Hy-Gain VB-214FM tuning for 144.200

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by K5TRI, Aug 31, 2017.

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  1. K5TRI

    K5TRI XML Subscriber QRZ Page

    Looking for the collective wisdom of the Zed hive-mind regarding this antenna.

    It's advertised as covering 144 - 148 MHz. When I put it together and tested it (before mounting it on the roof tower) it was resonant in the upper portion of the band around 147 MHz. I guess this could be expected given the model name. The problem however with this design is that it's the Beta match Hy-Gain uses and their recommendation to cut the elements for tuning.

    How do I cut an element for tuning which is already too short? Does anybody have experience with making this antenna work around 144.200? It seems both elements and the balun need adjustment.

    Would be fantastic if anybody could provide some measurements. I made new elements for the driven element based on Hy-Gain's sheet but of course no dice.
     
  2. W0AAT

    W0AAT XML Subscriber QRZ Page

    Measure element length at147, difference in frequency is about 1% so lengthen each element 1%... but as is it should work on 144.2... have you tried adjusting the beta match only? Looking at the manual have you measured the DE length? Has it been cut leaving you to short? An option would be slitting the DE ends and adding a little short stub to tune it with. Balun is wide band so that is not the problem.
     
  3. K5TRI

    K5TRI XML Subscriber QRZ Page

    Great idea with adding the stub to the DE, haven't thought about that. Already bought some aluminium tubing to cut new DE elements.
    I didn't adjust the beta match, will try that next once I find some suitable material to make a longer one.

    Will try and report back.


    73 Mike
     
  4. K8JD

    K8JD Ham Member QRZ Page

    Short piece of #12 wire and a small hose clamp on each end of each element.
    DON'T mess with the matching device !!!!!
    That should keep you busy for a day :D
     
  5. N8EKT

    N8EKT Ham Member QRZ Page

    The antenna is shipped with the proper lengths for 144 mhz

    The length of the driven element from the factory is 17.25 inches and at that length it is resonant on 144 MHz
     
  6. K5TRI

    K5TRI XML Subscriber QRZ Page

    I just returned from a trip and finally had some time to play around. The antenna is up on the roof and working
    with 1:1 on 144.200 after lots of cutting and lengthening and shortening again.

    I ended up making a new DE out of 1/2" OD aluminium tubing with two solid rods inside to make it more tuneable.

    The length I ended up with per element for some reason turned out to be 17" while I also made the hairpin longer to 8.5".

    Thanks for all who provided input.

    73 Mike K5TRI
     
    K3RW likes this.
  7. WA9SVD

    WA9SVD Ham Member QRZ Page

    One BIG problem is that 144.200 MHz is smack-dab at the SSB national calling frequency, and in the middle of the narrow linear/analog (NOT FM) often weak signal region of 2 Meters!
    FM has already encroached upon the satellite reserved areas, when there are plenty of frequencies available for FM simplex where it is less crowded; a FM signal in the weak signal area can wipe out signals MANY kHz away from its center frequency, and not even realize it!
    I'd RECOMMEND you adjust your antenna for the FM portion of the 2M band, (as Hy-Gain originally intended) with a center frequency of around 146.000 MHz; that will give you decent coverage of the FM frequencies, both for simplex and repeaters.
     
  8. K5TRI

    K5TRI XML Subscriber QRZ Page

    QRZ.com and web forums in general never cease to amaze ...

    Thanks for your recommendation but the antenna worked just fine this weekend in the ARRL VHF contest including MS work.
     
  9. W0AAT

    W0AAT XML Subscriber QRZ Page

    *beats head on desk*
     
  10. K5TRI

    K5TRI XML Subscriber QRZ Page

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