Distance issues

Discussion in 'CB Radio Forum' started by Danger07, Sep 1, 2012.

  1. Danger07

    Danger07 Light Load Member

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    Hey y'all so im guessing my result will be a new antenna but looking for any hints or tricks ya may know before doing that... i have a cobra 29lx. My ground is good cal/swr are where they should be, but in good flat terrain i seem to only get a mile and a half transmitting and receiving distance.... i have my cb hardwired and its run to a fiberglass antenna. The antenna goes about 2.5' above the cab of my truck... The antenna does have some of the wire exposed in a couple spots from the outter shell wearing off. Any thoughts?
     
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  3. mike5511

    mike5511 Road Train Member

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    New antenna, as long as you can get away with, at least 4ft - 6ft. Possibly a new coax. Recheck SWR. Test again on a nice quiet day, or night when the noise level is low, and probably on another channel other than 19.
     
  4. Danger07

    Danger07 Light Load Member

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    Thanks, I'll try the coax first, i know its not the best quality one... is there a brand you recommend?
     
  5. cadillacdude1975

    cadillacdude1975 Road Train Member

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    belkin is about the most used out there. they make cable/wire for almost every possible application.
     
  6. Xcis

    Xcis Medium Load Member

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    Danger07, if possible, check your SWR reading with an external meter but using a dummy load(s) instead of the antenna(s). The coax and antenna ground plane are not the problem if the reading is 1.0.
    .
    Can you borrow a different antenna from a friend and re-check the SWR reading and distance?
    .If you still have a problem with distance, you may need to have the radio checked by a competent tech (key word competent) to see that the power transistors (finals) are not damaged.
     
  7. handlebar

    handlebar Heavy Load Member

    Dangerguy, I'd try *all* of the suggestions above before you start "shotgunning" things by just throwing $$$ at everything. As Xcis proposes, try swapping out a real dummy load for the antenna at the far end of the coax. If the SWR is identical to what it was with the antenna, then the antenna is apparenntly OK. But it doesn't mean the coax isn't full of water, or shorted (or open) at just the right length from the radio to make a trap, then capacitively coupling a bit of signal across the small gap to the rest of the coax and on to the antenna. Because of that, it'd be great if you can also borrow a spare coax jumper to do two tests with: from the radio to the dummy load to check your indicated power output (for reference), and from radio to antenna to compare your range under the same quiet channel, low noise time of day as earlier mentioned so you're not trying to test on a Super Bowl conditions kind of time.
    Also remember that a fault in either the transmitter OR the receiver will be perceived as a "low range radio", because as soon as you get to the limit of whichever is shorter, you'll lost your two-way range, and won't be able to tell it you can't hear him/her/it, or he/she/it can't hear you.
    But it's important to keep what's known as the "scientific method" in mind as you do your test: change only one variable at a time, so you can tell which one is responsible when a change is perceived.
    Hope this helps.
    73,
    Handlebar
     
  8. Danger07

    Danger07 Light Load Member

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    Thanks for all the suggestions. Ill get to work! Normally i'm the one my friends come to when they want one installed or they are having issues with their radios. Ill give thses methods a go one at a time and see what i get from it. Thanks y'all
     
  9. mike5511

    mike5511 Road Train Member

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    Post what you find.....
     
  10. Danger07

    Danger07 Light Load Member

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    Ok do i honestly have not had the time to put these suggestions to use due to work... i did however get paid and went out and got a new coax... big difference! I went to the same place ihad tested before with my same buddy helping me text and w my rf gain all the way up i could still transmit and recieve at roughly 4 miles away.

    However i do have a new issue... being half asleep while buying my new coax i got a dual coax cable. I am now running dual whips on the bed of my pick up as before ionly used the one as i read that on a pick up truck the dual antennas can interfere with transmitting... since running dual antennas i have recieved an antenna warning on my cobra 29 lx when i tramsmit, when i just dead key i do not get the warning but only when i talk. I never got this running the single antenna. The store wont exchange the coax as its out of the packaging so is there a way i can just run the single antenna with the dual coax? Ive heard not to just leave the one coax end vacant and i saw why when i did it and the swr went sky high on me... is there a killer plug or end cap or something i can get?
    (####### mistake... i know... i know....)
     
  11. handlebar

    handlebar Heavy Load Member

    At this point, you have to terminate the second branch with a 50 ohm load of some kind. Since you've already got dual whips and mounts, etc., you might as well go ahead and go with symmetry and use the second antenna to terminate the second antenna feedline. Just because you won't gain any advantage over a single antenna with a single 50-ohm feedline doesn't mean you'll do any worse, since you already have the 75-ohm (or 72-ohm) harness for the duals. The only other choice would be to buy a dummy load to show a 50 ohm load to the connector on the "empty" end of the harness feeder. The power would get wasted, and the one working antenna would get just under half of the available power from the radio. At least by putting an actual antenna on there, you'll be splitting the output from the radio about in half and sending about half to each of the two antennas; I'm saying "about" because there's always a teensy bit of loss in any divider network, and in the impedance matching transformer that the harness makes to go from the 50 ohm output of your radio to two 75-ohm cables in parallel, then having the far end of each couple to a 50 ohm antenna.
    But every antenna system has some compromises. Hams have put up with them for years. We just put up what we've got room for, get as much of our available power as we can into them (often ignoring the physics) and get on the air. Even a horrible mismatch will get *some* signal into the ether.
    Sorta like the scientists who calculated that a bumblebee wouldn't be able to fly, but bumblebees don't under stand flight physics, so they just fly anyway.
    Since you already have the dual antennas, and have to terminate the second harness end, I'd use the second antenna. You'll probably find it works fine.
    73,
    Handlebar
     
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