Hola Filipe.
No es facil stackear multibandas y tener una mejoria constante en
todas las bandas. Alguna banda sera la beneficiada y otras las
perjudicadas. En 20 metros de torre, 3 antenas son demasiadas. Quizas
dos antenas de 11 elementos tipo las ob3-11 a 11m y 22m estara bien.
Mucha suerte!
Marcelo CX2DK/CW4MAX
2016-07-17 21:14 GMT-03:00, john@kk9a.com <john@kk9a.com>:
> Have you modeled this in NEC2? The antennas are really close together, even
> for 10m. I think a two stack would be a better option. Yes they should be
> fed with equal length coax.
>
> John KK9A
>
>
> To: towertalk@contesting.com
> Subject: [TowerTalk] Tribander Stacking
> From: Filipe Lopes <ct1ilt@gmail.com>
> Date: Sun, 17 Jul 2016 18:50:29 +0200
> List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
> Hello guys,
>
> I have read quite a few posts here but I still am not sure about the
> distances I should use to stack my tribanders.
>
> I am rebuilding my contest station CR6K in Portugal from scratch, meaning
> all antenas are gone, new antennas are being constructed and also a new
> self supporting cranck up tower 20m high is being built by my dad CT1CJJ.
>
> For this new tower I want to make a stack of 3 x tribanders (10 15 20m) 11
> elements each. I tried a few simulations with MMANA and HFTA and what I
> found is that my stacking distances are best at 5.4m (+- 17 feet) from each
> antenna, meaning I would have the 3 antennas at 11.4 m / 16.8 m / 22.2 m (
> 37 / 55 / 73 feet). I then read one post from someone who says that HFTA
> has some sort of bug that considers maximums at < than 0.5 wl.
>
> For info the top antenna will rotate when necessary and the other 2 will be
> fixed to USA and my QTH slopes down a lot towards USA. Also this is mainlly
> a USA tower because there is another tower dedicated to EU/ASIA.
>
> So my questions are:
>
> - Is a stack of 2 tribanders @ 60/90 feet enough?
> - If I consider the 3 tribanders the top one might be a lot towards EU
> and so the other 2 towards USA
> - Is 9 m (30 feet) the optimum stacking distance for tribanders?
> - Will it hurt having for example 30 feet stacking between the 2 bottom
> antennas and 17 feet between the second one and top one?
> - I know the coax lines between the antennas and the power splitter need
> to be electrically the same but does it matter how long they are, for
> example 3x 25m is ok?
>
>
> All comments and suggestions are welcome.
>
> Thank you so much.
>
> 73's Filipe Lopes
> CT1ILT - CR6K
> F4VPX - TM3M
>
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