couple of issues with radio

Discussion in 'CB Radio Forum' started by gunner76, Apr 16, 2014.

  1. gunner76

    gunner76 Medium Load Member

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    I'm having a couple of issues with my radio and have no clue how to work on these things other than the basic adjustments. First is I'm getting a whining noise coming through the speaker when ever the engine is running and can't seem to figure out what is causing it? Second problem the other day I was trying to talk to the guy behind me and he got on the radio and said I have a modulation problem because he could hear the mic key up but couldn't hear me talk. Any idea where to start with that? I have the dynamic turned all the way up and it didn't make a difference.
     
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  3. Steveo412

    Steveo412 Light Load Member

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    Whining sounds like a ground problem.
     
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  4. zukeepr

    zukeepr Bobtail Member

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    The whinning is coming from the alternator. Ground is the issue. Check coax and bracket for antenna. If its corroded change it. If it looks ok run a ground wire from bracket to frame. Could be something simple like coax lose at either end. But if your modulation is low I'm going to bet its in the antenna or broken coax
     
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  5. BigBearNY

    BigBearNY Light Load Member

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    OK grounding might help th whine. BUT have seen many cases where it wasn't enough. An inexpensive noise filter should help, if that's the case.

    No audio:

    Are yous using a power mike? Check battery or swiych to stock mic.
    Is mic. good? Verify on another compatible set or borrow an identically wired mic.
    Check wires in the mic connector, are they all connected and unbroken?
    Open set and are all wires to mic. connector solidly connected.

    If all the above appears OK... You might have a malfunctioning audio IC chip. Though this is least likely, as usually when these chips go, receive and transmigt audio are not present. But it is possible that the chip has malfunctioned.
     
  6. 43mack

    43mack Bobtail Member

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    what if the noise is coming through the antenna? grounding nor filters will "rectify" this issue.

    the rectifier in the alternator is most likely the culprit and the only fix for that it to repair or exchange the alternator
     
  7. BigBearNY

    BigBearNY Light Load Member

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    Nope... Gunner 76 specified a whining noise. Antenna noise manifests as a "staticky" noise and can often be cured with one of those little balls that attach with a set screw to the tip of the antenna. Better yet Wilson and K40's are designed to eliminate this noise. Many other antennas now come with the little ball attached.

    Now a true whine is surely alternator emitting some spurious harmonics/RF emissions. However the likelihood they are transmitting through the engine compartment to the radio is highly unlikely. It is more probable the power cord is acting like an antenna and transmitting noise through to the radio. I disagree on the diode. If that was the issue you would see a way high or way low reading on the gauge, or a rapidly fluctuating up and down movement corresponding to engine RPM's. Of course I am assuming that would have been mentioned. Also the am/fm radio in the car would be very noisy too if the diode were bad

    Of course it's easy enough to check without replacing the alternator. Professional type battery/alternator testers include a separate function that indicates bad diodes. Places like AutoZone, Pep Boys or R&S Strauss will dun the test for free.... Of course if you have a regular mechanic he would most likely have a tester like this too.
     
  8. gunner76

    gunner76 Medium Load Member

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    quick update on my problems. I went ahead and replaced the coax, antennas(went with Wilson 5000's), and mic(went with a road King 56) and now my cb works good,but I still have the whining problem that needs to be addressed.

    As far as it being a bad alternator diode I don't think that is the issue because I had to replace the alternator and the noise has been there with both of them. I also noticed that when the turn signals are on the whining fluctuates as the flashers go on/off. I checked the ground that goes from the mirror bracket to the door and it looks good, but the ground strap the goes from the door to the door jam is broke. Could this be the problem?
     
  9. Ridgeline

    Ridgeline Road Train Member

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    Two quick things,

    1 - the alternator needs a ground from the case to the engine and the engine to the chassis. This sometimes this causes issues. The diode pack is not the problem, if it was failing, then the alternator would also have issues. The issue you have with the turnsignals seems to confirm that it may be a alternator/chassis ground issue.

    2 - if nothing else, get a dc noise line filter, put it into the power line (both negative and positive). Good ones are not cheap.

    http://www.powerwerx.com/oem-connectors/dc-line-noise-filter-oem-t.html
     
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  10. BigBearNY

    BigBearNY Light Load Member

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    You know... This is probably the best solution. IF you are getting out good and there are no other problems... This saves ALPOT of time. They do work. I have to admit if noise is the only problem, I have gone pretty quick to a noise filter solution in the past. You can spend way too much time trying to fix the problem and never find it. Some noise issues, from what I have seen, refuse to be solved.
     
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  11. gunner76

    gunner76 Medium Load Member

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    thanks guys, I'm going to go ahead and order that noise filter instead of trying to chase down a gremlin that I may never find.
     
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