Ignition (I think) noise coming through vehicle 12volt power.

[JoshuaHufford]

So I recently installed a CDM1550ls with a remote head setup, and a Uniden BC125AT in my 2014 Subaru Outback, some pics of the install are in this thread.

2014 Subaru Outback Scanner and VHF Radio install.

Working on permanent installs in my personal vehicle which is a 2014 Subaru outback. This has been a work in progress but I thought I'd share what I've accomplished so far. First the roof. I removed the shark fin antenna on the back that is used for satellite radio (that I don't use) and used...

forums.radioreference.com

Anyway, I'm getting some noise through both of the radios when the engine is running, it matches engine RPM but it doesn't sound like alternator noise, had plenty of experience dealing with that with car audio equipment. This is more of random popping that increases in frequency with increased RPM. It isn't bad, stronger transmissions block the noise out but on fainter stuff it is quite apparent.

The noise goes away when the engine is shut off. The noise will also go away if I unplug the Uniden from car power and run it from the internal batteries regardless if the engine is running or not, and it goes away on the CDM if I run it from a battery regardless if the engine is running or not. The Uniden is being powered from a cigarette plug style jack that is inside the center console with a USB power adapter plugged into that. The CDM is currently in the back of the vehicle plugged into the power outlet in the back of the car. I haven't decided yet on the permanent location for the CDM radio so I haven't run permanent wires to it.

Is there some kind of filter I can get to help with this?

If I run power directly from the battery will it help with this? I don't transmit so my power needs for the radios are minimal, but if I get my license at some point I'll obviously have to run some wires up to the battery. If it will get rid of the noise I'll go ahead and do it now.

The car does not have spark plug wires or a distributor, it has 4 coil packs directly attached to each spark plug.

 

[a417]

The car does not have spark plug wires or a distributor, it has 4 coil packs directly attached to each spark plug.

They make noise, too. Do you hear the same noise on the AM radio?

 

[JoshuaHufford]

They make noise, too. Do you hear the same noise on the AM radio?

Haven't tried that. Don't listen to radio much, AM even less since the local news station broadcasts the same thing on FM, but I'll give it a try.

 

[CCHLLM]

Your power supply situation is sketchy at best and is highly likely the source of your noise woes. Adding filters is nothing more than a band-aid hack fix instead of locating the source of the noise and eliminating the problem. 40 years of professional radio installs and vehicle upfitting experience tells me that a proper install will likely eliminate the noise right off the bat. If it doesn't, it will make it much simpler to find and exorcise the devil noise.

First, never use any part of the vehicle wiring harness to power a two way radio or a quality scanner. Instead, by Motorola's own installation instructions, run a sufficiently sized fused power lead from the battery Positive terminal to each radio, or to a quality fuse block near the radios and run the radios off separate terminals and fuses on the block.

Second, ground the radio to the body or a chassis ground near the radio. Per Motorola's own installation instructions, do not run a negative wire from the battery Negative terminal to the radio ground lead. Newer cars check battery voltage through a device attached to the ground post, and attaching any device ground to the battery Negative terminal can skew the vehicle's sensing parameters.

There will be people that will tell you that you can do hack work and get away with it once you install a filter. Why not just do it right and enjoy the pride of workmanship and a clean install?

I drive a 2017 Outback with 4 radios installed and have no noise problems at all.

 

[mmckenna]

The Uniden is being powered from a cigarette plug style jack that is inside the center console with a USB power adapter plugged into that. The CDM is currently in the back of the vehicle plugged into the power outlet in the back of the car.

Sorry dude, but rookie mistake. As CCHLLM said, never draw your power from existing vehicle wiring. Some people get away with it, and each vehicle is going to be a bit different. I learned this a long time ago, and as said above, the commercial two way radio manufacturers are very clear on this in their install guides.

What you are hearing sounds like classic ignition noise.

Power feed off the battery and proper grounding will likely solve it. Do not rely on the coax shield or the long negative power lead as your ground. Ground the chassis of the radio to the body as close as you can.

 

[cmdrwill]

Ground the chassis of the radio to the body as close as you can.

negative power lead grounded to the vehicle body as close as you can to the radio.

 

[mmckenna]

negative power lead grounded to the vehicle body as close as you can to the radio.

Yep, I tend to do both, but that'll work. Just as long as you don't rely on the long wire back to the battery or the antenna mount.

 

[JoshuaHufford]

Thanks. Like I said I don't have the radio itself permanently mounted yet so this was just temporary power for now anyway.

 

[mmckenna]

Thanks. Like I said I don't have the radio itself permanently mounted yet so this was just temporary power for now anyway.

Understood. It's an easy fix.

 

[CCHLLM]

Sometimes temp installations need to be done so you can determine how you really want it installed. Let us know how it works out for you when you get the permanent electron herding system completed.

Inquiring minds need to know.

 

[a417]

Sometimes temp installations need to be done so you can determine how you really want it installed.

A proof-of-concept, if you will.

 

[JoshuaHufford]

I will certainly do it, might be a while yet, life is busy.....

 

[phask]

All the previous applies. BUT, newer cars with coil packs are much less prone to have ignition noise. There is just way less parts to cause issues. It's probably a good idea to check the plugs and packs, or just replace and use dielectric grease.

About all that can cause it is a cracked pack insulator, moisture, cracked plug,wrong plugs, maybe a missing mounting bolt causing a bad ground. Or a bad ground to the block.