Basically switching from a non-directional (circular) antenna pattern to a bi-directional (figure-eight) antenna pattern.
WRKO aims its signal from north northwest south southeast so as to protect KNBR 680 in San Francisco (which can be heard at night here in Montana) and WPTF 680 in Raleigh, NC, so it's very strong in NH and on the Cape. Strongest signal is toward the Cape and out toward the ocean.
Yes and I think stations in Toronto, Balt., and Binghamton have to be protected too. I was in VT last yr and was having trouble picking up WVMT Burlington (I was in Rutland and it was nr sunset). WCRN was OK; as for WRKO, it kept fading in and out and mostly I was getting Hannity...that was from Baltimore (99.7 from NH came in sometimes)
Aside from WBZ (1030), all of the Boston AM facilities are signal challenged in the western part of the market. 50,000 watt WEEI (850) also suffers when the night directional pattern kicks in since it protects co-channel KOA in Denver.
On the other hand, WBZ's directional pattern is very favorable with the signal directed over land, day and night, and very little of its 50 kilowatts serving the fish.
They probably have to drop their output power too. There are a few stations, used to be called “clear channels”, that pretty much stay the same 24/7...they pretty much have the only station (at least in the US) at that particular frequency. WSB Atlanta, WLS Chicago, the one in N.O. and others, you can hear them almost from anywhere in the US at night if conditions are right.
WOW! I had no idea the signal reached that far!
How 'bout them Warriors?? < |:)~