[TowerTalk] 3-Stack Tribander Issues

[GALE STEWARD]

FYI..

K3WW has a stack of three Skyhawks at 30/60/90 ft and it works great.

73, Stew...




--- On Wed, 2/24/10, Bill Conwell <wycpublic at gmail.com> wrote:

> From: Bill Conwell <wycpublic at gmail.com>
> Subject: [TowerTalk] 3-Stack Tribander Issues
> To: towertalk at contesting.com
> Date: Wednesday, February 24, 2010, 1:30 AM
> I’m thinking of building a 3-stack
> of tribanders.  Folks who are familiar
> with stacked monobanders give me doubtful looks. 
> I’m wondering who on the
> list has actual experience stacking tribanders, and what
> practical
> observations they can offer.
> 
> 
> 
> By way of background, I was an EE in a past life, with a
> bit of professional
> experience with phased arrays for VHF/UHF and shortwave
> broadcast, and
> radar.  So I appreciate the phased array concept.
> 
> 
> 
> My contemplated stack has 8.6m spacing between antennas
> (with the top
> antenna at 130’).  I recognize that half wave
> spacing has certain desirable
> attributes, and that my spacing is a bit large for 15m and
> a bit short for
> 20m.  But modeling suggests that’s not a big
> deal.  (I may cover 10m
> separately.)
> 
> 
> 
> I expect to turn the top two antennas in tandem, and have
> the bottom antenna
> independently rotatable.
> 
> 
> 
> I recognize that tribanders are, themselves,
> compromises.  However, current
> designs seem a vast improvement over the designs of 30
> years ago.  (I’m
> thinking of using one of the interlaced models, e.g., with
> 2 or 3 full sized
> elements per band.)
> 
> 
> 
> I’m not interested in longer boom yagis – narrow in
> azimuth and broad in
> elevation pattern (e.g., beaming Europe only to put a null
> on Africa, or
> beaming Japan only to put a null on NZ/Australia). 
> I’d rather have a
> broader azimuthal pattern, and a selection of different
> elevation patterns –
> depending on whether I drive antennas #1+#2+#3, or #1+#2,
> or # 2+#3, or
> #1+#3, or #1, or # 2 or# 3.
> 
> 
> 
> What issues/observations can folks with experience relate?
> 
> 
> 
> Tnx/73,
> 
> 
> 
> Bill, K2PO/7
> _______________________________________________
> 
> 
> 
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