Cavity Band Pass Filter, 868MHz / 915MHzCavity filters are a type of resonant filter used for either passing desired RF signals within a specified frequency range or rejecting RF signals within a range of frequencies. If you add the Filter to work with Hotspot, it could help the hotspot to better process radio signal in a complex radio environment. Details Parameters(868) S N Item Parameters 1 Center Frequency(F0) 868. 5MHz 2 Pass Band Frequency 867 ~ 870MHz 3 Pass Band Insertion Loss 2.