re: Why the cluster of radio towers north of Shreveport?

KEEL.. AM radio station. AM signals travel farther at night than they do in the daytime. So stations run more power and are omni directional in the day. At night when the signals go far, if the station isn't a "clear channel" station like WWL, then they have to reduce power and "point" the signal in a certain direction. They feed the signals to the towers in a phase, so the signal points mainly in one direction.

An AM transmitter uses the tower itself as the antenna, as opposed to an antenna on the tower. So the middle tower is the active one, and the others are like in a yagi configuration to protect other stations on the same frequency.

WWL is a clear channel station, no one else is supposed to be on 870, but that's not so much the case any longer.

KEEL Daytime vs. Nighttime coverage