Several years ago, before the station was dismantled, I ran the 15 meter
stack at K5XI during a contest. It had 4 KLM 5el Yagis, each separately
rotateable. During slow times I pointed each antenna toward a separate
area. When activity was heard, the best antenna was selected, then all
others were rotated in that direction and phased again until the run played
out.
Keith NM5G
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Jim Jarvis
Sent: Monday, April 04, 2005 10:28 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Multiple antennas-- offpointed stacks
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
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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