[TowerTalk] C31XR? ANT file - Problems

Guy Olinger, K2AV k2av@contesting.com
Tue, 22 Feb 2000 17:03:17 -0500

However innocently one may play around with dimensions, or think that
one has the answers, let the reader beware of antenna figures when their
source is not known.

I own a C31XR. There are problems with the model published in the
previous post.

At least three elements have been altered, including one in a very
sensitive part of the antenna, where even a 1/4 inch change in element
length gives an unexpected magnitude of change in performance
parameters. It is clear the modeler has not had the design up on a

On one band the C31 has an alternate spacing used for three feedline
configuration besides the single feedline configuration. The model in
the previous post is using the single feedline configuration. To model
the single feedline configuration correctly requires NEC-4. Any modeling
based on other engines using the single feedline configuration will give
erroneous results.

N6BT spent over two years designing the C31XR. That was because the
combination of elements was an exceedingly difficult design. He not only
modeled, but did a lot of up-and-down work to get the performance right,
in spite of the modeling difficulties. He paid for the NEC-4 time.

It is one thing to copy something for yourself and make changes for
yourself. It's your time, it's your paid-for aluminum, it's your living
with your results, it's your up-and-down-the-tower-time if you screw it
up. Publishing personally modified design, and passing it as the real
thing is another. Publishing the exact dimensions without permission is
copyright infringement. Changing a few measurements apparently to avoid
copyright infringement still results in copyright infringement in the

So one pays $$$$ for a C31 from Force 12. He spent two years designing
it, he buys the aluminum and miscellaneous parts, he fabricates, he pays
for the employees and overhead. It's the top tribander. The $$$$ is a
surprise? They get to eat too.

Disclaimer: NO affiliation with Force 12 here.

- - . . .   . . . - -     .   . . .     - - .   . - . .

73, Guy
Apex, NC, USA

----- Original Message -----
From: V.Kecman <kk@cg.yu>
To: <towertalk@contesting.com>
Sent: Tuesday, February 22, 2000 8:10 AM
Subject: [TowerTalk] C31XR? ANT file

> Too many people asked for the ANT file of the antenna that is VERY
> to C31XR.
> Force12 sells theirs for $$$$, and this one you can build yourself,
> your own tubing. Modelers should play variations, since this file does
> contain adequate information on closed transmission line technique,
but is
> good enough start. Compare this antena to TH6 file available at K5TR
> website.
> I also have C3 file.
> 73 Kele YU1AO/6
> Some people call this C31XR
> Free space
> 14 MHz

... data deleted ...

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