From: Subject: WINDOM ANTENNA Date: Sat, 6 Nov 2010 17:04:33 +0200 MIME-Version: 1.0 Content-Type: multipart/related; type="text/html"; boundary="----=_NextPart_000_0000_01CB7DD4.AF520D40" X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5994 This is a multi-part message in MIME format. ------=_NextPart_000_0000_01CB7DD4.AF520D40 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Content-Location: http://www.zcr.jp/~tada/JA7KPI/windom.html WINDOM ANTENNA

WINDOM=20 ANTENNA

I'm using homebrew Windom-Antenna recently.
In the total length of = this=20 antenna is 41m, height is about 11m, and diameter of element is = 2mm.
However,=20 it is up only about 4m height from a metallic roof.
I modified this = antenna=20 originally used as Inverted-V type of 80m band Dipole a little.
The = feeding=20 point of this antenna is located 13.6m from the edge of Element. Yes, it = is=20 Off-Centered.
BALUN of making which uses two cores, = converts=20 impedance into 1/4. The core is the one of about 4cm in the diameter. so = there's=20 no problem in the input power 100W at all. Because two cores are used, I = think=20 as much as 500W safe in power.
The diameter of the wire rolled in the = core is=20 about 1mm.
The VSWR to frequency is shown as = follows.

Freq. VSWR Freq. VSWR Freq. VSWR Freq. VSWR
3.525 1.1 14.050 1.8 18.070 3 28.150 2.5
3.570 1.4 14.100 1.7 18.160 3 28.500 2.0
3.795 1.6 14.150 1.6 21.050 >3 29.000 1.3
7.030 1.4 14.200 1.3 21.449 >3 29.300 1.1
7.060 1.3 14.349 1.2 - - 29.600 1.2
7.099 1.2 - - - - 29.699 1.3

3D"Structure In=20 21MHz, VSWR exceeds 3. However it is likely to QSO with the domestic = area, if=20 Antenna-Tuner is used. I did not obtain good results though I measured = its VSWR=20 with 10MHz and 24MHz besides <showing up>.
I think this easy = structural=20 wire antenna is Very FB. Because I can QRV on multi BANDs without = switching some=20 antennas.

By the way, I had one question. This antenna might be a name of = "Windom"=20 why?...
I thought it might designer's name or name of a place of = development=20 ground.=20

The answer's as following e-mails via = radio-amateur's=20 FWD-Net.

Dear friend, i have a self building Windom; it is a dipole = of 80=20 meter with the connection at 1/3 of the lenght: in this point the = impedance is=20 300 ohm, and with a balun 1:3 i obtain 50 ohm; for the band of the 21 = Mhz i=20 put a second dipole only for this band, connected ad the same mode of = the=20 other; the lenght of this is 2.3 + 4.6 meters.
In a test with a = vertical=20 groun plane 5 band, the windom result better in 14 7 3.5 Mhz; using a = good=20 antenna adapter, it can be used in 1.8 Mhz.
This antenna is named = Windom=20 because was bilded from Laurent Windom (W4DZZ ?) around the = 1930.
It' s not=20 a long time that i use this antenna and i have some thing to = understand about=20 it; in any way i'm really satisfate from this antenna.
I wish to = you to=20 have big satisfation using them.
Best 73 an good DX. Ciao de=20 Franco. IK1OWB@IK1JNS.IPIE.ITA.EU=20

Hello Tada !
The "Windom Antenna" was described by Loren G. = Windom (=20 QST, Sep 1929, pp 19-22, 84) so this kind of antenna was named after = its=20 inventor.
73 / Peter, DJ2ZS@db0gv.#hes.dl.eu=20

The windom is called after its inventor.
Here I use a windom = antenna on=20 80 - 10 m. the ntenna is 41 meter long.
13% off center I feed it = with=20 300-ohm open air-spaced feeder. I use an antenna tuner with the balun = coin=20 connected to the antenna tuner. The antenna hangs in zig-zag between = some=20 trees. I am very pleased with it, it works quite well locally and on = DX.=20 Thought this might be of interest to you..
Good luck!
73 de=20 Egil. LA8HF@LA4O.OSL.A.NOR.EU

Thanks to Franco, Peter and Egil. Best regards to you.
And thanks = for more=20 infos via the Internet. Those are ...

I just read an interesting article in Czech ham radio = magazine=20 "AMA".
The article itself was about history of the bobtail curtain = antenna, but there was an interesting note: Loren Windom first = described this=20 antenna, but he himself said that it was invented by someone else as a = modification of Hertz antenna.
I found some people to call the coax = fed=20 antenna with a balun "FD4" - but some other people call FD4 the = modification=20 mentioned by Franco IK1OWB (but the measures are doubled: 9.4+4.7=20 meters).
73 Jindra OK1FOU=20

Regarding the Windom, I have a long time experience with such an = antenna.=20
I designed mine in 1978. It is different from the "normal" ones = because I=20 use a different type of balun and this, from my point of view, is = superior to=20 the toroid one because the core does not saturate with high power or = reactive=20 loads.
From my point of view, this type of antenna is not rightly = called=20 "Windom", it should be called, probably, Long wire off center fed = antenna.=20
The reason is very simple; the Windom antenna was referenced to = ground as=20 the feed point was between an off-center side point and ground.
The = modern=20 type of "Windom" Antennas are off center fed but not referred to = ground. The=20 validity of calling them Windom is due to the idea of "off-center = feed".
73=20 Gian I7SWX=20

The windom antenna should never be configurated as an Interted = Vee
but=20 should be Flat Top as it was originately.
Matching network such as = the=20 Johnson Viking Matchbox is highly recommended
if fed all the way = with 300=20 ohms line.=20

This antenna is suitable for all traditionnal ham bands.
73 from = Cam. VE2SO

O-kay, Definitely maybe, it should not be called "Windom" that is not = single-wire fed or flat-top.
But I will call the antenna for = multiband=20 "Windom" in high regard.=20

Well, that is as same as a relation between = H-Hentenna and=20 Hentenna. You know Hentenna, don't you? Hentenna is a kind of Loop = antenna, but=20 H-Hentenna is not loop.
Anyway, H-Hentenna, that is one of = variation=20 of single-wire fed Windom (or 8JK). It was developed by=20 JR1FTE and expanded by JA7KPI in 1982. = For=20 more infos, see the LINKs below.

Back to = SHACK &=20 FIELDS of JA7KPI
H-Hentenna for=20 14MHz | H-Hentenna for=20 50MHz | 6el.H-Hentenna for=20 145MHz | Dualband = (145/435)=20 4el.H-Hentenna
Inverted Vee for = 160m with=20 NEC2 Consideration of very low = antenna in=20 comparison with wavelength
Back to=20 KPI Front Page | ZCR/bLOG = (written in=20 Japanese)
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