Mobile Line Noise

[sonoma]

the cobra 29 radios are fairly good about killing noise. are you turning on the NB/ANL switch to help cut down on the noise. you would be surprised at how many people do not turn them on.
sounds like the fuel pump. grounding is about the only thing to help cut down on noise. I had the same problem with my 2003 S10 and had to put the power wire to the battery. the ground wire to a seat bolt. put grounds on the engine to frame and grounds on the exhaust. also put a ground from the seat bolt to one of the bracket bolts to help with grounding. I still have a small amount of noise but now at least I can live with it. it is about 1 S unit on the radio meter so not too bad as it is now. I have seen some radios have a 3 S unit of noise and was very loud. my president Jackson radio does not have any noise to speak of when I run one of them. my galaxy 29hp and connex 3300 hp radios are very noisey . I have a lot of radios that I have collected over the years. last count base and mobiles I have 42. I have another connex due here Friday that I bought.
hope you can get the noise down I know it is hard to listen to a noisey radio

 

[543_Dallas]

Has anyone had luck with bypass caps across the fuel pump wires?

 

[sonoma]

I put a 1000uf cap on the power wires on my pickup. I tried different uf ratings of electro caps and tried a couple disk caps and some helped it. right now it has a 1000uf cap on it. tried all the way up to a 3000uf and grounding seemed to help the most. the hardest part is it needs to be as close to the fuel pump as possible and most of the wires are on top of the tank and hard to get to unless you drop the tank. even tried a filter like used on the old points type distributors . put the can to the frame and the lead to the hot wire.

 

[543_Dallas]

I put a 1000uf cap on the power wires on my pickup. I tried different uf ratings of electro caps and tried a couple disk caps and some helped it. right now it has a 1000uf cap on it. tried all the way up to a 3000uf and grounding seemed to help the most. the hardest part is it needs to be as close to the fuel pump as possible and most of the wires are on top of the tank and hard to get to unless you drop the tank. even tried a filter like used on the old points type distributors . put the can to the frame and the lead to the hot wire.

Access is the worst part. It's easier to pull the bed in most trucks but even then you'd be hacking the wiring as an experiment. I know some guys have had luck with bypass caps on electric cooling fans is why I asked.

What kind of antenna set up were you working with and what do you think about a temporary test with a borrowed mag mount antenna on the roof? Get the antenna up high with some sheet metal under it like it belongs. Most people aren't willing to do it but a hard roof mount has served me well. Low noise floor and no rfi issues with kilowatts.

The old timers loved the whips on the bumper but most of the radiation is happening at taillight level. Fuel pumps were mechanical and mounted on the engine block in those days.

 

[StrangeBrew]

Ford electric fuel pumps are known for noise, I've never tried it myself but a cap across the power wires as close as possible to the pump is usually the recommended fix.

 

[Mudfoot]

Fuel pump whine will likely be cured/suppressed by placing a cap across the leads directly at the pump itself. Of course, this can be a pain in most vehicles. I can't recall the fuel pump manufacture, but Carquest used to carry the brand. They were built with internal RFI suppression. I swapped one out in my 2000 XJ that helped tremendously.

Funny, but I now have an 99 XJ and it has hardly any RFI.

 

[Mudfoot]

Ford electric fuel pumps are known for noise, I've never tried it myself but a cap across the power wires as close as possible to the pump is usually the recommended fix.

FORD has several tech bulletins on the subject of noisy pumps. They used to have kits to install at the pump.

 

[Pamm r]

I did everything that was suggested above: My 2 gas tanks are metal. I used a continuity meter to test the tanks, truck bed , truck cab, hood, exhaust pipes, motor. All have ground straps and have good ground. I did unplug my coax with motor running and no noise at all. So I guess it's RF from my electric fuel pumps, ( FORD ). So what is a CAP and how hard is it to install?

 

[Mudfoot]

Here's a nice little read...

http://www.arrl.org/fuel-pump-noise

http://www.redwaveradio.com/2_49ccfef286b1431c_1.htm

 

[sonoma]

what year ford do you have? with 2 tanks was just wondering if the fuel pump is in the tanks, also you have a metal bumper which you can have but hard to mount a bracket to it. some of the older trucks had a inline fuel pump and when you switched from one tank to the other it was ahead of the valve. just a thought. if there is fuel pumps in each tank the power wires may be on the switching valve and would be easiest to put a capacitor on the power wires.

 

[Pamm r]

what year ford do you have? with 2 tanks was just wondering if the fuel pump is in the tanks, also you have a metal bumper which you can have but hard to mount a bracket to it. some of the older trucks had a inline fuel pump and when you switched from one tank to the other it was ahead of the valve. just a thought.

It's a restored 1992 model. It has a pump inside each tank I am told. Metal chorme bumper, checks all the grounds on the bumper to frame too, by what i just read it is the fuel pumps I guess

 

[sonoma]

look to see if it has a switching valve on the frame rail to switch from one tank to the other. it may have power wires at the switching valve for each tank so the pump is not running when the one tank is not in use. if it does you may be able to help some of the noise with a capacitor on each power wire at the valve. not sure if it would work there since the closest to the tank is best. metal tanks normally do not let rf out into the system. always a problem child some where. a couple years ago I had a few women drivers that were escort drivers for moving large item on the roads. a couple of them had bad noise like you are having and it took for ever to kill most of it out for them.

 

[Pamm r]

Thanks to all of y'all for dealing with all the questions. Now that Radio Shack is no longer in my area where to y'all order parts now?

 

[Sarasota Slim]

I've been known to order from Ebay. I generally stick with sellers that have a 97% approval rating or higher, and that have made several hundred sales. I also read reviews of the specific product, on several different sellers pages (when possible; kinda hard to do, though, if only one guy has what you want, lol). I also search for reviews of the product, elsewhere online. I probably go a little overboard with it, but I want to know exactly what I am buying, and I want a pretty good idea of what to expect from the thing, when I do get it.

There's other places, too, of course. And, I am sure the others who have followed this thread will have some good opinions on where to get stuff.

Have you considered moving your antenna? My buddy is planning to mount the antenna, on his truck, to the toolbox, in the middle, in between box and cab. He'll just bolt the mount directly to the box (metal box, of course ) and then put a couple of grounding straps (probably one on each end) to get a good ground between the box and the truck bed, which is, in turn, already grounded to the chassis. If I recall correctly, you have a 102" whip; if your truck is approximately the same height as my friends truck, that should put the top of your antenna somewhere between 13 & 14 feet. Your antenna will also be more centered. Anyway, just a thought.

 

[sonoma]

before you start buying any thing you think you might need, I have not seen where you have tried all the other ideas which could possibly fix your problem. have you tried moving the ground wire from the battery to a seat bolt? have you tried the grounding of the radio case to a seat bolt by hooking a ground wire to the radio case? these are 2 things you need to try 1st. have you tried putting ground straps on the exhaust? also using just a piece of wire like is used to hook the power up to the radio does not work good for grounding. the regular ground straps work better. such as the flat type cables that the factory uses. I will see if I can find some on ebay for an example. car part stores carry this type cables.