Antenna tuning question

Discussion in 'CB Radio Forum' started by dino360, Mar 2, 2014.

  1. dino360

    dino360 Bobtail Member

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    Mar 2, 2014
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    I've been away from the hobby for about 15 years and just getting back into it. I pulled my radios out of the barn and had them tested at a cb shop and they all test good. I'm working on installing a 29 ltd classic (already peaked and tuned) with a 3' firestik on the bed of my truck behind the cab. I'm using a 4"spring under it, 18ft of brand new rg8 coax, and tested the mount for continuity between the mount and truck frame.

    I started out with a 2.5 on ch1 and pegged out the radio Shack SWR meter way past 3 on ch40. I was able to get the readings as low as 1.8 on ch1 and about 3.2 on ch40. After several attempts cutting 1/4"at a time , the ch1 reading stated climbing back up and I now have 2.0 on ch1 and 3.2 on ch40. I stopped cutting for fear of ruining the antenna.

    Does anyone have any suggestions or advice for this situation?

    Thanks in advance
     
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  3. MsJamie

    MsJamie Road Train Member

    What's your reading on channel 19? (The middle of the band.)
     
  4. dino360

    dino360 Bobtail Member

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    Mar 2, 2014
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    I was checking ch20 which was originally about a 3.3 but has now dropped down to a 2.8.
     
  5. mike5511

    mike5511 Road Train Member

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    My experience is you won't get a very good SWR with that short of an antenna. If it is higher on 40 than 1, keep cutting a little off until it starts to go back up and then quit. If it is higher on 1 than 40, your gonna have to go longer.
    Some of these newer pickups don't have a very good RF ground. If that is the case with yours, you will have to get a 102" whip to over come it. You can also try bonding the cab to the bed with a couple of braided ground straps. I haven't
    found a cab that didn't have a decent RF ground yet so bonding may help a bunch. You will also get better SWR and performance if you mount that antenna about 2ft back from the cab.
     
  6. dino360

    dino360 Bobtail Member

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    Mar 2, 2014
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    I switched out to A 4' firestik II and was able to get the SWR down to a 1.9 on 1 and 40 with a 1.6 on 20. I have continuity between the mount and a bolt that holds the bed to the frame but should I run a ground from the mount directly to the frame?
     
  7. burnsey

    burnsey Light Load Member

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    Jan 24, 2014
    seacoast, NH
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    I have noticed that even though my multi-meter showed continuity between my antenna mount (also mounted on my pickup bed rail) and my pickup truck frame rail, I was still able to lower my SWR readings by grounding 1) pickup bed headboard to back wall of cab and 2) cab floor to frame rail. Was able to go from readings similar to yours to about 1.4 flat across the board (using a Wilson 2000). I simply ground some paint away, drilled a 3/32" hole, stripped a little bit of insulation off each end of a 12" length of 14ga stranded wire and looped the ends around a self drilling grounding screw which I inserted into each hole. Took less than an hour, including gathering my tools and putting them away. Sure doesn't hurt to try it if you've got the time to spare.
     
  8. dino360

    dino360 Bobtail Member

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    Mar 2, 2014
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    I made up a ground wire with an eye at each end which I will be running tomorrow from the mount directly to the frame. On my other truck (102 inch stainless whip with a4" spring) I had my SWR jump from 1.3 ch1 and 1.2 ch40 to 1.6 and 1.7 after running a ground from the mount directly to the frame.
     
  9. Razor3

    Razor3 Light Load Member

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    Things like this puzzle me. I read something on this fellas page http://truckers-more-cb-radio-range.com/page23.php that says to never run a ground from antenna. There's so much mixed information floating around. I think it boils down to personal trial and error experience.
     
  10. mike5511

    mike5511 Road Train Member

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    You don't want to run ground wires, you want to bond all your metal together. Bed to cab and both to frame. I'll bet if you get a couple braided bonding straps and get a good clean connection from the bed to the cab, You will see a difference.
     
    Razor3 Thanks this.
  11. Razor3

    Razor3 Light Load Member

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    Ok, I see what you're saying now. The challenge I will have to figure out is how to do this in a company tractor without making modifications to the truck.
    Maybe I'll get lucky, put the system together and get an swr reading of 1.1:1 right out the gate. haha Yeah, I know, wishful thinking.
     
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