WBZ-FM's antenna is in Newton, about 10 driving miles from Boston (acc. to google maps)...west of town.
WEEI-FM's antenna is in Peabody, about 17 driving miles from Boston (poss. less as the crow flies),
north of town. No doubt WEEI-FM will do well on North Shore, Merrimack Valley, and even into
SE New Hampshire and a small sliver of SW Maine. (Driving home last night from Northern NH I noticed
I couldn't pick up WEEI-FM till around Concord or Manchester). So while these areas will come in well,
there are some to the south where it would be lacking. There are simulcasts on Cape Cod and in
R.I. So while it's a fairly powerful signal, it is slightly to the north of downtown and not centered
as well as 98.5's is, as you'll see from the coverage maps. This could be one reason why they are
still on 850, to maybe cover those areas.
The complaints in the past were from people to the west who had trouble picking up 850 after dark.
Some of them may get 93.7 fine, but others, not necessarily. (There's an AM 1440 in Worcester they simulcast on; heck, if WAAF's rock format were not such a money maker you could poss. see them
simulcasting on 107.3 or even on 97.7 (a WAAF simulcast), south of town.
I did notice the WEEI simulcast on 103.7 from R.I. did pretty good south of Boston in places
like Canton, but not sure how well it does in other places. WEEI does have their simulcast "network"
to help out. WBZ-FM has no such network (other than for B's and Pats games of course) but the
signal is well centered over the Boston area.
A map of WEEI network stations
http://www.weei.com/weei/shows-schedules/network-stations.
While it does cover a good part of New England, many in VT and NH, and parts of ME and CT,
can't quite pick it up (on an affiliate; though of course there are Sox and C's network affiliates)
The coverage map for WEEI-FM (not totally accurate ) looks like it covers a lot of ground but is
centered just north of metro Boston (at least it's Peabody, not Lawrence or Lowell...a bit closer
to Boston than that). Living on the North Shore, about 6-8 miles from 93.7's stick (and working
about the same distance from it), I can picture WEEI-FM as being very powerful but it's true that
in many areas, particularly to the south, it's a lot weaker. If Entercom had a station that broadcast
from Newton or esp. from a downtown skyscraper like the Pru or Hancock, they'd be more centered
in metro Boston, but Peabody isn't all that far from downtown.
Compared to, say, if the 93.7 were out of Lawrence, the actual city of license...
--
From Boston Radio Archives: ARS, then owners of 93.7, moved it closer to Boston:
>>ARS quickly began working to move 93.7 closer to the center of the Boston market. In the summer of 1995, WEGQ began building a new 152-meter (498-foot) guyed tower at 100 Lakeland Park Drive in Peabody, easily visible from US 1 and the I-95/MA 128 interchange. “Eagle” signed on from the new tower in early 1996, with 34 kW at 179 m (587 ft) and a much-improved signal into downtown Boston and the South Shore.
http://bostonradio.org/stations/1919