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Odd CB radio problem

Discussion in 'Audio & Video' started by cko, May 11, 2011.

  1. May 11, 2011 at 6:57 AM
    #1
    cko

    cko [OP] Well-Known Member

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    So I know there are a thousand "CB problem" threads, but I can't for the life of me figure this one out. I have a Uniden PC78LTW and I'm running a 3' Firestik II with the Firering coax. The Uniden has a built in SWR meter.

    Symptoms: When I key the mic to tune the SWR, the needle stays still. The Tx/Rx button does light up when I key the mic, but there's no movement in the needle at all even when I move the calibration knob. The "antenna problem" light doesn't light up. There are no shorts and the mount is grounded to a bed bolt. The radio shouldn't be fried, as it worked before I transferred it from the 4Runner to the Taco. I know the mic and radio work to some extent because the PA attached to it also works.

    If I was a betting man, I'd think it was the antenna but as I said, the radio doesn't show a problem with the antenna.

    Anyone got anything? I'm rather frustrated.
     
  2. May 11, 2011 at 7:10 AM
    #2
    SoCaltaco65

    SoCaltaco65 Well-Known Member

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    Are you able to talk with anybody at distance ( 2 way comm)? not having an SWR meter move is not really a bad thing, keep in mind 1:1 Standing Wave Ratio ( SWR) is a good thing. Plus most CB's aren't equiped with the best electronics, the internal SWR circuit may just simply be marginal at best. find someone local with an inline SWR meter and re-check.
     
  3. May 11, 2011 at 9:37 AM
    #3
    RogueLeader

    RogueLeader Well-Known Member

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    If you have the antenna mounted on the bed, it may not be tall enough and you are reflecting the signal off of the cab. If the top of the antenna is below, or even with the top of the cab, it isn't long enough. That could be one of several problems. Also check the connectors. If you had to remove one of them to get the cable into the truck, it may not have been reassembled correctly.
     
  4. May 11, 2011 at 10:18 AM
    #4
    PreRunnerSeth

    PreRunnerSeth Well-Known Member

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    Have you tried using it? no movement of the needle indicates perfect SWR. You may just have a perfectly tuned antenna.
     
  5. May 11, 2011 at 11:05 AM
    #5
    EEtaco

    EEtaco Well-Known Member

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    Try an inline SWR/watt meter as someone else said, unhook your coax and check it with an ohm-meter for shorts, or contact the mfg because you might have blown your finals if you accidentally keyed the radio without the antenna on it.
     
  6. May 11, 2011 at 12:59 PM
    #6
    SoCaltaco65

    SoCaltaco65 Well-Known Member

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    Height would not have an effect on SWR for a moble antenna or at least an extremely minor one , merely direction gain, a vertical antenna is omni directional depending on its ground plan I.e. metal surfaces acting like counterpoise.
     
  7. May 11, 2011 at 1:09 PM
    #7
    bjmoose

    bjmoose Bullwinkle J. Moose

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    You can't have "perfect" SWR on every channel.

    Try it on channel 1, 20, and 40.

    If the needle moves a bit on two out of three, but not on the other one, then I'm with the ones who say you've lucked into perfect tuning.

    If the needle stays dead on all those channels, next step is to put an external SWR meter in line with the antenna and try that out.
     
  8. May 11, 2011 at 1:23 PM
    #8
    cko

    cko [OP] Well-Known Member

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    Thanks for the replies so far guys.

    I'm almost positive it's not perfect SWR. I didn't make it clear enough in the OP, but there is no movement in the needle--not during calibration, not when I flip to SWR, and not when I try to receive or transmit. When checking the SWR, there are two settings on the radio (and I presume on any other SWR meter): one for calibrate (where you turn a dial to match the needle to the right position) and one to flip to to determine SWR. There is no movement among either of those settings, and no movement when I actually try to transmit/receive. This is consistent among all channels, so I lean toward a problem rather than perfect SWR.

    I just took it out on the road again to get close to some truckers to check it. The only way I receive anything is by turning the gain all the way up and the squelch all the way down, in which case I can hear talking behind a lot of white noise. Even with volume at 10, squelch at 0, and signal gain at 10 the voices are mostly drowned out by noise. I receive one weather frequency nearly perfectly, but when it was on the 4Runner I could receive 3 or 4 with varying strength (not sure if this is relevant or the weather is on seperate frequencies).

    Finally, with the above settings I noticed a ton of noise from my vehicle--when I accelerate I get a loud drone, and when I let off the drone winds down. Sounds like a lot of interference from my vehicle is getting through.

    I'll look at buying an external SWR meter and trying that next. I may also run another ground to try and get a better connection, as I'm not positive that the one (the mount directly bolted to the bed bolt) is doing the trick. I read in another thread that someone had their ground to a separate place and was getting a lot of interference, then it got better when they ran it directly to the battery.

    If there's any other ideas, let me know. Thanks again for the help.

    Edit: bjmoose, I think it was actually your setup where you had an improvement with the battery ground vs. grounded to the frame.
     
  9. May 11, 2011 at 1:27 PM
    #9
    PreRunnerSeth

    PreRunnerSeth Well-Known Member

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    If the needle doesnt even move in calibration there is one of two things wrong, Either the meter is bad or you fried the radio. the fact that you can barely hear anything makes me want to think you had/have a serious antenna issue, but even with a serious antenna issue the needle should move and show a very high SWR. I hate to say it but I'm quite certain you damaged the radio.
     
  10. May 11, 2011 at 1:29 PM
    #10
    bjmoose

    bjmoose Bullwinkle J. Moose

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    You want your *antenna* grounded to the closest possible good connection to the body.

    You want your *radio* grounded back to the battery.
     
  11. May 11, 2011 at 1:53 PM
    #11
    cko

    cko [OP] Well-Known Member

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    I thought this at first, but I just don't see that being the case. The radio functioned perfectly in my 4Runner until one day I sliced the coax while folding the seats. I unplugged the power that day and hadn't touched it since (just back from 4 months in Spain). I get that it seems like the most likely option, I just can't see how it would happen. I'm gonna run a new ground from the mount in the bed tonight and see if there's any improvement. If not, I may have to drop the change on one of those little 520 units--I would just hate to drop the money on an entire radio if that's not the real issue here.
     
  12. May 11, 2011 at 3:29 PM
    #12
    PreRunnerSeth

    PreRunnerSeth Well-Known Member

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    If you sliced it and created a short or open and transmitted that way, you could have easily fried it.
     
  13. May 11, 2011 at 3:37 PM
    #13
    cko

    cko [OP] Well-Known Member

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    I didn't transmit after the cable was sliced.

    UPDATE:

    Played around a little with the radio power. Earlier I had it attached to a splitter in a cigarette plug, then I took out the splitter and plugged it directly into the plug.

    It helped, but now I only get intermittent function. For example, the needle will stay static while I receive transmissions, then after a few minutes (from jostling in the car? or some other cause?) it starts functioning perfectly as it should, with the needle moving when I key the mic and receive. Still getting tons of engine noise and a huge high pitched whine when I roll the windows up and down and hold the mic (even not keyed up). I'm starting to think bad ground on the radio could be a contributor?


    While it was working, SWR was at 1.7, 1.5, and 1.2 for channels 1, 19, and 40 respectively, so it's not the antenna. The problem is somewhere between the radio internals and power.

    Tomorrow I'm gonna chuck the cig plug adapter and wire up to the battery and see what happens. Will update tomorrow
     
  14. May 11, 2011 at 3:55 PM
    #14
    PreRunnerSeth

    PreRunnerSeth Well-Known Member

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    ok... this makes sense... bad connection. your voltage was probably dropping as you keyed up making things not function. wire it directly to the battery and i bet it works.
     
  15. May 11, 2011 at 11:19 PM
    #15
    FFRNDAN

    FFRNDAN Well-Known Member

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    I had a similar issue in my old Jimmy, I used the cig plug for power. This, if you know anything about radio install, is a HUGE no-no if you want a good install. You need to run a power and ground wire DIRECTLY to and from the battery for good, clean power. Remember to make sure your wire is of adequate guage. The power you get from your cig plug is "dirty" lots of noise is introduced from the alternator, spark plugs, ect. The battery acts as a sort of "buffer" minimizing this noise.

    Either that, or your radio is toast, I hope its the former :)
     
  16. May 12, 2011 at 1:42 PM
    #16
    cko

    cko [OP] Well-Known Member

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    Well today I hooked it up to the battery. No change at all. Still getting mounds of engine noise. When keying up, the needle still pegs hard left and no reaction when trying to tune.


    I'm thinking about cutting losses and getting a new radio, just hate the idea of spending a bunch on a new radio if it doesnt work either.
     
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