The WCNN pattern at night:
WCNN-AM Radio Station Coverage Map
IIRC part of the directional day time system was to protect a 680 class “B” in Sylvia NC that had 2 sites and directional antenna to maintain, which wisely moved to 540 5KW day 140 at night on one tower. That station has a translator that could go farther but that is another thread. Looking at the FCC web site:
https://transition.fcc.gov/fcc-bin/amq?call=&arn=&state=&city=&freq=680&fre2=680&single=on&type=0&facid=&class=&list=1&dist=&dlat2=&mlat2=&slat2=&NS=N&dlon2=&mlon2=&slon2=&EW=W&size=9&ThisTab=Results+to+This+Page/Tab
IMHO the closet station’s night time service to really worry about (besides WPFT) is WCTT Corbin KY:
WCTT-AM Radio Station Coverage Map
WCNN should able to put some more power to the west without interfering with Memphis’s WMFS night time service:
WMFS-AM Radio Station Coverage Map
I am surprised the Dickies haven’t hired an engineer to figure how to take a tower or two out of the night time pattern and go non directional daytime since they don’t have to worry about Sylva NC anymore. A less complicated the directional system has to be cheaper to maintain.