Road noise

[noman]

I have a cobra 29, I was in one truck and hardly got any noise coming through the radio. I switched trucks and now I getting a bunch of noise.
I made a noise filter I found on the net. That helped a little, I started running the power cables to the batteries, That helped even more. But
its no where near what I know it could be. I noticed the faster I go the louder it gets. And if I switch from from right lane to left lane it pretty much goings away, then when I switch back the noise comes back. Any thoughts on what mights be causing this?

 

[Moleculo]

And if I switch from from right lane to left lane it pretty much goings away, then when I switch back the noise comes back. Any thoughts on what mights be causing this?

This is the weird part. Different vehicles & engines will cause different amounts of radio frequency interference that your radio will pick up. However, I've never heard of anything where the noise level changes because of what lane you're in. Do you drive near a lot of power lines by any chance? Perhaps your radio is picking up power line noise when you're closing too them?

 

[noman]

No I'm not by power lines. Another thing I noticed is when I go over bridges
I get more noise.
One thing I was wondering is could the truck it self not be getiing a good
ground. I know everything grounds to the frame and that inturn gets grounded through the tires to the ground right?

Another thing I was wondering is could it be static build up and thats what is causing the noise?
I don't know I was in one truck and didn't pick up any noise. Then I switched trucks and now I'm getting alot of noise.

 

[Moleculo]

Yes it can be static build up. I have also heard rumors of certain trucks with radial tires that caused more noise in certain types of radios than other. I don't know if that's BS or if can really happen. Does that radio have a Noise Blanker (NB) button or switch? Does it help at all when you turn it on?

 

[W5LZ]

I didn't see any reference to it so, did you by chance swap antennas when you changed trucks, or the same one still? And since it's a diffeernt truck, is it mounted in 'about' the same place on the new one? Lot's of variations in that for lot's of reasons, so just a consideration.
Another thingy is that the vehicle's distance from 'dirt' ground really does make a difference. The vehicle it's self isn't the only 'ground' your antenna 'sees', it also uses the 'dirt' under it to some extent (capacitive or inductive coupling between the two). How much 'dirt' it may use depends on the frequency of use. Hf will typically use more 'dirt' ground than VHF or UHF, a function of wave length and all that stuff. You hear stories about adding graphite to bearing grease, etc, to increase conductivity. I don't think I'd recommend that really. It probably does increase conductivity but I think I'd rather not have to replace bearings because of any 'additions' I made to what lubricates them, you know? I tear up things too much without me 'helping' it along by doing something like that.
There's also two schools of thought about how a radio equipped velicle should be undercoated. One says that pink is the best color, the other says chrome plating everything under there to increase reflectivity is the way to go. You make up your own mind about that.
- 'Doc

 

[noman]

I have also heard of putting graphite dust on the brake drums. I didn't think
that sounded like a good idea. Everything is the same except the truck.

 

[towerdog]

graphite, couldn't you just drag a wire or cable

 

[noman]

I was told some truck stops sell rubber or plastic straps with metal in it.
You mount it to the axle and let it drag on the ground. Only problem with that is its not my truck and I'm not allowed to hard mount anything to the
truck.

 

[Slowmover]

(Someone, somewhere, will come across this in a search).

The HAM Radio Mobile Installation bible is:

www.K0BG.com

See section, Controlling Static

to cover those questions.

CB Radio installations are aided greatly in using that guide.


GATES 90331
is a graphite-impregnated static control strap for big trucks.
At end of each frame rail. (Replace as wears. Cheap).

Have a long look at a fuel tanker. Ask driver about static electricity build-up during delivery (grounding requirements). Static drains are part of their vehicle inspection pre-trip.

As to one tractor having problems the other didn’t (re CB) that’s a norm. Most problems are with coax damaged by previous operators. Bypass with higher quality coax a typical first step.

As to differences with the two-lanes of a four-lane highway, that’s a difference in steering caused by road camber. (Crown). Why it’s a problem with receive noise goes several directions.

First step is whether it’s thru power source, or thru coax. Disconnect coax and drive it.

— Graphite powder was added by operator to wheel bearing grease in old days to cut RFI.

— RF bonds to “jump” the Steer Axle kingpins (or balljoints & A-Frame bushings) was the way to connect axles (all; Drives also isolated from frame). Woven, braided copper strap used. Wider the better. Short. SS Muffler Clamps the example for attaching.

— Exhaust System the other. Same clamps. The longer it is, the more jumpers needed. (I’d suspect this first in lane differences; body alignment against chassis has changed). Think of the complete exhaust system as a competitor antenna you need to ground.

.

 

[kd9adh]

My guess is your truck has all synthetic fluids and static is not being discharged. I have the same problem in the 2016 Peterbuilt I drive. I did not have the problem till we switched to all synthetic. I tried all that you have with small amount of reduction. Bought a static strap but I have not tried it yet. I let you know when I install it if it works.

 

[Slowmover]

Might be an RF Bond left unconnected after truck service.