Bob, for those of us radio technologically challenged, what do you mean when you say city grade west of the Pearl River?
Bob is referring the the signal strength of the station itself.
"City Grade" is a term the FCC uses to refer to the area that the station can deliver a 70 dBu (or 3.16 mV/m) signal. I 'll save you the discussion of what those numbers actually mean (way beyond the scope of this board), but suffice it to say, that's the signal that the FCC considers sufficient for a station to cover its home city ("City of License") with a local-quality signal. Within the City Grade, the signal should penetrate buildings well, and flutter little on a moving vehicle's radio.
The City Grade signal's reach from the transmitter is a function of two things: 1) Effective Radiated Power, and 2) Antenna Height.
Now, in the case of 93.9, the City Grade does not reach the City of Jackson, as the transmitter for WRXW is well east of the City. The City Grade does not go west of the Pearl River, and just barely covers Pearl, the station's City of License (covering "most" of one's City of License with a City Grade is a requirement).
cover Jackson with a secondary signal, 60 dBu, or 1 mV/m. In many cases, that does well. But, in urban environments, the 60 dBu gets a bit rough, especially in spots as far south as Jackson, where the influence of the Gulf often allows distant signals to interfere with a local station's signal (sometimes, such interference can even be problematic in the City Grade. When I was PD of then-WMJW, a station in Ruston, LA would eat us up some mornings; I could hear the interference in my headphones).
So, in short, Bob is saying that WRXW will have some problems with its signal in the City. That can be a problem. Too bad 93.5 in Clinton limits how far west WRXW can move.