"Mike Coslo" wrote in message
...
Looking at the thing, I suspect that it is an OCF dipole. It isn't very
clear, but since they have a "L1" and an "L2", that gives us one clue.
Most center fed dipoles don't need an L1 and L2, because they assume
center fed, inherently 2 equal sides. Notice that they also say "this is
not a kit". That is a disclaimer that they put on their other OCF
antennas. Finally that 135 foot total length is typical of an OCF dipole.

OCF = off center fed?

i suspect the sides are equal in length. L1 and L2 are just designations
used in drawings to denote an element of some length.

Buxcomm sells a Windom too.


Dis ting is quackin' like a big ol' OCF duck!

And as such it should be a serviceable antenna.

Funny that some people are dissing BuxComm on technical matters in this
case............ ;^)

well the coax feed kind of sucks.

Gravity


- 73 de Mike KB3EIA -

On Tue, 27 Jun 2006 23:52:02 -0400, Mike Coslo
wrote:

Looking at the thing, I suspect that it is an OCF dipole. It isn't very
clear, but since they have a "L1" and an "L2", that gives us one clue.
Most center fed dipoles don't need an L1 and L2, because they assume
center fed, inherently 2 equal sides. Notice that they also say "this is
not a kit". That is a disclaimer that they put on their other OCF
antennas. Finally that 135 foot total length is typical of an OCF dipole.

Dis ting is quackin' like a big ol' OCF duck!

And as such it should be a serviceable antenna.

Funny that some people are dissing BuxComm on technical matters in this
case............ ;^)


Mike, we (you and I both) aren't sure of the detail, and that in
itself speaks heaps for the product information.

Whilst you have drawn a clue that the unspecified L1 and L2 suggest
that they are unequal, I drew a clue from the description of a
component as "centre insulator with eyehook", and if that product
detail is accurate (and we take the ordinary meaning of the word
centre to be a point that is equidistant from the extremities) then it
suggests centre fed.

I still think on balance of the published info, it is represented as
an "all-band dipole" on "80 through 10 meters" and appears to be a
135' centre fed dipole with a balun (of unknown type) and recommended
RG8/X feedline. Such a configuration will be likely to have high
system losses on at least some of the bands with practical lengths of
feedline as discussed earlier in the thread by several people.

Owen
--

On Wed, 28 Jun 2006 05:47:18 GMT, Owen Duffy wrote:

Mike, we (you and I both) aren't sure of the detail, and that in
itself speaks heaps for the product information.

Owen,

I found some information for this atnenna at

www.stroobandt.com/antennas/windom/windom.html

On the design attributed K4BT showing the dimensions to be:

L1= 13.4 meters (43.965 ft.)
L2= 27.1 meters (88.915 ft.)

Regards,
Danny, K6MHE

On Wed, 28 Jun 2006 10:09:55 -0700, Dan Richardson
k6mheatk6mhedotcom wrote:

On Wed, 28 Jun 2006 05:47:18 GMT, Owen Duffy wrote:

Mike, we (you and I both) aren't sure of the detail, and that in
itself speaks heaps for the product information.

Owen,

I found some information for this atnenna at

www.stroobandt.com/antennas/windom/windom.html

On the design attributed K4BT showing the dimensions to be:

L1= 13.4 meters (43.965 ft.)
L2= 27.1 meters (88.915 ft.)


Buxcomm's site does list a large number of antennas that are described
as "Windom" antennas, but the one that is subject of this thread is
not explicitly described in the product information as a Windom of any
kind, or as an off-centre fed dipole of any kind.

There is an apparent desire on the part of some to construct the case
that the subject antenna is a Windom on the basis of:
- designation of L1 and L2 on the diagram, although there are no
values stated to show that they are unequal;
- that elsewhere K4BT has described "coax fed Windoms".

There is nothing conclusive on the diagram at
http://www.commparts.com/catalog/ima...ts/8010ABD.gif to
suggest that this is a "coax fed Windom", though some infer that is
the case because of the L1, L2 designation though not values are
shown.

I argue that designation of a key component separating L1 and L2 as a
"center insulatore and eye hook" has more value than the undimensioned
L1, L2 designation.

What is becoming clearer, is that on the basis of the information
published on the commercial web site for this antenna, the buyer
cannot be sure of just what he is getting, much less how well it might
perform.

Owen
--

Owen Duffy wrote:
On Wed, 28 Jun 2006 10:09:55 -0700, Dan Richardson
k6mheatk6mhedotcom wrote:


On Wed, 28 Jun 2006 05:47:18 GMT, Owen Duffy wrote:


Mike, we (you and I both) aren't sure of the detail, and that in
itself speaks heaps for the product information.

Owen,

I found some information for this atnenna at

www.stroobandt.com/antennas/windom/windom.html

On the design attributed K4BT showing the dimensions to be:

L1= 13.4 meters (43.965 ft.)
L2= 27.1 meters (88.915 ft.)



Buxcomm's site does list a large number of antennas that are described
as "Windom" antennas, but the one that is subject of this thread is
not explicitly described in the product information as a Windom of any
kind, or as an off-centre fed dipole of any kind.

There is an apparent desire on the part of some to construct the case
that the subject antenna is a Windom on the basis of:
- designation of L1 and L2 on the diagram, although there are no
values stated to show that they are unequal;
- that elsewhere K4BT has described "coax fed Windoms".

There is nothing conclusive on the diagram at
http://www.commparts.com/catalog/ima...ts/8010ABD.gif to
suggest that this is a "coax fed Windom", though some infer that is
the case because of the L1, L2 designation though not values are
shown.

I argue that designation of a key component separating L1 and L2 as a
"center insulatore and eye hook" has more value than the undimensioned
L1, L2 designation.

What is becoming clearer, is that on the basis of the information
published on the commercial web site for this antenna, the buyer
cannot be sure of just what he is getting, much less how well it might
perform.

Of course someone could do an end run around us by just calling BuxComm
and getting the real scoop. 8^)

I don't doubt that someone might come to a different conclusion, but I
think my reasoning is pretty sound. I modeled an equal length version of
this in 4nec, and it just doesn't work very well. OTOH, turn it into an
OCF dipole, and it is a different story.

BuxComm has no need to sell an antenna as "multiband" when it isn't,
and when they have other comparably priced models that will work.


- 73 de Mike KB3EIA --

Mike Coslo wrote:
. . .
I don't doubt that someone might come to a different conclusion, but
I think my reasoning is pretty sound. I modeled an equal length version
of this in 4nec, and it just doesn't work very well. OTOH, turn it into
an OCF dipole, and it is a different story. . .

How did you possibly determine what the balun input impedance was when
terminated with the impedances the antenna presented on the various
bands? How did you model the balun? It's almost certainly a "voltage"
balun which will force common mode current onto the feedline when
terminated with an asymmetrical load. Because of the common mode
current, the outside of the feedline must be part of the model. Did you
model the antenna with various lengths and orientations of feedlines?

I don't believe that a valid model can be made of this type of antenna
without knowing and accounting for the major imperfections of the balun,
the common mode current it forces, and the feedline length and
orientation for the particular installation.

Roy Lewallen, W7EL

Roy Lewallen wrote:
Mike Coslo wrote:

. . .
I don't doubt that someone might come to a different conclusion,
but I think my reasoning is pretty sound. I modeled an equal length
version of this in 4nec, and it just doesn't work very well. OTOH,
turn it into an OCF dipole, and it is a different story. . .


How did you possibly determine what the balun input impedance was when
terminated with the impedances the antenna presented on the various
bands?

You are correct, I couldn't. But what I got was enough to tell me that
with the two sides of equal length, there wasn't much need to go any
further. Cannot some antenna characteristics be modeled without the
entire system in place? I'm no expert, so I'll ask the question: Is
there some Balun that will make a 135 foot equal length antenna perform
on 80-10 meters?


How did you model the balun? It's almost certainly a "voltage"
balun which will force common mode current onto the feedline when
terminated with an asymmetrical load. Because of the common mode
current, the outside of the feedline must be part of the model. Did you
model the antenna with various lengths and orientations of feedlines?

I don't believe that a valid model can be made of this type of antenna
without knowing and accounting for the major imperfections of the balun,
the common mode current it forces, and the feedline length and
orientation for the particular installation.

It isn't whether my model is exceptionally valid. I don't know what the
balun is that they use, so that sense it doesn't matter anyhow. You
would know much better the balun that would make this antenna work.

I'm just looking at what is there, and by looking at both the context of
the advertisement, references given for their other antennas and the
like, I'm just saying that I suspect that that antenna is a OCF dipole.

Their G5RV antennas do *not* have an L1 and L2 to designate length of
the sides. If that antenna has an equal length side, it is the only one
on the site that does. Yeah, I know they are not really G5RV's.

In addition, is BuxCom going to try to sell a product that apparently
doesn't work? I don't see any of the hype that tends to go along with
the "magic" antennas we sometimes hear about

All of the above just about convince me that the antenna in question is
an OCF dipole, and that the description and image is a big typo.

Others may take it at all at face value, disregard all the evidence to
the contrary, and assume that the sellers are just trying to hoodwink a
gullible public into buying a non-working product.

That doesn't make sense to me. YMMV

- 73 de Mike KB3EIA -

Mike Coslo wrote:
Roy Lewallen wrote:
Mike Coslo wrote:

. . .
I don't doubt that someone might come to a different conclusion,
but I think my reasoning is pretty sound. I modeled an equal length
version of this in 4nec, and it just doesn't work very well. OTOH,
turn it into an OCF dipole, and it is a different story. . .


How did you possibly determine what the balun input impedance was when
terminated with the impedances the antenna presented on the various
bands?

You are correct, I couldn't. But what I got was enough to tell me
that with the two sides of equal length, there wasn't much need to go
any further. Cannot some antenna characteristics be modeled without the
entire system in place?

Yes, but you have to at least include the whole antenna -- you can't
tell much about a two-element array by modeling a single isolated
element. In the case of an OCF dipole, unless heroic efforts are made to
keep common mode current off the feedline (which the balun doesn't
achieve), the feedline is part of the antenna so, like the second
element of an array, it can have a major impact on the both the pattern
and impedance and has to be included in the model. The balun, feedline
length, and feedline orientation all play a role in determining how much
current goes down the feedline part of the antenna and where that part
is. So you have to know at least that much to get a meaningful result.

I'm no expert, so I'll ask the question: Is
there some Balun that will make a 135 foot equal length antenna perform
on 80-10 meters?

"Perform" is one of those binary terms that depend on where you put the
dividing line. But the answer is that the only practical way you can
achieve a reasonable impedance match to a coax feedline on all bands
with a center fed 135 foot antenna is to introduce a fair amount of
loss. This could be in the form of a resistor at the feedpoint, for
example. Then you'll have an inefficient antenna at least on some bands.
Alternatively, you can have low loss at the feedpoint but a lousy
impedance match. Then you'd have a lot of loss in the feedline if you
fed it with coax. The bottom line is that you'll have poor efficiency on
at least some bands if you feed it with coax, no matter what you do --
short of putting either an adjustable or very elaborate fixed matching
network at the feedpoint.

Nearly any ham can measure the SWR but almost none can measure the
efficiency. So many antenna manufacturers have produced lossy antennas
which exhibit a low SWR. This is perfectly acceptable to many amateurs,
as evidenced by glowing reviews for a number of antennas which can be
shown to be quite inefficient such as the B&W T2FD or the Isotron. Those
amateurs would positively say that such antennas "perform", and this
can't be disputed since the judgment is entirely up to them.

. . .

Others may take it at all at face value, disregard all the evidence
to the contrary, and assume that the sellers are just trying to hoodwink
a gullible public into buying a non-working product.

That doesn't make sense to me. YMMV

"Working" is like "perform" -- the threshold is different for different
people. But a quick scan of reviews for the Buckmaster and Alpha-Delta
OCF antennas (the latter apparently manufactured by Buckmaster) show
high satisfaction from at least the users who have taken the time to
post reviews. Whether you or I would be happy with one depends on our
personal criteria.

Roy Lewallen, W7EL

Mike Coslo wrote:
I'm just looking at what is there, and by looking at both the context of
the advertisement, references given for their other antennas and the
like, I'm just saying that I suspect that that antenna is a OCF dipole.

At:

http://www.commparts.com/catalog/ind...sort=2a&page=2

The OCF's are labeled as Windoms and drawn with unequal elements.
The ones drawn with equal elements are not labeled as Windoms.
I would infer that they are different but I could be wrong. I sure
would like to know what's inside the "balun".
--
73, Cecil http://www.qsl.net/w5dxp

Roy Lewallen wrote:
Nearly any ham can measure the SWR but almost none can measure the
efficiency.

How about ten interested parties sending you $5 each so
you can buy and test one and review and report back here?
--
73, Cecil http://www.qsl.net/w5dxp