Background Noise

[ctvanover]

Hi! I'm New Here!

I have a Magnum S9 mounted in a 2000 379 Peterbilt. The Wilson 5000 antennas are co-phased with 95% shielded 9 foot coax. With the truck turned off I have little or no background noise. When I start the truck up there is some noise but not enough to hurt anything. After I pull out and get up to around 35 to 45 mph the background noise gets louder. Sometimes I have to squelch my radio almost half way to get it quite and then I can't hear as far as I should. I don't think it's picking up the alt. because I don't hear no whining with the revving of the engine.

Can someone here help?

Any & All Help will be Greatly Appreciated!

Chris

 

[park]

Your tires on the rig are building up static. You may have to try the old chain hanging off the back of the trailer trick !?

 

[W5LZ]

I really hate to tell you this but that strap/chain dragging thingy just doesn't work. In fact, it can cause even more static/noise, aside from being unsafe.
All moving objects will build up a charge caused by friction between two dissimilar materials, that's normal. That stuff the object moves through can be air, water, whatever. That strap/chain, since it's connected to the moving object and dragging on the ground, will also contribute to that charge build up. If there were a way of selecting what that strap or chain were made from so that it would build up an opposite change to the rest of the vehicle, it might bleed off the vehicle's charge. Don't hold your breath though, that is so unlikely that it just isn't gonna work. Ever noticed that fuel transports always use a grounding strap before pumping that fuel into a tank? (Or should!) Doesn't matter if that transporter is refueling a holding tank, vehicle, plane, whatever, the operator always connects a ground strap to the vehicle before refueling (or should!).
Ever seen a spark between gas nozzle and a vehicle when someone starts to pump gas into their car? If so, then the gas pump is defective, that nozzle is supposed to be grounded through the fuel line to the pump (and ever noticed that the inlet on fuel tanks are always metal and connected to the chassis of the vehicle mechanically/electrically? Not kidding, really!).
There is a 'problem' with some vehicles building up more static electricity than others. The 'cure' is providing an electrical discharge path back to ground. Can't do that with a dragging thingy while the vehicle is in motion though, only when it's not moving. The only exception that I'm aware of is on larger planes, a static discharge device on a trailing edge (usually a frayed braid strap, lots of 'sharp' points on the end). They do increase the discharge rate while the plane is in the air, but not when they are on the ground, different set of circumstances.
What can you do? Same old thingy about grounding all the separate parts of a vehicle to the chassis, which provides a path to ground eventually. Will it make the radio quiet? Nope, but it will help to some extent. But try the strap thingy if you'd like. But pay attention when refueling...
- 'Doc

(also make that strap easy to take off, you will.)

 

[dudmuck]

Tires should have graphite in the rubber material to prevent static buildup.

Often a corona ball is used at the tip of antenna to bleed off static.
As far as the drain hanging down on the road, use aircraft cable.
Could be a seasonal thing, is it dry in kentucky these days?

It must be that purple lightening around your truck.

 

[loosecannon]

if it is the tires, some graphite added inside the tire will help alot.
they used to make an apparatus to shoot the graphite in, but i dont know what people use these days.

are there other electrical devices in the truck that could be causing the noise?
such as an AC pump or something?

you should be running the power wires from your radio directly to the pos. and neg.terminals of a battery.
no cig plugs, no short neg. wire to vehicle body.
12ga. wires right out the back of the radio, right to the battery.
then connect a short copper strap from the metal chassis of the radio to the vehicles metal chassis.
you need to have a good electrical connection from your mirrors to the vehicle body. you will probably have to add a copper strap/wire to accomplish this.
also, a loose connection on one of your antennas might be causing the noise.
you wouldnt notice until you got down the road and the antenna was vibrating and shaking around.
try having a friend wiggle the coaxes, and poke at the antennas with a wooden object to see if you get any big static spikes.
just some suggestions.

with these trucks being all fiberglass, they are not very cb friendly anymore.
loosecannon

 

[Hardhead]

When you are rolling and have the static, if you put the clutch in and let the engine go to idle is the static still there?
If so it has to be something in the drive train, maybe tires.
If not, it could be the electronic injectors or related system.

 

[rabbiporkchop]

Proper co-phasing requires 1/4 wave coax per side or any odd multiple thereof. With a velocity factor of .66 for the typical RG59, 1/4 wave translates to roughly 6 feet. If 6 feet isn't enough to reach out to both antennae then you must add 1/2 wavelength to your coax bringing each phasing line to roughly 18 feet. Nuff said about transmission line theory. Not sure about the background noise situation though. Just had to put in my 2€ in regards to co-phasing. Rarely does anyone do it correctly.