" Windom antennas " article in HR

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AA7EJ, Mar 27, 2017.

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  1. AA7EJ

    AA7EJ Ham Member QRZ Page

    During spring cleanup of my man-cave I rediscovered this interesting article , at least interesting for me, in May 1978 issue of Ham Radio magazine.

    (Always thought that HR was one of the more tech oriented amateur radio periodicals.)



    Anyway,
    “Windom antennas” article author pointed out few interesting tidbits about the antenna.

    I always thought that the purpose of single line feed was to match glow in the dark PA technology high impedance output. However, after scanning through the article explanations about how characteristic impedance of single line ( transmission line ) varies it seems that the input would be near zero and the characteristic impedance would then rise toward the antenna feed point.


    The second interesting point is that the antenna has it its predecessor in “1/4 wavelength ( broadcast band ) vertical , grounded at the base and fed at some point up from the base with single line feed “.
    The author does not specifically states if such antenna was ever implemented on amateur bands nor if broadcasters added radials to it.

    I guess the archive copy of the article may be somewhere “on the net “, I did not look since I own the original.


    If feasible I would appreciate a discussion on merits / quirks ( please no “feed line radiates” Peanut gallery comments ) observed using TRUE windom antenna and not on how you made DXCC with 5 W using it.

    But any pertinent comments are always welcome / allowed.
    ( But I already know you love you dog / cat etc. etc. )

    73 Shirley
     
  2. KD8DEY

    KD8DEY Ham Member QRZ Page

    I'm confused.
    If there is only 1 feed line, not a pair, wouldnt it be a Marconi with a modified offset feedpoint,
    and not a windom?
     
  3. AA7EJ

    AA7EJ Ham Member QRZ Page

    The article covers "naming confusion" a little.
    It claims that "windom antenna" was first referenced by VK ham / source and the name stuck since calling it "off center fed Marconi " was too long. Go figure.
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I don't have the HR magazine article and haven't really looked for it, but how was a Windom antenna "first referenced" by a VK ham?

    It's named for its designer, Loren Windom, W8GZ and was first published in QST, September 1929 as “Notes on Ethereal Adornments: Practical Design Data for the Single-Wire-Fed Hertz Antenna.” You can download the whole article, today.
     
    WB5YUZ likes this.
  5. WR2E

    WR2E Ham Member QRZ Page

  6. AA7EJ

    AA7EJ Ham Member QRZ Page


    I should clarify - VK source used "windom" to describe the antenna proper first.

    The original article you are quoting used the "long name ".


    Here is HR link

    http://www.archive.org/details/1978-05-hamradiomag

    and the issue contents

    Ham Radio Magazine, Vol. 11 No. 5, May 1978
    Windom Antennas - John J Nagle - K4KJ
    Selective Receiving Antennas - Henry S. Keen, W5TRS
    Multiband Vertical Antenna System - Laidacker M. Seaberg, W0NCU
    RX Noise Bridge Calculations with the HP-25 Programmable Calculator - Leonard H. Anderson
    80-Meter Ground-Plane Antennas - Joseph D. Liga, K2INA
    Omega Matching Network Design - Harold F. Tolles, W7ITB
    Improved Indicator System for the Hy-Gain 400 Antenna Rotator - Guy Black, W4PSJ
    Calculating Antenna Bearings - H. Paul Shurch, N6TX
    OSCAR Az-El Antenna System - Alden T. Greenwood, WA1NXP
    1296MHz High-Gain Antenna - Paul F. Magee, W3AED
    Antenna Gain Calculations - Francis J. Witt, W1DTV
    A Second Look, Advertisers Index, Flea Market, Ham Mart, Ham Notebook, New Products, Presstop, Reader Service
     
  7. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    The original design used a single feed wire. All the "Windoms" that use coax are a modern phenomenon, and many (myself included) do not consider them Windoms at all.
     
  8. G3TXQ

    G3TXQ Ham Member QRZ Page

    I'm not convinced by his argument about a significantly tapering characteristic impedance for the single wire TL. That's not how it models in EZNEC - the current along the matched line varied by less than 6% along a 75ft length on 80m; also, the current is not a maximum at the base and a minimum at the antenna as he argues:

    [​IMG]

    EZNEC predicts the input resistance at the base of the TL to be 603 Ohms; K4KJ measured 590 Ohms on his experimental system - very close I'd say, and evidence that the model is giving believable results.

    Finally, the impedance formula (9) which he tends to dismiss at the bottom of Page 13 gives results in the same ball park that he measured (504 Ohms).

    Steve G3TXQ
     
    Last edited: Mar 28, 2017
  9. AA7EJ

    AA7EJ Ham Member QRZ Page

    I may be splitting hair, but in the associated drawing the line is pictured as "rising from the input toward the feed point".
    It is probably the only way to demonstrate the point of changing the distance from the reference - AKA ground.

    Not sure how would such demonstration work if the feed line is drawn "straight up" as you model it.

    But it does make perfect sense to have the input near 600 Ohms and not near zero as I envisioned.

    BTW
    "Hertz" is 1/2 wavelength long (dipole) antenna
    "Marconi" is 1/4 wavelength long antenna

    These could be viewed as "basic" antennas.

    The feeding and or orientation of either further specify / names the antenna.

    For example End fed Zepp = End fed Hertz = end fed dipole etc.

    The name really depends on what is customary or if one wants to be technical in the description of the antenna.
    Or be as vague as possible to confuse (the enemy) - such as "Carolina Windom".

    ( Any "discussion " about what is / is not a dipole will be cheerfully ignored (by me )).

    73 Shirley
     

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