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

[Tonno Vahk]

I wish to thank everybody for their comments on the topic, I am very glad to
find so active feedback.

The common opinion seems to be that low angles are as important as high
angles for maximizing the results. So for 10 meters the best idea would be
to have one long boom yagi as high as possible (e.g. 200 feet) and stack at
lower height (maybe 50-100 feet). It would give great flexibility to choose
optimum antenna for all periods.

I'd like to provoke you a bit more. Many guys say that if the beam is too
high its useless for most of the time when higher TOAs are needed. There is
one thing about this logic the keeps bothering me. Based on my modelling
experiences I see that a very high beam (e.g. 200 feet 10m beam) has many
other lobes besides the very low angle main lobe. With several sharp lobes
it covers all the angles up to 30-40 degrees having the same or even higher
gain on those lobes than the low antenna. In the same time the it has even
sharper nulls in between the high lobes. So it has to be that the signals
are generally coming in very sharp and there is a tendency to fall exactly
into those nulls. Only then can the low antenna perform better. Is it really
so? If I have very good gain at 7 and 9 degrees but null at 8, can the DX
signal fall exactly on this 8 degrees null and no QSO is possible or the
incoming signals are not so sharp really? I find that the higher the beam
goes the sharper the nulls are and thus at some height probably the high
beam will outperform any lower ones. Could it actually be so?? 

Another explanation is probably that the high beam loses a lot of higher
lobes when the terrain is not perfectly flat. I believe that in the presence
of obstacles and non-flat terrain the lower antennas are relatively more
dominant than with flat terrain. So the conclusion would be that the flatter
and more perfect your terrain is the higher you would want your beams to
be??

Tonno ES5TV

-----Original Message-----
From: K3BU@aol.com [mailto:K3BU@aol.com]
Sent: Friday, June 30, 2000 1:38 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Can take-off angle be too low?



In a message dated 6/29/2000 9:17:10 AM Eastern Daylight Time, 
tonno.vahk@hansa.ee writes:

> 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?


For top contester (gunning for top spots) every fraction of dB and coverage 
of as many angles as possible is very important and this is where one can
get 
edge on the competition (combined with knowledge of propagation, operating 
skills, station equipment).
    Stacked antennas give flexibility in switching angles, more antennas, 
more choice of angles. Low angles help mainly at the band opening and 
closings, but also during the middle of the opening, when some DX stuff is 
coming through.
    When I had my stacked Razor Beams 
(see some pictures at  <A
HREF="http://members.aol.com/ve3bmv/index.htm">VE3BM
V Home</A> ) 
they gave me 1 to 2 hours jump on propagation and ability to work stuff when

notables like W2PV (with Yagis) and others could not hear any more stations.
    Results in scores? My scores jumped by about 30 - 40% and for the first 
time in Canadian history I was able to corner all monoband records on 20 and

up, which were perpetually held by VE6 and VE7s.
    Generally at the height of sunspot cycle, angles are predominantly 
higher, at low cycle, they are low. This cycle is low and crazy.
    Unless you have antennas that can play at various angles, you will never

know what you are missing. There is nothing more enjoyable like when sitting

there and working the pileup that your competitors can't hear. (Razors give 
the edge!)

Yuri, K3BU, VE3BMV

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com