[TowerTalk] Takeoff angles - some practical experience

[Pete Smith]

At 01:20 PM 12/19/00 -0500, Robert Shohet wrote:
>...I thought
>it might be helpful for me to share some of my  observations strictly from
>the standpoint of a contester who has extensively guest-operated (and from
>home in the past three years) with all different kinds of antenna systems
>from all over the Northeast in all different contests for the past 20+
>years.


I think Bob's comments are very sound and obviously come from a strong
experiential base, at least for the Northeast.

He comments on the rapid variability of apparent arrival angles, and which
antenna height is consequently best at a given time.  A major undiscussed
variable in this situation is the antenna on the other end of the path.
VOACAP models frequently show 4-8 different propagation modes (and arrival
angles) simultaneously active over a given path from the US to Europe,
ranging from very low angles to the upper teens.  A low yagi on the far end
can discriminate so sharply against the best (low angle) mode for a high
yagi on the near end that a 1-2 S-unit difference is not out of the
question, as compared with a low yagi on this end that favors the same
(relatively high) arrival angle as the one in Europe.  

Then the very next QSO could be with a well-equipped European station with
a high yagi, and the situation would appear to flip.  In fact, all that has
happened is that the antenna on the far end now favors a different
propagation mode, and a different antenna on this end is optimum.

It appears to me that there is really a pretty good fit between theory, as
embodied in VOACAP predictions, and practical experience.  You can't
oversell the former, but neither should you ignore it in making station
design decisions.



73, Pete N4ZR

Contesting is ... Extreme Radio

The World Contest Station Database 
is back up and running at
http://www.qsl.net/n4zr 



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