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Ambitious antennas that underwhelmed

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by M0AGP, Dec 19, 2020.

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  1. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Mine was a home brew vertically oriented loop with several acute angles for the upper HF bands. In EZNEC it looked great. But upon building it I discovered that it was awful.

    This was very early in my use of NEC many years ago and I had unwittingly violated the ground rules with the acute angles. The average gain test was bad but I hadn’t bothered to learn about that either.

    A good learning experience. Worth the numerous looks from the neighbors when I mounted the contraption on a tall 2x4 in the back yard and fiddled with it for the day - temporarily of course - HOA...
     
    PU2OZT and M0AGP like this.
  2. KC9QBY

    KC9QBY Platinum Subscriber Platinum Subscriber QRZ Page

    In my EARLY learning days, home brew design, validated with a nameless Elmer who reported design oughta work. Radial field on ground indirectly connected via radial plate pass through connected coax shield to feedpoint of screwdriver about 20 ft above ground and radial field. Other half of antenna, shall I say, disconnected from other half. Spectacular fail. Asked Elmer WTH when he visited to diagnose. Apparently misunderstood my drawing of design. Yah, ya gotta connect that radial field AT the screwdriver feedpoint, DOH!! Hey, I learned. Comments? Ready, fire, aim, LOL. Forgive me father, for I have (radio gaffe) sinned.
     
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  3. UA3TW

    UA3TW Ham Member QRZ Page

    My great disappointment was this antenna
    It was developed to switch 4 directions at 21 MHz and 28 MHz. It had complex curcutry
    with 11 two-way relays and a number of coils and capacitors, whereas single band variant
    contains only 6 relays. It worked OK at 21 MHz as the model promised, but had poor performance at 28 MHz - 6db F/B only. I was so angry with it that when I disassembled it I even deleted the MMANA models of it.
    After all I think the reason was big coils for 28 MHz - I made them from calculation formulas and measured the inductance with a low frequency instrument. So their real reactance was quite different at the working frequency of 28 MHz. I measure all coils at a working frequency since then, especially big coils with too many turns for the frequency.
     

    Attached Files:

    Last edited: Dec 20, 2020
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  4. M0AGP

    M0AGP Ham Member QRZ Page

    The ZS6BKW is a very interesting antenna! I was nearly set on putting up a “detuned” version that would allow use of a tuner to easily add 30m and 15m. With the help of some gurus like Mike ‘ARK I pretty much worked out the details. And then I thought I would check the radiation patterns, expecting my inv vee version of the antenna to radiate like the “flat” version.

    Shocker! Despite the center being up nearly 40 feet, the main lobes on 20, 17 and 15m pointed straight up! This went counter to the dipole-derived intuition that if you are up half a wavelength you will be ok for low angle radiation. This antenna wasn’t built.

    I wonder if your ZS6BKW was an inv vee configuration too?
     
  5. M0AGP

    M0AGP Ham Member QRZ Page

    Mike I think we all would have expected this vertical to perform well - thanks for posting this. It seems vertical antennas are something of a crapshoot when it comes to performance, and the “confounding variables” are ones that are fully out of our control.
     
  6. AE1N

    AE1N Ham Member QRZ Page

    B.ARE YOU  SURE MY HEAD WILL HELP RECEPTION (2020_11_06 06_40_22 UTC).png
    ARE YOU SURE MY HEAD HELPS RECEPTION?


    A.THE OLDE HAM SHACK (2020_11_06 06_40_22 UTC).jpg
    THE OLDE HAM SHACK


    A.Building my beer can vertical1 (2020_11_06 06_40_22 UTC).jpg


    A.TRY IT WITH THE LINEAR THIS TIME! (2020_11_06 06_40_22 UTC).jpg
    TRY IT WITH THE LINEAR THIS TIME


    B.FIRST DAYTON vISITOR (2020_11_06 06_40_22 UTC).jpg
    FIRST DAYTON VISITOR


    A.NEXT TIME PUT THE BEAM TOGETHER OUTSIDE THE PATIO1 (2020_11_06 06_40_22 UTC).jpg


    B.Driving out the DX QSO Demons1 (2020_11_06 06_40_22 UTC).jpg


    A.New 160 Meter Loading Coil1 (2020_11_06 06_40_22 UTC).jpg


    A.Single Sideband Yagis (2020_11_06 06_40_22 UTC).jpg


    ---Layne AE1N
     
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  7. K3XR

    K3XR Ham Member QRZ Page

    When I first moved to this location owing to the property size and tall trees I installed a 500 ft horizontal loop. That was a complete waste of time.
     
  8. WB8VLC

    WB8VLC Ham Member QRZ Page

    The common thread in failed Arizona verticals was probably the poor near and far field ground in the mountains of central Arizona, the earth is mostly granite rock.

    I had even added in a near field radial field to the failed antennas to see if any improvement was possible but I didn't expect any and the outcome was the same with or without radials.
     
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  9. M0AGP

    M0AGP Ham Member QRZ Page

    That’s interesting - I guess this relates to the Fresnel zones described in another posting - propagation from verticals at low angles apparently depends on the quality of the ground quite far away.
     
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  10. AH7I

    AH7I Ham Member QRZ Page

    Novice Bob read that galvanized electric fence wire was a good, inexpensive, alternative to copper for antennas. He assembled a 40 m lazy H. It was total crap compared to the copper wire dipole it replaced.
     
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