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Old October 14th 06, 07:07 PM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Jul 2006
Posts: 2,951
Default Yagi Height Question

On 14 Oct 2006 08:20:07 -0700, "CW" wrote:

I was wondering why so relatively little attention is paid
to peaking the vertical component. Is it because of mechanical
complexity, lack of understanding, or something else?


Hi OM,

The single biggest factor is cost. You should be able to appreciate
the implication there.

The second (and related to cost) biggest factor would be wind load. A
taller tower is easier to push over.

Another factor would be the requirement for a very stout (cost again)
mast (more cost to lift more weight too); unless this is a telescoping
tower (costs more than a conventional one, doesn't it?).

About the cheapest consideration, the last one in this list, is what
you call "lack of understanding." The better question is:

What is the optimal angle for contact, not for launch?

Art recently came aboard here to seek validation for a secret design
that aimed "all" his power to England. When I did the modeling, that
optimal angle, depending upon
Frequency
Time of Day
Season
Sun spot cycle
varied from less than 6 degrees to as high as 12 degrees. FYI his
secret design is still secret.

Anyway, you can fulfill this last requirement (the cheapest) by using
two free software packages:
EZNEC for the launch characteristic of the NBS yagi vs. height;
VOAWIN (VOACAP VOAAREA) for propagation of that same antenna.

73's
Richard Clark, KB7QHC
 
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