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Re: [TowerTalk] Triband Stacking Distance or antenna height?

To: TOWERTALK@contesting.com
Subject: Re: [TowerTalk] Triband Stacking Distance or antenna height?
From: Bill via TowerTalk <towertalk@contesting.com>
Reply-to: Cqtestk4xs@aol.com
Date: Mon, 23 Feb 2015 20:02:37 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
I've had lots of experience stacking antennas....from monobanders,  to 
duobanders for WARC to tribanders.
 
I wouldn't think twice about putting up a stack for any band, if  money and 
labor was not an issue.  I'd rather have two three element Yagis  stacked 
than on e 6 el at the top height.  Why?  Flexibility is the  answer, as well 
as maintenance.
 
Triband stacks?  I had them out at KH6 at around 90/60/30  (KT36XA).  Yes, 
the middle one was probably not really a big  contributor for gain on 20, 
but the signal brought endless piles of EU and  NA on that band, since the 90 
over 30 was still in effect.  15 and 10  were where they really shined.  
Granted I was on a nice big hill, but I  could definitely tell how much better 
the stack worked rather than just the top  antenna.  I also have the same 
stack at my place now and although it is  down a little from the 4 high 
monoband stacks on 10, 15 and 20, it still is a  very able performer.
 
If the sale of my house goes through the triband stack will be  employed at 
my new QTH in the Caribbean.
 
K4XS
 
 
In a message dated 2/24/2015 12:11:45 A.M. Coordinated Universal Tim,  
rxdesign@ssvecnet.com writes:

Hello  Rich, I’m not sure if this will be inline with the thread you’ve 
created,  a new thread or somewhere entirely separate... sorry if not 
inline 
where I  intended it to be.

I've had what you're planning on doing - a 3 stack  of C31's. See the 
picture 
on QRZ.com call sign search (K9RX). It was taken  down in April of 2012 
after 
having been up for 6 1/2 years (we  moved).

I can tell you that first off there are few times that a  separate antenna 
will be better than the stack. On 10 meters it would  happen occasionally, 
15 
less often and 20 probably less than a couple  times all told! I had 
antennas 
at 41, 81, 121. I felt this was the best  overall spacing. If I had it to 
do 
over again I'd probably reduce it to  37' or so as it really is too far 
apart 
on 10 and for a relatively short  boom 20 if you model it you can find that 
37' is a slight increase in gain  over 40' (with a slight reduction in FB). 
So using single or dual stacks  just isn't something you'll end up doing 
much 
of. There's too much  coupling into the non-connected antennas and thus 
little change in overall  performance. Once - on 10 meters, the lowest 
antenna was 20 db stronger  than the top ... but the stack was just a bit 
down from the  stack.

And indeed - the overall heights matter just as much. My low  antenna at 
41' 
was really too low for 20 ... and it is beginning to be too  high on 10... 
that stated I'd probably go with that one at 45' and then  37' spacing from 
there putting the top antenna at 119'. Note however - its  really not that 
critical - just stack them 35' - 40' apart and around  these heights...

I sold mine - I hope to be in South Carolina soon  (this year - purchased 
11 
acres in Piedmont - just have to move and build  a house)... and this time 
I'm going with 2 stacks of 20m 5el and 15m 6 el  on a rotating tower... the 
pattern and gain is better overall.

The  C31 stack played quite nicely on 20... and on 15... but I never really 
 
felt it was doing what I'd expect on 10. I had it with a Force12 240N 2 el  
40 meter at 130' and their Magnum 80 meter rotary dipole at 136'. And the  
SWR on 15 was never great - I was one of those that had the 'notorious' 15  
SWR problems that I could never get quite right.

As an aside I'd  often ask people to guess which of the antennas/systems 
worked best  overall... most would say the 3 stack of C31's... but the best 
antenna on  that tower was the dipole on 80 at 136'... it was awesome. Why? 
Because it  was competing against mostly wire dipoles at 50' - 60'.

Gary,  K9RX



I've been following the mail on this subject. I'm going to  start my new 
tower this summer. The base and anchors are already in. It's  going to be a 
137' rotating 55g tower with three F12 C31XR's stacked. I've  been using 
HFTA 
to come up with the best compromise heights (compromise as  I'm trying to 
get 
the best results on all 3 bands). Then it dawned on me.  Should I be 
worried 
about stacking results or individual heights. Isn't  the height of an 
antenna 
for a specific band at a certain time of day more  of an advantage than the 
combined stacking?, and of course it's still a  compromise since we're 
talking about tribanders. Don't get me wrong, I'm  still going to try to 
come 
up with the best stacking distances for my  location, but it seems to me 
that 
the most important feature of a stack is  having 3 different heights to 
choose from, isn't it? I sure wish the  project was finished, it would have 
come in handy this past weekend. Rich  - N5ZC  

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