Topband: no response to query: feeding phased verticals at half wave spacing

[Rik van Riel]

On 11/22/2011 08:06 PM, Gerry Treas, K8GT wrote:
> Hi Dale,
>
> I'm no antenna expert, but certainly read as much of the experts publications as I can get my hands on, but having a Teflon brain, it doesn't stick very well.
>
> That said, the ARRL Antenna Book has a page that shows the patterns of various spacings and phasings of vertical antennas, which I found very enlightening.
>
Enlightening, but also somewhat misleading...

The patterns in the ARRL Antenna Book are correct if the
current in both elements is the same.

However, if you feed an array of antennas with delay lines,
those delay lines will act as impedance transformers for
the antenna impedance of each element (like all feedlines do).

This can result in each element getting different currents,
and the pattern no longer being what it was.

This makes feeding a phased array with delay lines much
trickier than one would imagine at first glance.