Many thanks Chris and Ken for your responce to mail below:
I trust that a brief description of the array will answer your questions.
The proposed antennas will be receive only 1-2m active Vertical ( FET/Bipolar
buffer amp) hence there will be no element mutual interaction. The centre
element is run in anti-phase compared to the outer elements, the amplitude is
the sum of the outer elements also. All 3 elements are combined using zero
delay for Element 1; 0.73x40m (95ns) for the centre (2) Element and 0.73x80m
(190ns) for the Element 3.
The delaylines provide near optimum phasing for reduced rear vertical lobe from
0.53MHz to 2.65MHz. Going above 2.65MHz or 0.35Lambda spacing the Gain and F/B
starts to reduce.
The array was modelled at 0.53,1.06,1.59, 2.12 and 2.65MHz using the degrees
phasing calculated from the delaylines i.e. the correct phasing tracks the
Eg. for 0.53MHz the phasing is 0, -162, -324 degrees and for 1.06MHz the
phasing 0, -143, -286 degrees. The delaylines were determined from a similar
model for a 3 Loop phased array.
I have used a similar phasing scheme for the MW 2 Element Phased loop array and
a Phased Vertical array.
Having struggled to model an 3 element endfire Active Vertical array using the
same Phasing lines from 0.53MHz to 2.12MHz. I find that I can achieve a very
good elevation plot with very low rear lobes (-30dB). Even the plot at 2.65MHz
only shows 2 small (-22dB) rear lobes!!! Also this model is very tolerant of
several dB amplitude difference on the outer elements providing that the centre
element is the sum of the 2 outer ones.
I have tried to do the same with the 4 Square, but there is always a large rear
lobe on the elevation plot 10-15dB higher than the 3 element endfire, no matter
how I adjust the phase. Am I doing something wrong or is there a fundamental
problem with the 4 Square?!
Both arrays have 40m Element spacing.
Andrew G8LUG (not active)"
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