[TowerTalk] Re: Stacked StepIrs

[Howard Klein]

I am attempting to answer the various posts which differ a bit, with a 
single E-mail. If I can answer other questions feel free to e-mail on or off 
reflector. I am certainly looking for a few answers myself, namely a means 
within my capability to objectively determine  if and what I have 
accomplished.

I think the stack works quit well. All opinions are subjective based on my 
experiences over my ham career. In the past I have stacked X-9's and have 
used a Telrex 326 as well as some lesser antennas. I can not come up with a 
reasonable way to gather more objective criteria.I believe the flexiblity of 
being able to use antennas at different heights is an advantage filling in 
elevation angles as well as both in phase which does lend an additional gain 
factor. I currently use the Comtek Stack2 Yagi System. It is very simple and 
straight forward. I previously used the Array Systems Stack Match which at 
the time offered only the three stack yagi box. This was a bit cumbersome 
with only a 2 stack and in my case did not supply the result I sought. I 
stack 2 antennas both monobanders at any given time (4 el SteppIR's). The 
top is at 75 feet and the bottom at about 40 ft. Both are on Hazers which 
allows for some adjustment of separation.The steps in fine tuning 
(hopefully) consists of plugging the default values into YO7.5. I  emphasize 
the gain, about 75% and optimize for a single yagi on a specific frequency 
in the middle of the band of interest. My problem here is that in my YO 
program when I enter the stacked pair it allows dimensions for only one data 
set. In other words I can not use different data for top and bottom 
antennas. Consequently I generally run for a single antenna at 75 ft. I then 
plug these figures into Eznec and where I can vary the dimensions for each 
antenna and vary the data for predicted max gain. These numbers are entered 
into the control box and then tested for acceptable SWR. If SWR looks too 
high I will adjust the driven elements first for acceptable SWR. If there is 
only a small physical difference I am done. If the difference is greater I 
adjust the passive elements but attempt to remain within the same 
proportions. In no case (all frequencies) are the dimensions for the upper 
and lower antennas the same. This indicates to me that there are 
environmental differences between the two antennas although I do attempt to 
make them the same within my control, i.e. equal cable lengths, etc. My SWR 
usually runs less than 1.5:1 for each antenna or the pair in phase. I wish I 
had a method for knowing what I am accomplishing other than a subjective 
feeling and how I come out in a pileup. I am wide open to ideas. I think it 
is a distinct advantage to be able to tune each each antenna's dimensions 
remotely.

Howard...K2HK

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