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

[n4kg@juno.com]

Interesting question.  Long delayed N4KG response below.

On Thu, 29 Jun 2000  "Tonno Vahk" <tonno.vahk@hansa.ee> writes:
> 
> Hi, I would like to hear your opinions about that topic. I have 
> found many contradictory thoughts on it and very few clear 
> and reasoned  statements really.
> 
> 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. To my mind it contradicts the somewhat common opinion that

> low angles get very little use. Would an efficient solution be to have 
> one stack at 230 feet (e.g. 5/5) and one at low height if there was so
high 
> tower available to be able to open the band early, be strong meanwhile
and 
> close it late? All this having flat ground in mind for simplicity.
> 
> 
> 73s Tonno ES5TV
> t.vahk@hansa.ee
> 

One or two sunspot cycles ago, N4AR had a 4 high 10M stack
at 35, 65, 95, and 125 ft (roughly 11, 20, 29, and 38 meters).
He noticed a severe echo on many (most?) European signals.

I attributed this to having the gain peak at too low an angle,
i.e., the arriving signals peaked at a higher angle where his
antenna had less gain due to pattern cutoff.

He installed a single 4L10 ( and later a 7L10) at 40 ft (12 meters)
and the echo went away.

It seems to me that if the ionosphere will support higher angles
several different modes (3 hops, 4 hops, etc) will be supported.
I *assume* that most Europeans do not have VERY high 
antennas, i.e., most likely in the 30 to 50 ft range, and therefore
the main lobes peak between 10 and 15 degrees with less gain
at lower angles.  Therefore, it is often best to also have a lower
antenna to match the angle of maximum radiation from the 
transmitter end.  I often find my lower antennas (40 ft) better during
the middle of openings to Europe than my higher antennas (60 and
80 ft).

de  Tom  N4KG





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