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How to tune a new 500 penetra

Discussion in 'CB Antennas' started by Jackal9999, May 5, 2018.

  1. Jackal9999

    Jackal9999 New Member

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    I put it together 22 feet 4 inches and the swr is high 3.5 on 1 and 2.5 on 40 how do I adjust this thing for a decent swr this wa
    S with a mfj259.


     

  2. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Welcome to WWDX Jackal9999! You have come to the right place. Although I am not familiar with your antenna, I am sure that someone who is will stop by sooner or later.
    Chris
     
  3. firerunner

    firerunner Active Member

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    where do you get a 1:1 match?
     
  4. firerunner

    firerunner Active Member

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  5. binrat

    binrat WDX Club Coordinator
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    I think too short as well.
     
  6. ExitThirteen

    ExitThirteen Grumpy and Cranky

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    It should be either 22 feet, 6.5 inches, or 22 feet, 9 inches. I can't remember 100% which measurement it's supposed to be, but I think it depends on if the little "static bars" on the tip of the antenna are at 90 degrees or 45 degrees... if they are 90 degrees, should be around 22 feet, 6.5 inches. If they are at 45 degrees, it should be about 22 feet, 9 inches. Thereabouts.

    ~Cheers~
     
  7. Road Squawker

    Road Squawker Sr. Member

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    what freq is "X = 0"...... or the lowest number?
     
    rabbiporkchop likes this.
  8. Ranch55

    Ranch55 Well-Known Member

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    1) Recheck all the horizontal radial length measurements ...... 105"
    2) Recheck and verify all the vertical section measurements .......

    What point at the top are you measuring from ?
    What point at the bottom are you measuring to ?
    Did you thoroughly clean all the joints before assembly ?

    Make sure that you have good coax ........

    Total antenna length from top of "top hat" screw to bottom of radial bracket (not bottom of coax connector) should come in at 22' 2-1/2" to 22' 4" for a frequency of 27.205 approx.
    The last Penetrator 500 that I tuned (about three months ago) ended up tuned on frequency 27.355 mhz at a total length of 22' even.
    R equaled 51.8 ohms ...... X equaled -0.48 ohms .... VSWR was at 1.02 ~ 1.04
     
    Robb likes this.
  9. JAF0

    JAF0 New Member

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    The trouble with the new Penetrater is the top hat rods aren't bent down at a 45* angle like the early P500, they're sticking straight out it which will act as a capacity hat, electrically lengthening it past .625 wave lengths.
    I junked the top hat & lengthened the radiating element to 267" and got a perfect match, with X = to less than 3 from ch1 to 40.
     
  10. Ranch55

    Ranch55 Well-Known Member

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    On the new model Penetrator 500, I will bend the top hat rods down at a 40 degree angle from horizontal.
    This has worked well and allowed for very good tuning .......
     
    JAF0 likes this.
  11. JAF0

    JAF0 New Member

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    So what did you find was the difference, if you tried it both ways?

    I don't use the top hat rods at all. Why defeat 15" of the top of your vertical by inverting the top 9", cancelling it along with the 6" inside the downward 45 degree rods?

    Just dump it and lengthen it to a full 267" vertical, centered on ch.20 for the best possible performance.
     
    hotrod likes this.

: Tor

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