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Feedback when Stereo is on.....

Discussion in 'Communication (CB | GPS | HAM)' started by 2Dogs, Sep 9, 2003.

  1. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    All,
    So when I hit hit the mike button with the stereo on I get a piercing high pitch squal from the rear speakers.

    I am guessing ground from the rear speaker amp.....?

    Any ideas?

    Thanks!
     
  2. rebelk5frk

    rebelk5frk 1/2 ton status

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    yeah, turn off you stereo before you try to talk on the radio. /forums/images/graemlins/grin.gif

    The problem is the RF is getting picked up in the audio lines going into the amplifier and is in turn heard by the microphone causing the feedback squeal. There isn't an easy way to get rid of the problem other than to turn off the stereo equipment while talking. (can't hear both at the same time very well anyway)

    You can try routing your wires differently, use better sheilding on all cables, etc, etc, etc, etc. All the work trying to remove the feedback will cost you a lot of time, aggrevation, and possibly money and may not ever be solved.

    Sorry I don't have better news for ya' but that's the way it normally is.
     
  3. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    OK thanks. But that is a bummer /forums/images/graemlins/frown.gif
     
  4. mrbill

    mrbill 1/2 ton status

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    So if I'm just starting to wire both my stereo and CB what can I do to protect against this? Shielded speaker wire?
     
  5. rebelk5frk

    rebelk5frk 1/2 ton status

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    Shield, shield, shield. It helps to keep the power, audio, and RF cables seperated as much as possible. Try to keep from crossing any power or audio wires with the coax.

    High quality double shielded coax and a properly grounded and matched antenna helps alot too. A lot of problems are caused with magnet mounts because they don't have a decent RF ground so a lot of RF ends up coming back inside the vehicle radiating from the shield of the coax.

    Another sometimes effective trick is to wrap and/or tape to the body all the audio/power cables with foil tape. The kind often used for ventilation systems. It acts as yet another shield to the cables.

    Using as short of wires as possible help decrease the chances of picking up stray RF.

    Keeping RF out of audio systems can be a bigger pain than eliminating ingition/alternator noise. Sometimes it doesn't take anything special then other times, no matter what you do, you can't keep it out.
     
  6. 4wood

    4wood 1/2 ton status

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    Is the insulation on a coax or speaker cable the shielding or is there something special you have to get as an extra?
     
  7. rebelk5frk

    rebelk5frk 1/2 ton status

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    The insulation is just that... insulation. The sheild on coaxial cable it the outer, normally braided, wire. Some higher quality cable will have extra sheilding such as a layer of foil, tighter braided wire, two layers of braided wire or some combination.

    Some cable will have it printed on the insulation how much it is sheilded. Most RG-58 is normally 95% shielded, for example. If it's not printed on the insulation then you have to find the specifications elsewhere.

    For extra sheilding you can do like I mentioned before, use foil tape to cover/hold down wires.
     

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