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102" mobile mount not working. Advice please

Discussion in 'CB Antennas' started by Red 5, Mar 1, 2015.

  1. Red 5

    Red 5 New Member

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    Hello all, first post. Pardon my ignorance, but something's fundamentally wrong here. I'm pretty sure it's all the pieces that make up the mounting of this... That and the ground /ground plane. When I check the SWR as it's pictured (including a ground to the frame of the suburban) it's off the charts. If I take it off the mount, connect it to the coax and hold it in my hand, the SWR drops to almost nothing. That is true if I connect the 102" to the Wilson magnetic mount on the roof. Of course you can't drive around with a 102" on a magnetic mount.
    The radio is a uniden am ssb, (can't remember the model number) it's something like pc122? Anyhoo, thanks in advance for any input.
    6169 red 5 socal on the side.


     

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    #1 Red 5, Mar 1, 2015
    Last edited: Mar 1, 2015

  2. binrat

    binrat WDX Club Coordinator
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    Red 5 likes this.
  3. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    It hard to tell in your pic but it looks like you have the white nylon insulator bushing on the wrong end.

    The base of the antenna should sit on top of this insulator and the insulator should sit on top of the mounting bracket. See pic below for an example.

    The antenna isn't grounded as people may think, the antenna bracket is grounded from the shield of the coax then grounded and bonded with the vehicle with a solid mounting scheme.


    [​IMG]
     
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  4. vkrules

    vkrules Sr. Member

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    as above .Looks like you grounded it out
     
    Red 5 likes this.
  5. Red 5

    Red 5 New Member

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    Thanks for the replies! Yes, there is an insulator there, but it's thinner than the one in your picture fourstringburn, and I'm quite sure that it's mashed down and not doing what it's supposed to.
    I will get the right one, or another one so it will be insulated properly.
    I'll give it another shot tomorrow, and post results. Thanks again!
     
  6. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    Looking at pic one, you have the 1/2 inch tall locknut causing your antenna problems.

    your insulator is ok.

    Take that locknut out and push the male end of the coax fitting thru the hole on the antenna bracket and place the nylon insulator on top of the bracket so the antenna sits on it, then you are good to go!
     
    tecnicoloco likes this.
  7. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    Here is the best diagram showing how to mount to a antenna bracket. In your case the 3/8 threaded adapter will be that heavy duty antenna holder you have. If that antenna holder is female, then you don't need the extra threaded adapter pictured here and vice-verse if it is male.


    [​IMG]
     
  8. Red 5

    Red 5 New Member

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    That is a great diagram! Thanks!
     
  9. M0GVZ

    M0GVZ Sr. Member

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    Not the most efficient way of mounting an antenna from a performance point of view. It may have good DC continuity but it doesn't make it a good RF ground.

    http://www.k0bg.com/antmount.html
     
    Red 5 likes this.
  10. Red 5

    Red 5 New Member

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    Great article, I'll need to go over it a few times. Was thinking about making a hitch mount. Also wondering if this would help it's current location.
     

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  11. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    No! Don't waste your money. For one that isn't a ground plane because it mounts on the hot side of the antenna, not the ground side. It also is far too short to be a ground plane radial since radials need to be 1/4 wavelength of the frequency your antenna is.


    Is this antenna on a semi truck mirror post?
     
  12. Red 5

    Red 5 New Member

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    It's a uniden ground plane I found on eBay. I figured since it's uniden, it's probably legit, no?
     
  13. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    It is a real product but it is snake oil!

    If it was a good product, everybody would be using them.

    Like I said, this doesn't mount to the ground side of your antenna, therefore it isn't a ground plane.

    It will add to your antenna length which isn't a bad thing except your running a1/4 wave antenna and that so called ground plane will probably make your antenna to long for CB frequencies.
     
    midnight special and Red 5 like this.
  14. Red 5

    Red 5 New Member

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    Thanks for the advice!
     
  15. jazzsinger

    jazzsinger Bullshit Buster

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    I'd be careful rg58c/u is marked with mil-c-17f/g or M17/28.

    I'd avoid anything that says rg58 type.

    And so you can solder the braid properly I'd go for amphenol 83/822 or amphenol 83/1sp both with an amphenol ug175 reducer.

    If body/tip is nickel plated file tip or holes to base brass and tin with solder to get a good contact.

    I usually mark holes on reducer when its screwed in and file those parts to base brass too then tin. Ensures you get a good solder joint.

    If your not confident soldering braid use good quality ps gland pressue plugs for 5mn coax.

    Depending which plugs you go for any silver plated parts will usually take solder ok.

    Heat the plug and take solder to work. Don't put solder on plug and take iron to solder.

    Hope that helps.
     

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