A term that has come to the fore in late 2008 and early 2009, as the federally mandated transition to digital TV occurs on February 17, 2009. “White spaces” refers to frequencies in the radio/TV band that have been allocated to broadcast by a national and/or international governing body, but are not used by a local station.
When TV stations change over to digital transmission, many frequencies will be freed up. Analog TV broadcast requires a “guard” band between channels, so many channels are “occupied” but left unused. Digital TV channels, on the other hand, can be broadcast on adjacent frequencies, without a “guard” band; this means all those former guard-band frequencies are now unused. These channels fall in the 700MHz band, covering UHF channels 52 to 69 and frequencies from 698 to 806MHz.
Unfortunately for UHF wireless mic and in-ear monitor users, those “white space” frequencies were auctioned off and reallocated to consumer usage.