All,

I refer to the diagram at http://www.vk1od.net/lost/Fig6.png which is
from an article by the then VK2ZAB (now VK3EJ) on stacking Yagis.

I have highlighted two of the diagrams with a yellow background, and seek
opinions on them.

Referring firstly to the left hand one:

I suggest that the figure is in error because the scenario is not ALWAYS
wrong.

My contention is that at a single frequency, the phase inversion as a
result of the left to right swap of one driven element (DE) wrt the other
can be fully compensated for by ensuring that low loss feedline to one DE
is an odd number of electrical half waves longer than to the other.

Where the low loss feedline to one DE is an odd number of electrical half
waves longer than to the other, the Yagis are driven in phase.

The outcome being that the pattern at that frequency is approximately the
same as if equal length feedline branches were used.

Referring now to the right hand one:

I suggest that the figure is in error because the scenario is not ALWAYS
wrong.

My contention is that at a single frequency, that where the low loss
feedline to one DE is an integral number of electrical full waves longer
than to the other, the Yagis are driven in phase.

The outcome being that the pattern at that frequency is approximately the
same as if equal length feedline branches were used.

Note that I am not trying to excite a purist discussion about branch vs
distributed feed arrangements for phased arrays.

Am I on the wrong track?

Owen