The problem with the lack of good, full-market FM signals in Boston seems fairly obvious. Scott Fybush, jump in here if you disagree.
Way back when, signals were allocated in big cities at 800 khz (not 600) intervals (still largely true) beginning in one of four patterns. This is where Boston got shafted.
Starting in the commercial band:
92.3, 93.1, 93.9....107.5 yielded potentially 20 class b or c stations. NY, Chicago, LA, Detroit, Houston follow this pattern, mostly.
92.5, 93.3, 94.1....107.7 also yielded up to 20 potential class b or c stations. Philadelphia, Seattle, San Francisco follow this pattern, mostly.
On the other hand, the two other patterns yielded a handful or more of class a signals. It would not matter now, but 101.7, for example is a traditional class a signal. Many have been upgraded, but where they are short-spaced, as in the northeast, no way.
92.1, 92.9, 93.7, 94.5...107.3 is the Boston pattern, mostly, and yielded in the old days only 13 class a signals. It is also mostly the pattern for Pittsburgh Phoenix, Atlanta, and Buffalo. It is filled with frequencies that would, in the old days been exclusively class a: 92.1, 95.3, 97.7, 99.3, 100.1, 100.9, 101.7, 104.9. Boston obviously deviates where it has a 99.5 and a 100.7 instead of a 99.3 and 100.9, but nevertheless, it is stuck with 97.7 as a class a, not because the frequency is restricted any longer, but because it is too short-spaced to upgrade to a class b, or b1, etc.
The last pattern, 92.7, 93.5, 94.3...107.1 is not often seen in large cities, and has an even greater number of what used to be exclusively class a frequencies. All of the ones mentioned in the previous sentence used to be.
Thanks to Vane A. Jones and those station guides he used to write for making this obvious.
I think this odd pattern is a big part of the problem in Boston. Even with the disadvantaged allocation pattern, some frequencies along it ended up far from the city: 96.1, 107.3 in Worcester and others in odd or multiple allocations in the area: lower power 95.3 for Harvard, two 104.9s, without others allocations to make up for it in the immediate area.
