"illegal" is a bit harsh. I prefer "gray area" seriously, though, the noise floor is similar on all frequencies. the proper gain comes from an antenna tuned to the frequency. I've noticed some antennas do better at the higher frequencies and totally crap out at the lower ones, or vice versa.
the only way to successfully reduce the noise floor is to get away from noise sources. period.
The SAW filter has the Digi-Key Part Number: XC993-ND