The video signal components B-Y and R-Y, often considered synonymous with Pb and Pr but more correctly adjusted to different levels relative to Y (luminance) compared with Pb and Pr. (We are not sure what the level change or normalizing factor is.) To produce the picture, theY is also needed. U and V are also used for PAL video. Use of U and V in NTSC composite video is common but it does not quite optimize the color horizontal resolution to the maximum sensitivity of the human eye to reddish orange and greenish blue as the NTSC specifications call for. See, also, I, Q and Prime Disclaimer.
UHF (Ultra High Frequency)-- Comment: Channels 70-83 are no longer used for TV broadcast and TV sets are no longer required to receive them. Other services such as cellular telephones use this part of the UHF frequencies, which as a whole extend from about 316 MHz to 3.16 GHz. Currently all U.S. HDTV broadcasts use UHF frequencies.

This definition is in context to Television. See more contextual defintions for U, V.