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Fm Radio Interference

Discussion in 'The Garage' started by dhcomp, Oct 16, 2005.

  1. dhcomp

    dhcomp 3/4 ton status Premium Member

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    Hey everyone,
    i know this is sorta a stereo question, but im posting it here because the cause probably isn't stereo related.

    I have a sony cd player thats a few years old, and now when the motor is running i get intereference in teh FM stations. Nothing has been altered on the truck since this problem started. Right after i fire up the truck the radio is clear for 15 -30 seconds and then it gets fuzzy. Plug wires are only like 2 years old (MSD superconductors).

    Where do you guys think this interference is coming from? Part of me wants to say the tuner on the deck is going out, but it sounds ok when the truck isn't running.

    Thanks!
     
  2. Blue85

    Blue85 Troll Premium Member

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    Actually, I do Automotive Electromagnetic Compatibility for a living.

    Generally, the first thing you do is address the noise source, but you could also check the radio grounds first in this case and look for any other obvious stuff. If this is a carb truck, the problem is very likely from ignition. Old plug wires are a common problem. Check the ground straps from the block to the body and make sure your ignition components are well grounded. I don't know who installed your ignition, but aftermarket stuff commonly gets installed poorly.

    Do you have any other aftermarket electronics on board? What does the AM band sound like?

    Now you should address the grounds on the radio (i.e. "the victim"). Make sure the unit itself is tied well to the chassis and that the antenna is well grounded (you may need to clean up the connection at the base). If you have any amps or anything else tied to the radio, disconnect them to see if it is a ground loop problem.
     
  3. dhcomp

    dhcomp 3/4 ton status Premium Member

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    Ok, ill check some of those grounds out. its a 94, so its not carb, and the ignition stuff is all stock...i just changed the wires.


    Thanks!
     
  4. bcrewcaptain

    bcrewcaptain Registered Member

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    yank the antenna plug from the back of the radio and see if you still get it..that way we can narrow it down to the antenna or the radio/power leads.
    9 times out of 10 something like that will either be a damaged antenna/antenna connector or an issue with the cable itself.
    FM, unlike AM needs the outer shield of the coax intact in order to work 100%
    if it has been damaged/shorting against the frame, or has been cut, it can certainly introduce that problem
    and if you're still using the fact ant, check all the adaptors and such inline as well!
    good luck, noise sucks
     

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