The frequencies used by UHF channels 70 through 83 were reallocated to the Land Mobile Radio System (Public Safety and Trunked Radio) and mobile phones in a CCIR worldwide convention in 1982, and thus were never used for digital TV but are listed here for theoretical use.
In certain metropolitan areas of the United States, Channels 14 through 20 have been allocated to Land Mobile Radio (LMR) use.
Channels 52 through 69 in the United States have been reallocated now that conversion to digital TV was completed on June 12, 2009. Channels 70 through 83 in the United States and Canada were re-allocated to AMPS cellular phone use in 1983.
On August 22, 2011, the United States' Federal Communications Commission announced a freeze on all future applications for broadcast stations requesting to use channel 51,to prevent adjacent-channel interference to the A-Block of the 700 MHz band. Later that year (on December 16, 2011), Industry Canada and the CRTC followed suit in placing a moratorium on future television stations using Channel 51 for broadcast use, to prevent adjacent-channel interference to the A-Block of the 700 MHz band.
Not all countries listed use ATSC (South Korea, Suriname, North America, etc.), which has a single VSB carrier wave. Other countries use COFDM modulation for DVB-T (Taiwan, Colombia, etc.)or ISDB-Tb (Philippines, Brazil and most of South American countries), which has dozens of carriers within the channel.
Channel 37 is reserved for radio astronomy in the United States, Canada, Bermuda and the Bahamas, thus there are no television stations assigned to it. Mexico also informally observes a ban on transmitters using this channel.