mbatchelor said:
Are there any stations currently in the US synchronizing stations on the same frequency?
Looks like everybody so far has assumed you were talking about FM only, but there have been numerous synchronized AM operations over the years. In Texas, for instance, KRVA 1600 Cockrell Hill/Dallas had a synchronous transmitter in Fort Worth, and just west of Dallas KKDA 730 Grand Prairie had one southeast of Fort Worth, licensed to suburban Forest Hill. The old KNUZ 1230 (now KQUE) in Houston operated a synchronized transmitter on the northwest side of the city for a number of years to supplement the anemic coverage from their downtown. It never worked that well, though. North of Houston, KMVL 1220 Madisonville set up such a station in the nearby town of Huntsville back in the late '90's; I heard it a few years ago but I'm not sure if it's still on.