CB noise help

[PG13]

I noticed today, that when I turn my truck off, keys out, and after a minute or so when the accessory power goes off, my radio static gets much quieter. Also my signal improves. Someone, who before when they are at a certain location I could barely hear, but when this happens I hear them clear as day. My radio is wired directly to the battery.

Radio: Cobra 29
Attenna: Sirio performer 5000 on a magnet mount directly on roof
Truck: 2014 Silverado
Any Suggestions?

 

[slowmover]

1). Power direct from battery. Negative to closest ground point.
2). Permanent antenna mount.
3). RF bonds across horizontal surfaces.
4). Common Mode Choke

Mobile Install Bible

— All mobile radio systems will have noise.

What matters are THE SYSTEMS (Power & Coax), not the specific gear installed.

 

[prcguy]

You need to run some tests to determine where the noise is coming from before you can fix it, otherwise you will spend a lot of unnecessary time and $$. Does the vehicle have a stock AM radio? If so does it get the same interference?

First I would get another 12v power source like a portable battery and run the radio from that with everything else the same. It will either be unchanged or it will be better. Then move the antenna to the far rear of the vehicle then to the front hood. You might even have to remove the radio from the vehicle and run it outside off a separate battery and use the antenna as a probe to sniff out the source of the noise.

The noise could be coming from a number of things, maybe the vehicle computer, maybe a fuel pump maybe something else. Some noise makers can be dealt with like bypass capacitors across a fuel pump but other things may not be so easy but it would be foolish to add any parts until you know what the noise source is.

 

[nonperson]

A little late to the thread but just incase some else may be looking for this information...

You can find an upfitter guide for the Silverados online. I got three radios installed in my 2014 Silverado using the guide and I have no detectable reception issues, engine noise or other interference on AM, SSB or FM and from 24 Mhz to 440 Mhz.


For the trucks with one battery.

Basically the positive power wire goes directly to the positive terminal on the battery and it is fused as close to the battery as possible. The ground wire does not and should not go directly to the battery! (The voltage sensor is on the ground wire side of the battery.) The ground wire goes to the chassis ground on the passenger side. I did cheat on this because I couldn't find the grounding point they talked about in the manual. I instead attached it to the chassis engine block grounding point on the driver's side.

The power wire(s) gets routed in front of the radiator to the driver's side and then into the cab of the truck. I also used wire loom for the entire run of the power wire. I kept the positive and negative wire lengths the same and since I was going to install three or more radios I used 4 gauge wire. It's over kill for what I have now. But I didn't want to worry about voltage drop etc or for any future additions and didn't want to run any more wires.

They suggest all antennas be mounted behind the B posts on the roof. Mounts on the bed rails, tools boxes etc are fine as well.

I can't remember the details in the manual on running the coax for NMO mounts. Just be very careful because these trucks have side curtain airbags. Look up the manual for more on this part.

Other than that, the mag mount antenna could be part of your problem.

 

[RFI-EMI-GUY]

I know that in my Ford Expedition there is a Body Control Module that has a computer that runs the accessory relays. Including lighting. A minute or two after powering off the vehicle, with doors locked, the BCM goes to sleep. In that mode it draws little current itself and the accessories and lighting get no power. your noise could be that module itself, or an accessory. One place I would check are any USB charging ports, OEM or aftermarket. Those create a lot of hash.

 

[Groundhog1960]

I ran a good ground cable from my negative battery post to an alternator bracket bolt
and my cb/antenna noise quieted down a lot.
Just a little info. Hope it helps.

 

[RC4]

I ran a good ground cable from my negative battery post to an alternator bracket bolt
and my cb/antenna noise quieted down a lot.
Just a little info. Hope it helps.

How much noise did you lose?

 

[tvengr]

Since the noise quits when accessories shut down, the noise is due to the computer or some other accessory. If you are using any USB power adapters, unplug them. USB adapters are notorious for emitting wideband RF noise. Try rerouting the antenna cable away from the vehicle computer and computer cables. If you are using a magnetic mount antenna, a permanently mounted antenna with a good ground connection to the vehicle body will often reduce noise. LED headlights are also a frequent source of noise. Clipping ferrite noise suppressors around LED headlight power cables will frequently reduce noise.

 

[Groundhog1960]

How much noise did you lose?

It help a lot with the whining noise I was getting from the alternator.
I had read in other places of people doing it claiming it worked and, it
worked for me also.

 

[n5mj]

Since the noise quits when accessories shut down, the noise is due to the computer or some other accessory. If you are using any USB power adapters, unplug them. USB adapters are notorious for emitting wideband RF noise. Try rerouting the antenna cable away from the vehicle computer and computer cables. If you are using a magnetic mount antenna, a permanently mounted antenna with a good ground connection to the vehicle body will often reduce noise. LED headlights are also a frequent source of noise. Clipping ferrite noise suppressors around LED headlight power cables will frequently reduce noise.

LED headlights, absolutely are huge RFI generators, in my case on 440 MHz.

Personal experience: attempting to find a noise-free antenna installation location in my 2022 Bronco. Radio is an Icom IC2730. Antennas tested were anything from a quarter wave to an SBB7. Huge 440 noise spectrum whenever the engine was running. Not as bad on 2m.

The RFI caused the AGC to actually reduce receiver sensititivity. Based on @tvengr post, I manually turned off the LED headlights. Noise completely vanished. Now to find where the wiring is buried to clip ferrites. Since the LED headlights were an option with this trim level, I did this to myself. Love the vehicle. Hate the ham-band RFI.

 

[slowmover]

LED headlights, absolutely are huge RFI generators, in my case on 440 MHz.

Personal experience: attempting to find a noise-free antenna installation location in my 2022 Bronco. Radio is an Icom IC2730. Antennas tested were anything from a quarter wave to an SBB7. Huge 440 noise spectrum whenever the engine was running. Not as bad on 2m.

The RFI caused the AGC to actually reduce receiver sensititivity. Based on @tvengr post, I manually turned off the LED headlights. Noise completely vanished. Now to find where the wiring is buried to clip ferrites. Since the LED headlights were an option with this trim level, I did this to myself. Love the vehicle. Hate the ham-band RFI.

I’d feel pretty confident were that my vehicle that a search would prevent me from having to re-invent the wheel. Bound to be someone out ahead.

 

[RC4]

I noticed today, that when I turn my truck off, keys out, and after a minute or so when the accessory power goes off, my radio static gets much quieter. Also my signal improves. Someone, who before when they are at a certain location I could barely hear, but when this happens I hear them clear as day. My radio is wired directly to the battery.

Radio: Cobra 29
Attenna: Sirio performer 5000 on a magnet mount directly on roof
Truck: 2014 Silverado
Any Suggestions?

I have the exact same issue in my 2018 Silverado. I even made a quick video on it. I’ve since gone to a mag mount antenna. A lot of the noise I was experiencing before has subsided. My issue is now tho I’m always getting right around 3 pounds of noise when I am driving or if the truck is on. But when I turn the truck off and open the door after 30sec the radio goes silent. No static nothing and I can hear everyone perfectly! But when I close the door and open it again the noise static comes back. Been trying to figure it out for a year. I’m running a 955 with a Stryker a10 mag antenna. The funny thing is when I put everything in my wife’s 23 4 runner I don’t get vehicle noise. It’s so quiet it’s amazing. Owell I’ll keep trying

 

[gary123]

A lot of noise is created by the Electronic Contol modules in the vehicle. If it is 'alive' or doing something the noise is present. Another big source is rearview/dashcams. Recently I had to repair an issue from the navigation screen in a 2022 vehicle.

The bad news is there is no quick fix. You have to identify the source then figure out how the noise is being radiated. The wire harness is often the culprit here. Then you have to start adding in shielding, chokes and ground straps. No two vehicles are the same. You could try consulting the local dealership and see if they can suggest what circuits are active during the conditions you are experiencing. Suggestion here is to wait until you have the no noise condition then try various things. Open drivers door time the duration of the noise, do the same with passenger door and tailgate. put key in ignition turn key to accessory, try the windows etc. Basically the more info you can provide on when the noise is present the easier it may be to track it down.

 

[mmckenna]

You could try consulting the local dealership and see if they can suggest what circuits are active during the conditions you are experiencing.

The manufacturer upfitter guides are a good place to start. GM has some pretty good documentation available.
Consider that there are tens of thousands of these trucks out in the world for public safety or public works use. All those trucks have radios installed in them. GM (as well as other big manufacturers) know this and design accordingly.

The upfitter guides will give you some specifics about where to mount antennas, where to run wiring, where to connect power, etc.

Usually these guides are designed around VHF, UHF, 7/800MHz, but they will often cover stuff down into the HF bands. Problem is, noise is a bigger issue down in the lower frequencies (usually).

Addressing this noise issue should start with the GM upfitter guide and include understanding professional radio installation procedures.
Running radios off cigarette lighter plugs, tapped wires, improperly installed antennas, is often the source of many issues. Cleaning up the install and doing it per the vehicle manufacturer guidelines will help quite a bit.

While not CB, I've had VHF, UHF and 800MHz radios installed in the mid-teen era GM trucks without issue.

 

[RC4]

A lot of noise is created by the Electronic Contol modules in the vehicle. If it is 'alive' or doing something the noise is present. Another big source is rearview/dashcams. Recently I had to repair an issue from the navigation screen in a 2022 vehicle.

The bad news is there is no quick fix. You have to identify the source then figure out how the noise is being radiated. The wire harness is often the culprit here. Then you have to start adding in shielding, chokes and ground straps. No two vehicles are the same. You could try consulting the local dealership and see if they can suggest what circuits are active during the conditions you are experiencing. Suggestion here is to wait until you have the no noise condition then try various things. Open drivers door time the duration of the noise, do the same with passenger door and tailgate. put key in ignition turn key to accessory, try the windows etc. Basically the more info you can provide on when the noise is present the easier it may be to track it down.

Well basically when the truck is on is when the noise is present. It’s not engine noise and it’s not the head lights. When I turn the truck off it takes about 30 sec and the noise disappears completely. I put my Radio and Stryker mag In my wife’s 23 4 runner trd pro and when I’m away from town the radio is silent. Wish my Chevy was like that. I also get noise when I turn my steering wheel left or right. I read a few days ago that putting a ground from my cab to my frame might help. Maybe I’ll try that and see what happens

 

[gary123]

mmckenna has great advice on the nature of noise on CBs and his recommendation of referring to the upfitter documentation is a easy list things to check. From your description when the noise is not present check and see if any interior lights work etc. If they do mark them down, this will eliminate those cricuits. Next turn the key to accessory and see if the noise starts. I suspect it will. This will then tell you that it is either the accessory switched module or one of the items controlled by that module. You may be able to narrow it down by pulling fuses BUT be warned verify with someone familiar with the vehicle that pulling a fuse is not going to create other issues... CYA time do it at your risk. I can only suggest generalities and basic trouble shooting processes.

 

[RC4]

A little late to the thread but just incase some else may be looking for this information...

You can find an upfitter guide for the Silverados online. I got three radios installed in my 2014 Silverado using the guide and I have no detectable reception issues, engine noise or other interference on AM, SSB or FM and from 24 Mhz to 440 Mhz.


For the trucks with one battery.

Basically the positive power wire goes directly to the positive terminal on the battery and it is fused as close to the battery as possible. The ground wire does not and should not go directly to the battery! (The voltage sensor is on the ground wire side of the battery.) The ground wire goes to the chassis ground on the passenger side. I did cheat on this because I couldn't find the grounding point they talked about in the manual. I instead attached it to the chassis engine block grounding point on the driver's side.

The power wire(s) gets routed in front of the radiator to the driver's side and then into the cab of the truck. I also used wire loom for the entire run of the power wire. I kept the positive and negative wire lengths the same and since I was going to install three or more radios I used 4 gauge wire. It's over kill for what I have now. But I didn't want to worry about voltage drop etc or for any future additions and didn't want to run any more wires.

They suggest all antennas be mounted behind the B posts on the roof. Mounts on the bed rails, tools boxes etc are fine as well.

I can't remember the details in the manual on running the coax for NMO mounts. Just be very careful because these trucks have side curtain airbags. Look up the manual for more on this part.

Other than that, the mag mount antenna could be part of your problem.

I also ran a hood fender mount and had the same issues. The noise is coming from inside the cab I believe. The moment I open the door or start the truck the noise appears. When I turn the truck off and open the door and close it, after 30 sec the noise is gone.

 

[RC4]

You need to run some tests to determine where the noise is coming from before you can fix it, otherwise you will spend a lot of unnecessary time and $$. Does the vehicle have a stock AM radio? If so does it get the same interference?

First I would get another 12v power source like a portable battery and run the radio from that with everything else the same. It will either be unchanged or it will be better. Then move the antenna to the far rear of the vehicle then to the front hood. You might even have to remove the radio from the vehicle and run it outside off a separate battery and use the antenna as a probe to sniff out the source of the noise.

The noise could be coming from a number of things, maybe the vehicle computer, maybe a fuel pump maybe something else. Some noise makers can be dealt with like bypass capacitors across a fuel pump but other things may not be so easy but it would be foolish to add any parts until you know what the noise source is.

The radio is stock yes. And I have used a president randy hand held in my truck and it does the same thing. The noise is definitely coming through the Antenna. I’ve used both hard mount antennas and mag. I’ve also tried different batteries and alternators. Not for the radio issue, either way it didn’t change a thing. I wish someone lived around my area in Portland Oregon I’d pay whatever it took to fix it. Tbh I never thought around the stock radio tho.. might be something to think about.

 

[nonperson]

I also ran a hood fender mount and had the same issues. The noise is coming from inside the cab I believe. The moment I open the door or start the truck the noise appears. When I turn the truck off and open the door and close it, after 30 sec the noise is gone.

If I remember correctly the upfitter guide I referenced covered the 2018 Silverado. But to be on the safe side I would recommend searching the web for that model year.

The fender mounts (in front of the cab) is the worst place IMO to mount an antenna for any transceiver. I would suggest mounting it on the roof behind the B posts or on the roof area above where your rear passengers sit, or about any wheres in the bed area. And ditch the mag mount. How do you have the radio powered? Do you have anything else plugged into any of the USB outlets or auxiliary powers ports (cig lighter)?

The retained accessory power or RAP can cause some RFI issues. I have a Kenwood 8180 for GMRS. When I programmed it I didn't put in any PL tones at the time. When I turn my 2014 Silverado off and open the door I will hear some RFI in it but it goes away as soon as I close the door. I believe once I reprogram it with PL tones I want notice it any more. Doesn't effect the Icom 5100 or the RCI 2950 at all. I do have a low pass filter for the RCI 2950 so the other two radio won't interfere with it. The antenna for it is mounted to the center, rear of my toolbox.

A good low pass filter is something else you can try if nothing else works. When I get around to redoing my console I'll try taking out the low pass filter and see if I have any RFI issues like you are experiencing.

 

[RC4]

If I remember correctly the upfitter guide I referenced covered the 2018 Silverado. But to be on the safe side I would recommend searching the web for that model year.

The fender mounts (in front of the cab) is the worst place IMO to mount an antenna for any transceiver. I would suggest mounting it on the roof behind the B posts or on the roof area above where your rear passengers sit, or about any wheres in the bed area. And ditch the mag mount. How do you have the radio powered? Do you have anything else plugged into any of the USB outlets or auxiliary powers ports (cig lighter)?

The retained accessory power or RAP can cause some RFI issues. I have a Kenwood 8180 for GMRS. When I programmed it I didn't put in any PL tones at the time. When I turn my 2014 Silverado off and open the door I will hear some RFI in it but it goes away as soon as I close the door. I believe once I reprogram it with PL tones I want notice it any more. Doesn't effect the Icom 5100 or the RCI 2950 at all. I do have a low pass filter for the RCI 2950 so the other two radio won't interfere with it. The antenna for it is mounted to the center, rear of my toolbox.

A good low pass filter is something else you can try if nothing else works. When I get around to redoing my console I'll try taking out the low pass filter and see if I have any RFI issues like you are experiencing.

I have 10 gauge wire going straight to my battery and grounded to my chassis. No usb being used. Damn GM lol