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Old 11-Apr-2020, 1:35 PM   #9
tripelo
Senior Member
 
Join Date: Jan 2010
Location: Dallas, TX
Posts: 173
Reference 2nd and 3rd images in previous post:

http://forum.tvfool.com/showpost.php...91&postcount=8

Since the 'East Antenna Only' and the 'West Antenna Only' showed evidence
of phase cancellation (dip in the spectrum), that seems to indicate
that the signal self interference is outside the antenna pairs.

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Reference 2nd image (green trace):

http://forum.tvfool.com/showpost.php...88&postcount=5

This antenna does not show the phase cancellation.

What could be the reason? Is this antenna at a different height?

Each of the dual antennas exhibit symptoms of phase cancellation and
the 3rd does not. If the 'blue-trace' antenna is at a different height,
then possibilities:

* It is at a height where ground reflection reinforces signal, whereas the
dual antennas are at a point where ground reflections interfere.

* Or, Some other source of external reflection may be present.

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The final scan with the Winegard CC-7870 coupler shows increased strength.
Most signals do vary if the station is not LOS and considerable distance
away. Could this be because the signal from the station varies with time?

Otherwise, it could mean that the Winegard CC-7870 coupler performs better
(less loss) than your previous combiner.

.
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