Laurence Glavin said:
After the moves of WKOX-AM 1200 and WBIX-AM 1060 away from Mt. Wayte Avenue in Framingham, there remained the possibility that WSRO-AM 650 might also have to find a new transmitter site if a decision was made to find a better use for the real estate it occupied. But it appears that WSRO will not only stay put, but use the two towers to install a directional pattern with higher power to replace its feeble (250 watts NDA days; 9 watts NDA nights) signal. I wonder if this can be accomplished quickly once FCC approval is obtained; or could there be objections by WNNZ-AM 640 and WRKO--AM 680?
If you believe WSRO's application, there is no basis for objections. However, it wouldn't be the first or the 1,000th, and probably not the 10,000th time a station has proposed a facility change, submitted an application that showed that there was no basis for objections and then had to refute strenuous objections from a station that claimed it would receive new, objectionable interference.
In this case, it appears that there is not close to being any prohibited overlap with WRKO. There IS prohibited overlap with WNNZ, however. BUT that overlap is less than what already exists with WSRO's existing lower power nondirectional operation. The problem area is just north of the Mass-Connecticut border and just west of the Connecticut-Rhode Island border. Indeed, if you look at WSRO's proposed daytime pattern, radiation in that direction (west-southwest of the the Framingham site) is significantly reduced compared to what it is at present, though normally prohibited overlap is not eliminated. So there is a clear basis for claiming that the increased power will be accompanied by a reduction in interference with WNNZ in the small and sparsely populated area where it now exists.
A question that WSRO's application does not address, however, is the stability of the proposed array. There is no chance of adding or moving a tower. WKOX went through that battle probably 15 years ago and lost its fight with the Town of Framingham. So WSRO was constrained to use the existing towers, which are quite tall enough for 650 and in a pretty good orientation for maximizing the population served and protecting the stations that require protection. But the towers are very close to each other (42.8 degrees at 650). That electrical distance may not set a record, but it has to come close. Arrays with closely spaced towers have a reputation for producing unstable patterns, and in this case, the tower height, which increases coupling between the towers, may exacerbate such problems. Fortunately, the power is relatively low.
I live about 15 miles from the site and very close to the pattern's radiation maximum. During the daytime, the inverse-distance field in my direction will be about 660 mV/m @ 1 km, which is about half of what WKOX produced when it was running 10 kW-D ND from the site. In the daytime, WKOX delivered ~3.2 mV/m where I live. Because of the much lower frequency, WSRO would deliver more than twice as much. I should get a more than adequate signal during the daytime (not strong enough to enable me to understand the Portuguese programming, though
At night, the signal strength will drop by a factor of ~5 to a little less than the equivalent of 250W from a tower of approximately 1/6 wavelength. Such a signal is unlikely to be listenable. Since I don't understand Portuguese, I guess it won't make much difference unless the station changes formats, which seems unlikely because the brokered-time foreign language programming is apparently quite profitable.
And before I forget, I have not looked into the possibility of objections from Canada. Remember, all of those now-dark AM allocations remain internationally notified and continue to require protection. I recall only one on 650--south of Montreal, but there are bound to be others. Because WSRO is a class D AM and will provide unprotected, low-power night service, the problems with Canada may not be significant, however.
