aaronread said:
FIRST: where is the aux tower going to go? If Harvard buys the land, I'd be flabbergasted if they allowed the tower...and the necessary field around it for a ground system...to remain there. Granted the tower is a third-level aux (WBZ already has a backup transmitter at the main Hull site) but it'd be "bad business" for WBZ to give up the SFR tower; if Hull ever gets hit with a really bad Nor'Easter or regular hurricane...a very distinct possibility every year...then the SFR is the only way they stay on the air.
A curiosity left over from WBZ's move from Millis to Hull in 1940--68 years ago--adds an interesting wrinkle to the aux story. AFAIK, the FCC rules for aux signals not co-located with the main is that certain contours must be completely contained within the corresponding contours of the main. For WBZ, this must include the 0.5 mV/m groundwave contour as well as others. The Hull site borders open water and back in 1940, GPS was about half a century away from being invented. Heck, any kind of a man-made satellite existed only in science fiction. Also, WBZ was a Class IA, so the need for pattern augmentations just didn't exist. As a result, WBZ's main pattern shows an inverse-distance signal of 0 along the 90-degree (due east) radial. That's a purely theoretical value but it means that a new aux not at the Hull site would be limited to a power of zero! Ridiculous, you say? Nowadays, measuring the actual radiation to the east of Hull would be no problem; use a boat; with GPS, you could easily determine your location within a few meters. So establishing the augmented field along a bunch of radials would be duck soup. But would the FCC allow WBZ to augment its pattern 68 years after it started using the Hull facility? My guess is yes--but only after a small hassle. And there are more severe implications about a replacement aux facility for WBZ; see below.
The following story is true and provides an example of how picky the FCC can be about really unimportant nonsense. WFAN and WCBS recently rebuilt their auxiliary facilities at their diplexed main site off City Island in the Bronx. The new aux tower is taller than its predecessor but considerably shorter than the main tower. Both stations wanted to run 35 kW day and night from the new aux tower, whereas they had run only 25 kW from the old aux. Well, you say, "how could THAT be any problem?" Both stations are former IAs, what station could possibly require protection? Yet, when the aux facilities were licensed, WCBS's night power was limited to 26 kW. The reason, it turns out, is WAMG, which didn't even exist until sometime in the 1990s. You see, the high-angle skywave from the auxiliary tower is greater than that from the main tower, which is 207 degrees at 880. So when WCBS is using the aux tower (say, during maintenance of the main tower), it must cut its power from 35 kW to 26 kW at sunset. Since WSRO is a daytimer that requires no protection at night, WFAN has no similar restriction.
Given that there is an AM 1030 in Puerto Rico, which east as well as south of Boston, I suspect that WBZ might have to build an aux facility with a two tower DA to more-or-less replicate the main pattern. The most obvious site for such an operation would be the WEZE site at Wellington Circle. The two towers are on the necessary east-west line but, at 1030, are too widely spaced to synthesize a cardioid pattern like WBZ's (a three-leaf clover, maybe--but not a cardioid). Adding a tower 1/3 of the way between WEZE's existing pair would allow synthesis of an almost exact replica of WBZ's existing pattern. WEZE's towers are tall enough to be quite efficient at 1030; in fact, some magic with top-loading might even enable the site to be licensed as an alternate main.
