Hi Darin,
Been there, done that. Tried most of the stuff you mention.
I recommend, as others have already said, a center fed dipole.
If you make the length the same as recommended by G5RV (about 27m
in total), it will probably present more favorable loads to your
matchbox than a full-size 80m dipole fed with the open wire.
However, I do not recommend inserting the balun at a specified
point (as G5RV recommends) and then continuing with coax. I
suggest running the openwire all the way to the shack. If you
get real unlucky, you might have to play with feedline lengths to
get desired results on all bands. "Good" lengths are suggested
on the DXE pages.
A great antenna, though rarely used (as far as I have seen and
heard) is a vertical dipole fed with openwire. I began using
this with a total length of 10m (2x 5m legs) about 12 years ago.
About 4 years ago I switched to a total length of 12m. With the
high bands going out in the near future, you might even want to
use a total length of 14 to 16 meters. This antenna has several
advantages. It radiates equally well in all directions with a
low angle takeoff, yet you do not need radials. Of course the
low angle radiation makes it less than favorable for local rag
chews.
Final suggestion: Using an external balun enables you to avoid
possibly burning out something within your matchbox - which
causes extra repair time. I stopped using the internal balun on
matchboxes after burning the first one out. Exception: OK to use
a 100w built-in balun for QRP work, or a Kilowatt balun for 100w
work. Otherwise, keep it outside. That way you can control the
situation by placing your hand on it to check the temperature.
Final - Final suggestion: The only good place to use a balun
(when using open wire feedline) is between the TX and the
matchbox (not between the matchbox and the feedline). However,
if the matchbox was not designed like this (only in the most
recent designs are), you will need to take very special care to
keep things insulated (floating above ground). This is the only
method which assures the balun sees its design impedances on both
sides, thus insuring it will operate as designed.
Gud luck and have fun!
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of D.Cy Gacuzana
Sent: Saturday, January 10, 2004 6:55 AM
To: tentec@contesting.com
Subject: [TenTec] Thoughts about the "Windom" or OCF antenna
Hi All... interesting posts on this, what appears to be, somwhat
controversial antenna, the Windom, or OCF dipole if not single
wire feed. I just happened to trip upon this what turned into a
balun thread, immediately after I accidentally stumbled upon the
DXE print ad, while searching for W9INN's ads in a real, not
virtual QST magazine. That prompted me to go on-line to
investigate DXE's "New!" baluns.
Two years ago (and still today), I was searching for an
inexpensive, efficient, no radial solution for an antenna. When I
first got my ticket again not long ago, I thought the Carolina
Windom to be the perfect magical solution, given it's claims and
reviews. I've come to now believe most of the raves were the
result of awesome propagation associated with the edge of the
solar peak of two years ago, or simply the windom was up a half
wave or more, combined with the fact that two years ago one could
truly work the world QRP with rain gutters, if not literally some
wet noodles.
When I finally could accept this, my mind turned to the idea of a
classic single wire Windom, however, Pegasus being my All Purpose
rig of choice,RF in the shack is absolutely intolerable. (I
can't do 15m over 20 Watts on my roof vertical, the computer goes
bug-nuts- probably correctable by a change in coax length, as the
air wound choke to augment my home-brew bead "balun" RF choke is
no longer an option, because I wanted to keep the coax as short
as possible, I have not enough slack to roll a choke. Indeed, I
IS a Newbie!).
I could add a jumper long enough to make a choke coil for that
band, but lately what I NEED is an 80m antenna with wider
bandwidth than my current roof vertical of the trapped genre
sporting 2 radials. So,
Next came the idea of a base fed T, however, at this point, my
thoughts were that now I was into the realms of Verticals, with
all their pros and cons.
I rather avoid a wires on the ground if possible. Next came the
idea of Cebiks center fed T, fed with twin-lead, but I knew of no
1:1 curent baluns available designed for such a purpose. As
well, most of my operating time appears to be rag chewing of the
CW variety- DX is fun, but I enjoy chatting a bit, so if DX
chatting a bit can be had, right-on. This seems rare, perhaps
there are language constraints. Most of my rag chews appear to be
North American, sometimes across the pond. So according to Cebiks
diagram, T= great DX+ center fed T= radials won't significantly
increase performance, BUT, T= big top-side NULL (guess that makes
it great for DX!). Close in newly made on air friends might hear
me poorly.
So next I thought, unbalanced T, and wait a minute what is that
really? Looks like a classic Windom to me, fed at a 45 degree
angle up top at the now Off Center. But, to crush that idea,
there was talk of all this, guess the experts call them "common
mode" currents on my feedline. To boot, I could not find any
data on how such a thing might perform, but I'm thinking the
pattern would be purposefully distorted so as to afford good
regional coverage as well as better than low horizontal wire
distance coverage. Such an antenna, with a properly designed
current balun slightly above ground-level might still hold some
experimental promise, perhaps utilizing 1/4 wave counterpoises
for each band of interest (maybe 8 wires on the ground is
tolerable).
The idea of a balun or matching transformer of some kind, at an
elevated feed point has never held appeal with me, because of the
weight as has been mentioned, and also because of what I
interpreted to be loss associated with mismatches that would
occur at some frequencies. I prefer the idea of having no balun
weight up there, running some sort of twinlead (thinking 300 ohm
windowline), using that feed as an impedance transformer via
judicial length selection, and accepting hopefully undectable by
ear, losses- at the tuner- comprised of components and a circuit
design which is intended to minimize those losses.
I realize I'm sounding very simply minded, but after all, I is a
newbie.
I have mostly only read Cebik and ARRL Antenna, and a lot of
posts concering baluns and tuners, geez, some of the debates can
sure get hot! Seen a few on the Top Band reflector when my Uncle
was thoughtful enough to forward pertinent posts to me and I got
curious so I went and read the thread.
But, before then, when I first heard of the Carolina Windom,
wanted to make my own, less lossy windom, as I was under the
probable misconception that there might be higher loss than need
be in a coaxial vertical radiator, and that two wires in parallel
would have less loss at high SWR while it was doing it's
"radiating." hi hi.
Since then, I've come to believe, that probably the main reason
an OCF might hold value, aside from being convenient, is to avoid
extreme impedances when operating at frequencies away from the
fundamental design frequency, in an effort to minimize losses in
places like baluns and tuners when using balanced feedline.
>From what I can gather, losses are readily available to be had,
especially within tuners of the T circuit variety "includes built
in 4:1 balun" (probably Voltage if an older/budget design)- as if
to imply this is the end all be all you need to connect to your
balanced line of a length chosen for the sake of physical
convenience, completely forgeting the impedance transformation
properties of feedlines in general. Just hook it up to enough
line to reach the apex of your all band inverted doublet Vee and
you'll be set to go! That was my interpretation. Plenty of us
non engineer "technologist" type newbies out here that read an ad
and see it that way.
So now, I'm leaning toward balanced feeline radiation not
contributing much toward the gain of a windom, (though am not
entirely convinced at all, that vertical feedline radiation on a
classic Windom contributes insignificant gain when the
single-wire feed approaches a quarter-wavelength or a skosh
longer), and therefore, I am hoping to believe that it may not
be significantly detrimental, in the same vein.
I do believe that for parallel line fed antennas, having no balun
at the feedpoint regardless of how you feed it, in a multiband
application, is probably the best choice.
In searching for an antenna that would offer the most high and
low angle radiation, for an all purpose multiband application, I
came upon Cebik's pages concerning the Center Fed Inverted L.
Also read his Antenna's From The Ground Up. For me, the appeal
of the 60-66' per leg inverted L seemed to fit well, with a good
compromise between horizontal and vertical radiation.
I have one tall pine tree, maybe 80' tall, roughly 8' the other
side of my fence. I'm thinking it may serve, as this tree's
lower branches have been supporting my improperly fed 40m OCF
wire for 2 years with no complaint. It's not my tree, how I wish!
But next, I realized, wait a minute, I want 40/30/20/17 and the
rest higher would be nice, too, however that whacko pattern fell.
Anyway, a mulit-high band horizontal dipole would be doable later
in the early summer, vertical GP even, heck, even bite the bullet
and get a GAP Titan, it covers the high bands, but- the big wire
antenna must do 17m on down, because with 4 kids who knows when
I'll be able to justify even but 320 bux on a Titan?
I am no mathmetician- and looking at a most basic graphic of
current/voltage distribution, and also evidenced by the
theoretical feedpoint figures Mr. Cebik included with his All
Band Inverted L compendium- I'm back to square one: Feeling the
need to avoid extreme impedances. Which of course on 40 and 20,
the center fed 80m 1/2 wave dipole has plenty to offer.
At this point I came full circle, and, as I already cut my 160m
G5RV to OCF 80m length and will soon hack the coax off, I came to
the conclusion that perhaps, this might work better for me, with
an appropriate feedline length. The end of the horizontal leg
may have to dangle 10 feet or so, and the "horizontal" leg also
would have to be slanted- apex around 70' (i hope!), the end of
it at about 30'. The vertical leg would simply dangle from 70'
mostly vertically, depending on the wind.
Whether or not I'd end up using one of the, for me, overkill
expensive but probably worth it DXE baluns, remains to be seen,
as the tuner I plan to use already has a 1:1 currrent balun- the
tuner I'm thinking about is an auto tuner Pi-L depending on
reactance values. I have no amp nor designs on obtaining one any
time soon. Mostly, I hear guys with amps calling CQ and often
are unable to hear the people answering, and for the ones they do
hear well enough to call back, 80W would have worked almost as
well anyway. Nothing against amps and their use, perhaps some
day.
So there it is, the whacko and unconventional OCF inverted L.
Any thoughts, comments, jokes, hoo-hahs or poo-poos are
appreciated.
Thanks in advance
73.
Darin, W3DCG, Newbie in Atlanta.
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