Rabbit73: Many thanks for your several good suggestions.
I am not using a preamp. The RG6 wire is about 35 - 45 feet, going straight-ish from the roof top DB4E to my tv. Yesterday evening I got the following reception data from my old Samsung vs. new Sony. I recorded signal strength and SNR for four representative stations, again just by changing the antenna cable from one tv to the other.
CBC (5-1): Samsung signal strength = 70%, SNR=26-29, vs. Sony 71%, 30
CTV (9-1): Samsung = 60%, 27, vs. Sony = 61%, 28.
PBS (17-1): Samsung =45%, 23, vs. Sony = 45%, SNR fluctuates between 0 - 12(!).
CITY (57-1): Samsung = 100%(!), 31, vs. Sony = 58%, 29.
As you see, most local (CN tower stations) are pretty consistent between the two sets, but note the wide variances for PBS and CITY. My (naive?) conclusion is that this is due to adjacent channel interference between RF 43 and 44, as you mentioned.
The end result is that all Toronto stations are solid, most Buffalo stations range from non existent to unwatchable (frequent blocky pixels, frozen pictures, etc.). Our requirements are pretty simple; if we had, in priority order, TVO, PBS, CBC, CTV, Global, we would be happy watchers. The rest of our needs can be handled by Netflix or similar.
Aiming the antenna more towards Buffalo. Our is at about 145 degrees True, so pretty much straight at Grand Island I believe. But you pointed out that the DB4E has a wide beam; do you know of one that might be better (narrower)? I looked at a few on the SaveAndReplay web site but most do not specify beam width.
Seems to me that a preamp would not resolve this? Wouldn't it just ramp everything up, including the CN tower?
Try an external TV tuner for the Sony.
I admit I did not think of adding a separate tuner for a new $1500 tv. Sounds kind of Rube-Goldberg-ish but what do I know! I was not even sure what they are - a google search showed several, but they all seem oriented more towards adding tv capability to a PC or laptop. If I tried one, I assume the directions would explain how to use it with a tv, bypassing the internal Sony tuner, etc., and maybe explain how to overcome many anticipated objections from my wife... "You bought *what*!? And I have to do *what* to change channels?!".
I have no idea what specs and features I should look for in an external tuner - can you suggest any candidates? If I try one, I will be sure to get it from a place with a liberal return policy.
Apologies for droning on like this, but I do appreciate your suggestions and intend to follow up.