[TowerTalk] TH6-DXX Band segment settings

[john simmons]

I've worked with modeling software quite a bit. Using the old rules of thumb for Yagi design, wider bands, such as 10 meters, getting too far from the design frequency causes the antenna to reverse direction.

Newer Yagi designs that are computer modeled are the ones to lust for. Traps are old school; interlaced 'monoband' elements are new school. This is a much, much better design.

Learning antenna modeling software is well worth your time! There are lots of online resources, but I bought all of ON8AU's books and AC6LA's AutoEZ. While we all want everything to be free, I found the tools I bought EXTREMELY helpful. Oh, and antenna modeling WORKS!

73
-de "Curly" John NI0K
QRZ.com<https://www.qrz.com/db/ni0k>
Hamshack Hotline<https://hamshackhotline.com/> call me: 6100271

On 11/8/2024 11:15 AM, Gerry Maira wrote:



        Thanks Jim. I believe the TH6 was designed for maximum gain and F/B
ratio, but I understand your point about utilizing software. I haven't
done much with modelling software but it's something I want to get
into a lot more in the future. Right now I think I can get acceptable
(to me) results from this antenna if I just set it up right.

73, Gerry KA2MGE

On 11/7/2024 12:52 PM, Richard Karlquist wrote:

        Consider this: the TH6DXX has 6 or maybe 7 dB gain over a dipole at
best. Using a tuner, the gain will never be less than a dipole. So it
will work as well as a dipole. For casual operation, that may work
just fine. It's only down 1 S unit.

        What Rick is getting at here is that element dimensions and spacing
is what determines DIRECTIVITY and pattern IN THREE DIMENSIONS, and
those three setting optimize FORWARD GAIN for those frequency ranges.
The antenna will WORK outside those ranges, but with much less gain.
This is the kind of error you make when SWR is your only criteria. The
antenna "loads," it radiates, but the pattern isn't great.

        It's worth spending time with a good modeling program to study this
with the many designs that are included with the ARRL Antenna Book, as
well as Dean Straw's (N6BV) YW software. It plots gain, FB, and, after
using the software to compute a match, SWR vs. frequency, I've used it
to design a few monobanders, built from aluminum and other hardware
scrounged from neighbor hams. I learned how to enter data by studying
the many provided files for designs. There is, no doubt, other
software. This is one I know. I also know and use NEC a lot, but not
for Yagis.

        73, Jim K9YC
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