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Discussion Starter #1
Hello, I have my cb radio's positive and negative power lines connected directly to the battery. The powerlines are run through the cab and around the engine as far away as possible from the ingnition cables. The case of the radio is grounded at the chassis, which seems to help alot to reduce SWR. when I'm driving I get alot of engine noise.

Its bothered me to the point where I put layers of aluminium foil over the power lines in the engine compartment. This worked a little but not enough. I have to turn the squelch on so high I cant even hear relatively strong singnals while driving.

Anybody know of any tips to get rid of engine interference? I have properly grounded the hood, radio, antenna, and engineblock. Other than this, I dont have any ideas as how to reduce this noise.
 

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i had this problem with an old receiver unit. turns out that i could receive signals but not send them. i just replaced it and there is little to no engine noise. before you could hear the spark plugs going off at idle and listen to them speed up as you got on the RPMs.
 

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Try making your ground cable as short as possible, preferably less than a foot. Works for car audio, I'm guessin it'd work for CB's
 

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Discussion Starter #4
I can still send fine to other units. No problems there. The noise seemed to be more proportional to high RPMs before I relocated my power lines. Now the noise doesnt seem to increase any with RPMs, but there is still a bunch of constant interference.


Also, when I disconnect my antenna I still get engine noise. So the only possible way for stray RFI to get to my radio would be through my power lines. Is there any material you know of to reduce RFI? I was thinking in maybe investing in a cheap RFI inline filter but I dont know how well this would work, and if it would even be worth my money.
 

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Check for a noise filter they make them I got one on my bko.got it at cb shop locally.Helps big time too.
 

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I'm an applications engineer at a company that makes EMI/RFI interference filter connectors used in military and commericail aircraft computer boxes. Basically the suggestions are right on:
Move cables as far away from high current sources as possible
or
Use sheilded cable - might be able to find power cables with a metal sheild layer built in. Similar to the aluminum foil idea. the sheild will need to be connected to ground.
or
Use a noise suppression filter
 

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Where is your antenna? How is the antenna cable run? It may not be your power cables.
 

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One of the wonderful sources of noise in the Broncos is the fuel pump. Since you say it is a constant noise this may be the issue. Sparks plugs create a popping noise and alternators a whine, both chaning with engine RPM.

Here is a great article that helps explain how to fix it. It is for Ham radio 10 meters, but will also apply to CB radio. which is 11 meters.

Good reading if you want to trouble shoot it

http://www.arrl.org/tis/info/fuel.html

Tony KI6FGI
 

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One of the wonderful sources of noise in the Broncos is the fuel pump. Since you say it is a constant noise this may be the issue. Sparks plugs create a popping noise and alternators a whine, both chaning with engine RPM.

Here is a great article that helps explain how to fix it. It is for Ham radio 10 meters, but will also apply to CB radio. which is 11 meters.

Good reading if you want to trouble shoot it

http://www.arrl.org/tis/info/fuel.html

Tony KI6FGI

Good lord like at the price of the ford filter:

F1PZ18B925A MSRP: $87.81 Team Ford: $63.15

FILTER-RADIO RECEIVE
 

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If you really want to do it yourself, there are multiple sites. Just google ford fuel pump rfi noise There are a lot of inexpensive remedies one can do. Some require dropping the tank to get to the filter, others do not. Depends on how bad you want to get rid of the noise
 

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Discussion Starter #13
well I know the interference is coming in through the power wires since there is still noise when I disconnect my antenna. If the noise IS being caused by the fuel pump (or anything else for that matter) will an in-line RFI filter on my radio's power cables work rather than attatching the filter to the pump? I'd rather not have to pay someone to disassemble my gas tank :toothless
 

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It may help. Radio Shack or a truck stop will have one. $15-$20 gamble.
 

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the filter will need to be right where the wires come out of the radio. any wire between the filter and the radio could pick up the noise and bring it into the radio. the metal cage around the radio will keep the interference off of the wires inside the radio, the filter will keep out the noise coming in on the power cables.

you could also find a ferrite inductor from an old USB or printer cable. the one from my camera has clips that can be undone. if you can find one like this, put it on your power wires right where they go into the radio. (the ferrite inducter is the barrel looking thing on the cable - see pic)


pic doesnt seem to work. heres the link http://www.pricegrabber.com/info_picture.php/masterid=1272894
 

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Discussion Starter #16
bmonkey27 thanks for that idea! Ive got plenty of old cables laying around and had no idea thats what those little barrel things are for. Thanks for helping me be cheap! :thumbup
 

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Discussion Starter #17
bmonkey27 once again thanks for that idea!! It solved the problem almost 100%!! I took apart 2 old power cables and wrapped my power wires around the ferrite cores as close to the radio as possible. Then I wrapped a layer of aluminium foil and heavy plastic over the cores followed by a layer of electrical tape. Now there's just about as much noise as there is when the engine is off. Much appreciated!!
 
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