Hi Gang,
Some folks mentioned that the top yagi is not "seen" on my short tower if I
should shunt feed it.
Is there any proof of that? Papers? EZNEC? Anecdotal evidence etc? (like you
removed the top yagi and the resonant freq on 160m remained the same ...)
I'd love to hear the comments.
I think I may have another stab at shunt feeding my tower and am curious
more than anything as to its true electrical height.
The reason for my curiosity is:
A) My Tee vertical slung in the trees is now working "fairly" well and the
top of it is just about the same as the tower....though the wire actually
slopes up at a 45º angle, so not really vertical....also the top loading
wires come towards the ground at almost 45º.
Certainly not an ideal "vertical". . .Picture an umbrella, opened, sitting
on the floor, with no material, and only 2 wires. That's about the shape of
it.
B) If the tower is only as tall as the first (lower) yagi (& the same as the
Tree Tee) I might not bother shunt feeding it.
TOWER SPECS:
48' Delhi, self supporting tower sunk into a massive block of concrete.
Bottom yagi is for 50MHz (elements are aprox 10' long we'll say) with a
30' boom.
Top yagi is 16' above that, identical to the first.
SOme have said the electrical height is:
48' tower + 1/2 the boom on the low yagi (15') + half of 1 element (5'), top
yagi & mast invisible - so aprox 68'.
Is there any chance it could be more like:
48'tower + 15' boom + 16' mast + 5 + 5 = 89' or am I dreaming? (I find it
hard to believe there is no current in the top yagi or the 16' mast--?
doesn't make sense)
I keep thinking back to my Cushcraft D40 rotatable dipole, which has
capacity hats nearish the element tips.....if the radio doesn't see anything
past the capacity hat, why have 4 foot (or whatever they are) element tips
at all?)
Thanks very much,
Mike
ve9aa
Mike, Coreen & Corey Smith
699 Rte 616 Keswick Ridge
NB
Canada
E6L 1T1
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160 meters is a serious band, it should be treated with respect. - TF4M
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