron / Textron Innovations Inc.
Original text by Neil Johnson WBØEMU, Scott Lichtsinn KBØNLY, Bob DeMattia K1IW, Robert Meister WA1MIK and Jeff Kincaid W6JK.
Front-view photos of the two-channel and multi-channel radios at the top of the page by Robert Meister WA1MIK.
Photos of the M10, M120, M130 and the GM300 radios (the links in the text) provided by WA6ILQ.
Edited text, artistic layout, photo of the rear of the MaxTrac and hand-coded HTML © Copyright 2005 and date of last update by Mike Morris WA6ILQ.

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.