Perhaps measuring the vswr while rotating would work better. There will
directions with lobes and others with nulls. If the instrument reading is
steady then you could assume the extra rf from the broadcast station is not an
issue. Maybe?
Gerald K5GW
In a message dated 7/29/2016 1:10:01 P.M. Central Daylight Time,
jim@audiosystemsgroup.com writes:
The limitation of this approach is that any Yagi has its intended
directivity only within a few percent of its design frequency. Away from
that frequency its directivity is best described as "undefined." So
while I agree that rotating the antenna may CHANGE the pickup from the
FM station, don't expect it to change much, or in any predictable manner.
:)
73, Jim K9YC
Fri,7/29/2016 9:14 AM, Jeff DePolo wrote:
> Assuming the yagi is mounted in the clear and can be rotated, first
point it
> at the FM station and make a measurement, and then rotate it 90 degrees
> (broadside) and take another measurement. If the apparent match/VSWR
> changes as the orientation is varied, that would be a good indication
that
> the test instrument is being overloaded or otherwise adversely affected
by
> the high-level off-channel RF.
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