I'm coming a little late to this conversation, but maybe my experience
will be illustrative - I had a tribander at 97 feet, with a 2-element
40-meter short yagi about 10 feet above it. Until I turned the 40-meter
yagi perpendicular to the tribander, it completely destroyed the
tribander's pattern and swr on 15. Once I did that, all these
deleterious effects went away.
73, Pete N4ZR
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On 9/1/2022 2:45 PM, Jim Brown wrote:
On 9/1/2022 11:09 AM, Kim Elmore wrote:
I have a KLM KT-34A about 8 ft from and perpendicular to 40CD2. They
each appear unaffected by the other, at least as far as VSWR values go.
I wouldn't expect to see interaction from the elements if they were
perpendicular, but MAYBE from the boom.
An easy way to check for interaction between antennas is to model the
victim as a dipole with the addition of the potentially interfering
antenna as a dipole at the planned spacing, and look for current
induced in the potentially interfering antenna when the victim antenna
is driven at its operating frequency. If there is significant current,
I'd start looking at it's vertical pattern, also varying the lengths
of the interfering antenna to simulate the effect of reflector and
directors of the interfering Yagi.
If interference disturbs the vertical pattern enough to matter, you
can play with spacing until the effect is minimal.
73, Jim K9YC
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