couple of issues with radio

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

  1. 43mack

    43mack Bobtail Member

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    disconnect the antenna from the back of the radio and see if the noise stops, if it does nothing you do to the alternator will make any difference because it's an RF issue and not a line issue.

    the only thing you can do in this case is to replace the alternator or the "faulty" components in that alternator
     
    gunner76 Thanks this.
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  3. sodapop243

    sodapop243 Bobtail Member

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    Do you know if the noise filter will get rid of fuel injector noise.
     
  4. 43mack

    43mack Bobtail Member

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    do the antenna check
     
  5. BigBearNY

    BigBearNY Light Load Member

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    In general, any noise that disappears when the ignition is off will be eliminated by a good quality filter. Other noises which come through then power lead will also be eliminated.
     
  6. Mudguppy

    Mudguppy Degenerate Immoralist

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    Hate to hijack, but I'm having issues as well. I run dedicated OS/OW loads, and we converted two "regular" daycabs into haul trucks (including adding third drive air axles, etc.) Unfortunately, we haven't had enough down time since the conversions to install the LED light bars we ordered several months ago. So until we can do so, we run single LED magnetic plug-in lights for our warning strobes. When pulling a load as soon as I turn the light on it causes static in a rhythm every time the light blinks. It causes me to have to turn the squelch knob 1/8 to 1/4 turn back to get rid of it, therefore drastically reducing the distance that I can rx. Does anyone know if the aforementioned noise filter will help, or do I just have to suck it up and deal with it until the permanent light bar gets installed? Also, will I possibly have issues with the permanent one as well? Thanks in advance!
     
  7. handlebar

    handlebar Heavy Load Member

    I concur with my learned colleagues above. With the antenna disconnected at the radio, nearly the only route for noise to enter the radio is via the power lead. Unless you feel like making a simple filter with an iron shackle, some windings of wire, and an electrolytic capacitor, the inline filter mentioned above *should* clear most things.

    Some noise sources are not necessarily going to be completely eliminated by a DC filter. Noises, like diseases, are usually better cured at their source (like by excising a poisonous stinger or irrigating a wound) than by treating the body after it's sick with antibiotics and vaccines. Fuel injectors, wiper motors, electric door motors, and the like, can often have their transmitted easily eliminated *at their sources* rather than downstream at the radio by fastening a capacitor of round 0.05 mfd with the shortest leads possible "across" their power leads, i.e., from the positive to negative voltage terminals that run them, right at the offending device. That capacitor shorts the noise just about where it's being generated right to the vehicle's "D.C. ground", so it never gets a chance to run back down the "big red wire" from said motor into the vehicle's wiring, whence it can wreak havoc with anything that can receive a.m. pulse-type noise. And unless your be-bop radio is set for a weak radio station, your CB (or a.m. ham station, if you're as olde a pharte as I am) is about the only device likely to be susceptible.
    But the DC filter is far and away the easiest and most convenient to install. It may not kill *all* your noises; if not, and unless you're comfortable choosing capacitor types for bypassing noise sources, I'd toodle myself off to a commercial two-way shop, pay the likely-more-expensive rates than a "turn and burn" roadside CB shop, and get it done right by folks who are (typically) FCC licensed to work on pretty sophisticated gear.
    Or an aircraft A&P mechanic or avionics tech, but expect to pay even more. Civilian aircraft radios are almost universally a.m. When most airplane radios are limited to about 3 watts output and even with what can seem like unlimited line-of-sight communications paths between radios, it doesn't take much noise generated by the engine to render their receivers pretty numb until they're *very* close to other aircraft competing for the same airspace.
    Hope that helps,
    73
     
  8. handlebar

    handlebar Heavy Load Member

    As mack says, alternators can fail either in their construction or in the manner in which their cases are grounded to the engine/chassis/battery's negative terminal. One shorted diode in an alternator can fail to rectify a pulse as the alternator turns, leaving residual AC on the line to the battery. An auto electric place can usually check an alternator and its diode pack easily (and free). I'm used to just putting an oscilloscope on the output lead of the alternator lead and looking for missing positive-going pulses (or pulses accompanied by a negative-going component).
    But assuming the alternator's diode array is intact, making sure the alternator's case is appropriately grounded as already noted can fix a wealth of ills.
    73
     
  9. MsJamie

    MsJamie Road Train Member

    Maybe.

    Since you are running temp lights, try this:

    While the lights are mounted on your truck, plug them in to a different power source (another truck), and see if that makes a difference. If it eliminates the interference, then it's a power line issue. If not, it's an RF issue. Running the CB off a separate battery will also work.

    You can always try making a temporary line choke (filter) by wrapping a good chunk of the cord (several feet) around a chunk of metal (steel/iron). Something like a piece of iron pipe. See if that reduces the interference. This can be either the light OR the CB cord.
     
  10. Mudguppy

    Mudguppy Degenerate Immoralist

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    d let

    *tips cap*
    Thank you ma'am! I'll give 'em a try tomorrow and letcha know. And I thank you for my heavy haul partner as well, who's having the exact same issue (trucks are identical Petes)
     
  11. sodapop243

    sodapop243 Bobtail Member

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    I'll do the antenna check and hopefully that works and I'll get that filter. Appreciate the help.
     
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