Trap adjustment question for Hustler vertical antennas

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KE0CU, Aug 1, 2020.

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  1. KE0CU

    KE0CU Ham Member QRZ Page

    Hi. I'm re-configuring my Hustler 4BTV back to it's original state and right off the bat I'm having trouble getting the 10 meter trap to fall into place. I will have to make many measurements on it. Doing this would be easier if I don't have the rest of the parts for the lower bands attached. I mean leave off the rest of the tubing and traps above the 10 meter trap off. Can I do this, at least to get the 10 meter trap in the ballpark?

    Thanks!

    Hank/ke0cu
     
  2. K8JD

    K8JD Ham Member QRZ Page

    The lower piece should be close to a ten Meter quarterwave or 8 Ft.
    BUT having the rest of the elements in place will make it tune a bit different . So tuning will have to be redone if you first, try it, with just the lower tubing alone.
     
  3. KE0CU

    KE0CU Ham Member QRZ Page

    Hi K8JD,

    I'm using just the lower 72 in tubing with the 10 meter trap.
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    It's not effective to tune it that way. Without the tubing above the trap, the trap isn't "trapping" anything, it's just end-loading the section below it.

    Normally Hustler traps require no tuning at all; the way the factory shipped them, they're perfect unless someone already pried the upper plastic seal off and changed the aluminum trap cover (which is the capacitor) to a different position -- not recommended by Hustler. Normally, the "tuning" is accomplished only by changing the aluminum tubing lengths, which is why they're adjustable in length.
     
  5. WS9K

    WS9K Ham Member QRZ Page

    keep it fully assembled
    It takes a little patience, but it's worth it.
    an antenna analyzer is handy here.
    have you deployed radials ?
     
  6. KE0CU

    KE0CU Ham Member QRZ Page

    I am using an MFJ analyzer. For reasons this and the other traps have been adjusted outside the manufacturer’s specs. I just trying to find an expedient way to tune them. I started by adjusting the 10 meter trap to DX Engineering specs a little over 9 in from memory but it was way off. Perhaps the trap has a defect. All these traps and tubes were originally used at this location with radials. Just trying to get back to original setup from many years ago.
     
  7. W2ASC

    W2ASC XML Subscriber QRZ Page

    Attached has factory dimensions of Hustler BTV traps. That should get you in the ballpark.
     

    Attached Files:

  8. N3PM

    N3PM Ham Member QRZ Page

  9. KE0CU

    KE0CU Ham Member QRZ Page

    Thanks for all the links, ideas, and support for this problem. I've moved all the trap covers and lengths to those suggested and resonance is pretty good on 15, 20, and 40 meters. 10 meter swr in the vicinity of 28.4 MHz is pretty flat but still about 2.5:1. Interestingly there is a sharp dip to a low swr at 48 MHz! I don't think things are quite right but for now I'll leave things as they are and use my tuner.

    Hank/ke0cu
     
  10. N5PNZ

    N5PNZ Ham Member QRZ Page

    I just went though this with my 4 btv. When ground mounted with radials it tuned perfectly. Moved to a roof mount with radials and 10 and 40 would not tune to the portions of the band that I use. I had read that elevated mount may require the 10 meter trap to need retuning. With the help of a NanoVNA I was able to get the trap adjusted to what I need. The trap is very sensitive to adjustments. 1/4 inch adjustments would cause significant movement in reasonance. My last adjustment was only 1/8 inch. The instructions I was following said to keep everything above the 10 meter off the antenna when tuning the trap. Once you get 10 done all the other bands need to be reset anyway. Never did get 40 tuned the way I wanted it,but it is tolerable. It tunes way lower in the band than I like. It is as short as I can make it.
     

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