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Programming a Motorola cdm1250 to access a gmrs repeater


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I've just gotten a hold of a used cdm1250. Seems like nice radio. I've got the software and cabling all sorted out so I can program it.

 

Simplex seems fine. I have all the channels programmed and all seems to be working.

 

I'm having trouble programming the repeaters to work. I'm pretty sure DPL/TPL codes are right - as I have the repeater working on a baby midland and a different HT. It does not seem to open the repeater. There are alot of other features here I am not familiar with, and I suspect something is interfering (signaling tab maybe?). Are there any good rules of thumb or common gotchas here someone could point me to? Is there just a stock GMRS codeplug someone can point me to or be might be willing to share that I can look at?

 

The only other issue i am having is with the coax connector - the mini-uhf. (that is the great thing about standards - everybody has one). I've purchased two different min-uhf-to so-239 adapters and I am not satisfied with the way either of them fit/thread on. I've just ordered a quality pigtail cable to try to solve that.

 

I suppose half the fun is figuring this stuff out. I would welcome any insights.

 

Jim

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When programming the CDM series of radios - you will need to pay attention to the "Personality assignment to Zone" tab way down at the bottom of the programming tree.

 

Basically, when you add a new channel into "Personality" and set it up with Frequency and PL, etc.  you're still not done. You need to drop down and assign that Personality to an actual channel position within the Zone.  It's a little strange, but once you understand it, you'll do fine. There's also a "wizard" setting that might help you.

 

Signaling is probably not where your problems are - it's mainly used for Push to Talk ID or Selective Calling. If you don't know what those items are - don't worry. You don't need them to access 99.89% of repeaters that are out there in the GMRS world.

 

I don't have a codeplug available at the moment, but if you're still having trouble come Monday - shoot me a message and i'll get you a copy of an example codeplug for GMRS.

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They used to sell a Mini-UHF to SO239 jumper cable. I suggest finding one of them vs an adapter. Used hundreds of them in my shop days for control station installs. 

 

I have one on order. With luck it will do the job. Despite ordering from two different places, I think I may have gotten the same adapter twice - and it is not quite right.

 

Thanks for the reply.

 

Jim

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I have one on order. With luck it will do the job. Despite ordering from two different places, I think I may have gotten the same adapter twice - and it is not quite right.

Jim,

 

Even with a decent quality connector, the mini-UHFs can be ornery. If it doesn’t want to stay snug, do this: Hand tighten the knob, being sure the little tabs are properly seated in their detents. You may have to hold it in place. Then GENTLY snug the knob with gas pliers just a bit, maybe a sixteenth to an eighth of a turn, no more.

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I find this thread interesting, because whenever I've looked into getting my CDM1250 (UHF) into service on the GMRS spectrum, I've come away uncertain whether it's kosher/legal to do so. Right now it's programmed for several local Amateur repeaters in my area but I've got loads of Personalities free. 

Is the CDM1250 type-approved for use as a GMRS base station?  Isn't the minimum power output too high?

Some of the answers above suggest that it's totally fine, and if it is, awesome. I also understand that some take the "If you don't get caught, why worry" attitude around questions like this, but -- speaking only for myself, and no judgment here -- "you do you," but I don't share that view. 

Thanks.

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2 hours ago, PlasticAstronaut said:

I find this thread interesting, because whenever I've looked into getting my CDM1250 (UHF) into service on the GMRS spectrum, I've come away uncertain whether it's kosher/legal to do so. Right now it's programmed for several local Amateur repeaters in my area but I've got loads of Personalities free. 

Is the CDM1250 type-approved for use as a GMRS base station?  Isn't the minimum power output too high?

Some of the answers above suggest that it's totally fine, and if it is, awesome. I also understand that some take the "If you don't get caught, why worry" attitude around questions like this, but -- speaking only for myself, and no judgment here -- "you do you," but I don't share that view. 

Thanks.

No, the CDM family is not type-accepted for GMRS use. It is Part 90, however.

The low power (30 watt) versions of the CDMs can be knocked down to 5 watts channel by channel. They won't do the 0.5 watts required on channels 8 through 14. This means that you could set up a CDM for 5 watts on channels 1 to 7 and 30 watts for 15 through 22. Remember that the difference between 30 watts out and 50 watts out doesn't really give you 40% more range in most real situations.

There's virtually no regular GMRS traffic in the area where I live except for a very few small businesses using bubble pack radios for in-store operations. If I chose to do so, I could easily setup a CDM for amateur and some GMRS channels and not interfere with anyone. They are rock solid radios with a very useful wide frequency spread.

Regardless of what band you decide to use your CDM in, I heartily recommend the addition of a Motorola external speaker. It vastly improves the audio quality of the radio, and for high-noise environments, give extra volume. The right plug for the accessory connector can be ordered from ebay seller mre1032. If you do that, get the one that has the ignition sense line as well as the speaker lines.

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A CDM radio is not Part 95 Type Certified. The CDM radios (and the matching HT portable series) are Part 90 Commercial.

I'm of the mindset that Part 90 meets and exceeds all standards for Part 95, and it appears that the FCC agrees:

https://transition.fcc.gov/oet/ea/presentations/files/nov17/54-Part-95-Misc-Eqpt-Filing-r1-TH.pdf

Quote

Several commenters are concerned that the proposal to prohibit combination radios would prevent GMRS licensees from using surplus Part 90 equipment in GMRS. ... This is not our intent. We will continue to certify equipment that meets the respective technical standards for Part 90 (land mobile) and Part 95 (GMRS) in both services, if requested. However, we are amending the language in new section 95.1761(c) to clarify the requirement in old section 95.655(a) that Part 95 GMRS radios will not be certified if they are equipped with the capabilities to operate in services that do not require equipment certification, such as the Amateur Radio Service.

So if you don't want to use Part 90 equipment, that's up to you. You're never going to find an example of the FCC fining someone for using Part 90 equipment, and you've got their own words above that basically say that their intent is NOT to prohibit users from operating with Part 90 equipment on GMRS.

I'd use a CDM radio for a base - but like Steve says above, you want to get the "mid power" version if you want to operate at lower power levels. There's a ton of information on the CDM series over at repeater-builder.com . 

Beware of Ebay refugees if you're looking at CDM radios. There's a bunch of hacks that people used to take the LS trunking models and flash them into Conventional configurations. Done right, there's nothing wrong with using one of those - but done wrong, you're just buying a headache.

 

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Great info Steve and radioguy - thank you for clarifying.  For the way I'm planning to use the radio, I think I'm OK.

I had heard a similar warning about reflashing of the LS models, and that it doesn't always work as intended -- not applicable to my situation but good to know. My two 1250s are eBay finds, but have always been Conventional only -- and I try to keep my tinkering in CPS to the bare minimum required to load 'em up with relevant freqs.  I've also learned the "Use a RIB box and the right cabling or you'll brick your radio" lesson the hard way once already.

Thanks.

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As said the CDM makes a great base radio. I only have the GMRS Main repeaters channels in mine with DIR vs tying up repeater and simplex. Works for me as I only talk on repeaters 99% of the time. I do have a second zone with all repeaters in Narrow band as I do have some setup as 12.5 on the air. They work much better for midlands.

 

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I do most of my CDM programming nowadays with a cheap USB cable. I've got the RIB box, but it's really only necessary when you're trying to do a Flash update for firmware. There are plenty of other "gotcha's" involved with programming though - and I'll agree that a real RIB with a genuine Serial port is your safest starting point. 

The audio quality on the CDM's is good - but I like them much more for wideband than narrow. The 12.5 narrowband always seemed to be lacking for volume - even if you jacked around with the gain control, audio compression and compandering. The newer XPR units seem to have better 12.5 analog audio - right out of the box.

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I went and got my GMRS license on the basis of cheap Chinese radios being available that were small enough to fit in the cubby holes of the daily driver car. My previous car had stacked Vertex VX-3200's (VHF and UHF) in the dash. New vehicle just does not have the room for Vertex or Motorola commercial mobiles. Then ended up going full tilt and using both a CDM1550LS+ and a XPR5550e for GMRS base stations. As another said above, watch out on the specific CDM series model you buy, for output power and flash (applies to XPR Trbo series as well). Noticed some people bought CDM1550LS+ as they have a full keypad on the faceplate, but some only have 16 conventional channels and the auction may have mentioned 160 (in trunking mode), or some other sale pitch. Buyer beware. But great for GMRS.

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