Thanks OldTVnut for co-channel interference;
NYC and Baltimore/DC both had the same analog channels. Baltimore is 160+ miles from NYC, with DC's transmitters (chs. 4,5,7,9) an additional 36 miles. Rare co-channel interference was noted only during summer e-skip periods by the venetian-blind effect and strange whine in the sound.
After digital transition, original channels 11 and 13 remain in NYC and in Baltimore. No other analog channels 11 & 13 were in the mid-atlantic.
But....Wilkes Barre, PA (100 miles WNW of NYC and 130 miles NNE of Baltimore) also moved formerly UHF WBRE and WYOU to these channels!
Talk about a crowded spectrum!
My loss: I received analog UHF's of WBRE and WYOU near perfect, even 83 miles away. Now I only get the UHF channels (same mountain transmitter farm) but WBRE and WYOU only a few days per month based on weather.
After consultation of other forums, I have concluded that VHF-DT will never provide the same coverage area as Analog VHF, where a 75 mile range was common and necessary.
Co-channel and noise IS the silent killer of DT reception. Its presence can only be discovered by using a spectrum analyzer, which I do not own.
As for UHF, trees and dirt are STILL formidable obstacles.
trees-and-uhf-reception.pdfSee attached article from UK expert.