Poor F/B ratio of a UHF TV 8 bay bowtie antenna; how to improve?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N2NJO, Nov 13, 2020.

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  1. N2NJO

    N2NJO Ham Member QRZ Page

    I wasn't sure where to put this. here or the V-U section. Since this is about a antenna, I choose here.

    The antenna(s) discussed are from Channel Master. Similar model number, similar basic design, but slightly difference performance. They are the 4228A (1st) & the 4228HD (2nd), both are 8 bay- bowtie reflector antennas. My preferred antenna for UHF TV reception.

    Long story short, between the original (US made) 4228A with web screening as a reflector, this newer cheaper version has 2 sets of 8 horizontal tubes but doing so, reduces the F/B ratio noticeable. Compared to the original when I swapped antennas, I'm getting phase cancellation of some stations that are 180 degrees apart from a smaller antenna aimed at those which I didn't have trouble before.
    Before anyone asks, the swap improved reception of certain stations facing NW at the cost of the ones SE due to cancellation from a poorer F/B ratio. [​IMG]
    A classic "robbing Peter to pay Paul" scenario

    The question is; anyone having suggestions to improve the F/B ratio?? Being aluminum, soldering to that won't work and I question just wrapping/tying some type of screening (similar to what CM used on the original design) to the existing reflector.

    FWIW;
    I did some close measurements between the original (1st) and the replacement (2nd) 4228 and found;
    VHF reception (at least on channels 7-9) was less,
    UHF channels below 29 were 1-2 db greater,
    Channels 31-36 were 1-2 db less.
    The comparisons were taken less than 3 hours apart to minimize reception differences.

    I attached 4 bay versions of these two designs. The one on the left is the current, the one on the right is the original (ignore the one in the middle). The 8-bay version are 2 4 bays side by side.
    Three 4-bay antennas.JPG
     
  2. W9GB

    W9GB Ham Member QRZ Page

    You are using a Gray Hoverman (Bow-Tie) UHF Antenna (Channels 14-51), 470-698 MHz
    NOT Useful for High-Band VHF channels (7-13) 174-216 MHz, without a VHF Dipole addition.


    The Smaller Square Mesh matches shorter Wavelengths of UHF (more efficient reflector).
    Larger tubes are a “Joke” for UHF ... ineffective ... hence Poor F/B ratio !!
    ADD Chicken Wire or Screen Door Mesh and watch improvement !
    ==
    Doyt R. Hoverman originally secured an Antenna Patent in 1959 and 1964.
    https://www.tvtechnology.com/opinions/tv-receive-antennas
    Both patents have now expired. AntennaCraft (Burlington, IA, across street from Winegard) sold these antennas beginning in late 1960s and was OEM for Radio Shack .
    Winegard (Burlington, IA); Jerrold (update New York); Channel-Master (North-Carolina) also had their versions.

    DIY Build a Gray Hoverman UHF Antenna
    You can ADD a Simple VHF Dipole for VHF channels.
    https://www.dudley.nu/projects/hoverman/index.html
    B115E768-3440-4F4A-8FAC-82FAE58CD67F.jpeg
    Another Builder, KJ4KAJ
    https://www.hamradio.me/antennas/superbowl-dtv-antenna.html
    Measurements
    https://www.hamradio.me/antennas/hoverman-tv-antenna-measurements.html
    3CAD8EC9-8DF9-4F7F-8446-F66268C805B7.jpeg
    One Internet Forum for Over-the-Air (OTA) TV and Antennas is SOLID SIGNAL.
    https://blog.solidsignal.com/category/tutorials/

    Stealth Hawk versus 8-BowTie Penny Loop
    https://blog.solidsignal.com/tutorials/stealthhawkantenna-vs-8-bowtie-pennyloop-antennas/
     
    Last edited: Nov 13, 2020
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    A TV-DXer! I love it!

    I haven't done that in ages, but way back before cable TV and DBS satellite TV, when I lived on a hilltop in northern NJ (1973-1978 timeframe) I was a TV-DXer also and had large rotatable LPDA antennas on a tower (same tower that supported my ham radio beams).

    I used to be able to pick up UHF-TV from Toronto, 350 miles to my northwest, 24 hours a day. I did live on a pretty good hilltop overlooking a large lake so that helped. They had some programming that did not exist in the States and was pretty interesting.

    Fun sub-hobby and I'm glad to see people are still doing it!

    No experience with the bow-tie systems. Always used a big log periodic horizontally polarized beam.
     
  4. W9GB

    W9GB Ham Member QRZ Page

    When you grow up in Fringe/Deep Fringe west-central Illinois, with only channel 7 (CBS) and channel 10 (NBC) barely covering you with a Grade A signal, it is Part of Life.
    So I learned about Antennas and VHF propagation, at an early age.

    BONUS of Living there (in the Middle of):
    Gates Radio (who built TV transmitters was HQ in Quincy)
    Motorola (built radios & TVs at Quincy, until 1970 sale to Panasonic)
    Winegard Antennas (who built the TV antennas at HQ in Burlington, IA)
    Rohn Towers (built TV Antenna towers at HQ at Peoria, IL)

    TV DX was trying to capture four VHF stations in Quad Cities (90 miles North) OR
    the four UHF stations in Peoria (also about 90 miles to NE).
    ==
    Macomb, IL had one of the first Cable TV systems in Illinois (mid-1960s),
    by erecting a 500 foot tower for the Antennas. Tower was high enough to permit receiving WGN (Cubs, Bears) and WFLD (White Sox, Bulls) via Microwave from Peoria or Quad Cities feeds.
    Smart group of local leaders back then, and Chicago sports fans.
    Successful? Yes, due to signups just for sports (HBO started this same era, ESPN decade later).
     
  5. W9GB

    W9GB Ham Member QRZ Page

    George J. Monser (1924-1998) was a southern California TV-DXer
    from his home near Santa Barbara (trying to catch San Diego UHF channels, 185 miles away).
    https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=730539

    A Raytheon engineer in the 1960s and 1970s for military projects,
    he wrote the book 1996 McGraw-Hill book, Antenna Design: A Practical Guide
    a couple of years before his death.
    F15CC4CA-D3C6-4715-A2D6-25ECB897CC9A.jpeg
    He wrote a Popular Electronics article in July 1969 for a Pyramidal VHF TV/FM antenna.
    His UHF Antenna design was featured in the December 1971 issue of Popular Electronics.

    Build a Mini-Pyramidal UHF TV Antenna , Page 40
    https://worldradiohistory.com/Archive-Poptronics/70s/1971/Poptronics-1971-12.pdf

    16AEBC94-D80F-434E-86B1-10D2C9D2F9F3.jpeg 5EE119F0-F262-41B5-8DEB-33AEC828AE04.jpeg
     
    Last edited: Nov 13, 2020
  6. N3DT

    N3DT Ham Member QRZ Page

    That Grey Hoverman looks suspiciously like the one I built back in 2008.
    hoverman pvc.jpg

    Later on when they changed channels I built a 4 el colinear which was somewhat smaller with the same gain but single freq. I get Virtual channel 26 (WETA-HD) most of the time from DC from 50 miles west of DC over 2 ridges. It fades sometimes (digitally). One day it finally fell from the tree I had it supported in (rope broke) at about 50' and broke to bits. I rebuilt a new one with #6 wire and a little more substantial support for the top and bottom elements. It's still up. I use a 75/300Ω transformer to feed a Kiltz amp and RG11 to bring it down to a splitter in the house. The 2 bay Hoverman out performed the colinear, plus it gets more channels, not that I watch any of them, maybe Grit sometimes.

    I got the idea from the Canadian TV enthusiasts forum back in 2008 or so. DigitalCA or something like that. But now we've also got availability of streaming from a TMobil cell site and ISP.

    https://www.digitalhome.ca/threads/introduction-to-the-gray-hoverman-tv-antenna.81982/
     
    W9GB likes this.
  7. W9GB

    W9GB Ham Member QRZ Page

  8. W9WQA

    W9WQA Ham Member QRZ Page

    i built the 4 bay ant with one piece of plastic and electric fence gal wire so cheap i gave them free with a $99 install!
    im near la porte in. on a line from chicago to s bend so an open ant gets all signals.
    some people were delighted with 40 channels and skipped the cable bill. saved a 100 a month. everybody happy. channels from 2 thru uhf...!!!
    mounted with a few 3 inch drywall screws..very cheep..

    btw, rad shack had an amp for 25 that was terrific, when needed. now menards is even cheaper
     
  9. N2NJO

    N2NJO Ham Member QRZ Page

    Thanks for the replies, but I should of stated that I was fully aware it's not meant for a VHF antenna. BUT, due to what others called a "fluke", it does work at high band VHF channels (at a reduced level).
    What I also should of also mentioned, I have no attention of buying or building (in this case) a antenna.

    And reception on VHF is not the issue! This is;
    Which brings me back to my original question; can (whatever is the best material that won't rust) be just 'added' to the existing reflector without a good or any electrical bond??
     
    W2VW likes this.
  10. W9GB

    W9GB Ham Member QRZ Page

    1.) Galvanized Chicken Wire and Wire Mesh exists (Resists rust).
    Most Farm Supply stores (Farm-Fleet, or equivalent in western NY) should carry.

    Patio and Storm door Screen Mesh is often Aluminum (just like most antennas).

    2.) Antenna theory 101 : Reflector is insulated from Driven Element.
    Given that design, wire ties to the Tubes (trying to act as UHF Reflector) should be sufficient.
     
    K4DDT likes this.

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