Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300megahertz (MHz) and 3gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (one decimeter). Radio waves with frequencies above the UHF band fall into the super-high frequency (SHF) or microwave frequency range. Lower frequency signals fall into the VHF (very high frequency) or lower bands.

UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, satellite phones, and numerous other applications.

The IEEE defines the UHF radar band as frequencies between 300MHz and 1GHz. Two other IEEE radar bands overlap the ITU UHF band: the L band between 1 and 2GHz and the S band between 2 and 4GHz.

UHF television antenna on a residence. This type of antenna, called a Yagi–Uda antenna, is widely used at UHF frequencies.

Propagation characteristics

Radio waves in the UHF band travel almost entirely by line-of-sight propagation (LOS) and ground reflection; unlike in the HF band there is little to no reflection from the ionosphere (skywave propagation), or ground wave. UHF radio waves are blocked by hills and cannot travel beyond the horizon, but can penetrate foliage and buildings for indoor reception. Since the wavelengths of UHF waves are comparable to the size of buildings, trees, vehicles and other common objects, reflection and diffraction from these objects can cause fading due to multipath propagation, especially in built-up urban areas. Atmospheric moisture reduces, or attenuates, the strength of UHF signals over long distances, and the attenuation increases with frequency. UHF TV signals are generally more degraded by moisture than lower bands, such as VHF TV signals.

As the visual horizon sets the maximum range of UHF transmission to between 30 and 40miles (48 to 64km) or less, depending on local terrain, the same frequency channels can be reused by other users in neighboring geographic areas (frequency reuse). Radio repeaters are used to retransmit UHF signals when a distance greater than the line of sight is required.

Occasionally when conditions are right, UHF radio waves can travel long distances by tropospheric ducting as the atmosphere warms and cools throughout the day.

Antennas

Retevis GMRS two-way radios operating on 462 and 467MHz in the UHF band, showing the short antennas used
Corner reflector UHF-TV antenna from 1950s

The length of an antenna is related to the length of the radio waves used. Due to the short wavelengths, UHF antennas are conveniently stubby and short; at UHF frequencies a quarter-wave monopole, the most common omnidirectional antenna is between 2.5 and 25cm long. UHF wavelengths are short enough that efficient transmitting antennas are small enough to mount on handheld and mobile devices, so these frequencies are used for two-way land mobile radio systems, such as walkie-talkies, two-way radios in vehicles, and for portable wireless devices; cordless phones and cell phones. Omnidirectional UHF antennas used on mobile devices are usually short whips, sleeve dipoles, rubber ducky antennas or the planar inverted F antenna (PIFA) used in cellphones. Higher gain omnidirectional UHF antennas can be made of collinear arrays of dipoles and are used for mobile base stations and cellular base station antennas.

The short wavelengths also allow high gain antennas to be conveniently small. High gain antennas for point-to-point communication links and UHF television reception are usually Yagi, log periodic, corner reflectors, or reflective array antennas. At the top end of the band, slot antennas and parabolic dishes become practical. For satellite communication, helical and turnstile antennas are used since satellites typically employ circular polarization which is not sensitive to the relative orientation of the transmitting and receiving antennas. For television broadcasting specialized vertical radiators that are mostly modifications of the slot antenna or reflective array antenna are used: the slotted cylinder, zig-zag, and panel antennas.

Applications

UHF television broadcasting channels are used for digital television, although much of the former bandwidth has been reallocated to land mobile radio system, trunked radio and mobile telephone use.

Since at UHF frequencies transmitting antennas are small enough to install on portable devices, the UHF spectrum is used worldwide for land mobile radio systems, two-way radios used for voice communication for commercial, industrial, public safety, and military purposes. Examples of personal radio services are GMRS, PMR446, and UHF CB.

The most rapidly-expanding use of the band is Wi-Fi (wireless LAN) networks in homes, offices, and public places. Wi-Fi IEEE 802.11 low band operates between 2412 and 2484MHz. A second widespread use is for cellphones, allowing handheld mobile phones be connected to the public switched telephone network and the Internet. Current 3G and 4G cellular networks use UHF, the frequencies varying among different carriers and countries. Satellite phones also use this frequency in the L band and S band.

Examples of UHF frequency allocations

Australia

  • 406–406.1MHz: Mobile satellite service
  • 450.4875–451.5125MHz: Fixed point-to-point link
  • 457.50625–459.9875MHz: Land mobile service
  • 476–477MHz: UHF citizens band (land mobile service)
  • 503–694MHz: UHF channels for television broadcasting

Canada

  • 430–450MHz: Amateur radio (70cm band)
  • 470–806MHz: Terrestrial television (with select channels in the 600 and 700MHz bands left vacant)
  • 1452–1492MHz: Digital Audio Broadcasting (L band)
  • Many other frequency assignments for Canada and Mexico are similar to their US counterparts

France

New Zealand

United Kingdom

  • 380–399.9MHz: Terrestrial Trunked Radio (TETRA) service for emergency use
  • 430–440MHz: Amateur radio (70cm band)
  • 446.0–446.2MHz: European unlicensed PMR service, PMR446
  • 457–464MHz: Scanning telemetry and telecontrol, assigned mostly to the water, gas, and electricity industries
  • 606–614MHz: Radio microphones and radio-astronomy
  • 470–862MHz: Previously used for analogue TV channels 21–69 (until 2012). Currently channels 21 to 37 and 39 to 48 are used for Freeview digital TV. Channels 55 to 56 were previously used by temporary muxes COM7 and COM8, channel 38 was used for radio astronomy but has been cleared to allow PMSE users access on a licensed, shared basis. 694–790MHz: i.e. channels 49 to 60 have been cleared, to allow these channels to be allocated for 5G cellular communication. 791–862MHz, i.e. channels 61 to 69 inclusive were previously used for licensed and shared wireless microphones (channel 69 only), has since been allocated to 4G cellular communications.
  • 863–865MHz: Used for licence-exempt wireless systems.
  • 863–870MHz: Short range devices, LPWAN IoT devices such as NarrowBand-IoT.
  • 870–960MHz: Cellular communications (GSM900 - Vodafone and O2 only) including GSM-R and future TETRA
  • 1240–1325MHz: Amateur radio (23cm band)
  • 1710–1880MHz: 2G cellular communications (GSM1800)
  • 1880–1900MHz: DECT cordless telephone
  • 1900–1980MHz: 3G cellular communications (mobile phone uplink)
  • 2110–2170MHz: 3G cellular communications (base station downlink)
  • 2310–2450MHz: Amateur radio (13cm band)

United States

UHF channels are used for digital television broadcasting on both over the air channels and cable television channels. Since 1962, UHF channel tuners (at the time, channels 14 to 83) have been required in television receivers by the All-Channel Receiver Act. However, because of their more limited range, and because few sets could receive them until older sets were replaced, UHF channels were less desirable to broadcasters than VHF channels (and licenses sold for lower prices).

A complete list of US television frequency allocations can be found at Pan-American television frequencies.

There is a considerable amount of lawful unlicensed activity (cordless phones, wireless networking) clustered around 900MHz and 2.4GHz, regulated under Title 47 CFR Part 15. These ISM bands—frequencies with a higher unlicensed power permitted for use originally by industrial, scientific and medical apparatus—are now some of the most crowded in the spectrum because they are open to everyone. The 2.45GHz frequency is the standard for use by microwave ovens, adjacent to the frequencies allocated for Bluetooth network devices.

The spectrum from 806MHz to 890MHz (UHF channels 70 to 83) was taken away from TV broadcast services in 1983, primarily for analog mobile telephony.

In 2009, as part of the transition from analog to digital over-the-air broadcast of television, the spectrum from 698MHz to 806MHz (UHF channels 52 to 69) was removed from TV broadcasting, making it available for other uses. Channel 55, for instance, was sold to Qualcomm for their MediaFLO service, which was later sold to AT&T, and discontinued in 2011. Some US broadcasters had been offered incentives to vacate this channel early, permitting its immediate mobile use. The FCC's scheduled auction for this newly available spectrum was completed in March 2008.

  • 225–420MHz: Government use, including meteorology, military aviation, and federal two-way use
  • 420–450MHz: Government radiolocation, amateur radio satellite and amateur radio (70cm band), MedRadio
  • 450–470MHz: UHF business band, General Mobile Radio Service, and Family Radio Service 2-way "walkie-talkies", public safety
  • 470–512MHz: Low-band TV channels 14 to 20 (shared with public safety land mobile 2-way radio in 12 major metropolitan areas scheduled to relocate to 700MHz band by 2023)
  • 512–608MHz: Medium-band TV channels 21 to 36
  • 608–614MHz: Channel 37 used for radio astronomy and wireless medical telemetry
  • 614–698MHz: Mobile broadband shared with TV channels 38 to 51 auctioned in April 2017. TV stations were relocated by 2020. 617–652MHz: Mobile broadband service downlink 652–663MHz: Wireless microphones (higher priority) and unlicensed devices (lower priority) 663–698MHz: Mobile broadband service uplink
  • 698–806MHz: Was auctioned in March 2008; bidders got full use after the transition to digital TV was completed on June 12, 2009 (formerly high-band UHF TV channels 52 to 69) and recently modified in 2021 for 5G UHF transmission bandwidth for 'over the air' channels 2 through 69 (virtual 1 through 36).
  • 806–816MHz: Public safety and commercial 2-way (formerly TV channels 70 to 72)
  • 817–824MHz: ESMR band for wideband mobile services (mobile phone) (formerly public safety and commercial 2-way)
  • 824–849MHz: Cellular A and B franchises, terminal (mobile phone) (formerly TV channels 73 to 77)
  • 849–851MHz: Commercial aviation air-ground systems
  • 851–861MHz: Public safety and commercial 2-way (formerly TV channels 77 to 80)
  • 862–869MHz: ESMR band for wideband mobile services (base station) (formerly public safety and commercial 2-way)
  • 869–894MHz: Cellular A and B franchises, base station (formerly TV channels 80 to 83)
  • 894–896MHz: Commercial aviation air-ground systems
  • 896–901MHz: Commercial 2-way radio
  • 901–902MHz: Narrowband PCS: commercial narrowband mobile services
  • 902–928MHz: ISM band, amateur radio (33cm band), cordless phones and stereo, radio-frequency identification, datalinks
  • 928–929MHz: SCADA, alarm monitoring, meter reading systems and other narrowband services for a company's internal use
  • 929–930MHz: Pagers
  • 930–931MHz: Narrowband PCS: commercial narrowband mobile services
  • 931–932MHz: Pagers
  • 932–935MHz: Fixed microwave services: distribution of video, audio and other data
  • 935–940MHz: Commercial 2-way radio
  • 940–941MHz: Narrowband PCS: commercial narrowband mobile services
  • 941–960MHz: Mixed studio-transmitter fixed links, SCADA, other.
  • 960–1215MHz: Aeronautical radionavigation
  • 1240–1300MHz: Amateur radio (23cm band)
  • 1300–1350MHz: Long range radar systems
  • 1350–1390MHz: Military air traffic control and mobile telemetry systems at test ranges
  • 1390–1395MHz: Proposed wireless medical telemetry service. TerreStar failed to provide service by the required deadline.
  • 1395–1400MHz: Wireless medical telemetry service
  • 1400–1427MHz: Earth exploration, radio astronomy, and space research
  • 1427–1432MHz: Wireless medical telemetry service
  • 1432–1435MHz: Proposed wireless medical telemetry service. TerreStar failed to provide service by the required deadline.
  • 1435–1525MHz: Military use mostly for aeronautical mobile telemetry (therefore not available for Digital Audio Broadcasting, unlike Canada/Europe)
  • 1525–1559MHz: Skyterra downlink (Ligado is seeking FCC permission for terrestrial use) 1526–1536MHz: proposed Ligado downlink 1536–1559MHz: proposed guard band
  • 1559–1610MHz: Radio Navigation Satellite Services (RNSS) Upper L-band 1563–1587MHz: GPS L1 band 1593–1610MHz: GLONASS G1 band 1559–1591MHz: Galileo E1 band (overlapping with GPS L1)
  • 1610–1660.5MHz: Mobile Satellite Service 1610–1618: Globalstar uplink 1618–1626.5MHz: Iridium uplink and downlink 1626.5–1660.5MHz: Skyterra uplink (Ligado is seeking FCC permission for terrestrial use) 1627.5–1637.5MHz: proposed Ligado uplink 1 1646.5–1656.5MHz: proposed Ligado uplink 2
  • 1660.5–1668.4MHz: Radio astronomy observations. Transmitting is not permitted.
  • 1668.4–1670MHz: Radio astronomy observations. Weather balloons may utilize the spectrum after an advance notice.
  • 1670–1675MHz: Geostationary Operational Environmental Satellite transmissions to three Earth stations in Wallops Island, Virginia; Greenbelt, Maryland and Fairbanks, Alaska. Nationwide broadband service license in this range is held by a subsidiary of Crown Castle International Corp. who is trying to provide service in cooperation with Ligado Networks.
  • 1675–1695MHz: Meteorological federal users
  • 1695–1780MHz: AWS mobile phone uplink (UL) operating band 1695–1755MHz: AWS-3 blocks A1 and B1 1710–1755MHz: AWS-1 blocks A, B, C, D, E, F 1755–1780MHz: AWS-3 blocks G, H, I, J (various federal agencies transitioning by 2025)
  • 1780–1850MHz: exclusive federal use (Air Force satellite communications, Army's cellular-like communication system, other agencies)
  • 1850–1920MHz: PCS mobile phone—order is A, D, B, E, F, C, G, H blocks. A, B, C = 15MHz; D, E, F, G, H = 5MHz
  • 1920–1930MHz: DECT cordless telephone
  • 1930–2000MHz: PCS base stations—order is A, D, B, E, F, C, G, H blocks. A, B, C = 15MHz; D, E, F, G, H = 5MHz
  • 2000–2020MHz: lower AWS-4 downlink (mobile broadband)
  • 2020–2110MHz: Cable antenna relay service, local television transmission service, TV broadcast auxiliary service, Earth exploration satellite service
  • 2110–2200MHz: AWS mobile broadband downlink 2110–2155MHz: AWS-1 blocks A, B, C, D, E, F 2155–2180MHz: AWS-3 blocks G, H, I, J 2180–2200MHz: upper AWS-4
  • 2200–2290MHz: NASA satellite tracking, telemetry and control (space-to-Earth, space-to-space)
  • 2290–2300MHz: NASA Deep Space Network
  • 2300–2305MHz: Amateur radio (13cm band, lower segment)
  • 2305–2315MHz: WCS mobile broadband service uplink blocks A and B
  • 2315–2320MHz: WCS block C (AT&T is pursuing smart grid deployment)
  • 2320–2345MHz: Satellite radio
  • 2345–2350MHz: WCS block D (AT&T is pursuing smart grid deployment)
  • 2350–2360MHz: WCS mobile broadband service downlink blocks A and B
  • 2360–2390MHz: Aircraft landing and safety systems
  • 2390–2395MHz: Aircraft landing and safety systems (secondary deployment in a dozen of airports), amateur radio otherwise
  • 2395–2400MHz: Amateur radio (13cm band, upper segment)
  • 2400–2483.5MHz: ISM, IEEE 802.11, 802.11b, 802.11g, 802.11n wireless LAN, IEEE 802.15.4-2006, Bluetooth, radio-controlled aircraft (strictly for spread spectrum use), microwave ovens, Zigbee
  • 2483.5–2495MHz: Globalstar downlink and terrestrial low power service suitable for TD-LTE small cells
  • 2495–2690MHz: Educational broadcast and broadband radio Services
  • 2690–2700MHz: Receive-only range for radio astronomy and space research

See also

External links

  • Tomislav Stimac, "". IK1QFK Home Page (vlf.it).