Well an F16 could be from several different guard bases, Otis, Syracuse, Burlington, etc. They could be doing training, CAP missions, Touch and Go's someplace. Long story short, they can be using alot of frequenices, civilan VHF, check your local approch controls, CAP/Huntress frequencies 200/300MHz. Their own squadron freqs, multiple air-to-air frequencies. If they are using an MOA, there are frequencies reserved for that airspace when the reserve the airspace for use. Good Luck!!!