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  MX-series Information,
Modifications and Notes

Written by Mike Morris WA6ILQ
Web page maintained by Robert Meister WA1MIK
I know nothing about this equipment so please don't ask!

Contributions and additional listings are both requested and welcome!

The "MX Series" includes several crystal based (actually channel element based) and synthesized products that were first introduced in 1975. This series of radios included the MX310, MX320, MX330, MX340, MX350 and MX360 handhelds (the last two are rare), the PX300 and PX500 packsets, the MTR300 firetower repeater, the "APCOR" emergency medical repeater (also called the paramedic suitcase radio), and several others. One of the design goals was receiver performance equal to a MICOR station. Until the Saber series came out these were the top-of-the-line handheld radios. Due to the fact that the "narrowband" units are what is considered today as wideband they will be illegal to use in commercial and public safety use when the narrowband rules go into effect.

There were some MXnnn-R radios produced for the military that had two major differences - the first was a dark finish on the external metal pieces (the standard radios were just too reflective for night time and special ops use) and the entire design was "ruggedized". Even the frame surrounding the main board was different. Many of the exterior case parts and some of the internal parts are not interchangeable between a standard and a -R version.

The MX series used tiny channel elelments, the synthesized units (those with the model names ending in "S", like MX320S) used 256 x 8 PROMS. You may find these chips referred to in some literature as "code plugs". The factory PROMS are numbered with NLN5096A, NLN5096B, NLN5096C or NLN5096D and many were made without the "NLN" on the label. All were / are programmed using the R1801A suitcase programmer fitted with the RTL5070 series adapter module (the one that I saw was a RTL5070D) and the RTL4809D software package (which itself was a set of PROMs that were installed inside the suitcase programmer). The A and B chips are one time devices and once you program a channel that's it. If there are empty channels you can still program them, but you are stuck with what's there. The C and D series chips are EEPROMS and can be electrically erased and reprogrammed. I suspect the later radios that had a zone switch (and up to 48 channels) used a larger PROM.

Anyone know what the regular (non-Motorola) part number is for the chips?

Anyone know of a way to program them without the suitcase? There has got to be a way to calculate what each byte needs to be for a given frequency, and then burning that bit pattern into a chip is pretty trivial...

The standard single unit desktop rapid (one hour) charger was the NLN8858A. The NLN4038A was the 220 Volt version of it. The single unit standard rate (14 hour) desktop charger was the NLN8856A. The NLN4036A was the 220 volt version. Due to the wide variety of power plugs around the world the 220 volt chargers were delivered without a mains power plug and one was fitted locally. Here are some photos of the NLN8858 charger provided by Rich N7FDM (click on each link):
Top view         Front view         Label on bottom

The regular speaker-mic is the NMN6071B. (Other than the connector that attaches to the radio, the speaker-mic itself is probably identical to the NMN6081B used on the MT500/PT500 series of radios. A manual for the 6081B can be found on the MT500 Information page on this web site.) The public safety one (used only on UHF, complete with the High/Low switch) is the NMN6072A. The 8505355K04 antenna is designed for 440-470 MHz, the 8505309N11 is for 470-512 MHz.
The military wanted a waterproof speaker-mic and that's the NMN6124B (with a velcro patch) or the NMN6125B (with a swivel clip).

If you are at all serious about the MX Series you will want to subscribe to the Yahoo group devoted to the PX and MX Series radios

MX300 Series Model Numbers
We know this table is not complete, if anyone wishes to add some details please let us know.
Sample model number: H43SXU-3180
H 4 3 S X U
Type Encryption ?


1 watt
68-88 MHz
but I've not seen one
Channel Element
Non Encrypted
2.5 W
136-174 MHz
Digital Encrypted
5 W
403-470 MHz
800 MHz

Sample model number: H43SXU-3180
3 1 8 0
Squelch Channel
Wide Band
(15 kHz deviation)
2 Channels
Narrow Band
(5 kHz)
4 Channels
6 Channels
8 Channels

The antennas are the same as used on other pre-SMA-fitting handhelds and the "correct" factory antennas are:

Other parts:

MX300 Parts List and Accessories List   1.2 MB PDF file

Note: All of the manuals below are out-of-print and no longer available. Parts availability is also a problem, especially for the channel elements, PL tone and DPL code elements, and the frequency and tone PROMS for the synthesized radios. See the comments above regarding the one-time PROMS and re-usable PROMS (called EEPROMS).

KJ6VU has a nice web page with some MX information at http://www.qsl.net/kj6vu/mx.html.

VK1KRF in Australia has a web page on how to substitute an inexpensive common 24 pin EPROM for the Moto code plug - but it requires disassembling an old code plug module and some careful soldering. See http://www.qsl.net/vk1krf/MX300/MX300.htm.

The MX300 Series Theory and Maintenance Manual   5 MB PDF. This is the starting point for understanding these radios. Part number 6881013C70-A.
MX300 VHF Service Manual   4.8 MB PDF. This covers the H23AAU 1 watt, H33AAU 2.5 watt and H43AAU 6 watt one through eight channel models. Part number 6881013C71-B.
MX300 UHF Service Manual   3.5 MB PDF. This covers the H24AAU 1 watt, H34AAU 2 watt and H44AAU 5 watt one through eight channel models. Part number 6881013C75-B.
MX300-S VHF Service Manual   4 MB PDF. This covers the H23SSU 1 watt, H33SSU 2.5 watt and H43SSU 6 watt synthesized models that held up to 12 channels in each of (up to) 4 zones. Part number 6881022C10-A.
MX300-S UHF Service Manual   18 MB PDF. This covers the H24SSU 1 watt, H34SSU 2 watt and H44SSU 5 watt synthesized models that held up to 12 channels in each of (up to) 4 zones. Part number 6881022C15-B.
Servicing MX Portable Radios   4.5 MB PDF. This is a training course handout. The last section covers the synthesized radios.
MTR300 Sales Brochure   530 kB PDF. This manual covers the MBC33CKA / MBC34CKA fire tower lookout repeater radio that is based on the MX Series Handheld components built into slide-in modules and sized to fit a Spectra-Tac chassis. Note that this unit was made by Motorola Canada (hence the MB prefix in front of the C3xCKA model numbers).
MTR300 Installation Manual   3.6 MB PDF. This manual covers the MBC33CKA / MBC34CKA fire tower lookout repeater radio that is based on the MX Series Handheld components. Part number 6802900A35-A.

Other manuals relevant to the MX Series are:

Contact Information:

The author can be contacted at: his-callsign // at // repeater-builder // dot // com.

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This web page created January 2007

Motorola®, MX, PL and DPL and a whole bunch of other names are registered trademarks of Motorola Inc.

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.