Thanks Jim, and thanks to the others that have replied to my question.
You are correct regarding the article in the ARRL Antenna Compendium
article. An earlier work by Frank Witt, AI1H appears in volume 2 of the
compendium series, pp 110-118. That article contains the formulas he
derived and used to develop the "Coaxial Resonator Match" that was further
developed to become the 80M DX Special by Ed Parsons, K1TR. I have the
compendium series and have worked through those formulas a couple of times
and come up with the lengths of the coaxial match sections that comprise
part of the antenna system, however I am a little uncertain of a couple of
installation specific basic variables ( Dipole Q and Dipole radiation
resistance at center) and ended up using default values as used within the
original article. Thereafter I was wondering if anyone else had done a
similar translation and if my values are comparable. One would think the
values would simply be scalable for 40M from the original 80M version, but
my calculations were not such, close but not precisely scaled to 40M from
80M.
Mr. Witt wrote that he developed a spreadsheet simulation that he used to
derive the final values. The calculation is an iterative process and such a
spreadsheet would certainly be handy.
I will certainly review your article on SimSmith.
Thanks again.
Sam
VE5SF
-----Original Message-----
From: CQ-Contest <cq-contest-bounces+ve5sf=sasktel.net@contesting.com> On
Behalf Of Jim Brown
Sent: Friday, March 22, 2024 11:40 PM
To: cq-contest@contesting.com
Subject: Re: [CQ-Contest] "DX Special" by K1TR for 40M?
On 3/22/2024 4:00 PM, john@kk9a.com wrote:
> W6NL wrote the following post and article on broadband dipoles:
> http://lists.contesting.com/archives/html/Towertalk/1997-11/msg00695.h
> tml
> https://www.arrl.org/files/file/QEX_Next_Issue/Nov-Dec2018/Leeson.pdf
Dave told me about ten years ago when I asked if he minded that I wrote it
up,that the concept was much older than him, and that he had been teaching
it for years.
I went through the concept as part of a tutorial on using SimSmith for
transmission line calcs, and for designing matching networks. It's here.
http://k9yc.com/PacificonSmithChart.pdf
There's another method of broadbanding that involves using sections of
transmission line as part of the dipole. It was published in one of the very
nice ARRL Antenna Compendiums. Over the years, I've acquired a set.
I'd go look it up, but they're in an outbuilding with the shack, and it's
raining a lot. :) N6BV told me about 15 years ago that a lot the pieces in
those books never made it to QST.
73, Jim K9YC
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