RE: WBPS-AM 890 Transmitting Unmodulated Carrier

[dan.strassberg@att.net]

Except during the transitional period when the Sewell 
St, Ashland site was being converted from 1060 to 890, 
WBPS has used the same facilities at night. The day 
pattern was just recently slightly modified, however. 
Radiation out the back of the array--toward Worcester--
was increased a fair amount. The depth of the null to 
the north that protects WMVU was reduced somewhat; by 
symmetry, the null to the south was made less severe; 
and the signal due east, toward Boston, was reduced but 
very slightly. Overall, the augmented pattern RMS 
increased by several percent--enough that the station 
can now claim to be radiating the equivalent of slightly 
more than 50 kW by day from an antenna having the Class 
B minimun=m efficiency of 281.7 mV/m/kW @ 1 km.

There is something odd about the nighttime 
augmentations. The augmentation centered at 90 degrees 
(due east), increases the field in that direction by 
something like 80% of the unaugmented value. This is a 
very large augmentation in line with the pattern 
maximum. Usually, when you see such large augmentations, 
they are in nulls. I suppose this could be the result of 
a railroad tower that is nearly due east of the array, 
in the vicinity of 1/2 wavelength east of the farthest-
east tower, and probably not detuned. But it could also 
be the result of, umm, optimistic proofs of performance 
aimed at saving the (then) station ownership the cost of 
changing the COL from Dedham to Wellesley. The COL 
change had been applied for because, presumably, the 
nighttime interference-free signal did not cover enough 
of Dedham. After the proofs were completed, however, the 
application was withdrawn. Despite the similarity of the 
day and night patterns, the day pattern has no 
corresponding augmentation.
--
dan.strassberg@att.net
617-558-4205
eFax 707-215-6367
 
> Do you know if WBPS 890 has during the course of its operational history
> changed it's pattern/transmitter output or moved transmitter/antenna?