>The information you seek has been published by Dean Straw, N6BV,
>in a book titled "All The Right Angles." Combined with this
>book, the software "Yagi Terrain Analysis and Design" (YTAD)
>available in the ARRL's latest "ARRL Antenna Book" will allow
>you to do the calculations you desire fairly accurately.
I think the latest ARRL antenna book and the associtaed
files provide more than enough info and most of what is
in the "all the right angles" book.
If you use YT (the current version of YTAD) on the
20m antenna heights mentioned 90' and 120' (over flat terrain) I
see very little change in the low angle gain. The thing
that does change quite a bit is the locatoin of the
first null in the pattern.
At arrival angles of 14-18 degrees this diffrence looks
like it could be well over 10db. You really need to
model it over your terrain profile to get an idea of what
might happen in your case.
I am one that is always suspect of "models" and much prefer the
real world and experiance. Having said that I feel very
good about the data on arrival angles that N6BV has published.
I have been lucky enough to use antennas at many diffrent heights
(see http://www.kkn.net/~k5tr/)
over an entire solar cycle plus on most of the bands and my experiances
fit well with his calulations and models.
--
George Fremin III "I'm talkin' 'bout that outlaw X
Austin, Texas It's cuttin' through the air.... "
K5TR (ex.WB5VZL)
512/416-7010 -- "Heard it on the X"
geoiii@kkn.net -- ZZ Top
http://www.kkn.net/~k5tr
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