[Scan-DC] Antenna pattern for DCA @ 119.1 MHz?

[Andrew Clegg]

I've noticed that the 119.1 MHz tower frequency from DCA is surprisingly weak. I can barely hear the tower 4 miles away from a rooftop up 220 ft. Even in the parking lot at Gravelly Point, the signal isn't exactly gangbusters. The planes come in fine at both. On the other hand, the 134.35 MHz simulcast frequency that the tower uses to communicate with helicopters comes in loud and clear 4 miles away, and the 257.6 MHz simulcast channel in the milair band comes in reasonably well too.
Does someone on the list know if by chance the 119.1 MHz DCA antenna has a significant electrical uptilt that keeps the pattern along the horizon very low? That would seem odd, because even ~10 miles away, where the tower first starts communicating with inbound planes, the planes are at a relatively low elevation as seen from the airport. But I can't seem to figure out why 119.1 is so weak. Maybe the 119.1 antenna on the southeast side of the tower and blocked to the west (where I am) and the north (where Gravelly Point is)? That would seem odd too.
Any ideas? This has puzzled me for several years.
73,Andy