[TowerTalk] phased verticals

[Tom Rauch]

> wave line will reach between the two.  I can then coil up both a 1/4
> wave line to feed the closest vertical and a 1/2 wave line to switch
> in series with the 1/4 wave line.

Or you can simply switch in a 180 degree transformer, but the 
coax line is probably easier.  
> 
> I have been reading  ON4UN's book on Low Band DX'ing, and now am not
> sure if this will work.   Specifically, section 4.5.1 on page 11-37
> talks about "current-force feeding" and he says; "to preserve
> symmetry, the T junction where the lines to the elements join, must be
> located at the center of the array".

You do not need to "current force feed" two elements that are fed in 
phase, or 180 degrees out of phase because mutual impedances 
are equal (or should be if the array is built correctly). The situation 
where elements are in or out of phase is much different than the 
four square, where each element group (front, middle two, and rear) 
has a different impedance. 

It is still a good idea to keep the lines exactly the same length to 
the common point, rather than making one 180 degrees longer than 
the other, because current distribution and phase errors caused by 
standing waves or line loss will be less. There would be nothing 
wrong with using two equal length lines, each as short as possible, 
between each antenna and a common point as long as you do your 
impedance matching somewhere between the common point and 
the rig. You can use a conventional choke balun, if it is a good one, 
to get the 180-degree phase flip.



 
> To do this you have to use two 3/4 wave feed lines for the in-phase
> pattern and then a 1/2 wave delay line at the switch box.   In my
> case, this means another 300 ft or so of coax.
> 
> I am not by any means an "antenna expert", but I cannot figure out
> what difference it makes whether the switch box (or T) is located in
> the center of the array (to preserve symmetry) or at one end.  
> Electrically,  it seems that it makes no difference where the switch
> box (or T) is.    Am I missing something or does the "physical"
> symmetry of the "T" or switch box make a difference?
> 
> Thanks for any help on this.
> 
> Dick Williams  K8ZTT
> 
> 
> 
> 
> 
> List Sponsored by AN Wireless:  AN Wireless handles Rohn tower
> systems, Trylon Titan towers, coax, hardline and more. Also check out
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> 
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73, Tom W8JI
W8JI@contesting.com 

List Sponsored by AN Wireless:  AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 100 feet for under $1500!!  http://www.anwireless.com

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