W8JI's observations reminded me of some of the doubts
I've had, when taking the lower yagi in a stack, and
pointing it stateside. (Or, in w3gm's case, putting a 3el
up at 25', fixed west & splitting the power.)
My comment was...it is sometimes effective.
'Sometimes' may be explained by Tom's general interference
pattern/fading observation, which I believe to be correct.
Which brings me to the point of this post...
It seems that some contesters feel it's OK to split a stack, and
off-point the stacked antennas. Top on EU, or JA, and
lower on SA. Or, the upper 2 stacked in the run direction, and
the lower one pointed to pick up stray mults. These things are
within 1 wavelength of each other, and have to interact.
Tom observes that the pattern resulting from two co-fed antennas
is the vector sum of the two patterns.
on key bands, N2RM has main towers with stacks, and secondary
towers with single yagi's at 70' or so, for mult chasing. These
are separated horizontally by several wavelengths. I never noticed
any interaction. Played well.
It's never easy to judge performance in the heat of battle, but
my feeling has been that splitting and offpointing a stack has
had compromised results. I wonder what others have observed.
n2ea
jimjarvis@ieee.org
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