Anyone have a sugestion for noise in big truck ?

[bubby1]

2005 peterbilt with ignition off NO noise turn key to acc. position all kinds of static.I unplugged coax from radio noise is gone.Its a diesel engine so mechanical fuel pump.It does it when all the accecorys off even headlights,heater fan, sterio,as long as key is on so is the noise and I can hear it in the background when I recieve.Sounds like a helicopter in the cab I'm lost here.The truck does have a factory stereo amp behind passenger seat but like I said even with it off I still here the noise.Every so often I can turn the squelch down to normal but that is few and far between,and I watch guages to see if engine fan or something but to no avail.Could it be alt noise possibly?The only thing I could relate it to was I have one faulty guage in truck( fuel psi )and the needle goes nuts back and forth almost in sequence with noise but it is not a electical guage.Anyone?

 

[Robb]

Sounds like an electric fuel pump still...

 

[mackmobile43]

Injector noise, you might try an inline noise filter on the power cord.
You can find then in truck stops but this one in the link is good.
If that doesn't stop it then it may get pricey trying to isolate the leads from the injectors.

Magnum Filter Cord / Magnum ra-H&Y Electronics

 

[bubby1]

Thanx guys for the help.You might be on to something mack someone else had mentioned that the injectors were on the same frequency as cb if thats possible 27.185 ch19 I believe.

 

[kevin IB/379 Stringbean]

I have a 2000 with a 3406.It took me a year to finally find my noise.It was the digital Cat onboard diagnotics.It was a very irritating high pitched whine that got even worse with a recieved signal.Kind of like when you charge your phone through the cig lighter.I pulled the small panel to the left of the steering collumn that it was on and unplugged it.Noise was gone.Dont know if you have one of these,but if you do,you might try this.

 

[Moleculo]

If you can't find the source of the noise and eliminate it, you can purchase a DSP speaker or speaker module. They're not cheap, but you'll be amazed at how much noise it will get rid of.

 

[Chop]

just curious, what radio are you using? some radios have better filtering than others.

 

[Captain Kilowatt]

If you can't find the source of the noise and eliminate it, you can purchase a DSP speaker or speaker module. They're not cheap, but you'll be amazed at how much noise it will get rid of.

The only problem with audio DSP like that is that it does nothing to recover the actual signal. If the noise is S-8 then it takes a signal stronger than S-8 to even be heard with or without the DSP. Eliminating or reducing the noise is still the best bet. I know I paid $200 for the DSP unit in my FT-857 when they first came out and wish I had never bought it. Audio DSP is a waste of money IMHO and true RF DSP is the only way to go.

 

[bubby1]

Radio is a magnum s3.By chance where is the power supplied from to the roof mounted power points?I noticed when the headliner was down that the 2 wires coming off the power points lead to a small white connector which had a tag that read cb.I could not follow any further due to all the wiring up there so much in fact that I could barely get my hands in there.

 

[mackmobile43]

Radio is a magnum s3.By chance where is the power supplied from to the roof mounted power points?I noticed when the headliner was down that the 2 wires coming off the power points lead to a small white connector which had a tag that read cb.I could not follow any further due to all the wiring up there so much in fact that I could barely get my hands in there.

Yes that goes to a switched circuit which is fine normally, give this a try, run the power directly to the batteries and see what happens.

 

[bubby1]

Already tried mack and no difference.Just frustrated at this point know what I mean.On another note yesterday seemed to be different ALOT more like normal only heard the noise a couple times over the course of day with the wet roads and all dont know if that was related to less radio traffic being a saturday or what hmmmmmm...

 

[mackmobile43]

Already tried mack and no difference.Just frustrated at this point know what I mean.On another note yesterday seemed to be different ALOT more like normal only heard the noise a couple times over the course of day with the wet roads and all dont know if that was related to less radio traffic being a saturday or what hmmmmmm...

Re-read your first post and it seems you're getting the interference through the antenna so the only other route would be to find where the interference is imitating from and shield it there.

Not sure which 2005 Peterbilt you've got but it's a good idea to make sure your antenna has a good path to ground and or it's counterpoise which is to bond the cab to the frame via some good flat straps and depending on the mounting scenario of the antennas you may need to bond the antenna mounts to that same counterpoise.

And as someone said those magnum radios are more sensitive to interference radiating from the trucks electronics and when driving in the rain your system is probably seeing a better counterpoise due to the conductive properties of the water on the vehicle.

 

[bubby1]

Thanx for the help mack.Im only running a single francis(was a 5000 trucker just switched in hopes of less noise with a fiberglass whip) antenna with belden rg8x and good SWRs so never thought it was a ground issue.Dont know anything bout counterpoise though?

 

[mackmobile43]

Do you have a fiberglass cab or metal, no metal no counterpoise.

 

[bubby1]

Hood and roof are fiberglass.