Both for me are within 75 miles:
(from passengers & takeoffs/landings), but also LHR
are big, big, big from number of planes and area.
Smallest: AHN (Athens, GA
- where I live), 5000' runway, 1 ticketer/baggage handler, 3 TSA
folks & sometimes an off duty Athens police officer and 1 gate. Oh, and one commercial plane, Beech 1900 (US Airways) two roundtrips per day(M-F), one per day (S+S) to one destination - Charlotte. Also, one coke machine and one snack machine.
Planes are almost always full though.