Ambitious antennas that underwhelmed

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

ad: L-HROutlet
ad: l-rl
ad: Subscribe
ad: Left-3
ad: Left-2
ad: abrind-2
ad: L-MFJ
  1. M0AGP

    M0AGP Ham Member QRZ Page

    In this thread it would be great to hear about people’s homebrew antennas that were ambitious but that for whatever reason underwhelmed when it came to performance.

    Given that we learn from others via books and websites, there is nothing like failing a few times yourself to teach you some good lessons! But we rarely hear about other people’s failures. The point of this thread is to tell others about stuff that was built that sounded like it should work, but that didn’t live up to expectations.

    I will start off the thread with the story of my stealth 7 element Yagi for the 10m band – around 1977.

    This antenna had a boom length of something like 40 feet, 7 elements and was not rotatable - it was just wires stapled to the roof of my dad’s house! I started with just the driven element, which was a standard dipole fed by RG8. I cut it to the “correct” length for 28.2 MHz and found it was nowhere near resonant! Lesson 1: nearby conductors make a difference… The house has aluminum rain gutters and whilst there was virtually zero wiring in the attic there was enough interaction with conducting stuff that the resonant length had to be materially adjusted. I kept this percentage adjustment in mind, contacted a nearby ham buddy who was luckily directly in the (theoretical) beam path and got a signal report. I had worked out the beam direction to be Santa Barbara, CA - you can see I had high hopes! I didn’t have access to a great circle bearing calculator, so tediously worked out the math myself (and got it wrong numerous time initially).

    I then added a reflector that was several percent longer (guided by the 1976 ARRL Antenna Book for the section on shorter Yagis I expect) and got signal reports from my buddy, adjusting the director spacing for max gain. Then I added a director that was several percent shorter than the driven element, optimized it with my buddy (each time I had to go up a ladder onto the roof of the 2 story house to move the element). Note that I didn’t go back and check whether the spacing from driven to reflector was still optimal, but I was too impatient for that! And I was taking up a lot of my buddy's time...

    Finally it was done but annoyingly had quite a low 2:1 SWR bandwidth – less than 300kHz from memory, maybe due to using wire, and it never hit 1:1, which at the time I thought was a problem. I seem to remember the spacing of elements 4 and outward was wider than the first 3 elements and was about uniform-ish. The directors all had shortened by a bit – can’t remember how I worked that out - it may have been a guess.

    Just as I was finishing this project my friend and quasi-Elmer W9MZZ gave me an old 3 element 10m beam! I cleaned it all up and built a tower out of wood about 20-some feet tall that could tilt-over onto the house roof so I could make adjustments. I got an old TV rotator and used that to turn the beam – what a joy!

    Then came comparisons with the 7 element beam: in the direction with the most gain, which was slightly off bore (?!?) it was at best only about 1-2dB better than the 3 element beam! I had expected more like 4dB better for some reason.

    I also found that the F/B ratio was terrible, and that I could hear signals off the sides pretty well.

    When the 10-X contest came up, we were lucky with a few openings and I found that using the roof beam I could hold a frequency and run Californians for hours – using the 7 element beam! But it was later clear from QSL cards I got that the contacts were not concentrated in Santa Barbara - more like San Diego/LA.

    Knowing what I think to be true now, the roof beam never had a chance of performing like a true 7 element yagi. For one thing, all the elements were inverted vees, which are more or less omnidirectional when you have a 120 angle, which I think was ballpark the roof angle.

    I expect that an EZNEC analysis of such a thing would show that it performs nowhere near a real Yagi even in free space.

    So there’s my ambitious antenna that underwhelmed. Let’s hear about yours!
     
    PU2OZT, UA3TW, N0TZU and 1 other person like this.
  2. N5CM

    N5CM Ham Member QRZ Page

    At some point many moons ago, I built a double bazooka for 80m. I was expecting great bandwidth and was disappointed. The antenna worked OK, but bandwidth was nothing to write home about.
     
    M0AGP likes this.
  3. WA4SIX

    WA4SIX Ham Member QRZ Page

    All of my homebrew antennas worked as good as they could, for what they were. Each taught me something new.
    In that light, all of them were a success.

    Ed
     
    WA7ARK and M0AGP like this.
  4. WB8VLC

    WB8VLC Ham Member QRZ Page

    Mine was around 1992 at my Prescott, Az. qth.

    I built some 20, 17 and 15 meter half squares and armed With all sorts of Antenna books and data and ham magazine articles claiming the antennas good performance and even after I tried several different variations of feeding this piece of crap of which I even made it so the support masts could be moved around the yard thereby making it rotatable.

    After months of wasted time fiddling with them and even changing over to bobtail curtains it was obvious that these antennas were absolute dogs on upper HF.

    Even low reference dipoles outperformed those bobtails and half squares.

    Fortunately I was presented with a 2element 5 band ''lightning bolt' quad from my wife who felt sorry for me and really wanted me to keep a sched with her father and uncle on cw.

    I still have the quad at my Prescott home and I never went back to using any kind of vertical, vertical array and such for 20 and above and I never regretted swearing away verticals.

    These days I only use quads, moxons and aluminum element yagis for 20 to 6 meters and I'm very satisfied with these antennas even when they are only around 25 to 35 feet high.
     
    M0AGP likes this.
  5. VK3YE

    VK3YE Ham Member QRZ Page

    My main failures have been with phased verticals.

    Played around with various separation distances and bits of coax between them and could never get the nulls and directionality claimed.

    But enough people have so must have been something I did - or didn't - do.
     
    M0AGP likes this.
  6. G1DFN

    G1DFN Ham Member QRZ Page

    Not so much an "underwhelming" antenna job, rather the other way. I purchased a Sigma SX 360 HF after reading all the gumph and it performed "fair to middling". Then we had a windy day and the fibre glass snapped and it fell off my tower. A write off, but no probs. I salvaged the mounting bracket and the 6-1 unun, purchased a 6mtr fibre glass fishing whip from Mr Woo, took out the top section (about 18inches solid F G) and fitted the whip to the mounting bracket. A 5.5mtr length of 1mm solid copper wire was shoved up the middle and soldered to the unun and (after sealing every orifice) it was mounted on my tower at 50ft up, fed with RG213 and I gave it a test. SWR 1.1 on 17mtrs? ok on 20, 15 and 10 ( but I got a tribander 3ele for those bands). First call on 17mtr with 400watts and boom, China. Since then I've made contact with VK, JA, PY, LU, CX, CE,ZS, most of Europe and the middle and far east and Stateside to W6, California. The "little whip" as my club mates call it just about bends double in strong winds, then pops up straight again when it calms down. The sx360 cost £149.00, was crap and lasted less than 6 months. The "little whip" cost £6.99p ,about $9.00, plus the few bits I could salvage from the Sigma and has been going 4 years now. I'm rather chuffed with it to say the least.
     
    Last edited by a moderator: Dec 19, 2020
    KI5LTA, M0AGP and K2CD like this.
  7. KB1CKT

    KB1CKT Ham Member QRZ Page

    Only made a couple but so far, 2 out of 3 have not been what I wanted. I'll keep playing though.

    The ZS6BKW I made worked better on 80m than 17m or 20m, and all bands were like 25 or 35 ohm at resonance. ??? No idea why. It's still up but I think the 40/20/10 fan I sorta made works better on 40 & 20. That fan used a 20m Radiowavz dipole and I added 40m & 10m elements, but the balun is reactive and so 10m is useless; also the element separators also broke in some high winds.

    But one has to start somewhere.
     
    M0AGP likes this.
  8. M0AGP

    M0AGP Ham Member QRZ Page

    Here's an Owen Duffy link to the double bazooka. Looks like it is more broadband than a dipole, but not by a huge amount https://owenduffy.net/antenna/DoubleBazooka/index.htm

    So it’s not that you built it wrong...
     
  9. M0AGP

    M0AGP Ham Member QRZ Page

    Not a huge amount of data, but that’s two people having trouble with phased verticals. I know some people get very good results with them - I wonder if there is a common thread there?
     
  10. WA7ARK

    WA7ARK Ham Member QRZ Page

    I am underwhelmed by the vertical antenna in this picture:
    upload_2020-12-19_16-56-8.png
    It sits on a 70 x 90 ft steel building in lieu of radials. The base is 23ft agl. The vertical pipe is 2inch od seamless aluminum. I have tried various lengths from 43ft down to 36ft.

    There is a remote tuner just below the roof within 18 inches from the base of the monopole. The tuner can almost be seen here:
    upload_2020-12-19_17-10-46.png

    I have used this vertical on various bands from 80m on up to 10m. It has been up for several years in various re-incarnations. It is always my "worst" HF antenna when compared to others... I attribute its mediocre performance to our crummy Arizona dirt beyond the extent of the building. It does not work DX better, it is noisier, and it sucks at working surrounding states. Totally disappointed with vertical antennas.
     
    M0AGP and AB6RF like this.

Share This Page