[TowerTalk] 4square/spitfire alternative

[Pete Smith]

At 09:30 AM 2/22/2005, Jim Jarvis wrote:
>The unanswered question, though, is CAN THIS BE DONE USING
>MONOPOLES FED AGAINST GROUND, USING THE SAME FEEDLINE SCHEME?
>I think it's a worthy experiment, but needs to be modelled
>for spacing.  I suspect a 1/4 wave element spacing with a
>3/8 wave feedline might work ok, based on the typical cardoid
>pattern which derives from 90 degree spacing fed 90 degrees
>out.


Interesting idea, Jim.  I think, though, that you're mixing two feed 
schemes.  This arrangement is not all-driven, but rather a variation on the 
Yagi-Uda parasitic concept.  The feedline's length is only important 
insofar as how much equivalent inductance (and loss) it adds to the center 
of the parasitic elements, when the feeders for the non-driven elements are 
left open-circuit.  It would be simple enough to model the scheme you 
describe, either using transmission lines or (preferably) using lumped R 
and Xl values derived from the feedlines used.  I expect that the spacing 
would be quite non-critical.

73, Pete N4ZR