Programming the Maxon SM-4150M or the GE Monogram Mobile Radios

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Back to Home Programming the Maxon SM-4150M
or the GE Monogram Mobile Radios
By Scott Lichtsinn KBØNLY
Turned into an article by Robert W. Meister WA1MIK

I recently ended up with some Maxon SM-4150M mobile radios that I wanted to program. After searching online I only found tidbits of information available on these.

Turns out they are the same as the GE Monogram series. I had assumed GE produced them for Maxon and then rebranded them as their own; it's the other way around: Maxon made them for both companies; GE just put their label on them. They can be programmed with a suitable serial programming cable; the receptacle is inside the radio so you must remove the top cover to plug it in. The schematic of this cable is available online and with some time and effort and money it could be duplicated. There is also a schematic of the SM-4000 programming interface available online as well, so feel free to build one if you prefer, but that will also require purchasing the correct connector to mate with the socket on the circuit board as well as some other components for level conversion. For me, it's always better to be free or cheap, so I found an alternative: since the radio must be opened anyway, just remove the serial EEPROM and reprogram it directly.

The photo below shows the location of the serial EEPROM and the programming connector, next to the microprocessor:

Things You'll Need:

You will need the SM-4000 programming software. It's an OLD DOS-based program but I did find it worked fine on my Win2k-based workbench computer. This software is available from various online web sites, one being www.mods.dk under 'Misc' in the 'Other' category.

You also need a hex-editor program (I use Hex Workshop by BPSoft) to edit the file generated by the SM-4000 program, and a serial EEPROM programmer capable of dealing with the 93C56 Serial EEPROM memory chip used in the radio. I used an inexpensive Willem-style programmer.

Comparing The Data:

I determined the frequencies that were in the radio by using a frequency counter next to the radio (with a dummy load attached) to detect them. Using the programming software, I created a file that had the same frequencies as the radio. I removed the EEPROM from the radio and read it with my EEPROM software, saving that data to a disk file. I was then able to compare the EEPROM data to the file I created with the software; this allowed me to find the starting and ending locations of the data that I needed to copy from the file the program generated. The program creates a file with more info than is needed for the chip; I presume this information is sent to the programming interface for some purpose.

The contents of the radio's EEPROM file, all 256 bytes of it, viewed using Hex Workshop, are shown below.

00000000 26 C1 17 A6 E1 17 87 C4 00 B7 E6 00 14 C4 17 94 &...............
00000010 E4 17 1D C4 17 9D E4 17 AA C3 17 2A E4 17 0E C4 ...........*....
00000020 00 8E E4 00 99 C4 00 09 E7 17 9E C3 00 1E E4 16 ................
00000030 05 C4 00 85 E4 18 0B C4 00 8B E4 17 9E C1 00 1E ................
00000040 E2 13 93 C4 16 03 E7 16 2F C4 16 9F E6 16 3E C4 ......../.....>.
00000050 16 AE E6 16 80 C3 00 B8 E4 00 86 C3 00 BE E4 00 ................
00000060 64 18 82 70 57 BC 9C 87 B6 AB 8E 93 5C 3E 21 15 d..pW.......\>!.
00000070 00 00 A0 12 3B 70 03 30 00 00 00 00 00 00 FF FF ....;p.0........
00000080 FF FF FF FF FF FF 00 00 00 00 FF FF FF FF FF FF ................
00000090 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
000000A0 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
000000B0 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
000000C0 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
000000D0 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
000000E0 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
000000F0 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................

I then viewed the file generated by the SM-4000 program with Hex Workshop. (This software saves its output as a .CHN file but it is still a hex-format file.) I've put a line through the extra data contained in this file indicating I'm deleting all bytes before hex address 5E and all bytes after hex address 15F. Only the 256 bytes from hex address 5F through hex address 15E (inclusive) should remain.

00000000 30 38 32 33 33 42 32 00 00 8F 00 00 07 53 4D 2D 08233B2......SM-
00000010 34 31 35 30 75 6D 62 65 72 20 6E 6F 74 20 73 65 4150umber not se
00000020 6C 65 63 74 65 64 00 00 00 00 00 00 00 00 00 00 lected..........
00000030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000050 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00 26 ...............&
00000060 C1 17 A6 E1 17 87 C4 00 B7 E6 00 14 C4 17 94 E4 ................
00000070 17 1D C4 17 9D E4 17 AA C3 17 2A E4 17 0E C4 00 ..........*.....
00000080 8E E4 00 99 C4 00 09 E7 17 9E C3 00 1E E4 16 05 ................
00000090 C4 00 85 E4 18 0B C4 00 8B E4 17 9E C1 00 1E E2 ................
000000A0 13 93 C4 16 03 E7 16 2F C4 16 9F E6 16 3E C4 16 ......./.....>..
000000B0 AE E6 16 80 C3 00 B8 E4 00 86 C3 00 BE E4 00 64 ...............d
000000C0 18 82 70 57 BC 9C 87 B6 AB 8E 93 5C 3E 21 15 00 ..pW.......\>!..
000000D0 00 A0 12 3B 70 03 30 00 00 00 00 00 00 FF FF FF ...;p.0.........
000000E0 FF FF FF FF FF 00 00 00 00 FF FF FF FF FF FF FF ................
000000F0 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
00000100 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
00000110 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
00000120 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
00000130 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
00000140 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
00000150 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
00000160 FF FF 00 00 4E 6F 20 52 65 63 6F 72 64 20 49 6E ....No Record In
00000170 66 6F 72 6D 61 74 69 6F 6E 00 00 00 00 00 00 00 formation.......
00000180 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000190 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000001A0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000001B0 00 00 00 00                                     ....

After deleting all of the crossed out information and saving the file with Hex Workshop to a .BIN file for my EPROM burner software, I was able to burn the data to the EEPROM. After reinstalling it, the radio still functioned!

Summary:

So here's the process: use the SM-4000 software to create a new file with all the frequencies that you want the radio to have, save it, open it with Hex Workshop, delete the crossed out portion of the data, save that to a .BIN file, and burn that data the EEPROM. Success!

You will know right away when you turn the radio on if it's programmed correctly; if you hear the rising tones when you power the radio on, it has passed its self-checks. If you get no rising tones it will display 'Er 01' on the display for an EEPROM error. I found no problems getting it to lock on frequency between 144-174 MHz, even though the rated split is 148-165 MHz. I haven't been able to locate a service manual and I don't know what there is for VCO or front-end adjustments on these units. I haven't looked in the service manual (LBI-38864B) but I can say from testing that it works fine as-is in the ham band. It's possible though that because mine were programmed at the bottom of their range that the tuning is close enough; if yours has programming at the upper end of the radios range, adjustments may be necessary.

Contact Information:

The author can be contacted at: kb0nly [ at ] mchsi [ dot ] com.

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This page originally posted on Wednesday 21-Jul-2010.

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