[TowerTalk] A Question of GAIN

[Guy Olinger, K2AV]

Trying hard to keep this apples and oranges and not mix the two.

1) The change in maximum peak gain (peak gain forward counting peak at *any*
angle of takeoff on *either* beam or combination) is going to be 5 dB or so.
This is just math and modeling.

2) The change at a *single* takeoff angle, the one where all the qso smoke
is, might be enormous. Some single yagi patterns, at height, have nulls at
10 degrees! It's entirely possible that a single yagi has a null at the best
takeoff angle for condition x at time y. In this case going to the stack
will be like night and day on the other end.

3) Having a switchable stack allows managing the takeoff angle, one
combination creating peaks where another has a null or is pretty well down
on the pattern.

4) Individual location geography modifies 2) and 3) to a huge extent. (Play
around with the "Terrain Analyzer" [TA] program to convince yourself of
this.)

I think 2) and 3) are what all the anecdotal evidence is about, not 1).
When folks are talking about 10 or 20 dB, 5db stack gain barely begins to
explain it.  As to 4), there are some locations where their single yagis
look as good on TA as stacks do at others. This is not helpful for getting
exact inference from anecdotal evidence.

73, Guy.

------------

Guy L. Olinger  K2AV
k2av@qsl.net
Apex, NC, USA



-----Original Message-----
From: Mike Lamb <n7ml@imt.net>
To: CQK8DO@aol.com <CQK8DO@aol.com>
Cc: towertalk@contesting.com <towertalk@contesting.com>
Date: Monday, October 19, 1998 11:52 AM
Subject: Re: [TowerTalk] A Question of GAIN


>
>Denny,  I must disagree with you based strictly on experience.  Others,
please
>forgive me repeating myself from an earlier message.  I have six stacked
triband
>yagis on a 190 ft. rotating tower.  It works well enough that I can often
get a
>major European pile-up going anytime there is propagation.  Over the years
I have
>made a habit of asking stations that I hear in the pileup who are 10 or 20
dB
>above the crowd what antenna they are using.  Invariably, the the response
is
>either a stack or a quad!!!!  Also, I have a stack switch that allows me to
check
>signal strengths of any combination of pairs of antennas.  After playing
around
>with the switch for the first six months or so, now I just leave all
antennas
>switched in at all times.  The whole stack is almost always (at least 85%
of the
>time) better than any other lesser combination.  I am enough of a believer
in
>stacks that I use them for the tribands, 40 and six meters and none are a
>disappointment considering the added expense and effort.
>
>73/Mike, N7ML



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