Date: Thu, 25 Apr 2019 00:37:24 -0500
From: Greg Best <gregbestconsultant@yahoo.com>
To: towertalk@contesting.com
Subject: Re: MODEL FOR TOWER
<Thanks to you all for your questions, thoughts, and input. My original
question was about interaction with the tower and really asking the question as
to whether someone besides me has addressed the issue before. (Better to take
advantage of work done <before rather than recreate the wheel.). For your
further consideration, the tower face at 60 ft is about 30 inches and it is 3
sided. The mount would likely be fixed on EU or a small robust sidearm with
?rotator on a post? realizing that I would not be able to turn it <fully
around. All of the bracing is an X.
<braces using 1.5 inchs angle steel above and below the 60 ft level. The
spacing between the DE & D1 is 106 inches, so I do have some room. The balance
point is abt 63 inches from the DE. The 20 m beam is a Wilson 204CD. I am not
familiar with the NEC command to ?<mirror ? the wires. Is it ?copy? or
something else?
<Tks. Greg N9GB
## If you are using the OEM wilson 204CD ele dimensions, and ele
spacings, they are 99% likely to be incorrect. I owned several wilson
yagis back in the day..and none of them worked to an optimum level. And
everybody else that I knew who owned any wilson yagi product stated the same
thing.
You folks that model this stuff in software, how do you factor in the
myriad of swages on each ele ??? How do you model the actual swaged
portion, where it jumps down 2 or more sizes of tubing. I once asked K6STI
about this when using several versions of his infamous YO program, and never
got a straight answer. Do you take the average or what? Considering the
sheer total number of swages used on a typ 20m yagi, like the wilson or
Hy-gain 204BA, I can see it being very easy to screw everything up while trying
to model an optimum electrical design.
## and how do you propose to tweak the ele lengths, and or spacings, to
factor in.... aka compensate for the 30 inch face width of his tower..at the
60 ft level ? He may as well use an optimum design for 60 ft above real
ground...mount it, and be done with it. The vertical legs of his tower will
have minimal to no effect on his 20m els..since the legs are at right angles to
the els. His tower uses X bracing, and based on my own past experience
using a 33 inch wide tower with X bracing..and side mounting a 20m yagi, their
will be no interaction, due to the tower. The X bracing is all at an angle...
its not horizontal. The effort should be put into modeling the old wilson
204CD..and coming up with better
ele dimensions...and spacings.
Jim VE7RF
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