CB Interference Issues

Hey all, just installed a Cobra 75 with a 4' Firestick II, mounted on a relentless fab mount. (Stud mount, scraped off powdercoat, spring also installed)

This is set up currently like this:
CB->grounded to inside cab (bolt behind kick panel)/power to a relay-> relay to a otrattw switch and to auxiliary fuse block with 3A fuse.

Got some engine noise interference (mild to moderate). The most interference I get is from my HIDs and LED bar and pods, when I cut these auxiliary lights on, I have to turn my squelch up to like 80%. It's ridiculous. (Moderate to severe)

So, I want to keep a switch/relay combo for the CB so my volume is always preset and such.

My question is instead of running relay to aux fuse block, I run the 30 pin on the relay to the battery, and 87 pin to the CB and 86 pin to switch, will the noise be reduced?

Anyone with experience with this to help me out?

 

Power straight to the battery is always your best bet. I would give that a shot first. Also try grounding using the battery ground. Good luck!

 

CBs really do not draw enough current to need a relay. I steer clear of any under dash connections and run direct to the battery with a 5A fuse and a cutoff switch. I use a ground in the cab and have zero noise. If any noise shows up doing this I would run the ground to the battery as well.

 

Ok guys, thanks for the tips, I'm about to go out and troubleshoot it a couple different ways and see what happens, will report back.

 

Ok, so I tried a few different configurations today as suggested above. All of them still gave me engine noise. The noise was the least going straight to the battery, both power/ground and with the relay going to battery instead of fuse block. However, I still got interference with my LED bar, so, I rewired the led bar wires away from the CB relay, then tucked my CB relay under the fuse block and this got rid of all my LED interference, from hid headlights too. My SWR was also slightly lower, from 1:6-1:8 to about 1:4-1:6 on channels 1,19, and 40. Not 100% happy, but close enough! I hear noise filters are hit or miss, so I'm not gonna waste my time on that, there is no "whining" coming in, just increased static.

Thanks again to those who chimed in.

 

Welcome to the world of AM radio, don't expect a radio the costs less than $120 to have very good noise suppression. Both of your lighting systems use switching power supplies they are inherently noisy you might try toroid chokes on the power supplies for the lights.

 

picture of how antenna is mounted

 

It's on a relentless fab hood mount.

 

I don't understand the point of a switch, it is not needed, and it seems you are sacraficing performance for it.

 

I was wanting to look how you have the antenna mounted not sure why you scraped off the powder coat.

 

In my post above, I wrote that the HID, and LED interference is pretty much gone, all I really get now is some mild engine noise, I know why I get the noise at this point, and I am receiving/transmitting well with the current relay/switch. I scraped off the powder coat where the mount would contact the ground plane to make sure I got a more solid ground to the antenna, doing so got my SWR from 2 to 1:8. With the switch relay straight to battery, my SWR went from 1:8 to 1:5, mild engine noise. I want a switch so my volume is preset and I never have to touch the transmitter, plus the switch looks cool.

Antenna, spring, stud mount, washer, nylon washer, relentless mount, coax, bolt is how it's mounted

It's pouring outside right now, or I would get you a pic

 

I also want to add that in my post above I wrote that having a relay/switch to battery vs. no switch or relay and CB going straight to battery had no noticeable differences, both got rid of my HID interference and both had mild engine noise

 

Tried grounding the accessories, lighting, etc. Near the actual accessory? Then only run the power wire? That solved my issue. Same cobra 75 you have.

 

Where is your antenna mounted? Don't believe your noise is coming in through your DC wiring.

 

His is on the good. Mine is on my ARB bumper

Mine was for sure the negative being coupled with the positive on the long run from the front to back of the truck. As soon as I grounded the negs in the rest. Everything was gravy. No more rf noise with them on

 

I'm not sure what you are saying nor do I understand why you would run two wires in the first place. DC grounds will have no effect on high voltage noise from the engine.

 

Me? I was referring to the light interference he was getting and that I was too. 2 wires? Every manufacturer sends a 2 wire or more harness with all their products. Rigid lights do the same also. That is where my interference was.

As to why I did. Because the manufacturer suggested I use their harness. When I spoke to them on the phone, they still recommended against splitting the harness for whatever reason.

 

KISS

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S imple

Stupid

No need for a switch on a CB IMHO. No need for anything other than a small inline fuse close to the battery.

What size cable do you have? Is it shielded? I am running a 9' highly shielded cable, with strait battery power, and never hear any static.

 

OK if it is a LED system it can make all kinds of noise they use switching power supplies. If the ground wire is open at one end (connected to the light) it can become a transmitting antenna the fix as you said was to ground it at the light that makes sense. I believe the OP is dealing with common ign. noise.

 

Another good rule of thumb is to use an Antenna that has a Ground Plane. The firesticks do not and rely on the antenna cable to do the grounding. If you look at the Wilson antenna's, they have a separate ground plane to run which in turn will improve your reception. The other thing to check is that if you have a bunch of slack in your lead to your Antenna do not coil it up as this serves as a "choke" in the line. Try to spread it out as much as possible. Just thinking out loud here. Hope it helps.