[TowerTalk] TWO VERTICALS One Fed 90degrees Behind The Other

[w8ji.tom]

Hi Dick,

> What's incorrect about it? Are systems
> based on hybrid couplers like Comtek's "incorrect"?

I haven't seen the Comtek, so I can't comment on it except to say many
people are very happy with it. I have no idea what they do, but it
obviously works.

Speaking of typical phased antenna systems, builders often think equal
power applied to two elements means equal radiation. That's only true in
the case of two phase shift conditions, 0 degrees and 180 degrees. For all
other phase angles, equal power (applied to two perfectly identical
antennas) will insure the radiation from each element is NOT equal and the
pattern is not optimized for maximum F/B or gain.

I think I described the general rules for the optimum condition (two
element array) for obtaining equal currents in a current fed antenna, and
if the antenna is voltage-fed at the voltage maxima equal radiation from
each element occurs when the voltages are equal and the currents and power
are not.

In a four square the optimum condition is where all four current fed
elements have equal currents at the feedpoints, and since the resistance at
each feedpoint (except the two middle elements share a common impedance) is
different the elements do not have equal power applied. I think the
Handbook covers this.

73 Tom

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