The proposed three-tower day (including critical hours) pattern is a straightforward modified cardioid facing due east. It would use the three center towers of the five-tower in-line array. The two end towers, which WBIX had specified for use 24/7, would be used only at night (by WBIX; WAMG uses all five towers 24/7). The CP was based on using the night pattern 24/7 with 50 kW during daylight hours (including CH) and with no change in the 2.5 kW nighttime operation. The night pattern is best described as a teardrop.
The modified application makes more sense than the granted CP. Although the signal in Boston would be ~15% less, the coverage lost by this latest proposed single-site setup (compared with the present two-site operation) would be quite a bit less. Coverage is still lost in central Mass (bye-bye Worcester), southwestern NH, and southeastern VT, but not as much as with the granted CP, and to partly make up for it, more coverage would be gained in south-coastal Mass and Cape Cod.
I am still amazed at the incredibly low soil conductivity WBIX claims exists in the vicinity of its Ashland site (just east of Route 126). Take a look at the third-adjacent overlap map in one of the figures. This map shows WBIX's granted and proposed daytime 25 mV/m contours and WBZ's 25 mV/m DA-1 contour. No prohibited overlap is shown. But WBZ does run a cardioid pattern with 50 kW into two half-wave towers and WBIX would run a modified cardioid with 50 kW into three > half-wave towers. WBZ has the tremendous advantage of salt water in essentially all directions for the first seven to 15 miles or so depending on the direction. WBIX, OTOH, is surrounded by low-conductivity earth. It appears that WBIX's 25 mV/m encloses an area less than 1/3 as large as WBZ's 25 mV/m. And WBZ's advantage still appears to be at least 2:1 if you subtract the salt water within its 25 mV/m. The difference is pretty dramatic considering that the facilities are so nearly identical. The conductivity of the salt water is what makes the difference.
Oh, and the three-tower setup should cost less because the phasor will be simpler and no additions or modifications are required to two of the five ATUs. But because the day and night patterns will be different, more engineering work is required. But chances are WBIX will file to use Method of Moments, which will obviate the need for an extensive proof of performance.
