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Radio Equipment Installation Forum Forum for discussing how to install radio communications equipment in Mobile, Base, Command Post, EOC, etc configurations.

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Old 03-25-2014, 4:55 PM
Join Date: Jan 2013
Location: Worcester, Mass.
Posts: 5
Default CDM Install Questio

So I am having a debate with another member of my department over the installation of a CDM1550 into our ATV. There is a battery buried in the rear of our side by side, and an accessory power terminal under the hood, which is switched and not constant. I wired the power to there, tapped a new ground into the frame, and planned on doing the jumper mod to activate the ignition sense feature. My comrade was supposed to crimp on the antenna connection today and connect it to the radio, completing the installation. Instead, he pulled all of my nice, clean wiring apart, as well as half of the brand new ATV body panels to run wiring directly to the battery. He claims the radio must have constant 12v power. My contention is that the CDMs in our engines do not have constant 12v due to he battery disconnect switches and they work just fine. Which one of us is right? Also, when I completed the installation yesterday I tested the radio and it worked fine and seemed to have sufficient power for transmitting. Thanks for the help!

Last edited by dhirons; 03-25-2014 at 4:56 PM.. Reason: Spelling
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Old 03-25-2014, 5:46 PM
mmckenna's Avatar
Join Date: Jul 2005
Location: SNCZCA51
Posts: 2,586

You don't need constant 12volts, switching the power is fine.

I've always wired them directly to the batter, even on my Polaris Ranger. Getting clean power is important, and I don't trust that the factory wiring will support a CDM running full power. I'd prefer to run the power feed directly off the battery, and running the ignition sense to the switched power. Some of these ATV's and SxS's have some noisy electrical systems.
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Old 03-25-2014, 8:32 PM
Join Date: Mar 2010
Posts: 220

I also run directly to the battery if possible. Usually after I examine the small #16 high temp wire that feeds the terminals. Some accessory termianls are however feed with beefy wire, so it all depends. Its wise that the ground be kept directly attached to the frame and not running that along with the +12 to the battery. Reason being, other than keeping the wiring run as short as possible, IF for whatever reason the negative becomes detached that goes to the battery and the radio is still attached, and the CDM is grounded itself or antenna it will try to pull ground thru the radio. Which would make for a very bad day. I never advise grounding direct to the battery.
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Old 03-25-2014, 10:19 PM
mmckenna's Avatar
Join Date: Jul 2005
Location: SNCZCA51
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Originally Posted by 12dbsinad View Post
Its wise that the ground be kept directly attached to the frame and not running that along with the +12 to the battery.
That is a very good point. One of my first installs many years ago I grounded at the negative terminal on the battery. The alternator whine was awful. I moved the ground to the body near the radio and the noise went away. Pretty sure I grounded my CDM750 at the frame behind the dash on the Polaris.
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Old 03-26-2014, 9:28 AM
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I have installed an estimated 450-500 mobile radios into everything from ATV's to forklift's, aircraft and boats. Always run power to the battery and then ground to the frame. However, you may need to add additional grounding to the frame of that ATV. Smaller vehicles tend to have grounds made for their electrical system. There is little to no anticipation that there may be high amperage radios added. You may need to add ground straps, conductive grease, scrape off paint and add lugs to the frame to get a good ground.
With the exception of Ford and GM vehicles bought for law enforcement, I have yet to find good grounds with factory vehicles.
Boats are another issue, make sure zincs are replaced and through hull grounds are not corroded.
Boats and ATV's, if their ground corrodes or do not provide an adequate ground, may ground through the antenna connector and the radio case. This could damage the radio or antenna.
Older vehicles that tend to have some radio noise, often have corroding grounds between their frame and alternator, frame and engine or the ground bus used for the radio itself. Cleaning the corrosion off and adding larger ground braid straps can prevent or correct this.
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Old 03-27-2014, 12:40 AM
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Join Date: Dec 2012
Location: Connecticut
Posts: 459

You mentioned testing the radio after you installed it... It's never a good idea to transmit without the antenna connected (assuming yours wasn't hooked up when you did this) because you can pretty much fry up the boards.
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