On 2/18/2011 7:12 AM, GEORGE WALLNER wrote:
> So if you can add
> top loading, do it. Don't worry about it being
> assymetrical: the high angle radiation will be a small
> percentage of the overall energy radiated (better then
> burning it in the ground, anyway).
I agree conmpletely. The details of the geometry of top loading can
have a SMALL effect on the total picture. It's a lot like radials --
don't worry about ideal, just try to do MORE. :)
My Tee vertical is 86 ft vertical and more than 100 ft horizontal over
sloping earth. It makes the electrical length greater than a quarter
wave, so that the feedpoint Z is 50 + j 250 (that is, inductive), and
the current maxima is moved up the wire a bit. I then added capacitance
in series (a few hundred pF) to tune out the inductance, yielding 50
ohms to match the coax.
Another un-related trick, learned years ago from the ARRL Antenna Book
-- I doubled up on the vertical wires, using two of them in parallel at
top and bottom, but spaced apart roughly 4 inches. It increases the SWR
bandwidth enough that I can work up to about 1920 kHz during a contest
without needing an antenna tuner for my Titan 425 tube amp. My vertical
uses #10 THHN stranded wire.
73, Jim K9YC
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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