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If they are all coming from the same source why is reception inconsistent?
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While it is correct in that all the stations mentioned transmit from the Empire State Building, there are some differences that that come into play that are outside that condition.
In NYC, channels 7, 11, & 13 transmit on those real operating channels. ALL of the other stations with channel numbers below 13 no longer utilize those channels which they used for their original analog broadcasts. In other words, they are now UHF stations, regardless of their original channel number.
UHF and VHF signals behave differently in several ways.
First, the shorter wavelengths of UHF signals do not bend as readily as do the longer VHF wavelengths, a process called diffraction (see
http://en.wikipedia.org/wiki/Radio_p...on#Diffraction and
http://www.hdtvprimer.com/ANTENNAS/g...ml#diffraction for discussion). This tends to adversely affect UHF far more than VHF.
Secondly, the water content in trees tends to have a greater amount of attenuation and scattering at UHF frequencies than at VHF frequencies. See
http://www.hdtvprimer.com/ANTENNAS/glossaryR.html#trees and
http://www.hdtvprimer.com/ANTENNAS/siting.html This problem is less in the winter when leaves are off the trees.
Based on your TVFool plot, it can be seen that you are in low-lying terrain relative to the signal path from NYC much like as is depicted in this image:
The conclusion would be then that the bulk of the possible signals from the ESB are going over your head with very little arriving at your antenna.
Best advice is to try a combination of several things for those UHF signals: High-gain antenna with suitable pre-amplifier, roof/tower as high as feasible, and to mount the antenna as far back from any trees as is possible.
I live is a similarly impaired location, about 20 miles outside St Louis, in a valley and am surrounded by trees. My TVFool plot suggests that a simple two or four bay UHF antenna should be fine, but, it took an 11' modified 91XG mounted 45' in the air plus a pre-amp to achieve reliable reception most of the time for most of the channels. Still, when a particular sycamore tree in our yard that is unavoidably in the signal path leafs out in the spring, I usually loose my local flea-powered PBS station until autumn. The wife won't let me cut it down so we just deal with it.
As always, YMMV.
Cheers!