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Ultra high frequency
View on Wikipediafrom Wikipedia
| Ultra high frequency (ITU) | |
|---|---|
Frequency range | 300 MHz to 3 GHz |
Wavelength range | 1 m to 10 cm |
Related bands | |
| Ultra high frequency (IEEE) | |
Frequency range | 300 MHz to 1 GHz |
Wavelength range | 1 m to 30 cm |
Related bands | |
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Ultra high frequency (UHF) is the ITU designation[1][2] 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 decimetre). 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 300 MHz and 1 GHz.[3] 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.
Propagation characteristics
[edit]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.[4] 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 40 miles (48 to 64 km) 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
[edit]
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
[edit]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 2484 MHz. 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
[edit]Australia
[edit]- 406–406.1 MHz: Mobile satellite service[5]
- 450.4875–451.5125 MHz: Fixed point-to-point link
- 457.50625–459.9875 MHz: Land mobile service
- 476–477 MHz: UHF citizens band (land mobile service)
- 503–694 MHz: UHF channels for television broadcasting
Canada
[edit]- 430–450 MHz: Amateur radio (70 cm band)
- 470–806 MHz: Terrestrial television (with select channels in the 600 and 700 MHz bands left vacant)
- 1452–1492 MHz: Digital Audio Broadcasting (L band)[6]
- Many other frequency assignments for Canada and Mexico are similar to their US counterparts
France
[edit]- 380-400 MHz: Terrestrial Trunked Radio for Police
- 430-440 MHz: Amateur radio (70 cm band)
- 446.0–446.2 MHz : European unlicensed PMR service, PMR446
- 470-694 MHz: Terrestrial television
New Zealand
[edit]- 406.1–420 MHz: Land mobile service
- 430–440 MHz: Amateur radio (70 cm band) and amateur radio satellite
- 476–477 MHz: PRS Personal Radio Service (Land mobile service)
- 485–502 MHz: Analog and P25 emergency services use
- 510–622 MHz: Terrestrial television
- 960–1215 MHz: Aeronautical radionavigation
- 1240–1300 MHz: Amateur radio (23 cm band)
United Kingdom
[edit]- 380–399.9 MHz: Terrestrial Trunked Radio (TETRA) service for emergency use
- 430–440 MHz: Amateur radio (70 cm band)
- 446.0–446.2 MHz : European unlicensed PMR service, PMR446
- 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 to 37 and 39 to 48 are used for Freeview digital TV.[7] 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.
- 694–790 MHz:[8] i.e. channels 49 to 60 have been cleared, to allow these channels to be allocated for 5G cellular communication.
- 791–862 MHz,[9] 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.
- 863–865 MHz: Used for licence-exempt wireless systems.
- 863–870 MHz: Short range devices, LPWAN IoT devices such as NarrowBand-IoT.
- 870–960 MHz: Cellular communications (GSM900 - Vodafone and O2 only) including GSM-R and future TETRA
- 1240–1325 MHz: Amateur radio (23 cm band)
- 1710–1880 MHz: 2G cellular communications (GSM1800)
- 1880–1900 MHz: DECT cordless telephone
- 1900–1980 MHz: 3G cellular communications (mobile phone uplink)
- 2110–2170 MHz: 3G cellular communications (base station downlink)
- 2310–2450 MHz: Amateur radio (13 cm band)
United States
[edit]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 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 and 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 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 698 MHz to 806 MHz (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.[10]
- 225–420 MHz: Government use, including meteorology, military aviation, and federal two-way use[11]
- 420–450 MHz: Government radiolocation, amateur radio satellite and amateur radio (70 cm band), MedRadio[12]
- 450–470 MHz: UHF business band, General Mobile Radio Service, and Family Radio Service 2-way "walkie-talkies", public safety
- 470–512 MHz: 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 700 MHz band by 2023[13])
- 512–608 MHz: Medium-band TV channels 21 to 36
- 608–614 MHz: Channel 37 used for radio astronomy and wireless medical telemetry[14]
- 614–698 MHz: Mobile broadband shared with TV channels 38 to 51 auctioned in April 2017. TV stations were relocated by 2020.
- 617–652 MHz: Mobile broadband service downlink
- 652–663 MHz: Wireless microphones (higher priority) and unlicensed devices (lower priority)
- 663–698 MHz: Mobile broadband service uplink
- 698–806 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 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).
- 806–816 MHz: Public safety and commercial 2-way (formerly TV channels 70 to 72)
- 817–824 MHz: ESMR band for wideband mobile services (mobile phone) (formerly public safety and commercial 2-way)
- 824–849 MHz: Cellular A and B franchises, terminal (mobile phone) (formerly TV channels 73 to 77)
- 849–851 MHz: Commercial aviation air-ground systems
- 851–861 MHz: Public safety and commercial 2-way (formerly TV channels 77 to 80)
- 862–869 MHz: ESMR band for wideband mobile services (base station) (formerly public safety and commercial 2-way)
- 869–894 MHz: Cellular A and B franchises, base station (formerly TV channels 80 to 83)
- 894–896 MHz: Commercial aviation air-ground systems
- 896–901 MHz: Commercial 2-way radio
- 901–902 MHz: Narrowband PCS: commercial narrowband mobile services
- 902–928 MHz: ISM band, amateur radio (33 cm band), cordless phones and stereo, radio-frequency identification, datalinks
- 928–929 MHz: SCADA, alarm monitoring, meter reading systems and other narrowband services for a company's internal use
- 929–930 MHz: Pagers
- 930–931 MHz: Narrowband PCS: commercial narrowband mobile services
- 931–932 MHz: Pagers
- 932–935 MHz: Fixed microwave services: distribution of video, audio and other data
- 935–940 MHz: Commercial 2-way radio
- 940–941 MHz: Narrowband PCS: commercial narrowband mobile services
- 941–960 MHz: Mixed studio-transmitter fixed links, SCADA, other.
- 960–1215 MHz: Aeronautical radionavigation
- 1240–1300 MHz: Amateur radio (23 cm band)
- 1300–1350 MHz: Long range radar systems
- 1350–1390 MHz: Military air traffic control and mobile telemetry systems at test ranges
- 1390–1395 MHz: Proposed wireless medical telemetry service. TerreStar failed to provide service by the required deadline.[15]
- 1395–1400 MHz: Wireless medical telemetry service
- 1400–1427 MHz: Earth exploration, radio astronomy, and space research
- 1427–1432 MHz: Wireless medical telemetry service
- 1432–1435 MHz: Proposed wireless medical telemetry service. TerreStar failed to provide service by the required deadline.[15]
- 1435–1525 MHz: Military use mostly for aeronautical mobile telemetry (therefore not available for Digital Audio Broadcasting, unlike Canada/Europe)
- 1525–1559 MHz: Skyterra downlink (Ligado is seeking FCC permission for terrestrial use[16])
- 1526–1536 MHz: proposed Ligado downlink
- 1536–1559 MHz: proposed guard band
- 1559–1610 MHz: Radio Navigation Satellite Services (RNSS) Upper L-band
- 1610–1660.5 MHz: Mobile Satellite Service
- 1660.5–1668.4 MHz: Radio astronomy observations. Transmitting is not permitted.
- 1668.4–1670 MHz: Radio astronomy observations. Weather balloons may utilize the spectrum after an advance notice.
- 1670–1675 MHz: 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.[18]
- 1675–1695 MHz: Meteorological federal users
- 1695–1780 MHz: AWS mobile phone uplink (UL) operating band
- 1695–1755 MHz: AWS-3 blocks A1 and B1
- 1710–1755 MHz: AWS-1 blocks A, B, C, D, E, F
- 1755–1780 MHz: AWS-3 blocks G, H, I, J (various federal agencies transitioning by 2025[19])
- 1780–1850 MHz: exclusive federal use (Air Force satellite communications, Army's cellular-like communication system, other agencies)
- 1850–1920 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
- 1920–1930 MHz: DECT cordless telephone
- 1930–2000 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
- 2000–2020 MHz: lower AWS-4 downlink (mobile broadband)
- 2020–2110 MHz: Cable antenna relay service, local television transmission service, TV broadcast auxiliary service, Earth exploration satellite service
- 2110–2200 MHz: AWS mobile broadband downlink
- 2110–2155 MHz: AWS-1 blocks A, B, C, D, E, F
- 2155–2180 MHz: AWS-3 blocks G, H, I, J
- 2180–2200 MHz: upper AWS-4
- 2200–2290 MHz: NASA satellite tracking, telemetry and control (space-to-Earth, space-to-space)
- 2290–2300 MHz: NASA Deep Space Network
- 2300–2305 MHz: Amateur radio (13 cm band, lower segment)
- 2305–2315 MHz: WCS mobile broadband service uplink blocks A and B
- 2315–2320 MHz: WCS block C (AT&T is pursuing smart grid deployment[20])
- 2320–2345 MHz: Satellite radio
- 2345–2350 MHz: WCS block D (AT&T is pursuing smart grid deployment[20])
- 2350–2360 MHz: WCS mobile broadband service downlink blocks A and B
- 2360–2390 MHz: Aircraft landing and safety systems
- 2390–2395 MHz: Aircraft landing and safety systems (secondary deployment in a dozen of airports), amateur radio otherwise
- 2395–2400 MHz: Amateur radio (13 cm band, upper segment)
- 2400–2483.5 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
- 2483.5–2495 MHz: Globalstar downlink and terrestrial low power service suitable for TD-LTE small cells[21]
- 2495–2690 MHz: Educational broadcast and broadband radio Services[22]
- 2690–2700 MHz: Receive-only range for radio astronomy and space research
See also
[edit]References
[edit]- ^ US Federal Standard 1037B: Telecommunications, Glossary of Telecommunications Terms. Office of Technology Standards, General Services Administration. 3 June 1991. pp. S-18.
- ^ Final Acts WRC-15 (PDF). World Radiocommunication Conference. Geneva, Switzerland: International Telecommunications Union. 2015. p. 4. Retrieved 2025-01-12.
- ^ "IEEE 521-2002 - IEEE Standard Letter Designations for Radar-Frequency Bands". IEEE. Retrieved 17 December 2017.
- ^ Seybold, John S. (2005). Introduction to RF Propagation. John Wiley and Sons. pp. 55–58. ISBN 0471743682.
- ^ "400 MHz Plan" (PDF). acma.gov. Archived from the original (PDF) on April 4, 2019. Retrieved November 3, 2019.
- ^ "Digital Audio Broadcasting (DAB) - History of Canadian Broadcasting". Broadcasting-history.ca. Retrieved 15 October 2017.
- ^ "What is 700MHz Clearance?". Freeview.[dead link]
- ^ "Decision to make the 700 MHz band available for mobile data - statement" (PDF). Retrieved 4 April 2020.
- ^ "800 MHz & 2.6 GHz Combined Award". The Office of Communications. May 9, 2012. Retrieved 2014-11-21.
- ^ Hansell, Saul (March 18, 2008). "Going Once…Going Twice…The 700 Mhz Spectrum is Sold". Bits.blos.nytimes.com. Retrieved 15 October 2017.
- ^ [1] [dead link]
- ^ "Federal Government Spectrum Use Reports 225 MHz – 7.125 GHz". NTIA. Dec 2015 – Aug 2017. Retrieved October 21, 2019.
- ^ "T-Band Report" (PDF). NPSTC. March 15, 2013. Retrieved 17 December 2017.
- ^ "Wireless Medical Telemetry Service (WMTS)". Federal Communications Commission. March 8, 2017. Retrieved 17 December 2017.
- ^ a b "TerreStar Corporation Request for Temporary Waiver of Substantial Service Requirements for 1.4 GHz Licenses" (PDF). FCC. 2017-10-10. Retrieved 2017-10-11.
- ^ a b c "Ligado Ex Parte re Iridium Analysis (PUBLIC 11-2-2016)" (PDF). Ecfsapi.fcc.gov. Archived from the original (PDF) on 2022-08-19. Retrieved 17 December 2017.
- ^ "Galileo Signal Plan". Navipedia. Archived from the original on Dec 23, 2017. Retrieved 17 December 2017.
- ^ "Request for waiver and public interest statement". FCC. 2016-06-04. Retrieved 2018-04-02.
- ^ "AWS-3 Transition". Ntia.doc.gov. January 29, 2015. Retrieved 17 December 2017.
- ^ a b "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. Archived from the original (PDF) on 3 July 2022. Retrieved 17 December 2017.
- ^ "Globalstar Overview" (PDF). Globalstar.com. 2017. Archived (PDF) from the original on August 2, 2017. Retrieved 17 December 2017.
- ^ "Broadband Radio Service & Education Broadband Service". The FCC. February 2016. Retrieved 2018-06-05.[dead link]
External links
[edit]- U.S. cable television channel frequencies
- Tomislav Stimac, "Definition of frequency bands (VLF, ELF... etc.)". IK1QFK Home Page (vlf.it).
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Ultra high frequency
View on Grokipediafrom Grokipedia
Ultra high frequency (UHF) is the International Telecommunication Union (ITU) designation for the portion of the radio spectrum spanning frequencies from 300 MHz to 3 GHz, corresponding to wavelengths between 1 meter and 10 centimeters.
UHF signals exhibit line-of-sight propagation characteristics, meaning they travel in straight lines with limited diffraction around obstacles, resulting in shorter effective ranges compared to lower frequency bands, though they can penetrate buildings and foliage better than higher microwave frequencies.[1] This propagation behavior makes UHF suitable for short- to medium-range communications in urban and indoor environments, where smaller antenna sizes are advantageous due to the shorter wavelengths.[1]
Key applications of UHF include television broadcasting (particularly channels 14–36 in the United States[2]), mobile phone networks, wireless local area networks like Wi-Fi, Bluetooth devices, GPS navigation, two-way radios for public safety, and satellite communications.[3] Additionally, UHF is employed in military communications, aerospace telemetry, and unmanned aerial vehicle (UAV) control systems, leveraging its capacity for high-bandwidth data transmission over moderate distances.[1]
Fundamentals
Frequency Range
Ultra high frequency (UHF) is designated by the International Telecommunication Union Radiocommunication Sector (ITU-R) as band 9 in its standard nomenclature for frequency allocations, encompassing the range from 300 MHz to 3 GHz.[4] This band is positioned immediately above the very high frequency (VHF) band, which spans 30 MHz to 300 MHz (ITU-R band 8), and below the super high frequency (SHF) band, covering 3 GHz to 30 GHz (ITU-R band 10).[4] Historically, the UHF band has been referred to using metric prefixes based on wavelength, specifically as the decimetric wave band, corresponding to wavelengths between 1 meter and 10 centimeters. This naming convention aligns with the ITU-R's recognition of decimetric waves for the 300 MHz to 3 GHz range, emphasizing the band's position in the electromagnetic spectrum where propagation characteristics begin to favor shorter wavelengths suitable for certain applications. Within the broader UHF spectrum, several sub-bands are commonly delineated for specific uses, such as the L-band (1 GHz to 2 GHz) and the S-band (2 GHz to 4 GHz), with the latter partially overlapping the upper limit of UHF at 3 GHz. These sub-divisions, often rooted in radar and military nomenclature but adopted internationally, facilitate targeted frequency planning without altering the primary ITU-R boundaries.Wavelength and Properties
The wavelength of ultra high frequency (UHF) electromagnetic waves is determined by the formula , where is the speed of light in vacuum ( m/s) and is the frequency in hertz.[5] For the UHF band spanning 300 MHz to 3 GHz, this yields wavelengths ranging from 1 meter at the lower end to 10 cm at the upper end.[4] A key property of UHF waves stems from their relatively short wavelengths, which permit the design of compact antennas proportional in size to the wavelength, enabling efficient use in portable and space-constrained applications compared to lower-frequency bands like HF or VHF.[6] However, these shorter wavelengths also result in greater atmospheric absorption than at lower frequencies, with attenuation increasing due to interactions with atmospheric gases and moisture, though remaining low overall below 3 GHz.[6] UHF signals demonstrate moderate penetration through obstacles such as buildings and foliage, outperforming higher-frequency microwaves (above 3 GHz) where attenuation is more severe, but underperforming compared to lower-frequency HF waves that diffract and propagate more effectively around or through dense materials.[7] As radiofrequency electromagnetic radiation, UHF waves are non-ionizing, lacking sufficient photon energy to remove electrons from atoms and thus safe for typical human exposures in communication and broadcasting uses.[9]Propagation Characteristics
Line-of-Sight Propagation
Ultra high frequency (UHF) signals predominantly rely on line-of-sight (LOS) propagation as their primary transmission mode, owing to the relatively short wavelengths in the 10 to 100 cm range that restrict significant diffraction around obstacles and minimize ground wave effects compared to lower frequency bands.[10] This characteristic makes UHF suitable for direct, unobstructed paths between transmitter and receiver, with typical operational ranges of 50 to 100 km without the use of repeaters, influenced by factors such as antenna elevation and atmospheric conditions. A key limitation in LOS propagation is free-space path loss, which represents the signal attenuation in an ideal, unobstructed environment and increases proportionally to the square of both the propagation distance and the frequency.[11] For UHF frequencies (300 MHz to 3 GHz), this results in progressively greater loss at the upper end of the band and over extended distances, necessitating higher transmitter power or directional antennas to maintain reliable communication links. The Earth's curvature imposes an additional constraint on LOS range by defining the radio horizon, beyond which direct signals are blocked unless elevated antennas are used. The approximate distance to this horizon is given by the [formula , where is in kilometers and is the effective antenna height in meters above ground level (accounting for standard atmospheric refraction). This geometric limit typically confines practical UHF LOS paths to tens of kilometers for ground-based systems but can extend further with elevated installations. UHF LOS propagation plays a critical role in point-to-point links, such as microwave relay networks used for telecommunications backhaul and television signal distribution, where chains of repeaters extend coverage across regions by maintaining clear sightlines between stations.[12]Obstacle and Environmental Effects
Ultra high frequency (UHF) signals, while primarily propagating via line-of-sight paths, can experience limited non-line-of-sight coverage through diffraction and reflection mechanisms when encountering obstacles such as hills, buildings, or fences. Diffraction occurs as waves bend around the edges of these obstructions, following models like knife-edge diffraction, which predict transmission losses in agreement with measurements for UHF frequencies. Reflections from surfaces like building walls or terrain further contribute to signal redirection, allowing partial propagation beyond direct visibility, though with significant attenuation depending on the obstacle geometry and frequency within the 300-3000 MHz band.[13][14] Environmental factors introduce additional signal degradation through absorption and scattering. In vegetated areas, UHF waves are attenuated by foliage, with specific rates typically ranging from 0.05 to 0.5 dB per meter through trees in full leaf, increasing by about 20% for leaf-on conditions compared to leafless trees at around 1 GHz.[15] Rain causes minimal additional loss at UHF, often less than 1 dB/km even in heavy precipitation, due to the relatively long wavelengths. Urban clutter, including buildings and structures, exacerbates attenuation, with additional losses ranging from 0 to 40 dB (median around 27 dB in building shadows) in heavily built-up areas compared to open areas.[16] Multipath fading arises from multiple signal paths due to reflections off environmental elements like vehicles, buildings, and terrain in mobile scenarios, leading to constructive and destructive interference that causes rapid signal fluctuations. In urban mobile environments, these reflections from surrounding structures dominate, resulting in Rayleigh or Rician fading distributions characteristic of UHF channels. Such fading can degrade reception quality, particularly in dynamic settings where the receiver moves through varying clutter.[17][18] UHF's moderate penetration capability, with building entry losses of 5 to 28 dB depending on construction, makes it well-suited for urban television broadcasting where signals can propagate indoors despite obstacles. In contrast, rural areas benefit from fewer obstructions but often require signal boosters to overcome path losses over longer distances and maintain reliable coverage.[19]Antennas
Common Types
Ultra high frequency (UHF) antennas are designed to operate efficiently within the 300 MHz to 3 GHz range, where wavelengths typically span from 1 meter to 10 centimeters, enabling compact structures suitable for various applications. Common types include simple wire-based designs for omnidirectional coverage and more complex arrays for directional performance, optimized to match the relatively short wavelengths of UHF signals. These antennas prioritize portability and ease of integration due to their small physical size compared to lower-frequency counterparts. Dipole and monopole antennas represent the simplest and most fundamental designs for UHF operation, providing omnidirectional radiation patterns ideal for broad coverage. A half-wave dipole consists of two collinear conductors each approximately a quarter-wavelength long, totaling about λ/2, which at a mid-UHF frequency of 1.8 GHz equates to roughly 8.3 cm in length for efficient resonance. Monopoles, often used in vertical configurations over a ground plane, are similarly sized at λ/4 (about 4.2 cm at 1.8 GHz) and function as half of a dipole, offering comparable performance in mobile or base station setups. These antennas are widely employed in basic broadcasting and communication systems due to their low cost and straightforward construction. For enhanced directionality, particularly in television reception, Yagi-Uda arrays are a prevalent choice in the UHF band. These end-fire arrays feature a driven element (typically a dipole), a reflector, and multiple directors—usually 5 to 15 elements in total—arranged along a boom to achieve gains of 10 to 15 dBi, focusing energy in a narrow beam for improved signal capture over distances. Their design exploits UHF's line-of-sight propagation needs, making them effective for rooftop or attic installations in digital TV setups. Compact antennas like helical and patch designs are optimized for mobile and portable UHF devices, where space constraints demand small footprints. Helical antennas, with their coiled wire structure, produce circular polarization to mitigate multipath fading in dynamic environments, such as handheld RFID readers or satellite links in the UHF range. Patch antennas, flat and conformal, also support circular polarization and are integrated into smartphones or GPS devices for UHF wireless communications, offering broad bandwidth in a low-profile form factor. Parabolic dish antennas serve point-to-point UHF links, especially effective above 1 GHz where higher directivity is achievable. These reflector-based designs use a curved dish to focus signals onto a feed horn, providing high gain for microwave relay or backhaul applications in the upper UHF spectrum. The small size of UHF antennas enhances their portability; for instance, rabbit ears antennas—adjustable dipole pairs—serve as compact indoor receivers for UHF television broadcasts, easily positioned on tables without permanent mounting.Design and Performance
UHF antennas are engineered with a focus on key performance metrics that ensure effective radiation and impedance matching within the 300 MHz to 3 GHz range. Gain, measured in decibels isotropic (dBi), indicates the antenna's directive properties, typically achieving 2 to 10 dBi for standard designs like yagis or patches, depending on element count and configuration. Bandwidth defines the operational frequency span, often specified at the -10 dB return loss point, with practical UHF antennas offering 5-20% fractional bandwidth to cover allocated channels without retuning. Voltage standing wave ratio (VSWR) is targeted below 2:1 across the band to minimize reflected power and maximize transmitted efficiency, while the standard input impedance of 50 ohms aligns with common RF transmission lines and transceivers for optimal power transfer.[20][21][22] Efficiency considerations in UHF antenna design emphasize low material losses, which are minimal due to the compact scales and high conductivity of metals like copper or aluminum, often yielding radiation efficiencies exceeding 90% in optimized structures. However, feedline losses become more pronounced at UHF than at VHF, with attenuation increasing roughly proportionally to frequency; for instance, RG-58 coax exhibits about 5 dB/100 ft at 150 MHz (VHF) but 10 dB/100 ft at 450 MHz (UHF), requiring low-loss alternatives like LMR-400 to preserve signal integrity over longer runs.[23][24][25] Polarization choices balance simplicity and robustness against environmental effects, with linear polarization (vertical or horizontal) suiting fixed installations for its ease of implementation, while circular polarization—achieved via crossed dipoles or helices—reduces multipath-induced fading by accepting signals with varying orientations, enhancing link reliability in dynamic scenarios.[26] In space-constrained applications, such as mobile handsets, miniaturization via meandering techniques folds the radiator to reduce size by 50% or more while maintaining resonance, though this introduces trade-offs like reduced efficiency to 50-70% from elevated ohmic losses and near-field coupling. These methods, common in planar inverted-F or meander line antennas, prioritize compactness over peak performance to fit regulatory standards for portable devices.[27][28]Applications
Broadcasting
Ultra high frequency (UHF) bands play a central role in over-the-air television broadcasting, particularly for channels that extend beyond the lower-frequency very high frequency (VHF) allocations. In the analog National Television System Committee (NTSC) standard used historically in North America, UHF television channels spanned 14 through 83, with channels 14-36 occupying the frequency range of 470-608 MHz and channels 38-83 covering higher portions up to approximately 890 MHz.[29] This allocation allowed for a larger number of channels compared to VHF, accommodating growing demand for broadcast content, though UHF signals suffer from greater attenuation over distance and through obstacles than VHF signals.[30] The transition from analog to digital broadcasting significantly optimized UHF spectrum usage. In the United States, the Advanced Television Systems Committee (ATSC) digital standard repurposed the UHF band, limiting full-power stations primarily to channels 14-51 (470-698 MHz) following the 2009 analog switch-off, which freed up higher channels for other services like public safety communications. Internationally, the Digital Video Broadcasting - Terrestrial 2 (DVB-T2) standard, adopted in Europe and other regions, enhanced efficiency with advanced modulation and error correction, enabling high-definition and multiple sub-channels within the same bandwidth; this facilitated widespread analog switch-offs in the 2000s and 2010s, such as the UK's completion in 2012. UHF also supports certain radio broadcasting applications, though less dominantly than television. Upper extensions of the FM band (88-108 MHz, technically VHF) sometimes overlap with transitional services, but digital audio broadcasting (DAB) primarily utilizes VHF Band III (174-240 MHz); however, some implementations explore UHF L-band (1452-1492 MHz) for improved capacity in urban areas.[31] In select regions, portions of the 470-790 MHz UHF TV band have been considered for secondary digital radio trials, but primary radio use remains limited due to TV priority.[32] Due to higher propagation losses at UHF frequencies, television transmitters require substantially more power than VHF counterparts to achieve comparable coverage areas. UHF stations can operate with effective radiated power (ERP) up to 1 MW (1000 kW) for channels 14-36 when antenna height above average terrain (HAAT) is 365 meters or less, contrasting with VHF limits around 100-316 kW.[33] This increased power compensates for the inverse relationship between frequency and signal range in line-of-sight propagation. Reception typically relies on directional Yagi-Uda antennas tuned to UHF bands for optimal signal capture.[34] As of 2025, advancements like ATSC 3.0 (NextGen TV) are expanding UHF broadcasting capabilities in the United States, enabling 4K ultra-high-definition video, high dynamic range (HDR), and immersive audio such as Dolby Atmos within the existing 14-36 channel allocations.[35] The Federal Communications Commission has authorized voluntary transitions to ATSC 3.0, with over 90 markets deploying it as of October 2025, covering approximately 70% of the U.S. population; in February 2025, the National Association of Broadcasters petitioned for a two-stage mandatory transition beginning in top 55 markets by 2028.[36] This improves spectral efficiency and supports interactive features while maintaining compatibility with legacy ATSC 1.0 receivers via simulcasting.[37]Wireless Communications
Ultra high frequency (UHF) spectrum plays a pivotal role in modern wireless communications, particularly in cellular networks, where it supports a range of technologies from legacy systems to advanced 5G deployments. In cellular applications, UHF bands enable reliable mobile connectivity with varying trade-offs in coverage and capacity. For instance, the 700 MHz band, designated as LTE Band 12, provides enhanced penetration for indoor and rural coverage in 4G networks.[38] Similarly, the 1.8–2.1 GHz range has been widely used for UMTS and GSM technologies, facilitating voice and early data services in 3G and 2G systems across global deployments.[39] In 5G New Radio (NR), mid-band UHF frequencies from 2.5 to 3.7 GHz form a core portion of sub-6 GHz spectrum, balancing data throughput with propagation characteristics suitable for suburban and urban environments.[40] Beyond cellular, UHF underpins short-range personal and local area networks through the 2.4 GHz ISM band, which operates without licensing restrictions for industrial, scientific, and medical applications. This band hosts Wi-Fi standards such as 802.11b/g/n, enabling wireless internet access in homes, offices, and public hotspots with data rates up to several hundred Mbps.[41] Bluetooth Low Energy (BLE) also utilizes the 2.4 GHz ISM band for low-power device interconnectivity, supporting applications like wearables and smart home ecosystems with minimal energy consumption.[41] These unlicensed uses leverage UHF's favorable wavelength for compact antennas and moderate range, typically up to 100 meters indoors. Recent advancements highlight UHF's evolving role in next-generation wireless, including spectrum auctions for 5G expansion. The C-band, spanning 3.7–4.2 GHz, has seen significant reallocation for terrestrial 5G use, with the FCC auctioning portions like the lower 3.7–3.98 GHz in 2021 and proposing up to 180 MHz in the upper 3.98–4.2 GHz for further 5G and potential 6G applications as of 2025.[42] UHF enables high data rates in 5G, reaching up to 1 Gbps in mid-band deployments, though urban coverage faces challenges from line-of-sight limitations and signal attenuation by buildings.[43] Looking ahead, 2024–2025 spectrum reallocations in UHF bands are underway to support 6G planning, with international bodies identifying clean UHF portions for future mobile broadband to enhance capacity and integration with emerging technologies.[44] Meanwhile, Wi-Fi 6E extends beyond UHF into the super high frequency (SHF) starting at 5.925 GHz, providing additional unlicensed spectrum for higher-capacity local networks while building on UHF foundations.[45]Radar and Sensing
Ultra high frequency (UHF) signals, spanning 300 MHz to 3 GHz, are widely employed in radar and sensing applications due to their balance of propagation characteristics, resolution capabilities, and penetration properties compared to higher microwave bands. These frequencies enable precise detection and tracking in various environments, leveraging the relatively longer wavelengths for reduced attenuation in certain media while achieving sufficient angular and range resolution for practical use. UHF radars often utilize directional antennas to focus energy, enhancing signal-to-noise ratios in line-of-sight scenarios.[46] In air traffic control, UHF radars operating in the L-band portion (1-2 GHz) provide precision tracking of aircraft over long ranges, typically up to 200-400 km, supporting en-route surveillance and separation assurance. These systems, such as primary surveillance radars, detect non-cooperative targets by transmitting pulses and measuring echoes, with the frequency range chosen for minimal weather interference and adequate resolution for identifying aircraft positions and velocities. The Federal Aviation Administration relies on such UHF-based radars for safe airspace management, where beam widths around 1-2 degrees allow for accurate azimuthal discrimination.[46][47] Ground penetrating radar (GPR) utilizes the lower UHF spectrum (300-900 MHz) for subsurface imaging, enabling detection of buried objects like utilities, voids, or archaeological features at depths up to 10 meters in low-conductivity soils such as dry sand. At these frequencies, electromagnetic waves penetrate the ground with less attenuation than higher bands, while providing vertical resolutions on the order of 0.3-1 meter, depending on the pulse bandwidth. Airborne and ground-based GPR systems in this range have been developed for applications including mine detection and environmental assessment, where the trade-off between depth and clarity is optimized for real-time imaging.[48] Weather radar systems overlapping the upper UHF with S-band (2-4 GHz) are essential for precipitation mapping, detecting rain, snow, and hail through backscattered signals from hydrometeors. Operating around 2.7-3 GHz, these radars achieve range resolutions of 250 meters or better, allowing for volume scans that delineate storm structures and forecast severe weather events. The National Oceanic and Atmospheric Administration's networks, including phased-array prototypes, use this band for its sensitivity to larger raindrops and reduced attenuation in heavy precipitation, supporting quantitative estimates of rainfall accumulation over wide areas.[49] UHF radars offer a theoretical resolution approximating λ/2, yielding about 50 cm at 300 MHz, which is particularly advantageous in military surveillance for distinguishing targets amid clutter like foliage or urban structures. This wavelength-dependent capability supports foliage penetration (FOPEN) radars, which operate in the lower UHF to image vehicles and personnel hidden under vegetation, providing ground resolutions sufficient for tactical reconnaissance without the fine detail loss of higher frequencies. Post-2020 developments in UHF radar for drone detection have integrated these systems into counter-unmanned aerial vehicle (C-UAV) networks, enhancing detection of small, low-radar-cross-section targets at ranges up to several kilometers by exploiting the band's ability to mitigate multipath and stealth effects.[50][51]Industrial Uses
Ultra high frequency (UHF) waves are employed in microwave ovens operating at 2.45 GHz within the Industrial, Scientific, and Medical (ISM) band to achieve dielectric heating of food through the excitation of water molecules.[52] Typical household microwave ovens deliver power outputs between 600 and 1200 watts, enabling efficient and rapid cooking while minimizing energy loss.[53] In industrial inventory management, UHF radio-frequency identification (RFID) systems utilize the 860-960 MHz frequency range to enable passive tag reading for tracking assets and goods without line-of-sight requirements.[54] These systems support read ranges of up to 10 meters, facilitating high-speed scanning in warehouses and supply chains for improved operational efficiency.[54] Medical diathermy applications leverage UHF at 434 MHz to generate deep tissue heating for therapeutic purposes, such as alleviating muscle injuries and promoting recovery through controlled hyperthermia.[55] This frequency allows for targeted energy absorption in biological tissues, enhancing blood flow and reducing inflammation without invasive procedures.[56] UHF plasma generation plays a critical role in semiconductor manufacturing, where frequencies around 500 MHz are used in electron cyclotron resonance (ECR) systems to create high-density plasmas for precise etching of dielectric films.[57] These processes enable the fabrication of advanced microelectronic components by providing uniform etching profiles essential for high-aspect-ratio structures in integrated circuits.[58]History
Origins and Early Experiments
The foundations of ultra high frequency (UHF) communications were laid in the early 20th century through experiments with higher radio frequencies, building on Heinrich Hertz's demonstrations of electromagnetic wave propagation in the 1880s. While Guglielmo Marconi's work in the 1910s and 1920s advanced shortwave (HF/VHF) technologies for improved directivity and skywave propagation, UHF experimentation began in earnest with amateur radio operators in the 1920s, exploring frequencies above 50 MHz.[59] Following regulatory allocations, U.S. amateurs gained access to the 60 MHz band (5-meter wavelength) in July 1924, enabling the first documented two-way contacts and marking the onset of organized ultra-high frequency experimentation. These trials revealed challenges like atmospheric absorption but confirmed the viability of line-of-sight propagation, paving the way for applications beyond long-distance signaling. By the mid-1920s, experimenters achieved transmissions approaching 100 MHz in laboratory settings, though limited by vacuum tube technology.[60] The 1930s saw UHF frequencies applied to radar prototypes amid rising geopolitical tensions leading to World War II preparations. While early British experiments by Robert Watson-Watt in 1935 used VHF frequencies around 25 MHz for aircraft detection, German engineers under Telefunken developed decimeter-wave radars operating at approximately 500 MHz by the late 1930s, such as prototypes for the Würzburg system, demonstrating enhanced resolution for target detection over shorter ranges. These efforts highlighted UHF's advantages in precision sensing, though propagation limitations restricted use to line-of-sight scenarios.[61][62][63] A landmark public demonstration of early high-frequency potential occurred during the 1936 Berlin Olympics, where experimental television broadcasts utilized electronic systems in the 46–50 MHz (VHF) range for signal transmission trials, though primary distribution to viewing halls relied on coaxial cables. These closed-circuit transmissions, employing 180- and 375-line formats, represented the first major televised event and underscored the role of higher frequencies in high-bandwidth video applications. Preceding the war, laboratory demonstrations of 500 MHz point-to-point links further validated UHF for reliable short-range communications, with German tests achieving viable data transfer over several kilometers. The term "ultra high frequency" was formally defined and integrated into international nomenclature at the 1947 International Telecommunication Union Radio Conference in Atlantic City, standardizing the 300-3000 MHz band for global allocations.[64][65]Modern Developments and Standardization
Following World War II, the commercialization of ultra high frequency (UHF) bands accelerated with regulatory efforts to expand television broadcasting capacity. In 1952, the U.S. Federal Communications Commission (FCC) issued its Sixth Report and Order, allocating 70 UHF channels (14–83) alongside 12 very high frequency (VHF) channels, creating a total of 82 television channels to accommodate growing demand and support the emerging color television era.[66] This expansion was crucial for the color TV boom, as the NTSC-compatible standard approved by the FCC in 1953 required additional spectrum for nationwide rollout, with UHF providing the necessary bandwidth for more stations and programming.[67] From the 1980s to the 2000s, UHF bands underwent a significant shift toward digital technologies and mobile communications. The transition to digital television, initiated in the U.S. with the FCC's 1996 adoption of ATSC standards, leveraged UHF spectrum for efficient high-definition broadcasting, culminating in the full analog-to-digital switchover in 2009 that freed up 108 MHz of UHF for other uses. Concurrently, the Global System for Mobile Communications (GSM), standardized by the European Telecommunications Standards Institute (ETSI) in 1990 and deployed starting in 1991, utilized UHF bands around 900 MHz and 1.8 GHz, enabling the rapid growth of second-generation (2G) cellular networks worldwide. Key milestones in the 2010s included spectrum auctions for fourth-generation (4G) Long-Term Evolution (LTE) networks, which repurposed UHF bands like the 700 MHz "digital dividend" for mobile broadband; for instance, the FCC's Auction 73 in 2008 raised $19.6 billion, marking a pivotal commercialization of UHF for high-speed data services. In the 2020s, fifth-generation (5G) deployments further advanced UHF utilization, alongside developments in adjacent spectrum; for example, the FCC's 2021 Auction 107 reallocated C-band spectrum (3.7–3.98 GHz, in the SHF band adjacent to upper UHF) for mid-band 5G, generating over $81 billion in bids from carriers like Verizon and AT&T to support enhanced mobile coverage.[68] Regulatory evolution continued through international efforts, exemplified by the International Telecommunication Union (ITU) World Radiocommunication Conference (WRC-23) in 2023, which provided a secondary allocation to the mobile service in the 470–694 MHz UHF band for Region 1 (Europe, Africa, and the Middle East), supporting potential future uses including International Mobile Telecommunications-2030 (IMT-2030) alongside primary broadcasting services. As of November 2025, several Region 1 countries are implementing these allocations, with ongoing studies for IMT-2030 integration in UHF bands to improve capacity for emerging 6G systems.[69]Frequency Allocations
International Framework
The International Telecommunication Union Radiocommunication Sector (ITU-R) organizes global frequency management through its Radio Regulations, dividing the world into three regions to promote harmonized allocations and reduce cross-border interference. Region 1 covers Europe, Africa, the Middle East, Mongolia, and parts of the former Soviet Union; Region 2 encompasses the Americas; and Region 3 includes most of Asia and the Pacific. Within the ultra high frequency (UHF) range of 300 MHz to 3 GHz, these regions define specific band usages, such as for terrestrial broadcasting, where allocations like 470-694 MHz are primary for digital TV in Region 1, while 470-608 MHz and 614-698 MHz serve similar purposes in Region 2, ensuring compatibility across international boundaries.[70][71] Certain UHF sub-bands are designated internationally as Industrial, Scientific, and Medical (ISM) bands, permitting unlicensed, low-power operations for devices such as wireless sensors, remote controls, and short-range communications without requiring individual spectrum licenses. Key examples include the 433.05-434.79 MHz band (centered at approximately 433 MHz) available primarily in Region 1 for applications like RFID and telemetry; the 902-928 MHz band (centered at 915 MHz) in Region 2 for similar unlicensed uses in North America; and the globally harmonized 2.400-2.4835 GHz band, widely utilized for Wi-Fi, Bluetooth, and microwave ovens. Operations in these bands must adhere to ITU-R limits on radiated emissions to protect licensed services.[72] The ITU identifies specific UHF bands for International Mobile Telecommunications (IMT) to support global mobile broadband expansion, allowing administrations to allocate them for cellular networks while coordinating with co-primary services. Globally identified bands include 450-470 MHz for rural and public safety mobile services, 790-960 MHz for wide-area coverage, and 2.500-2.690 GHz for higher-capacity 3G/4G/5G deployments, with regional variations to accommodate existing uses. These identifications enable flexible implementation but require international coordination to avoid interference.[73] World Radiocommunication Conferences (WRCs) periodically refine UHF allocations to balance competing demands, as exemplified by WRC-19 outcomes that expanded IMT access in bands like 694-790 MHz in Region 1 while maintaining primary status for broadcasting in lower sub-bands such as 470-694 MHz to protect digital terrestrial TV services. WRC-23 retained the primary allocation to broadcasting in the 470-694 MHz band in Region 1, with secondary allocations to mobile service (except aeronautical mobile) in parts thereof for several countries, to be reviewed at WRC-31. These decisions incorporate studies on sharing feasibility and interference mitigation, ensuring continued viability for legacy broadcasting amid mobile growth.[74][75]United States
In the United States, ultra high frequency (UHF) spectrum allocations are managed by the Federal Communications Commission (FCC) in coordination with the National Telecommunications and Information Administration (NTIA), adhering to International Telecommunication Union (ITU) Region 2 guidelines for harmonized global use.[76] These allocations prioritize broadcasting, mobile broadband, public safety, and industrial applications within the 300–3000 MHz range, with approximately 800 MHz dedicated across key UHF bands for licensed and unlicensed operations. Television broadcasting in the UHF band is confined to channels 14 through 36, spanning 470–608 MHz, following the completion of the digital television transition on June 12, 2009, which mandated full-power stations to cease analog transmissions.[77] This reconfiguration reclaimed higher UHF channels for other services, enhancing spectrum efficiency for digital signals that support high-definition and multiple subchannels per 6 MHz allotment. In 2017, the FCC's incentive auction repurposed an additional 84 MHz from the 600 MHz band (formerly TV channels 38–51, 614–698 MHz) for licensed mobile broadband use, generating nearly $20 billion while relocating affected broadcasters to lower channels.[78] Mobile wireless services dominate higher UHF allocations, particularly the Advanced Wireless Services (AWS) bands encompassing 1.7–2.1 GHz, which enable 4G LTE and 5G deployments with paired uplink/downlink spectrum blocks such as AWS-1 (1710–1755 MHz uplink, 2110–2155 MHz downlink) and AWS-3 (1695–1710 MHz and 1755–1780 MHz uplink, 2110–2120 MHz and 2155–2180 MHz downlink).[79] These bands support wide-area coverage for cellular networks, licensed on an Economic Area basis to carriers like Verizon and AT&T for enhanced capacity in urban environments.[80] Other notable UHF allocations include the 902–928 MHz ISM band, designated for unlicensed industrial, scientific, and medical applications such as wireless sensors, RFID systems, and amateur radio, operating under Part 15 rules with power limits to prevent interference.[81] Public safety communications utilize the 700 MHz band (698–806 MHz), allocating 24 MHz for broadband (758–768 MHz uplink, 788–798 MHz downlink) to support nationwide interoperable networks for first responders, including voice, data, and video via LTE technology.[82]European Union
In the European Union, UHF frequency allocations are harmonized across member states primarily through the European Conference of Postal and Telecommunications Administrations (CEPT) and the European Telecommunications Standards Institute (ETSI), promoting efficient spectrum use for broadcasting, mobile services, and short-range applications while aligning with broader European Commission policies.[83] This framework supports ITU Region 1 allocations, ensuring compatibility with neighboring regions for cross-border operations. The 470–694 MHz band is designated for terrestrial television broadcasting using Digital Video Broadcasting – Terrestrial 2 (DVB-T2) standards, providing high-definition and ultra-high-definition services to households.[84] The adjacent 700 MHz band (694–790 MHz) was progressively cleared of broadcasting uses by June 2020 to enable deployment of 5G networks, as mandated by European Commission Decision (EU) 2017/899, which balances legacy TV services with mobile broadband expansion.[84] For mobile communications, the 800 MHz (791–862 MHz) and 900 MHz (880–915 MHz paired with 925–960 MHz) bands support Long-Term Evolution (LTE) networks, offering wide-area coverage for voice and data services under harmonized conditions set by CEPT ECC Decisions (02)02 and (06)09.[85] These lower UHF bands are prized for their propagation characteristics, enabling rural connectivity. Additional UHF allocations include the 863–870 MHz band for short-range devices (SRD), such as wireless sensors and alarms, governed by CEPT ERC Recommendation 70-03, which specifies power limits and duty cycles to minimize interference.[86] The 2.4 GHz ISM band (2.4–2.4835 GHz) is available for unlicensed applications like Wi-Fi and Bluetooth, regulated by ETSI EN 300 328 to ensure coexistence through adaptive frequency hopping and transmit power caps of 100 mW e.i.r.p. A 2023 European Commission decision facilitates sharing in the 600 MHz sub-band (around 594–606 MHz) within the 470–694 MHz range for professional mobile radio (PMR) and programme-making and special events (PMSE) uses, allowing secondary land mobile operations alongside primary broadcasting to support professional communications without disrupting TV services.[87] In total, the EU has harmonized approximately 1 GHz of UHF spectrum across these key bands for diverse applications. Ongoing 6G trials in 2025 explore enhanced utilization of UHF bands such as 700 MHz for ultra-reliable low-latency communications in future networks.[88]Other Regions
In the Asia-Pacific region, UHF allocations reflect a balance between legacy broadcasting and emerging mobile services, influenced by national priorities and international agreements. Japan designates the 470-710 MHz band primarily for terrestrial television broadcasting, supporting digital TV services across multiple channels while accommodating limited mobile uses in adjacent segments.[89] In China, the 2.6 GHz band within the UHF range has been allocated for 5G deployments, with state-owned operators like China Mobile receiving spectrum in 2515-2675 MHz to enable large-scale network rollouts.[90] Australia reallocated its UHF TV band post-2010s digital switchover, confining broadcasting to 520-694 MHz (channels 28-51) to free the 694-820 MHz "digital dividend" for mobile broadband, a process completed by 2014 to support LTE and subsequent 5G expansions.[91] Africa's UHF spectrum management emphasizes gradual digital migration amid infrastructure challenges, with limited mobile allocations in the 800 MHz band to prioritize broadcasting. The International Telecommunication Union (ITU) has advocated for the "digital dividend" in the 700-800 MHz range, urging African nations to clear analog TV signals by 2030 to enable mobile services, though implementation varies due to resource constraints in sub-Saharan countries.[92] By 2025, several states have begun trials in the 790-862 MHz segment for LTE, but widespread adoption remains slow compared to other regions. In Latin America, UHF allocations show significant variation in TV band usage, often extending from 470-806 MHz with gaps for mobile services, driven by diverse national digital transition timelines. Brazil has allocated the 700 MHz band (698-806 MHz) for LTE and 5G mobile broadband since 2014, clearing TV operations progressively to mitigate interference while maintaining primary broadcasting in lower UHF segments like 470-608 MHz and 614-698 MHz.[93] A notable example in the region is India's 2022 spectrum auction, which fetched approximately $19 billion, primarily for mid-band spectrum won by Reliance Jio for nationwide 5G coverage, highlighting aggressive strategies.[94] These regional differences stem from post-WRC-23 implementations by 2025, where countries adapt the global framework—such as protecting 470-694 MHz for broadcasting while allowing flexible mobile uses in higher UHF bands—to local needs like rural connectivity in Africa or urban 5G density in Asia.[75]References
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