Hello Guy,
I forgot to tell you that I have a single KT-34a that is on an 89 foot
self-supporting crank up tower. I have at times put in a coax switch that
allows A/B testing. When I am working a European pileup in the middle of an
opening, I will typically see about 10 dB in favor of the stack. When the band
is just starting to open or close, I will see as much as 30 dB difference in
both rcv and tx. That is due entirely to the very low angle which is similar
to a single yagi on a very high hill like you mentioned.
73/Mike, N7ML
Guy Olinger, K2AV wrote:
> 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>
To: <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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