The point to point transmission and reception of TV and radio signals is affected by many variables. Atmospheric moisture, solar wind, physical obstructions (such as mountains and buildings), and time of day all affect the signal transmission and the degradation of signal reception. All radio waves are partly absorbed by atmospheric moisture. Atmospheric absorption reduces, or attenuates, the strength of radio signals over long distances. The effects of attenuation degradation increases with frequency. UHF TV signals are generally more degraded by moisture than lower bands, such as VHF TV signals.
The ionosphere, a layer of the Earth's atmosphere, is filled with charged particles that can reflect some radio waves. Amateur radio enthusiasts primarily use this quality of the ionosphere to help propagate lower frequency HF signals around the world: the waves are trapped, bouncing around in the upper layers of the ionosphere until they are refracted down at another point on the Earth. This is called skywave transmission. UHF TV signals are not carried along the ionosphere but can be reflected off of the charged particles down at another point on Earth in order to reach farther than the typical line-of-sight transmission distances; this is the skip distance. UHF transmission and reception are enhanced or degraded by tropospheric ducting as the atmosphere warms and cools throughout the day.
The main advantage of UHF transmission is the short wavelength that is produced by the high frequency. The size of transmission and reception antennas is related to the size of the radio wave. The UHF antenna is stubby and short. Smaller and less conspicuous antennas can be used with higher frequency bands.
The major disadvantage of UHF is its limited broadcast range, often called line-of-sight between the TV station's transmission antenna and customer's reception antenna, as opposed to VHF's longer broadcast range.
UHF is widely used in two-way radio systems and cordless telephones, whose transmission and reception antennas are closely spaced. Transmissions generated by two-way radios and cordless telephones do not travel far enough to interfere with local transmissions. Several public-safety and business communications are handled on UHF. Applications such as GMRS, PMR446, UHF CB, 802.11b ("WiFi") and the widely adapted GSM and UMTS cellular networks, also use UHF cellular frequencies. A repeater propagates UHF signals when a distance greater than the line of sight is required.
UHF spectrum is used world-wide for land mobile radio systems for commercial, industrial, public safety, and military purposes. Many personal radio services use frequencies allocated in the UHF band, although exact frequencies in use differ significantly between countries.
457–464 MHz: Scanning telemetry and telecontrol, assigned mostly to the water, gas, and electricity industries
606–614 MHz: Radio microphones and radio-astronomy
470–862 MHz: Previously used for analogue TV channels 21–69 (until 2012). Currently channels 21–30 and 39–60 are used for Freeview digital TV, channel 36 is used for radar, channel 38 is used for radio astronomy, channel 69 is used for licenced and licence-exempt wireless microphones.
870–960 MHz: Cellular communications (GSM900 - Vodafone and O2 only) including GSM-R and future TETRA
There is a considerable amount of lawful unlicensed activity (cordless phones, wireless networking) clustered around 900 MHz and 2.4 GHz. These ISM bands – open frequencies with a higher unlicensed power permitted for use originally by Industrial, Scientific, Medical apparatus – are now becoming some of the most crowded in the spectrum because they are open to everyone. The 2.45 GHz frequency is the standard for use by microwave ovens.
UHF taboo frequencies, in early television broadcast engineering, were limitations on local channel assignments imposed on broadcasters by inadequate adjacent channel and image frequency interference rejection in the first UHF TV tuner designs. These problems have been corrected in modern digital television receivers.
The spectrum from 806 MHz to 890 MHz (UHF channels 70–83) was taken away from TV broadcast services in 1983, primarily for analogue mobile telephony.