Ultra high frequency

Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (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, and numerous other applications.

Ultra high frequency
Ultra high frequency (ITU)
Frequency range
300 MHz to 3 GHz
Wavelength range
1 m to 1 dm
Related bands
Ultra high frequency (IEEE)
Frequency range
300 MHz to 3 GHz
Wavelength range
1 m to 3 dm
Related bands

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

UHF television antenna on a residence. This type of antenna, called a Yagi-Uda antenna, is widely used at UHF frequencies.
Another antenna type common at UHF; a reflective array TV antenna consisting of two high-bandwidth "bow tie" dipoles in front of a flat reflector screen. The antenna is oriented so as to receive vertically-polarized radio waves.

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.[2] 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.

Since UHF transmission is limited by the visual horizon to 30–40 miles (48–64 km) and usually to shorter distances by local terrain, it allows the same frequency channels to 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

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 25 cm 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 fulfilled the demand for additional over-the-air television channels in urban areas. Today, much of the bandwidth has been reallocated to land mobile radio system, trunked radio and mobile telephone use. UHF channels are still used for digital television.

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. Some wireless computer networks use UHF frequencies. The widely adopted GSM and UMTS cellular networks use UHF cellular frequencies.

Major telecommunications providers have deployed voice and data cellular networks in VHF/UHF range. This allows mobile phones and mobile computing devices to be connected to the public switched telephone network and the Internet.

UHF radars are said to be effective at tracking stealth fighters, if not stealth bombers.[3]

Wi-Fi operates at 2412 MHz-2484 MHz. LTE also operates on UHF frequencies

Examples of UHF frequency allocations

Australia

  • UHF citizens band (Land mobile service): 476–477 MHz
  • Television broadcasting uses UHF channels between 503 and 694 MHz
  • Fixed point-to-point Link 450.4875 - 451.5125 MHz
  • Land mobile service 457.50625 - 459.9875 MHz
  • Mobile satellite service: 406.0000 - 406.1000 MHz
  • Segment and Service examples: Land mobile for private, Australian, State and Territory Government, Rail industry and Mobile-Satellite[4]

Canada

  • 430–450 MHz: Amateur radio (70 cm band)
  • 470–806 MHz: Terrestrial television (with select channels in the 700 MHz band left vacant)
  • 1452–1492 MHz: Digital Audio Broadcasting (L band)[5]
  • Many other frequency assignments for Canada and Mexico are similar to their US counterparts

United Kingdom

  • 380399.9 MHz: Terrestrial Trunked Radio (TETRA) service for emergency use
  • 430440 MHz: Amateur radio (70 cm band)
  • 446.0446.2 MHz : European unlicensed PMR service => PMR446
  • 457464 MHz: Scanning telemetry and telecontrol, assigned mostly to the water, gas, and electricity industries
  • 606614 MHz: Radio microphones and radio-astronomy
  • 470862 MHz: Previously used for analogue TV channels 21–69 (until 2012).
    • Currently channels 21–37, 39–48, plus 55 and 56, are used for Freeview digital TV.[6] Channel 38 was used for radio astronomy but has been cleared to allow PMSE users access on a licensed, shared basis.
    • 694-790 MHz:[7] i.e. Channels 49-60 are in the process of being cleared, to allow these channels to be allocated for 5G cellular communication, however, Channels 55 and 56 are being used for COM 7 and COM 8 multiplexes for HD services.
    • 791–862 MHz,[8] i.e. channels 61–69 inclusive were previously used for licensed and shared wireless microphones (channel 69 only), has since been allocated to 4G cellular communications.
  • 863865 MHz: Used for licence-exempt wireless systems.
  • 863870 MHz: Short range devices, LPWAN IoT devices such as NarrowBand-IoT.
  • 870960 MHz: Cellular communications (GSM900 - Vodafone and O2 only) including GSM-R and future TETRA
  • 12401325 MHz: Amateur radio (23 cm band)
  • 17101880 MHz: 2G Cellular communications (GSM1800)
  • 18801900 MHz: DECT cordless telephone
  • 19001980 MHz: 3G cellular communications - mobile phone uplink
  • 21102170 MHz: 3G cellular communications - base station downlink
  • 23102450 MHz: Amateur radio (13 cm 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 14-83) 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 North American Television Frequencies.

There is a considerable amount of lawful unlicensed activity (cordless phones, wireless networking) clustered around 900 MHz and 2.4 GHz, regulated under Title 47 CFR Part 15. These ISM bands – frequencies with a higher unlicensed power permitted for use originally by Industrial, Scientific, Medical apparatus – are now 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, adjacent to the frequencies allocated for Bluetooth network devices.

The spectrum from 806 MHz to 890 MHz (UHF channels 70–83) 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 698 MHz to 806 MHz (UHF channels 52–69) 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.[9]

The FCC has allowed Americans to connect any device and any application to the 22 MHz of radio spectrum that people are calling the 700 MHz band. The FCC did not include a wholesale condition, which would have required the owner of the band to resell bandwidth to third parties who could then service the end user. Google argued that the wholesale requirement would have stimulated internet competition. As of 2007, 96% of the country's broadband access was controlled by DSL and cable providers. A wholesale condition could have meant a third option for internet service.[10]

  • 225420 MHz: Government use, including meteorology, military aviation, and federal two-way use[11]
  • 420450 MHz: Government radiolocation, amateur radio satellite and amateur radio (70 cm band), MedRadio[12]
  • 450470 MHz: UHF business band, General Mobile Radio Service, and Family Radio Service 2-way "walkie-talkies", public safety
  • 470512 MHz: Low-band TV channels 1420 (shared with public safety land mobile 2-way radio in 12 major metropolitan areas scheduled to relocate to 700 MHz band by 2023[13])
  • 512608 MHz: Medium-band TV channels 2136
  • 608614 MHz: Channel 37 used for radio astronomy and wireless medical telemetry[14]
  • 614698 MHz: Mobile broadband shared with TV channels 3851 auctioned in April 2017. TV stations will relocate by 2020.
    • 617652 MHz: Mobile broadband service downlink
    • 652663 MHz: Wireless microphones (higher priority) and unlicensed devices (lower priority)
    • 663698 MHz: Mobile broadband service uplink
  • 698806 MHz: 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 5269)
  • 806816 MHz: Public safety and commercial 2-way (formerly TV channels 7072)
  • 817824 MHz: ESMR band for wideband mobile services (mobile phone) (formerly public safety and commercial 2-way)
  • 824849 MHz: Cellular A & B franchises, terminal (mobile phone) (formerly TV channels 7377)
  • 849851 MHz: Commercial aviation air-ground systems (Gogo)
  • 851861 MHz: Public safety and commercial 2-way (formerly TV channels 7780)
  • 862869 MHz: ESMR band for wideband mobile services (base station) (formerly public safety and commercial 2-way)
  • 869894 MHz: Cellular A & B franchises, base station (formerly TV channels 8083)
  • 894896 MHz: Commercial aviation air-ground systems (Gogo)
  • 896901 MHz: Commercial 2-way radio
  • 901902 MHz: Narrowband PCS: commercial narrowband mobile services
  • 902928 MHz: ISM band, amateur radio (33 cm band), cordless phones and stereo, radio-frequency identification, datalinks
  • 928929 MHz: SCADA, alarm monitoring, meter reading systems and other narrowband services for a company internal use
  • 929930 MHz: Pagers
  • 930931 MHz: Narrowband PCS: commercial narrowband mobile services
  • 931932 MHz: Pagers
  • 932935 MHz: Fixed microwave services: distribution of video, audio and other data
  • 935940 MHz: Commercial 2-way radio
  • 940941 MHz: Narrowband PCS: commercial narrowband mobile services
  • 941960 MHz: Mixed studio-transmitter fixed links, SCADA, other.
  • 9601215 MHz: Aeronautical radionavigation
  • 12401300 MHz: Amateur radio (23 cm band)
  • 13001350 MHz: Long range radar systems
  • 13501390 MHz: Military air traffic control and mobile telemetry systems at test ranges
  • 13901395 MHz: Proposed wireless medical telemetry service. TerreStar failed to provide service by the required deadline.[15]
  • 13951400 MHz: Wireless medical telemetry service
  • 14001427 MHz: Earth exploration, radio astronomy, and space research
  • 14271432 MHz: Wireless medical telemetry service
  • 14321435 MHz: Proposed wireless medical telemetry service. TerreStar failed to provide service by the required deadline.[15]
  • 14351525 MHz: Military use mostly for aeronautical mobile telemetry (therefore not available for Digital Audio Broadcasting, unlike Canada/Europe)
  • 15251559 MHz: Skyterra downlink (Ligado is seeking FCC permission for terrestrial use[16])
    • 15261536 MHz: proposed Ligado downlink
    • 15361559 MHz: proposed guard band
  • 15591610 MHz: Radio Navigation Satellite Services (RNSS) Upper L-band
    • 15631587 MHz: GPS L1 band
    • 15931610 MHz: GLONASS G1 band
    • 15591591 MHz: Galileo E1 band (overlapping with GPS L1[17])
  • 16101660.5 MHz: Mobile Satellite Service
    • 16101618: Globalstar uplink
    • 16181626.5 MHz: Iridium uplink and downlink[16]
    • 1626.51660.5 MHz: Skyterra uplink (Ligado is seeking FCC permission for terrestrial use[16])
      • 1627.51637.5 MHz: proposed Ligado uplink 1
      • 1646.51656.5 MHz: proposed Ligado uplink 2
  • 1660.51668.4 MHz: Radio astronomy observations. Transmitting is not permitted.
  • 1668.41670 MHz: Radio astronomy observations. Weather balloons may utilize the spectrum after an advance notice.
  • 16701675 MHz: Geostationary Operational Environmental Satellite transmissions to three earth stations in Wallops Island, VA; Greenbelt, MD and Fairbanks, AK. 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.[18]
  • 16751695 MHz: Meteorological federal users
  • 16951780 MHz: AWS mobile phone uplink (UL) operating band
    • 16951755 MHz: AWS-3 blocks A1 and B1
    • 17101755 MHz: AWS-1 blocks A, B, C, D, E, F
    • 17551780 MHz: AWS-3 blocks G, H, I, J (various federal agencies transitioning by 2025[19])
  • 17801850 MHz: exclusive federal use (Air Force satellite communications, Army's cellular-like communication system, other agencies)
  • 18501920 MHz: PCS mobile phone—order is A, D, B, E, F, C, G, H blocks. A, B, C = 15 MHz; D, E, F, G, H = 5 MHz
  • 19201930 MHz: DECT cordless telephone
  • 19302000 MHz: PCS base stations—order is A, D, B, E, F, C, G, H blocks. A, B, C = 15 MHz; D, E, F, G, H = 5 MHz
  • 20002020 MHz: lower AWS-4 downlink (mobile broadband)
  • 20202110 MHz: Cable Antenna Relay service, Local Television Transmission service, TV Broadcast Auxiliary service, Earth Exploration Satellite service
  • 21102200 MHz: AWS mobile broadband downlink
    • 21102155 MHz: AWS-1 blocks A, B, C, D, E, F
    • 21552180 MHz: AWS-3 blocks G, H, I, J
    • 21802200 MHz: upper AWS-4
  • 22002290 MHz: NASA satellite tracking, telemetry and control (space-to-Earth, space-to-space)
  • 22902300 MHz: NASA Deep Space Network
  • 23002305 MHz: Amateur radio (13 cm band, lower segment)
  • 23052315 MHz: WCS mobile broadband service uplink blocks A and B
  • 23152320 MHz: WCS block C (AT&T is pursuing smart grid deployment[20])
  • 23202345 MHz: Satellite radio (Sirius XM)
  • 23452350 MHz: WCS block D (AT&T is pursuing smart grid deployment[20])
  • 23502360 MHz: WCS mobile broadband service downlink blocks A and B
  • 23602390 MHz: Aircraft landing and safety systems
  • 23902395 MHz: Aircraft landing and safety systems (secondary deployment in a dozen of airports), amateur radio otherwise
  • 23952400 MHz: Amateur radio (13 cm band, upper segment)
  • 24002483.5 MHz: 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
  • 2483.52495 MHz: Globalstar downlink and Terrestrial Low Power Service suitable for TD-LTE small cells[21]
  • 24952690 MHz: Educational Broadcast and Broadband Radio Services[22]
  • 26902700 MHz: Receive-only range for radio astronomy and space research

See also

References

  1. "IEEE 521-2002 - IEEE Standard Letter Designations for Radar-Frequency Bands". Standards.ieee.org. Retrieved 17 December 2017.
  2. Seybold, John S. (2005). Introduction to RF Propagation. John Wiley and Sons. pp. 55–58. ISBN 0471743682.
  3. MINNICK, WENDELL (22 November 2014). "China's Anti-Stealth Radar Comes to Fruition". Defensenews.com. Gannett. Retrieved 25 November 2014.
  4. "400 MHz Plan" (PDF). acma.gov. Archived from the original (PDF) on April 4, 2019. Retrieved November 3, 2019.
  5. "Digital Audio Broadcasting (DAB) - History of Canadian Broadcasting". Broadcasting-history.ca. Retrieved 15 October 2017.
  6. "What is 700MHz Clearance?". Freeview.
  7. "Decision to make the 700 MHz band available for mobile data - statement" (PDF). Retrieved 4 April 2020.
  8. "800 MHz & 2.6 GHz Combined Award". The Office of Communications. May 9, 2012. Retrieved 2014-11-21.
  9. Hansell, Saul (March 18, 2008). "Going Once…Going Twice…The 700 Mhz Spectrum is Sold". Bits.blos.nytimes.com. Retrieved 15 October 2017.
  10. FCC opens up US wireless spectrum, The Register, 1 August 2007, Cade Metz
  11. "Federal Government Spectrum Use Reports 225 MHz – 7.125 GHz". NTIA. Dec 2015 – Aug 2017. Retrieved October 21, 2019.
  12. "T-Band Report" (PDF). Npstc.org. March 15, 2013. Retrieved 17 December 2017.
  13. "Wireless Medical Telemetry Service (WMTS)". Fcc.gov. Retrieved 17 December 2017.
  14. "TerreStar Corporation Request for Temporary Waiver of Substantial Service Requirements for 1.4 GHz Licenses" (PDF). the FCC. 2017-10-10. Retrieved 2017-10-11.
  15. "Ligado Ex Parte re Iridium Analysis (PUBLIC 11-2-2016)" (PDF). Ecfsapi.fcc.gov. Retrieved 17 December 2017.
  16. "Galileo Signal Plan". Navipedia.net. Retrieved 17 December 2017.
  17. "REQUEST FOR WAIVER AND PUBLIC INTEREST STATEMENT". FCC. 2016-06-04. Retrieved 2018-04-02.
  18. "AWS-3 Transition". Ntia.doc.gov. January 29, 2015. Retrieved 17 December 2017.
  19. "AT&T Mobility Petition for Limited Waiver of Interim Performance Requirement for 2.3 GHz WCS C and D Block Licenses" (PDF). Ecfsapi.fcc.gov. Retrieved 17 December 2017.
  20. "Globalstar Overview" (PDF). Globalstar.com. 2017. Archived (PDF) from the original on August 2, 2017. Retrieved 17 December 2017.
  21. "Broadband Radio Service & Education Broadband Service". The FCC. Retrieved 2018-06-05.
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