The NDB at Atlanta Regional is FFC. Sometimes the AIRNAV website is not 100% accurate, so I looked up FFC on the aviation approach plates. FFC is listed on 316 kHz for the NDB 31 and ILS/LOC 31 (as the LOM) approach at Atlanta Regional on the current plates.
Yup, found pretty much the same thing.
The NDB associated with Atlanta Regional Airport Falcon Field is located at PECAT intersection 5.1nm from the threshold of RWY 31 on the 192 radial off the Atlanta VORTAC 116.9.
Frequency given is 316 and ID as FFC.
However, the OP is certain that the identifier heard is FF.
Various internet sources also give the ID as FF. Also, dug up some old approach plates which show the ID as FF.
The whole thing is a bit confusing but all part of the fun chasing these NDBs.
edit: Also found a beacon listed as FF in Minnesota but unlikely that the OP is hearing this as the frequency given is 337.