|[AMRadio] Windom Antenna|
Mike Dorworth, K4XM
k4xm at arczip.com
Mon Dec 27 17:36:38 EST 2004
Okay, let us try again. I thought the question was.." how can it be
RESONANT" at more than one place..Mr. Windom clearly shows that it is and
how to prove it. A antenna cut for twenty works great on 10, a forty meter
job works great on twenty and ten, an 80 meter works 80-40-20-10 etc. It is
always RESONANT on all harmonics.The single wire feeder shows about 600 ohms
to ground and is worked against ground from the link or output. If the wire
were fed in the center of the antenna, then the antenna WOULD NOT RADIATE at
all, only acting as a top load capacitance. Also the length of the feeder is
of no matter and 1200 feet works fine. Sure there is a little radiation from
the feeder, but not too much. The straight away part insures that the RF
picked up from the antenna (SORTA ) cancels out..These antennas work well
with old Boat Anchor PI-Network outputs, those that go to 600 Ohms. There
are no Standing waves on this type of antenna to feeder connection on the
FEEDER!..I can e-mail the original QST article as an attachment (jPEG) for
those wishing to read further on Mr. Windom's discovery.. Happy antenna
experimenting in '05..73 de Mike, K4XM
----- Original Message -----
From: "Geoff/W5OMR" <w5omr at w5omr.shacknet.nu>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Monday, December 27, 2004 12:28 PM
Subject: Re: [AMRadio] Windom Antenna
> > In QST magazine for September 1929 the original Windom Antenna article
> > starts on page 19. It clearly shows that it is exactly resonant on all
> > it's design bands, so long as there is an harmonic relationship.
> > etc. There are diagrams included which show how this is determined with
> > RF ammeter and a rolling trolley after which very precise and repeatable
> > formulas were derived. Of course this is the single wire fed version.
> > later 300 Ohm job is merely wishful thinking.The length in feet is
> > 468, divided by desired frequency in Kc. For the lowest desired band.
> > tap is always feet times 25 divided by 180. I might add that antennas
> > as temporary during this nasty winter weather last 20 to 30 times longer
> > than summer installed permanent antennas. happy antenna experimenting.
> > K4XM, Mike.
> So, in order for this to work, you have to decide what frequency you're
> to operate on, on the HIGHEST frequency the antenna will cover.
> ie: 29MC /2 = 14.5, 7.25, 3.625, 18.125Mc.
> that being the case, then
> L = 468/f(L)
> L = 468/18.125
> L = 258.20689655172413793103448275862
> Now, you said that the 'tap is always feet times 25 divided by 180'
> T = 258.207ft * 25 / 180
> T = 6455.17 / 180
> T = 35.862068965517241379310344827586
> Single wire feeding it? Fed against Ground? Doesn't the single feed-line
> become part of the radiating antenna?
> Even if someone were to take, say the output of a link and feed it
> open wire feed-line, the open wire line would have to go all the way to
> point of the antenna, wouldn't it?
> I'm sorry if I'm seeming a little dense, but I can't get unwrapped from
> 'single wire fed version' of this antenna.
> Open wire output from the link has *2* wires. I can see attaching them to
> open wire line, and feeding this Wyndom antenna at 1.8125, and having the
> antenna resonant on 3.6250, 7.250, 14.5 (oops - can't operate there) and
> but I simply fail to understand how one wire is going to feed an antenna
> has two posts to connect to.
> Certainly has me thinking, though. Now, if I could just come up with land
> had 300' (for guy supports on both sides)
> I'll have to work CW on 3.6250, forget about 20m and enjoy a
> antenna on 10m (when the band is open). Pardon the sarcasm ;-)
> Seriously, here. Surely, there must be something I'm missing, to be able
> this antenna on all bands, with acceptable VSWR.
> 'Splain it to me, please.
> Happy New Year
> 73 = Best Regards,
> AMRadio mailing list
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