[TowerTalk] Stacking question

[Jim Thomson]

Date: Tue, 9 Aug 2016 06:57:06 -0400
From: "john at kk9a.com" <john at kk9a.com>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Stacking question

There is a lot of information about stacking in books such as W2PV's Yagi
Antenna Design.

John KK9A

##  take the w2pv info with a grain of salt.  In one of his lectures, he put the top 20m yagi
at 150 ft.   Then tried the bottom yagi at  65/75/85 ft. On his software, the gain peaked with 
bottom yagi at 75 ft.   The premise was, the bottom yagi was placed midway between top yagi...and
the dirt !   IMO,  if the top 20m yagi was instead at  200 ft,   you would not place the bottom  20m yagi
at 100 ft...more like 130-140 ft.   Then w2pv  tried modeling a 3 high stack, at  150/100/50..which smoked everything. 

##  stick with HFTA, and enter everything  correctly.   If you plan on buying 450 ft of tower, instead of
3 x  150 ft towers,  have at least one of em  up 190-200  ft .   A buddy has a 3 x stack on  20m on his  190 ft
rotating tower.   Then a 2 x stack on both 15m..and also 40m.  ( 40m is   90/180 )     Then a 2 el 80m yagi at 190 ft. 
Ok, then you can really smoke on  80 /40 /20 /15m.   The 2  stack on 40m is a flame thrower.  The 3 stack on 20m is
a flame thrower on steroids.   2 el on 80m at 190 ft is pure gravy...loads of gain, quiet, lotsa FS...and good FB. 
Then single yagis on 6/10/12/17.   It all fits on a single 190 ft rotating tower.  

##  But it all has to be designed for local WX.   IE: factor in expected max wind speed and any possible icing. 
Rotary towers are great... except everything is pointed in the same direction.   With ring rotors etc, its a real
advantage being able to point  each 40m yagi..in a different direction.   Then u get to blast away..in 2 simultaneous
directions.    But it all depends on the application, location, DX mode, fun mode, MM or MS mode etc. 

Jim   VE7RF