On 12/27/2011 8:04 AM, Eddy Swynar wrote:
> And in 25 words, or less, explain why."
My last paragraph attempted to do that. But antennas and radio are far
to complex to describe their behavior in 25 words or less. One must
struggle to get one's mind around the laws of physics. We can do
relatively simple math to describe the behaviour of a simple antenna in
free space, or over an ideal earth with nothing in the way, and the
patterns are pretty and fairly easy to understand.
Trees, rain gutters, buildings, wiring in those buildings, towers,
feedlines to other antennas, even losses in the earth itself that vary
from one spot to another, are all complications that are incredibly
difficult to model mathematically. What I have attempted, and what Doug
and Roger chimed in to contribute to, are some careful observations of
how antennas we have built have worked around one set of these
complications -- trees.
To Doug -- my 160M Tee vertical that works well is more or less in the
middle of the clearing around my house and shack, which we here in the
California mountains have learned is critical for survival in a wild
fire. The top of the Tee is suspended from a redwood on one end and big
Madrone on the other. I have a 170 ft loaded horizontal dipole for
160M at 110 ft in that clearing, and when I first had both it and the
Tee vertical, I spent a lot of time switching between the two antennas
in contests. What I learned in that first year of very actively
comparing them was that on any given path, at any given time, one might
be better than the other, and it was difficult to predict which would be
better. BUT -- in the daylight hours (160M contests start at 2PM out
here), the vertical was ALWAYS at least 10dB better. I found that I
could consistently work everything I could hear out to about 1,000 miles
(Seattle, Denver, New Mexico, AZ) before dark, and for a few hours after
dark, with the vertical, whereas I wouldn't even get "QRZ?" with the
horizontal dipole for those distant stations. And that's a horizontal
dipole at 110 ft!
And Eddy -- I've heard you a few times during contests in the morning
hours, but you don't hear me calling (even though I work a lot of east
coast stations).
73, Jim K9YC
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