[TowerTalk] Can take-off angle be too low?

[k6ll@juno.com]

On Thu, 29 Jun 2000 16:15:41 +0300 "Tonno Vahk" <tonno.vahk@hansa.ee>
writes:

> How important is it to have the ability of running very low 
> elevation angles
> in upper HF contesting? How much does it add to the score if one can 
> run 10
> meters with beams higher than 200 feet and get the take-off angle 
> down to
> 2-3 degrees? Here assuming one has also lower beams available. N6BV
> statistics actually indicate the high theoretical QSO precentage at 
> 1-3
> degrees. 

I think the N6BV statistics are essentially correct. It all comes
down to how much money you want to spend to achieve a certain level of
performance. The program YTAD, available from the ARRL Web Site, is
very valuable in answering this type of question. Updated elevation
statistics for the newer program YT should be used with YTAD. Those are
available for download also. Or, you can buy the ARRL Antenna Book,
which includes the newer YT program.

The "take-off angle" is defined as the angle of the first maximum.
Don't get too hung up on this number. Instead, look at the gain
at each angle of consideration. Even though the take-off angle
may be a little high, there may still be plenty of gain at the
lower angles. Start your analysis with a low tower, and then try
to talk yourself into spending more money for a higher tower and
another antenna in the stack, looking at the increase in dB that
YTAD shows you. Some people feel pain at $200 per dB, and some
are willing to spend $2000 or more for one dB!

I think some of the high-angle statistics in the N6BV files are for
those time periods when the MUF is very high, way above the frequency
under consideration. During those periods, a single op multiband
contester would probably be on a higher band (except for 10 meters,
where there is no higher HF band), so the importance of those high
angle modes may be somewhat discounted.

Dave Hachadorian, K6LL
Yuma, AZ
K6LL@juno.com

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