[TowerTalk] phasing multiband verticals

[Terry Conboy]

On 2009-03-09 9:55 PM, N7mal wrote:
> I am going to step in & out of this thread many times only because of my 
> experiences/work at/on phased vertical arrays.
> Who and more importantly WHY was the decision made that the phasing must be 
> done at the antennas.?.?.?. You can do the phasing in the shack and not have 
> to run a voltage to the antennas and also isolate the stray R.F. path back 
> into the shack.
> Why not run 2 equal lengths of coax from the antennas back into the shack, 
> preferably not in a length of 1/4 wave multiples. (Wavelengths are 
> calculated with velocity factor in all phased arrays)
I think one reason that hams would rather put the phasing network close 
to the antenna elements is that the pattern bandwidth is almost always 
better the closer these networks are to the antenna elements.  
Broadcasters who never change frequency usually don't care, unless they 
have issues with the instantaneous bandwidth for digital modulation.  Of 
course, if you bring longer feeders into the shack, you always have the 
option of using multiple phasing networks for different parts of each 
band to overcome the decreased bandwidth.  So it depends if you would 
rather weatherproof remote switches or add complexity in the shack.

I don't understand the problem with feedlines of 1/4 wl multiples.  
Several popular amateur phasing schemes are specifically designed to use 
odd multiples of 1/4 wl lines.

73, Terry N6RY