CB radio help. High SWR readings

Discussion in 'Communication & Navigation' started by chudly, Jun 18, 2017.

  1. chudly

    chudly

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    I installed the following in my 100 series
    1) cobra 75 wx st

    2) firering I just checked my order. I got the MU-r18 Amazon.com: Firestik Antenna FireStik MU8R18 18-Foot Single Antenna Coaxial Cable: Electronics
    There's another one that's K-8r8 Amazon.com: FireStik K-8R18 18 foot Fire-Flex coax cable with Fire-Ring: Electronics
    What is the difference between the 2?


    3) antenna spring Amazon.com: Firestik SS-3H Heavy Duty Stainless Steel Antenna Spring: Automotive

    4) labrak mount

    I got a SWR meter and my readings are high. Ch 1 and 40.
    When I flip the switch the needle drops from the end down to 3.

    What am I doing wrong here? I ran power for the CB to the cigarette lighter. I grounded the ground wire on the unit to a screw by the shifter. The box for the CB is just sitting under the center console not bolted down.

    Am I using the meter incorrectly? Did I miss something in the installation?

    Thanks
     
  2. Lucky Strike

    Lucky Strike

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  3. chudly

    chudly

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    Here's my setup with the fire ring

    20170618_014558.jpg
     
  4. Lucky Strike

    Lucky Strike

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    You can try running power & ground directly to the cb itself, also bring a ground wire to the antenna mount to see if that helps (just throw up a temp wire) also how tall is the antenna. it should be atleast 1' taller than the tallest object on your roof, rtt etc.

    what's your swr reading at channel 20?

    I had similar issues, I went from 2.5 to 2.1 just by moving my antenna another 14" away from my windshield. Apparently this curve is very common. I want a lower swr and it's either the cable (fire ring here too), height of the antenna, mounting location, or grounding plane
     
    Last edited: Jun 18, 2017
  5. 1911

    1911 chupacabra

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    Not much ground plane under your antenna; you may need a 1/2-wave antenna to get reasonable SWR. A lot of CB antennas are 1/4-wave and they need a good ground plane to work well.
     
  6. chudly

    chudly

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    I have a 4 ft firestik so it's about 2 feet over the roof of the car.
    What do you mean by bring a ground wire to the antenna?

    I didn't check ch 20 since ch 1 and 40 I was getting 3 at those channels.



    This is the antenna I have FIRESTIK II 4 FOOT 5/8 WAVE CB ANTENNA
     
  7. Lucky Strike

    Lucky Strike

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    You need to check channel 20 to make sure your getting a parabolic swr reading. if your getting the same swr reading across all the channels something else is wrong , i.e. pinched cable etc.

    You can just run a temporary wire from the ground of the battery terminal to the mounting bracket bolt to see if that helps the swr reading. if it does you don't have a good/strong ground at the bracket & as such at the antenna itself

    Also my radio says anything over 2 is not acceptable and since I only use the cb when I'm wheeling, I just spot tune it before I go out and adjust it so the low point it at the channel were using. it kinda sucks but it takes like 1.5 minutes
     
    Last edited: Jun 18, 2017
  8. 1911

    1911 chupacabra

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    A 5/8-wave antenna also needs a ground plane to reflect off of to tune up well. You will get a little bit of a ground plane from your roof, since the antenna sticks up 2 feet above it, but probably not enough. Try a 1/2-wave antenna; they are much more forgiving of (lack of) ground plane.
     
  9. chudly

    chudly

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    I'm wondering if my Labrak antenna mount is giving me a bad ground. I tried to test continuity and nothing. I sanded down the 2 holes for the mounting bolts and tested from there and then there was continuity. Do I need to sand the whole bracket down?

    my ch 20 is just barely lower if anything. It's almost all the same. I wonder if my SWR is bad? Is there anyway to check that?

    Also, I was able to hear some chatter when I was on ch 20. nothing really on the other channels.

    Might have to run to home depot or something tomorrow to pick up a wire and run it from the battery to the bracket and see if it's a ground issue.
     
  10. Lucky Strike

    Lucky Strike

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    You def have an issue. run a temp ground wire directly to the bracket. do not try to transmit with your cb, listening is ok.

    High swr on all channels is a significant indicator that you have a ground issue or other installation issue
     
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  11. chudly

    chudly

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    I sanded off some of the powder coat on the bracket by the firering and where it mounts to the car. I also removed the spring and my SWR reading went down to 2. By removing the tip of the antenna completely the reading went down a little bit more too. Is it possible that the antenna is just entirely too long?

    I also noticed the that reading is different depending on if I hold the meter horizontally or vertically. Is this a faulty meter?
     
  12. Lucky Strike

    Lucky Strike

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    Are your readings the same on every channel or are your results parabolic? your antenna has the adjustable threaded tip, you need to adjust it so the reading on 1 & 40 are the same or similar and you need to put the tip back after you adjust it.
     
  13. chudly

    chudly

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    So turns out my SWR meter was bad. Tested out a friend's meter before hitting the trails this weekend and got readings of 1.5-1.8
     
  14. Ravenkeeper

    Ravenkeeper

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    As stated above, your antenna mount needs to be grounded to the chassis. (Number 1 cause to HIGH SWR is lack of ground plane, but an ungrounded mount just adds to it.) I would leave the spring in, Firestiks are pretty rigid and the lack of spring can damage the "internal workings" of the antenna. I've smacked mine on a few parking structures, trees, and drive-thrus, when I had it on my '10 Ridgeline.
     
  15. Joel Kasper

    Joel Kasper

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    This may go without saying but look at the diagram and make sue you follow it. Also remember you may need to grind off some powder coat for a good ground connection.

    CB antenna.gif
     
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  16. Ravenkeeper

    Ravenkeeper

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    [​IMG]

    As stated above, I would put the spring back in, but right on top of the mount. This would put a larger base against the mount bracket.
     
    Last edited: Feb 18, 2018
  17. chudly

    chudly

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    oh this was resolved. I had everything right....it was a bad SWR meter giving me faulty readings. ha
     
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