TV band devices or TVBDs are unlicensed radio frequency devices operating in the vacant channels or white spaces between US television channels in the range of 54 to 698 MHz.
Fixed devices must be location-aware, query an FCC-mandated database at least daily to retrieve a list of usable channels at their location, and must also monitor the spectrum locally.
They may transmit only within the TV channels where both the database indicates operation is permissible, and no signals are detected locally.
They may either retrieve a list of permissible channels from an associated fixed station, or may accept a lower output power of 50 mW EIRP and use only spectrum sensing. Fixed devices may not be located at sites where the height above average terrain (HAAT) is greater than 76 meters.