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Hum from HV in CB (paging the hams)

Discussion in 'Gen 4 Prius Accessories and Modifications' started by Ranko Kohime, Apr 6, 2018.

  1. Ranko Kohime

    Ranko Kohime Member

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    I installed a CB (President McKinley) in my Prius, and at first I was using a Wilson 500 magmount, with the cable entering the passenger door, and snaking around behind the passenger seat, and being loosely coiled around the footwell before connecting to the radio.

    Reception was great, but I wasn't happy about having to remove and re-do the cable each time I went to the car wash, so after a windshield chip and a dog jumping up and scratching the drivers door, I mustered the courage to drill a hole in the roof to install a Wilson 1000. Which works great, 1.0:1 SWR and reaching out just as well as the mag mount (5-10 miles typically)

    However, when I'm depleting or charging the battery, I get a lot of noise and hum in the CB now. (1, and sometimes 2 bars of pure noise) I have the antenna cable snaking from the center of the roof to the B-pillar, forward and down the A-pillar, then behind the glove box. The radio itself is connected directly to the 12V battery through a distro block in the center console.

    Would I be better off running the cable down the B-pillar, and under the carpet, or am I looking at a grounding issue? The Wilson is grounded to the roof, but I'm not certain the roof itself is grounded.
     
    #1 Ranko Kohime, Apr 6, 2018
  2. KK6PD

    KK6PD _ . _ . / _ _ . _

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    it would do you no good! it's not a antenna problem, but a power problem. you have dirty power when hooked to an external charging system. ideally you would want to run power, 2 lines, plus & ground, directly to the battery terminals. but with 5 watts out, there's not that much current draw. the fact that the problem clears up when you stop charging kinda explains it!
     
    #2 KK6PD, Apr 6, 2018
  3. Ranko Kohime

    Ranko Kohime Member

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    I'm not sure I understand... Are you saying I would have to power the CB from a separate battery to avoid this interference?

    I'm already running a dedicated plus and negative directly to the 12v battery
     
    #3 Ranko Kohime, Apr 6, 2018
  4. sam spade 2

    sam spade 2 Senior Member

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    That's not what he said at all.
    This is a Gen 4 sub-forum.
    No external power allowed. ;)

    But.....1-2 bars of electrical noise is probably not bad, generally.

    IF.....he did not have that happen with the other antenna configuration, then it IS highly likely that he has an antenna problem.
    But it might not be something that is easily fixable.
    Just turn up the squelch a bit.
     
    #4 sam spade 2, Apr 6, 2018
  5. KK6PD

    KK6PD _ . _ . / _ _ . _

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    considering CB is Amplitude Modulation, of course you are going to pick up on any ole noise around!
     
    #5 KK6PD, Apr 6, 2018
  6. William Redoubt

    William Redoubt Senior Member

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    That's right. Old am radio tuned to a place on the dial where there is no signal is the best harmonic distortion meter made for the money.
     
    #6 William Redoubt, Apr 6, 2018
  7. Ranko Kohime

    Ranko Kohime Member

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    Wouldn't stop me from hanging the longest extension cord out the hatch while I drive. :ROFLMAO:

    That's with the RF gain cranked down a fair bit. If I had the RF gain maxed out, my gate would probably be open continuously at any squelch setting.

    That's my thinking, I'm just hoping there's an easy reasonable solution.
     
    #7 Ranko Kohime, Apr 7, 2018
  8. sam spade 2

    sam spade 2 Senior Member

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    That's worse than your first report made it appear.
    I'm now wondering how you determined that your effective "range" is about the same as with the other antenna.

    But don't ASSume how bad it will be with the gain all the way UP; try it and see.
    Also be sure your have any automatic noise limiter switch in the ON position.

    And be sure that the coax shield is actually connected to ground at BOTH ends.
    Unplug from radio and check the shield resistance to ground.
     
    #8 sam spade 2, Apr 7, 2018
  9. Ranko Kohime

    Ranko Kohime Member

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    Sitting in a specific location, talking to a friend at another specific location, and achieving the same received signal on both sides, using each antenna.

    Noise Blanking and Automatic Noise Limiter are both on. Cranking the RF gain gives me between 4 and 5 bars of static, out of a possible 12. That requires about 2/3 squelch.

    Hmm, 1/2 ohm to ground... Time to run a ground line to the roof, I guess.
     
    #9 Ranko Kohime, Apr 7, 2018
  10. sam spade 2

    sam spade 2 Senior Member

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    The point IS.......that if your tests did indeed yield similar range, in BOTH directions, then having the squelch set a bit higher really is NOT causing a significant problem.

    The length of the shield wire might yield 1/2 ohm.
    Measure from roof to negative battery terminal before running extra wires there.
     
    #10 sam spade 2, Apr 8, 2018
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