DX...Skip and dead areas......questions

[Don]

>From what I  understand, stations with big DX signals like the former clear 
channels, maintain their groundwave/local signal at night...and as you move 
away from that area there is a "dead zone" before the Skywave/Skip/DX signal 
coverage begins.

WBZ claims a big signal at night...but if you drive due west from Boston, 
you will find that after Worcester, WBZ's signal is fluttering and 
unreliable.  But when you get to Albany it's pretty strong and reliable.

Someone from this list (I think it was Martin Waters) was in CT, and said he 
couldn't get a decent signal from WBZ day or night.  When I think about it, 
WBZ has a lot of listeners in Mass, NH, and even RI...but not so much in 
Vermont, W Mass, and CT.  Which is strange (to me anyway) for a station that 
covers 38 states.

Here's the question:  Does the area of the "dead zone" depend on the 
frequency of the station?  i.e....I mentioned that WBZ (1030AM) is pretty 
reliable in Albany and Upstate NY.  However, WGY (810AM (which is 
directional towards New England) is occaisionally listenable, but not a 
reliable night signal.  You would think it would be pretty equal going both 
ways.

Does the difference between 810 and 1030 alter the area of the "dead zone" 
between ground wave and sky wave?

Thanks for your help...this is something I've never understood fully.  ;-)

D