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Stretching the Frequency Range of the Motorola "Commercial Series" Radios (CM200, CM300 and PM400 mobiles, CP200, CP200 XLS, PR400 handhelds) Researched, Compiled, HTML'd and Maintained by Mike Morris WA6ILQ |
Back in January of 2020 I was asked if there was any way to use a VHF CM300 mobile radio made for the 146-174 MHz range below 146 MHz. A number of radios had been purchased for expanding a fleet but the installation had been delayed (internal corporate politics) and they were still in the boxes. An amateur radio special event was coming up and having a dozen extra mobile radios would be useful... The amateur radio repeater that the event was going to use was on a 145 MHz channel. I said "Maybe..." and one of the CM300s (model M50KQF9AA1AN) was handed to me, still in the box. I made a few phone calls and followed up on a couple of leads. Below is the result of the research and some office desktop experimentation on the CPS... I was not able to run the test radio past a service monitor. And I had to give the radio back so that it could be used for the event, and then reprogrammed with the saved fleet codeplug and installed in a fleet vehicle.
YOU CAN HELP ON THIS PAGE!
My only hands-on experience (so far) with tricking a Commercial Series radio to go out of range was the above experience with the one VHF CM300.
I'd be interested in YOUR results... both VHF and UHF. If I get any contributions with some hands-on VHF and UHF results from readers I will update this page with real-world numbers.If you have a service monitor I'd be interested in what your receiver sensitivity and RF power is at 146.100 and 146.00 MHz, and at increments out of range... at 145.90, 145.80, 145.70, 145.60, etcetera all the way down to 144.20, 144.10 and 144.00 plus one measurement out of band at 143.90 MHz. Does your transmitter RF power output change at those frequencies? Does the deviation change? If your service monitor has a spectrum analyzer were there any signal purity issues?
If your radio is UHF I'd be interested in your measurements of receive sensitivity and RF power in-range and at similar increments out of range, plus any other issues?
UPDATE January 2025: Jordan Carter K9NZF reported complete success on
a 438-470 MHz UHF CM300 in an email to repeater-builder.
Please see his letter below.
Jordan can be contacted by way of the email address on his QRZ page.
The CM200 / CM300 / PM400 mobile radios and the CP200 / CP200XLS / PR400 portables were spec'd on VHF for 146-174 MHz but you might loose a little sensitivity and transmit RF power going below 146 MHz. Tricking the radio to operate out of the design range depends on the tolerances of the individual RF components inside the radio... most VHF radios will work down to 144 MHz. Most 438-470 UHF radios should work from 430 to 473 MHz, a few might not. An email reported that this process was successful in stretching the receive side of a 465-495 MHz radio down to 462 MHz receive for GMRS.
The CM200 and PM400 mobiles use the same synthesizer / controller design as the CM300 that I played with. The CP200, CP200XLS and PR400 are the portables in the same product line and should work the same (disclaimer: I have never had the opportunity to actually touch a CP / PR handheld much less program one). From emailed reports this process described below has been succcessful on both CM200 and PM400 mobiles, a UHF CP200 and a VHF PR400 handleld.
Sort Sequence
Numerical
ValueCodeplug
Element Value
0 = A5
A0 = 5
1 = A4
A1 = 4
2 = A7
A2 = 7
3 = A6
A3 = 6
4 = A1
A4 = 1
5 = A0
A5 = 0
6 = A3
A6 = 3
7 = A2
A7 = 2
8 = AD
A8 = D
9 = AC
A9 = C
BB = "."
I do not know what the base frequency is for a VHF low range (model M50J...) radio (136-152 MHz) or for
the 438-470 MHz or 465-495 MHz range UHF radios. If someone would be willing to let me
know what they find then I'll update this writeup and add a table.
Those with UHF radios will need to make the appropriate changes for their situation.
If you are going to contribute some real world sensitivity and power measurements to this page (i.e.
down to 143.something on VHF) please consider using 143.0 MHz for your new low end.
When you need to change the programming in this radio DO NOT read the radio!!!
Somehow the modified codeplug is still telling the CPS that it's still a 146-174 MHz radio !
If you download the radio the CPS will think all of the frequencies below 146 MHz are errors and
it will "fix" all of the errors without asking!
The end result is that you will have to re‑hex‑edit the codeplug from scratch and re-enter
all of the below‑146 MHz frequencies. This is the voice of experience !
Instead of reading the radio just treat this radio as a write-only device.
Load the saved codeplug from your hard drive into the CPS, make the necessary changes, save the modfied
codeplug and then write it to the radio.
There has to be a better way where we can change the band edges in the radio so that the CPS does not
"fix" the out of band frequencies when downloaded. I spent about 15 hours researching
that and could not break the code before I had to give the radio back. Maybe the codeplug includes the
model number? Maybe there is a model number to frequency range table in the CPS? Maybe the codeplug
includes the frequency range but the values are in a different numeric format? I do not know.
But a bunch of emailed reports says the above method works for them.
As promised above, here is Jordan Carter's email:
I have been a long-time Repeater Builder lurker (about 28 years), so I thought it was about time I made a contribution! I was programming a UHF CM300 for a friend and one of the channels that he wanted in it was 437.800 for the ISS. Being a 438-470 MHz radio, it wouldn't take it. So off to Repeater Builder I went to see what the process was to convince it to go where I needed it to, where I found your information on moving the VHF CM300 down to 144-145 MHz. I followed your instructions for the VHF and was able to move it down to 436.000 so I could enter 437.800. 438.000 = A1 A6 AD BB A5 A5 A5 There are 15 instances in the codeplug. I changed them to A1 A6 A3 BB A5 A5 A5, which of course equals 436.000. After I did that, I went ahead and took it down to 420.000 (A1 A7 A5 BB A5 A5 A5) and documented the following: 438.000 MHz .33uV 36W 437.000 MHz .33uV 36W 436.000 MHz .33uV 36W 435.000 MHz .34uV 37W 434.000 MHz .34uV 37W 433.000 MHz .34uV 37W 432.000 MHz .34uV 37W 431.000 MHz .34uV 37W 430.000 MHz .37uV 37W 429.000 MHz .37uV 37W 428.000 MHz .37uV 38W 427.000 MHz .37uV 38W 426.000 MHz .39uV 38W 425.000 MHz .41uV 38W 424.000 MHz .43uV 39W 423.000 MHz .43uV 39W 422.000 MHz .45uV 39W 421.000 MHz .52uV 39W The next step was 420.0 MHz, where the receiver went deaf (max output of my service monitor is 700+ µv), so I switched to 100 KHz steps to see where it unlocked: 420.900 MHz .52uV 39W 420.800 MHz .52uV 39W 420.700 MHz .54uV 39W 420.600 MHz .54uV 39W 420.500 MHz .56uV 39W 420.400 MHz .58uV 39W 420.300 MHz .58uV 39W 420.200 MHz .58uV 39W 420.100 MHz .58uV 39W 420.000 MHz Unlock on RX, 39W TX Note: I did not observe any anomalies on the spectrum analyzer while testing transmit power, but more in depth testing would probably be advised if someone were to be using an out of band radio as a transmitter. Service Monitor: Motorola R2600 Radio Model Number: AAM50RPF9AA1AN Windows XP Pro CPS Version R05.16 Feel free to modify and edit this information as you see fit. Thanks & 73, Jordan Carter K9NZF email: (callsign) @ (callsign) .com
Contact Information:
The author, Mike Morris WA6ILQ, can be contacted here.
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This page was created 13-Nov-2023 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.