One common interaction is between a resonant antenna and a nearby
antenna on the second harmonic of the first. For example, 40M interferes
with the 20M pattern.
There's an easy fix for this -- the 40M antenna should be shorted at the
feedpoint on 20M. This is easily accomplished with a shorted stub that
is a quarter wave at the resonance of the lower frequency antenna,
located either at the feedpoint of the 40M antenna or some multiple of
20M half waves along the 40M feedine. As it turns out, this is the same
stub needed for 2nd harmonic suppression on the 40M antenna, and at the
optimum location for harmonic suppression.
73, Jim K9YC
On Mon,5/1/2017 9:48 AM, Kelly Taylor wrote:
Doesn’t Optibeam use stubs on their 40-10m multibanders to minimize interaction
between 40 and other bands?
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