Loosely, the group of microwave frequencies from 4 GHz to 6 GHz used in satellite communications. 2. The band of satellite downlink frequencies between 3. 7 and 4. 2 GHz. Note 1: For federal procurement purposes, the radio frequency band (s) must be specified using the upper and lower limits of the band, per 47 CFR 300. Note 2: Letter designators of radio frequency bands are imprecise, and in the international community are deprecated and obsolete.