If this is a repeat visit you can jump down to the articles. If not, you really want to read through this page at least once.

This page is oriented towards the USA marketed radios, simply because it was compiled by USA residents; they described the radios they were familiar with. The Maxtrac, Radius and GM300 series are/were sold all over the world, and the product line was customized for the local marketplace with region-specific model numbers, for example the UK/European region has models that are never seen in the USA (like the GM900), and the Australian market has models that are never seen in Europe.
As an example there are 220-240 MHz, 64 channel Radius mobiles and 16 channel GP300 handhelds made by Moto Australia for the Asian market (specifically the Philippines) that would be very popular in the USA Amateur market. If anyone has model information for the non-USA radios we'd be happy to add them.

Next, an eBay warning:

Attention EBay buyers: 1) No matter WHAT the model tag says, no MaxTrac, Radius, M-series or GM300 will ever operate over the entire frequency range listed on its model tag / label. Each unit will do only a portion of that model tag frequency spread, called a "split", a "bandsplit" or a "range". This is a simple law of physics. If you buy the wrong range radio for your application (one example is a GM300 built for 490-520 MHz and you want to use it on a 462 MHz GMRS frequency) you will have a nice doorstop. It is not practical to range-change a MaxTrac, Radius, or GM300 series radio. On the Maxtrac, Radius "LRA" and GM300 series (which includes the M10, M120, M130 and GM300 models) radios the third character in the model number indicates the frequency band where a 1 indicates 30-50 MHz (low band), a 3 indicates 136-174 MHz (high band), and a 4 indicates 406-520 MHz (UHF). A 5 indicates either 800 or 900 MHz, later on 5 was reserved for 800 MHz and a 7 indicated 900 MHz. MaxTrac "MGA", "MJA", "MQA", "MWA" series: Unfortunately, there are only two ways to determine the split of your radio. You have to either open the radio up and look at the part number of the RF board, or you have to read the radio (with the programming software, commonly called RSS). If radio programming, the RIB and the RSS are new to you I suggest you read the "RSS and RIB" page on the Motorola page at this web site, and scroll down on this page to the heading below titled "Programming and the Radio Service Software (RSS)". Note that the RF board is not the only part that changes between splits, it's simply the easiest one to check. Just take the top cover off your radio then lift the shield on the RF board and look at the number stamped in black ink. This link jumps into the middle of the article page: MaxTrac, MaxTrac 50, 100, 300, 820, 840, LS, Radius M100, M206, M208, M214, M216, and VR100. On the Radius "LRA" and GM300 series (which includes the M10, M120, M130 and GM300 models) radios the split is encoded in the model number. Only the underlined characters in the examples below are used to decode the split information. The Radius product line is very broad and includes mobiles and handhelds. The Radius "LRA" series of mobiles is derived from the Maxtrac (more details below). Their model numbers are in the format of: DnnLRA7nnnaa As mentioned above, the n is the band, and the nn is the split: 29: 403-430 MHz 32: 23-36 MHz 33: 36-42 MHz 34: 42-50 MHz A5: 136-174, 449-470 or 806-871 (non T/A) depending on if the band indication is "3", "4" or "5" A6: 806-871 (with T/A) What's T/A ? The hams call it simplex, the commercial two-way radio world calls it talk-around, where you talk around the repeater instead of going through it. The A6 radios have a simplex/repeat function, the A5 radios are repeat only. The GM300 series (which includes the M10, M120, M130 and GM300 models) uses a different format from the Radius LRA series: MnnXXXnnanaa, where "n" is a number and "a" is a letter and XXX is three letters, for example in M33XVC00F2AA or M44GMC20C1AA. The tenth character is translated as follows: If it's a high band radio (the third character is a "3") and the tenth character is a 1 then it's a 136-162 MHz (low split high band, sometimes called a "range 1") radio and is ideal for amateur radio 2M, VHF commercial and public safety, for Civil Air Patrol and weather. Note that CAP is going to nationwide narrowband in the 2009-2011, and some areas are fully narrowband as I type this, so wideband-only radios are a poor investment for CAP frequencies. If it's a UHF radio (the third character is a "4") and the tenth character is a 1 then it's a 403-430 MHz (low split UHF, sometimes called "range 1", or "government range") radio. This range WILL NOT work for 440-450 MHz amateur radio, or for GMRS. If it's a high band radio (the third character is a "3") and the tenth character is a 2 then it's a 146-174 MHz (high split high band, sometimes called a "range 2") radio. Yes, they will work down at 144-145 MHz just fine, but not a whole lot lower (i.e. I wouldn't try anything below 143). If it's a UHF radio (the third character is a "4") and the tenth character is a 3 then it's a 438-470 MHz (sometimes called a "range 3") radio. Ideal for amateur radio UHF, commercial, public safety and GMRS. If it's a UHF radio (the third character is a "4") and the tenth character is a 4 then it's a 465-490 MHz (sometimes called a "range 4") radio. Will do 470 and 480 MHz public safety, might be pushed to GMRS (depends on the individual radio, most will make it to 462), otherwise good for parts. If it's a UHF radio (the third character is a "4") and the tenth character is a 5 then it's a 490-520 MHz (sometimes called a "range 5") radio. Good for parts only (unless you have some local public safety frequencies on or around 508 / 511 MHz and want to monitor them). 2) Another eBay warning: The D03, D04, M03 and M04 models (where the second character is a zero) are two watt rated radios that were designed and marketed for the Low Power Industrial (LPI) radio service (think "in-plant forklifts", golf courses and similar low power usage). The PA deck has the standard driver transistor and a jumper in place of the final. Later LPI RF boards have a different driver transistor and no jumper - the area where the PA transistor used to be was redesigned. You will find "03" and "04" LPI radios advertised occasionally on eBay as 8, 10 or even 15 watt radios. I've seen one do 10 watts with the power control cranked all the way to the top, however I think the person advertising a D04GMC as a 15 watt radio was drugged, dreaming or had seen too many CB antenna advertisements. They will do 2 watts all day long (for example, as a point-to-point link radio), and will do 7 or 8 watts intermittently. One of the LPI radios makes a great garage repeater transmitter when set to 2w, and if you need more power it can drive an external amplifier to whatever power level you can afford. And the external amp can be continuous duty...

Overview and History:

On this web page we are going to attempt to provide an overview of several series of radios. The MaxTrac series of radios 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).

As it was related to me, the MaxTrac history can be traced back to the Motorola GmbH (also known as Motorola of Germany) product line called the MC‑Micro (anybody have some details on the MC‑Micro, or a few external and internal photos of a mobile ?).

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 220 MHz 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, but the RSS was very poor and would fail if run on anything faster than a 12 MHz 286-based machine. Despite that it remains a popular unit and many are still in service. They do have a few problems but field fixes (either by Moto themselves or by individual 2-way shops) are available for all of them.

When Moto USA marketing needed a simple-to-install dash mount radio (think "as easy as a CB radio") the USA engineering staff "americanized" the German MC‑Micro design (sometimes referred to as the German MaxTrac).

Later on, when they decided to sell through retail and mail-order channels they created the Radius product line just for that sales channel. They took the MaxTrac 50, 100, and 300 models and did both a front panel cosmetic update and a firmware rewrite and came up with the "Radius LRA" units (these are the models with "LRA" in the center of the model number). Over 90% of the boards and parts in LRA series is identical to the MaxTrac product line and most can be mixed, matched, and swapped between the two radio series. See the Radius M100, M206, M208, M214, M216 radio models and board info article by WA1MIK below for a breakdown of model numbers, board numbers, etc. Note that while a few of the Moto manuals state "M100 and M200", there is no M200 model, the valid names are M100, M206, M208, M214 and M216. The M100, M206 and M214 models were introduced in the first wave, the M208 and M216 replaced the M206 and M214 in the second wave.

At the time these radios were on the current sales sheets, the MaxTrac was a "Motorola direct sales channel" product. At that time, trunking products were more or less reserved for direct sales (system engineering was involved), so initially the LRA Radius line did not have any trunked models. The Radius LRA series was marketed by Moto for many years as a retail and mail-order product with no system engineering other than a salesperson over the phone.

When 800 MHz channels were allocated to business Moto took the existing MaxTrac chassis and designed an 800 MHz RF board to plug into it and a final amp to drop into the afterburner position... and then had to live with the problems that were created in using a logic / audio board that couldn't handle some problems that trunking created (note that while Moto calls it the "Logic" board in all the documentation, it's really a logic and audio board).

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.

The later GM300 series was a update or redesign to fix some of the problems (like adding a temperature sensing thermistor to the PA deck, and an attenuator (switchable on a per-channel basis) to the receiver to reduce the intermod). The result of that redesign is the single channel M10, the two channel M120 and M130 and the 16-channel GM300.

Because MaxTrac was the first series marketed in the US, and the later Radius and GM300 series radios are so similar to them 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 an LRA 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 M10 was derived from the GM300 and 90% of the MaxTrac and LRA Radius RF boards are identical. 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.

Series Name	Model Names	Model Number Strings (See note 1)	RSS (See note 3)
MaxTrac	MaxTrac, MaxTrac 50, 100, 300, 8-anything	"MGA", "MJA", "MQA", "MWA", a very few "LRA" (see note 2)	RVN4019 or 4020
Trunked MaxTrac	MaxTrac, MaxTrac 50, 100, 300, 8-anything	"MGA", "MJA", "MQA", "MWA", (see note 2)	RVN4043
MaxTrac LS	MaxTrac LS (800 & 900 MHz trunking)	Some "LRA", "UGQ" and "UJQ"	RVN4152
Radius	Radius M100, M206, M208, M214, M216, and VR100	Almost all "LRA", and a few "MJA"	HVN9173
GM300	Radius M10, M120, M130 and GM300 radios, plus GR300, GR400 and GR500 repeaters (see note 4)	"GMC", "GMK", "GMR", "XVC", "XQC"	HVN8177
There were also some data radios that were based on various MaxTrac, Radius and GM300 models (including the M10). We have no information on these or on the VR100... Contributions are welcome.

Table notes:
1) The strings referred to are the ones in the center of the model number. A typical model number is M33GMC09C3AC which is part of the GMC series.
If a model name conflicts with a model number then the model number takes precedence (front panels are easy to change).
2) The MJA, GMC, and GMR series are conventional, the MQA was trunking-only, the MWA series was dual mode (trunking and conventional for talk-around). I'm not sure if the UGQ and UJQ were trunking only or dual mode.
3) The RVN4018 came on 5.25 inch floppies, all the rest came on 3.5 inch disks. For additional information on RSS please see the "Programming and the Radio Service Software (RSS)" section below.
4) The GR series repeaters were normally shipped with GM300 family radios, but these repeater cabinets have been seen with every possible combination of radios that have 16-pin accessory connectors. The most common are M10, M120, Radius LRA, MaxTrac 300 and GM300.

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 has 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 8-channel GM300 will do 12 channels, and a 16-channel GM300 does 24, 32 or even 40 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 and RKR1225 repeaters that were built from it).

The low band, high band and UHF MaxTrac logic / audio 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 Hydroelectric 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", an "S" or an "X" model (see the "Figuring out what you have" page 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 space so he or 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 (implemented with zero-ohm surface-mounted resistors) are moved around. The firmware is a special chip labeled VLN5443A. All of this is described in the manual revision 6802950A44-A, part of the 68P80102W84 MaxTrac manual, described below.

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

The special 99-channel logic board 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. I've been told that someone could just add additional entries to the MDF file for 99 channel VHF and UHF radios, but I think it would take someone with an advanced debugging package that could "look" into the MaxTrac RSS and see where the problems/limitations are before you could have a 99 channel high band or UHF MaxTrac.

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 two chip resistors on the bottom of the board (used as jumpers). The biggest problem is locating the special firmware and the special RSS.

Or if anyone has modified a HLN9313 logic board and then patched the RSS to support a 99 channel configuration (low band, high band, or UHF) and would like to do an article let us know - even anonymously.

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 (a block of binary data) 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 a slow PC with a real serial port.

The MaxTrac was designed in the days when the bleeding edge software development computers were 25, 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 talks to the serial port hardware directly and it runs only on slow 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 (referred to as firmware). 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 program. 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 conventional firmware 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 get to blank and reinitialize the logic board. Occasionally you find the stock firmware in an antistatic wrapper 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). Neither will work on the MaxTrac LS (trunking) models. Later versions were offered on 3.5 inch disks only. The most recent version was used in preparation of the articles below. It is Moto part number RVN4019K, identified on the startup screen as Revision R07.02.00a, and dated 25-Jun-97.

The Radius M100, M206, M208, M214, M216, and VR100 radios use a different RSS, model HVN9173 commonly called RADMBL (short for Radius Mobile). It was available on 3.5 inch media only.

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. This 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). Yes, the DeskTrac RSS contains two separate RSS packages, one for the radios and the other for the control board. Note that the white plastic case that was designed for the DeskTrac was also used for the Spectra series radios under a different name. More details on the DeskTrac below.

To do any logic board swapping in a MaxTrac you will need the MaxTrac Lab RSS, a totally different package. And there are at least two different versions of the Lab software "out there".

It's interesting but Moto's RSS software can do things the radio can't - so 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: if you've changed any of the I/O pins go through them 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.
Always plan on reprogramming any newly acquired radio to meet your own requirements.

Likewise, don't forget to archive your original codeplug.   It's better to have a backup and never need it than to need it and not have it.

When you acquire your MaxTrac or Radius radio remember to download and save the original (i.e. commercial frequencies) code plug (for one thing, it contains the tuning information). If you screw something up you will want to be able to backstep to something that is known to be good. If you have access to 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. Hard drive space is CHEAP. Personally I copy any code plug that I want to archive to an archive directory on my hard drive, and that gets copied to two different CD-RWs (with the media from different manufacturers). More details and some CD-RW media suggestions are on the RSS / RIB pages at this web site.

Limitations:

Above all, remember that the MaxTrac, M-series, Radius 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 as a 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. And if it's an IRLP-linked repeater then the user count just increased to add all the users on the other end of the link or reflector.

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 circuitry 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). Due to the timer design the MaxTrac and Radius radios assume that there is no fan.

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 a strategically placed fan), 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, any mobile radio (Motorola or otherwise) 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, however 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 economically 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. It's one thing to use a GR300 (or similar) in a shopping mall environment to talk to the rent‑a‑cops or to tell housekeeping to clean up little Johnny's spilled ice cream cone, but you want something with a higher duty cycle as your primary disaster services repeater.

These radios were designed for a range of RF power - for example, the D44 (or M44) 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 outside 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 (from the RF board) on MaxTracs, Radiuses, and GM300s 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 (that's 20-50mW), but +23.5dBm for the 900 MHz models (there's where you get 220mW). 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, Tools, and Hardware Oddities:

(This section covers the mobile radios - see the Overview article below for additional information on the DeskTrac station)

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) will be found below and in the Interfacing articles.

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 a number of 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 as working on the radio. And after a while the bits get loose in the handle and won't stay put, so you spend more time looking for the dropped bits on the floor (or wedging a piece of paper or foil into the handle to keep the bit in place).

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.

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 - and test both the receiver and the transmitter separately. First check to make sure all the screws that hold the boards in place are tight. If they are at all loose you will have an unstable microphonic radio.

If yor new-to-you radio is off-frequency 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 microdrop 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.

If the entire radio is waaaay off frequency (both transmitter and receiver) and cleaning the pins doesn't help AND it is NOT vibration sensitive... well, this is very rare these days, but does show up once in a while...
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 since it's a stock item you won't have to wait for it). 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 replacement 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 data on the label on your old crystal should be a good starting point. See the paragraph titled "Reference Oscillator Coarse Adjustment Procedure" on the GM300 info page linked from the article list below.

If the transmitter is on frequency then the main crystal is fine. If just the receiver is off frequency (or seems dead) then you will need to check the frequency of the second oscillator crystal. The VHF high band, UHF, and 800 MHz MaxTracs and Radiuses use a 44.645 MHz, crystal, part number 4880008K02, which has been replaced with 4880606B02 for about $20US as of August 2008. If you have a M10, M120, M130 or GM300s look before you order the replacement as some used the 44.645 MHz crystal and some used a 44.845 MHz crystal (4880908W04). The VHF low band radio uses a 10.245 MHz crystal (48-80908W01). Again, the "real" Moto part is probably the cheapest (and since it's a stock item you won't have to wait for it). At this moment I don't have the receiver oscillator info for the 900 MHz radios.

There is one exception to the "off frequency" info above. If you have a trunking 900 MHz MaxTrac that has been converted to conventional, and it is about 12.5 KHz off frequency, check the firmware chip part number !   For example, if it's programmed to 927.5000 and you find it transmitting on or near 927.4875 or 927.5125 (and it's consistently off the same amount across the band) that's the second thing you check (the first, as mentioned above, is the pins that connect the two boards). The 900 MHz radios use unique firmware and having a VHF / UHF / 800 MHz chip in a 900 MHz radio will cause multiple problems, but the most visible and easiest to check is that its off frequency !   DO NOT just "make do" and program the radio 12.5 KHz off so that it lands on your target frequency, use the correct firmware !   The off-frequency problem is just the most visible of the problems you will have with using VHF / UHF / 800 MHz firmware in a 900 MHz radio.

If you are not going to be using the accesory connector in the radio (i.e. using it as a mobile) then you can ignore the next couple of paragraphs. On the other hand, if you are going to be using it as a link receiver, as a control receiver, or as an IRLP radio, then you need to pay attention.

There is a 3-pin jumper on the logic / audio board of all the MaxTrac, Radius and GM300 radios that selects the mode of pin 11 in the accessory connector. A shorting jumper selects the "A" position or the "B" position. Note that this jumper does not affect the speaker audio, it only affects one pin in the accessory connector. In the "A" position the pin is fed a constant level of un-muted flat audio (i.e. not de-emphasized). In the "B" position (the factory default) the pin is fed a constant level of squelch-muted normal audio (i.e. de-emphasized) which makes it ideal as a source of receiver audio for feeding to a port on a repeater controller, or to an IRLP card. Needless to say, unless you specifically want de-emphasized audio you want this jumper in position "B". So the first time you have any new-to-you radio open for the first time you will want to verify the setting of this jumper (and in reality, all of the jumpers).

More details on this jumper and on this topic in these articles:

• MaxTrac and Radius Logic Board Jumpers
• GM300 family Logic Board Jumpers
• Flat Audio, and Pre & De Emphasis explained

Replacing the Antenna Connector in the radio:     (hint: don't do it unless you really have to)

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 for the mini-UHF connector in the most of the service manuals is/was 2889309U01. The part has been renumbered in the last service manual (only the last digit changed) to 2889309U03, and will set you back about US$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.

The problem is that it's a lot more work than you would expect due to the way the radio was designed and put together (the antenna connector is on the bottom of the RF amplifier board, which is a major pain to remove), so don't proceed unless you really have to. If the only problem you have is worn teeth and the antenna cable connector becomes loose on its own try slipping a tiny O-ring on the center pin of the plug, then tightening the connector enough to compress the O-ring about halfway. The increased friction will prevent the antenna connector from coming loose. Note that this trick is only a stopgap, you WILL have to replace the connector eventually. By the way, this same trick (with a larger diameter o-ring) works on full size PL-259s (it's a very common trick used on CB radios installed in the big 18-wheel trucks).

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 much 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.

So if you really have to change it, you need to use a soldering gun to heat each lead, then remove as much solder as possible from the joint. Then 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 will be able to wiggle it out and do a better cleaning job on the leads and holes. Another idea is to chop the old power connector apart using a Dremel Moto-Tool equipped with a rotary saw blade, then remove the individual pieces.

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 clinch the nut down TIGHT. Then reinstall the circuit board, then solder the center pin of the antenna jack, and finally reinstall the DC connector.

Should you decide to replace the DC power connector (since it's already out) the new one is part number 0980255E01. Moto parts price (at the time of this writing - early 2006) is around $11 each.

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 soldered jumper wire inside the radio bridging the two pins together.
3) a PC style two-pin option jumper inserted in the back of the radio (not recommended in a mobile environment),
4) and I've seen one radio where the previous owner bent the two pins together (so they were touching) and then soldered them together. It required replacing the accessory connector before you could insert an accessory plug into the back of that particular 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 and Radius LRA series radios and both sides of the speaker in the later M10, M120, M130 or GM300 series radios is / are hot, and grounding a hot wire (even momentarily) will let the lifetime supply of magic smoke out. The MaxTrac and Radius LRA series uses two inexpensive individual transistors as an audio output stage, the GM300 series uses an expensive audio power module.

Above shows where to put the PC jumper - the rightmost two vertical pins.
By the way, the exposed power pin is the positive pin.

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 of ground) causes the radio to transmit the alarm signal. The speaker jumper shown above is only usable on radios that have the alert function disabled in the programming of the radio codeplug (which is one of the first things I do when I program a new-to-me radio). More details can be found on the Interfacing pages.

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 place are designed to not come out (as you would expect). 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.

Or if you have a piece of 0.020 inch steel shim stock around you can make one. Look on the "Keys Page" elsewhere at this web site for a photo and the measurements.

There's an instruction sheet that explains how to remove the pins in the GM300 article listed below. open that article, 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 (both companies part numbers are in the interfacing articles below).

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, soldered to another, 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 !! It's dead anyway, just 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 50 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 the connector. It's easier to chop the circuit board into tiny pieces (one or two pins each) with a saw blade in a Dremel Moto-Tool and then unsolder the fragments of PC board from the pins. It's a lot of work to save less than US$6.

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 (photo), 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 2-pin connector that Motorola used and you may find one in someones junk box or at a PC repair shop.

Some radios have this sticker, some don't. Believe it and heed it.
Run all MaxTrac, Radius and GM300 speakers as ungrounded (floating) loads.

Microphones, and 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 or the microphone does not make contact or is making intermittent contact. Don't attempt to clean it, you are just wasting your time (been there, done that several times). 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... was salvaging someone else's screwup). Just use a large pair of diagonal cutters and chop apart the plastic body of the old jack (relax, you are replacing the jack because it's dead anyway), then bend all of 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 and standing up in the breeze 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.

Note that the base station and mobile microphones for the MaxTrac, Radius, GM300 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 pinout 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. Addtional parts information is in the parts catalog PDFs linked in the article table below. Note that there are errors in these catalogs, so always check with Motorola's Parts ID group before placing your orders. Since pin 1 and pin 2 in the mobile microphone jacks are unused we take advantage of that in the interfacing article. Both pins ARE wired on the DeskTrac tabletop base / repeater, and one is wired to power, so be careful.

If anybody wants to contribute additional schematic scans for the list below, we will post them.

• HMN1035 Palm Microphone, full size (schematic)
  (uses Hang-Up Clip HLN4606A)
• HMN1038 Standard beige base station (desktop) microphone, with PL defeating "Monitor" button (schematic). The black version is the HMN3000 (see below). The cord is available as a repair kit, as 30-80043N04 or as HKN4291 "Microphone Cable Kit"
• HMN1056D Compact Palm Microphone (uses Hang-Up Clip HLN4433 or 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 serious effort. 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 bottom of the microphone itself with a telephone style RJ-series plug.
• HMN3596A palm microphone (black) (schematic)
• HMN3174B palm mike (Radius, black) with green/red LED (schematic)
• HMN4016A Noise Canceling mobile microphone
• HMN1037B non-backlit DTMF Microphone
• HMN3000B black base station (desktop) microphone.
• RMN5068A black base station (desktop) microphone.
• HMN3013A non-backlit DTMF Microphone, for 820/840 Series
• HMN3031B base station (desktop) microphone similar to HMN3000 listed above but used on carrier squelch radios, does not have a PL defeat button
• TDN8305A or B (photo), or TDN8310 Backlit DTMF Microphone (does anyone know the difference between the 8305 and 8310?)
• TMN6169A Backlit DTMF with Autodial Last Number Redial
• AAREX4617A Telephone style handset   (photo 1   photo 2)     (2008 price is over US$120)

The larger 1035 microphone sounds much better than the 1056 microphone, so if you have a choice pick the 1035. The replacement mike 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 mikes (like a David Clark aircraft headset).

If you have an old junker carrier-squelch-only microphone (i.e. no PL hangup function built into the hangup button) that has been 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 mike jack is vertical, with the locking clip to the right. Motorola numbered the pins with pin 1 at the top, nearest to the volume control. This is backwards from the common RJ45 Ethernet connector. The DeskTrac has a horizontal mic jack with the locking clip at the bottom, and the pins numbered from left to right like ethernet. Six of the pin functions are the same as the MaxTrac. The 900 MHz GTX mobile also has a horizontal microphone jack with the locking clip at the bottom, but it's numbered from right to left to match the MaxTrac. MaxTrac, Radius, GM300 and GTX Pin Description DeskTrac and Ethernet Pin 1 On the low band, high band, UHF and 800 radios both pin 1 and pin 2 are fed to the logic board but unused. On 900 MHz radios these pins never leave the front panel board but are unused. 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. Unless off-hook scan is enabled in the radio this pin must be grounded to allow the radio to enter scan mode. 6 4 Ground 5 5 Microphone audio and preamp DC bias voltage. 4 6 PTT (ground to transmit). 3 7 The radio schematic labels this pin as "SCI+" in some books and "SPI+" in others (and the books don't agree - some say Serial Programmable Interface, others Serial Peripheral Interface). Either way, it's the bidirectional programming data lead, which is used by the RIB for programming the radio, so leave this pin taped off inside the microphone. Some microphone cords do not even 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. In the radios the audio level coming from the radio on this pin is a fixed level (not affected by the volume control) which works very well as a source of repeat audio (i.e. de-emphasized). 1

Table Notes:
1: On the low band, high band, UHF and 800 MHz MaxTrac radios, the microphone jack pins 1 and 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 obtained 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 on pin 1 with +12vDC.   I've been told of, but not personally seen, similarly modified MaxTrac mobiles. 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. My conjecture is that this mod was done for one of three reasons:

1. To power a low-drain outboard device.   One of the DeskTracs 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 think "commercial 2-way radio autopatch").
2. To allow the use of a MaraTrac programming cable (which is identical to that of a MaxTrac except for one additional wire in it to power the RIB from the +12vDC that is on pin 1 of the MaraTrac programming connector). This makes for easier programming as the tech does not need to crawl around on the floor hunting for a convenient unused AC outlet to plug in the RIBs wall-wart power transformer.
3. To run a packet TNC that was interfaced to the DeskTrac through the microphone jack.

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. I was going to pick it up and salvage it, but several emails to the owners and moderators listed email addreses were ignored, and despite spending over six hours on the phone with yahoogroups getting transferred around a dozen different people I couldn't find anyone that could make anything happen (they did, however, excel at saying "that's not my job, let me transfer you").

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."

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 never was a M200 model... this book 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     This covers the XVC series of radios.
	M120 Service Manual   6880902Z98, was about $29 (but has been canceled)
	M130 Service Manual   6880903Z65, about $30
	Radius M100, M206, M208, M214 and M216 Service Manual   6880101W58, was about $45 when it was available. This is the manual that covers the Radius LRA series. It's NLA, but not really needed - this manual covers all the Radius LRA radios, and they used MaxTrac boards. The board diagrams and service section of the 101W45 manual is the same as the MaxTrac Detailed Service Manual, which can be downloaded below. The difference was in the LRA model table and that is in the article titled "Radius M100, M206, M208, M214, M216 radio models and board info" below.
	MaxTrac Detailed Service Manual   6880102W84, was about $30 but is no longer available (NLA). This is the low band, high band, UHF, and 800 MHz MaxTrac service manual that covers the MGA, MJA, MQA, MWA and AHA models. If you pop a cover on any of those models then you want this book on your shelf... it's chock full of good stuff. You occasionally see these books on eBay and the other auction sites.   Until then... Part 1 Pages 001 thru 058   4.3 MB PDF Part one has the manual index, model charts, assembly breakdown tables, performance spec tables, options, general information, block diagrams and the front panels Part 2 Pages 059 thru 081   15.4 MB PDF Part 2 has all of the Logic boards including the HLN5172, HLN5173, HLN9123 and HLN9313. Part 3 Pages 082 thru 125   41.4 MB PDF Part 3 has all of the RF boards including the HLB4099 (29.7-36), HLB4100 (36-42), HLB,4101 (42-50), HLD4321 (136-162), HLD4322B (146-174), HLD4322C (144-174), HLE9310 (449-470), HLE4424 (?), HLE4425 (403-430), HLF4095B (800 non-talkaround, single VCO), HLF9122A (talkaround, dual VCO). Part 4 Pages 126 thru 163   17.1 MB PDF Part 4 has the PA deck info, radio disassembly / assembly procedures and the exploded parts lists Total download of the MaxTrac service manual is 75.3 MB. 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 the GMC and GMR models of the GM300 radio. This is another one you want on your shelf... You occasionally see these on eBay and the other auction sites.   Until then... Part 1 Pages 001 thru 030   14.4 MB PDF Part 1: the cover page and the manual revisions (including the HLN8070D and HLN8074E Logic boards, the HLD8265A and 8266A RF boards and the first part of the HLD8293A PA Deck). Part 2 Pages 031 thru 072   14.5 MB PDF Part 2: Pages 1-6 of this file has the rest of the revisions including part 2 of the HLD8293A PA Deck and the accessory connector instructions. Page 7 of this part is the first page of the basic manual. The rest of part 2 is the table of contents, the model charts, accessory lists, performance specifications, disassembly and re-assembly instructions, alignment instructions, theory of operation, a list of jumper-selectable options, the HLD8029A, HLD8031A, and part of the HLE8229A and HLE8230A RF boards. Part 3 Pages 073 thru 077   9.9 MB PDF Part 3: the rest of the HLE8229A and HLE8230A RF boards, plus the HLE8300A, HLE8301A, HLE8263A and HLE8264A RF boards. Part 4 Pages 078 thru 085   8.4 MB PDF Part 4: the HLE8227A and HLE8228A RF boards, and the HLN8074A and HLN8070A logic boards. Part 5 Pages 086 thru 144   15.1 MB PDF Part 5: the HLD8299A, HLD8033A, HLD8287A, HLE8275A, HLE8267A, HLE8034A, HLE8271A, HLE8284A, HLE8269A PA Decks, 01-80704Y83 filter board, HLN8075A Display board, HLN8071 Volume/mic jack board, HMN3596A/HMN3413A/01-80704Y98 microphone, radio exploded view, and all parts lists. Total download of the GM300 service manual is 62mb.
	MaxTrac 900 MHz Service Manual   6802980G40   was about $12 but is No Longer Available (NLA). This is the 900 MHz MaxTrac Conventional service manual. It deals with the 12w radios. If you have the 30 watt radio you need the supplement below. Other than the test modes, this covers the trunking models as well. You occasionally see these on eBay and other auction sites. By popular demand, this manual was donated by Bob WA1MIK and scanned by Eric WB6FLY. 25MB PDF file.
	MaxTrac 900 MHz 30 watt Power Amplifier Supplement   IMR200   probably not available separately. This is the 30 watt Power Amplifier Instruction Manual Revision (supplement) that came with a 6802977G10 Trunking Service Manual. It applies to conventional radios as well; the only difference is the firmware and front panel escutcheon. Note that 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. This manual was donated by Bob WA1MIK and scanned by Eric WB6FLY. 580 kB PDF file.
	The 900 MHz MaxTrac trunked radio service manual is part number 6802977G10 (NLA).

Some additional GM300 information is available from Colin Lowe G1IVG at http://www.g1ivg.com/motgm300.htm (offsite link).

Mounting Brackets:

The locking MaxTrac / Spectra mobile mounting bracket is HLN-4426A. Unless the lock has been changed (and that is easily done, and many fleet sales had nonstandard locks) the standard 2135 mobile key will open it . More key info is on the radio keys page. The non-locking HLN5189A trunion bracket is listed for the MaxTrac 820-840 series but will fit any MaxTrac series, Radius M100, M206, M208, M214 or M216 series, or GM300 series radio. Due to the oversize (heavy) heatsink on the high power low band MaxTrac there is a heavy duty bracket, part number 07D80911W01.
Note that the exterior threaded holes in the side of the radio for the mobile bracket are metric threaded - 5.0mm by 0.8 thread.

DC power:

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 a little 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.
The "official" power cord for the MaxTrac is the part number HKN4191B "high power mobile to battery cable". The buyers guide rates it as a 20 amp cable.

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 to 25 watts) situations, and the other for high power (25 to 60 watts) situations.

This table lists the kit contents:

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

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. Moto themselves used to have a "split kit" but they discontinued it (a photo of a remote mount GM300 is in the "Adding additional channels to the GM300" article below). Valley Industrial Company (at 800-260-6025) saw a need and filled it with a product called the "Quick-Mount QM1". Unfortunately Valley Industrial seems to have evaporated. The "Quickmount" name has been acquired by IDA Corporation. They make a remote mount / dual control head kit for the CDM750/1250/1550 radio. At the time of this writing (January 2005) there seems to be no source of remote mount hardware or kits for a MaxTrac, LRA Radius or GM300 series radio.

DeskTrac info:   (tabletop base and repeater stations)

If you do any DeskTrac servicing that involves the Logic or RF boards in the radio chassis inside the DeskTrac you will want the W84 manual mentioned above as well as the DeskTrac manual since it does not cover the MaxTrac radios at all. The DeskTrac controller is programmed separately from the radios. There is a switch hidden behind the snap-cap in the middle of the front panel, below the Power LED, that selects which unit is programmed. Position 1 is used to program the transmitter, position 2 is used to program the receiver, and position 3 selects the controller. DeskTrac RSS RVN4079 and MaxTrac RSS RVN4019 are both required for complete programming of a DeskTrac. The DeskTrac Service Manual 6802993G65 is very helpful to program and set up the station. Fortunately, as of July 2009 it is still available from Motorola Parts for about $65. It covers all of the LnnSUM series units (where "nn" = 51, 43, 53, 24, 44, 54, 35, 45, 27 or 37). A trailing "T" indicated a factory repeater (i.e. two radio chassis inside). These intermittent duty tabletop stations were found in shopping malls, school districts, and other low-duty-cycle applications. A front panel microphone jack and speaker allowed the repeater versions to be used as dispatch points as well. They were replaced in the product line with the GR1225 series.

For more information on the DeskTrac station read the Overview article that is linked further down on this web page. It contains a LOT of information, including a model number chart.

DeskTrac stations were originally shipped with one (or two, if a repeater) MaxTrac radio(s) inside, but surplus ones have been seen with Radius LRA and GM300s. The internal wiring connects to the accessory connector and requires 16-pin radio(s). Contrary to popular belief, DeskTracs were NEVER made with Spectra radios inside. There's a similar-looking Spectra desktop station, often called a Consolette, but the DeskTrac model name is specific to MaxTrac-based desktop stations.

As shown in the table in the microphone section above, the DeskTrac has one weirdness that has caught some people. 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 pin 1 in the DeskTrac has a positive DC voltage on it.

GR series Repeaters:

Motorola sold a series of low-end consumer grade repeaters including the GR300 (photo) tabletop unit, the GR400 wallmount, and the GR500 (photo) wallmount unit that was intended for low duty cycle situations / applications like school campuses, 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 GR300 repeaters were shipped with two GM300 radios in them, a controller and a power supply all in a metal housing (which is part number HLN3052A). The in-band repeaters had a mobile duplexer inside. Since there were two separate 16-channel transceivers involved this allowed in-band repeat, or simple 1-way or 2-way crossband repeating, and one spare unit could be pre-programmed for all the frequencies used in an area and the radios from it substituted into a failed unit rapidly.

Does anyone have PDFs of the glossy brochure and spec sheets for the GR300, GR400 and GR500 ?

Surplus GR300 / 400 / 500 units have been seen with almost any two MaxTrac, Radius or GM series (M10, M120, M130 or GM300) radios that have 16-pin accessory connections. Moto made the GRs with a variety of interchangeable controllers but the most common is a very basic controller called by two different names, depending on which literature you read. In some it's called the "GR300 Basic Controller" (despite the fact it was used on other models as well), in others its the "Repeater Interface Communications Kit" or "RICK", model number HLN3333B. The RICK is so basic that it does not even have an identifier as that is not required in many commercial services or in GMRS.

A RICK-based repeater is not legal in the amateur radio service since the RICK does not have an IDer or any way of remotely shutting off the repeater short of driving to it and hitting a front panel switch. The simplest way to get remote control and an IDer is to replace the RICK with another controller - the NHRC-4 or the ICS Basic are both good inexpensive single-port units. The standard controller functions can be used to disable the repeat function, and for absolute (or backup) control just wire the transmit radio for ignition control and have a digital output pin switch the ignition control pin high (to enable the transmitter) or low (to disable it).

As simple as the RICK looks, it is complex inside. You really need the book, and at about US$5 it's really worth it. Until you get it, here's the schematic. It's a highly detailed 300 KB file, it will take a while to load. You will want to print it. To use a RICK on two MaxTracs you will need at least the HKN9837 Intercabling Kit, and probably the HLN9822 Hardware Kit and the JLN9839 Mounting Hardware Kit.

If you have a way to remotely shut the repeater off, perhaps with a logic output from another repeater's controller at the same site, an alternative method of IDing the RICK that has been used with some success is to purchase an ID-O-Matic kit from NØXAS (at http://www.hamgadgets.com) and patch it into the RICK transmitter audio. The back of the RICK has a RJ45 Plug (VOX mode only) and a 16-pin plug (normal use) for the receiver, and a second set for the transmitter. If you use the 16-pin plugs for the radios that leaves the RJ45 on the transmit side open for the cable from the ID-O-Matic - pin 2 and pin 6 is ground, pin 3 is mic audio, and pin 4 is PTT.

The GR300 power supply is the HPN9041 or HPN8393, both of which are made by Astron for Moto, and are unusual (for Astron) in that they come with a 120v / 240v switch.
The GR1225, the RKR1225 and some GR400s used the HPN9033 that was built by DuraComm for Moto.
The GR500 power supply is the HPN9005 that is made by StarWerks, Inc. at 847-397-3600.
All of the above can be fitted with the HLN9455 Battery Revert Accessory - a combination battery charger, monitor, and switchover control unit that was also used in the CDR700, GR1225, GR1225 and RKR1225 repeaters.

The GR series optional internal duplexer kit comes with som really poor cabling. On more than one occasion folks have replaced the cabling with RG142 or RG400 and reduced the local desense at least 3db, and one time by 5.5db.

The GR series manuals listed below only cover the specific 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 Associates 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 with through-hole parts?)
  
  

The i50R "Basic Interconnect" manual section was scanned and the schematics are here and the setup / configuration is here.

The GR1225 was a follow-on to the GR300/400/500 series. It was based on the R1225 full duplex radio that was based on the GM300. Yes, the single chassis had two antenna jacks. The PDF of the GR1225 brochure and spec sheet is here. The radio is no longer in production but when you can find them they are found in high band and UHF models and was switchable from 12.5 KHz to 25 KHz on a per channel basis. The radio has a fairly decent internal controller with a carrier delay (hang-in) timer, a timeout timer, a MCW IDer, and a courtesy beep, but the GR1225 cabinet has a slot for an additional controller. Moto offered several optional controllers, most of which are the same as the GR300. The cabinet also had space for an internal mobile duplexer and a slot for the HLN9455 Battery Revert board mentioned above.

The available models of the GR1225 were:

• NH5165 – GR1225 146-174 MHz, 1-10 Watt (adjustable)
• NH5158 – GR1225 146-174 MHz, 25-50 Watt (adjustable)
• NH5164 – GR1225 444-474 MHz, 1-10 Watt (adjustable)
• NH5157 – GR1225 444-474 MHz, 25-45 Watt (adjustable)

There was also a kit to swap the two radio chassis in a GR400 or GR500 for the R1225 radio (this allowed a GR400 or GR500 to be narrow-banded, and the two radios that were removed could be used elsewhere as mobiles or sold).

The RKR1225 was a rack-mounted GR1225. Here's the brochure. It was discontinued in October of 2008.

The GR125 / RKR1225 has been replaced by the CDR500 (desktop) and CDR700 (wall mount) in the current sales guide. Click here for the CDR500/700 brochure.

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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 many other names are trademarks of Motorola Inc.
Torx is a trademark of the Camcar Division of Textron / Textron Innovations Inc.
Moto-Tool is a trademark of Dremel, Inc.
Original text by Neil Johnson WBØEMU, Scott Lichtsinn KBØNLY, Bob DeMattia K1IW, Robert Meister WA1MIK, Jeff Kincaid W6JK, Will Martin KA6LSD, Don Best N6ALD, and Mike Morris WA6ILQ.
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, several photos on this page and the hand-coded HTML is © 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.