Just to contribute my stats... I'm high up in Manchester CT (near hartford) and I recently went HDTV--- bought a used DTC100 recently (the one mentioned in this thread, I think), and here are my average signal strengths:
via my Terk TV42 satellite attached antenna, no amp (omnidirectional):
ABC 10-x: 80-88
the rest is unreliable and drops out with average peaks of 25-35.
via my brand new Radioshack 'Amplified Indoor Antenna' (Color Supreme 170) at $19.95 -- i couldn't find a double bowtie. It has 10 db built in gain and is essentially as standard as it gets :
CBS WFSB 33-x (3-x): 55-65
NBC springfield WWLP 22-x (11-x): 75
PBS out of springfield 58-x (57-x): 75
ABC 40 out of springfield -- something around 50-60s, i forget. but my abc 10 is better, so i don't remember. I also get wcdc 19 out of adams even,
So basically, I get all major networks digital, and everything in Hidef except NBC (since there is no local hidef nbc broadcast). minimal dropouts. With the terk TV42 alone, only ABC was practically useable for me. I don't have to manually switch or combine my two antennas since the DTC100 has two antenna inputs. Perhaps sometime I'll try a combiner, though. Might make things more superfluous.
PBS HDTV demos are soooo beautiful..
I'm a happy guy!