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Old 5-Oct-2016, 5:44 PM   #34
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,569
Quote:
at this point I have [to] conclude that the loss of DB4e from the stack or the combiner are the cause
That got me wondering about the UHF antenna change. It wouldn't be gain, so maybe it is a slight change of antenna location or the form factor of the antenna.

I did a terrain profile that shows how the curvature of the earth blocks the direct signal and causes it to graze the surface and be subjected to ground clutter interference.



The ground clutter interference will cause scattering of the signal so that it presents a non-uniform wave front to the antenna. This non-uniform field makes the location of the antenna very critical, because there will be hot spots and cold spots.







It is also possible to have a non-uniform field in the vertical direction. Moving a UHF antenna a little as 6 inches up or down can make a difference. That would be easier for you to do than moving it in a horizontal direction. I wonder how the DB4e would do now?

http://www.hdtvprimer.com/antennas/siting.html
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File Type: jpg Non-uniform fields HDTVPRIMER snip2_1.jpg (142.5 KB, 2431 views)
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Last edited by rabbit73; 5-Oct-2016 at 6:50 PM.
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