I am building a new station at my vacation place in Northern CA. I will run
a C-31XR for 10-20 meters, and want to stack a 40 meter yagi with the C-31.
The rotor will be a Tail Twister. The station will be used primarily for
domestic contesting - Sweepstakes, NAQP, CQP, etc. I have steeply sloping
foreground to the US.
I have the remains of an old Telrex 3-29 40 meter yagi. The boom is pretty
beefy, and 29 feet long. I plan to design and build a 40 meter yagi from
the parts, either a 2 element 50 ohm direct dipole feed yagi on about 22' of
the boom, or a 3 element beta match fed 3 element yagi on all 29'. I have
two questions:
1) The 2 element yagi will be lighter, put less torque on the rotor, have
less effective wind area, etc. It will also have .5 - 1 db less gain than
the 3 element, and a fair bit less front-to-back ratio. Any thoughts on
which way to go? Am I just asking for huge mechanical issues if I put up
the 3 ele., especially with the rotor?
2) I have to choose whether to use full size 40 meter elements, or to load
them somehow (probably capacity hats at the ends of the elements. 4 2'
spokes shortens the elements to about 56' - 8' of hat spokes saves 5.5' of
tip length (per side). Maybe F12 style linear loading line the new N
elements.). It seems clear that electrically, the full size elements are
better. Mechanically, it isn't clear to me which way to go. Any thoughts
on why the shortened elements might be better? Less torque on the
mast/rotor?
Thanks much!
***dan, K6IF
P.S. My web site, including the 10 meter contest story, will be back on the
air soon at http://www.k6if.com . My ISP went out of business rather
suddenly, crashing my old site.
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