High frequency - wikipedia High frequency For high speed algorithmic trading, see high - frequency trading. High frequency Frequency range 3 to 30 MHz Wavelength range 100 to 10 m ITU radio bands 1 ( ELF ) 2 ( SLF ) 3 ( ULF ) 4 ( VLF ) 5 ( LF ) 6 ( MF ) 7 ( HF ) 8 ( VHF ) 9 ( UHF ) 10 ( SHF ) 11 ( EHF ) 12 ( THF ) EU / NATO / US ECM radio bands IEEE radio bands HF VHF UHF X V mm Other TV and radio bands II III IV V VI HF 's position in the electromagnetic spectrum. High frequency ( HF ) is the ITU designation for the range of radio frequency electromagnetic waves ( radio waves ) between 3 and 30 megahertz ( MHz ). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters ( ten to one hundred metres ). Frequencies immediately below HF are denoted medium frequency ( MF ), while the next band of higher frequencies is known as the very high frequency ( VHF ) band. The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere -- a method known as `` skip '' or `` skywave '' propagation -- these frequencies are suitable for long - distance communication across intercontinental distances. The band is used by international shortwave broadcasting stations ( 2.31 -- 25.82 MHz ), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses. Contents 1 Propagation characteristics 2 Uses 3 Antennas 4 See also 5 References 6 Further reading 7 External links Propagation characteristics A modern Icom M700Pro two - way radio for marine HF radio communications. The dominant means of long distance communication in this band is skywave ( `` skip '' ) propagation, in which radio waves directed at an angle into the sky refract back to Earth from layers of ionized atoms in the ionosphere. By this method HF radio waves can travel beyond the horizon, around the curve of the Earth, and can be received at intercontinental distances. However, suitability of this portion of the spectrum for such communication varies greatly with a complex combination of factors : Sunlight / darkness at site of transmission and reception Transmitter / receiver proximity to solar terminator Season Sunspot cycle Solar activity Polar aurora At any point in time, for a given `` skip '' communication path between two points, the frequencies at which communication is possible are specified by these parameters Maximum usable frequency ( MUF ) Lowest usable high frequency ( LUF ) and a Frequency of optimum transmission ( FOT ) The maximum usable frequency regularly drops below 10 MHz in darkness during the winter months, while in summer during daylight it can easily surpass 30 MHz. It depends on the angle of incidence of the waves ; it is lowest when the waves are directed straight upwards, and is higher with less acute angles. This means that at longer distances, where the waves graze the ionosphere at a very blunt angle, the MUF may be much higher. The lowest usable frequency depends on the absorption in the lower layer of the ionosphere ( the D - layer ). This absorption is stronger at low frequencies and is also stronger with increased solar activity ( for example in daylight ) ; total absorption often occurs at frequencies below 5 MHz during daytime. The result of these two factors is that the usable spectrum shifts towards the lower frequencies and into the Medium Frequency ( MF ) range during winter nights, while on a day in full summer the higher frequencies tend to be more usable, often into the lower VHF range. When all factors are at their optimum, worldwide communication is possible on HF. At many other times it is possible to make contact across and between continents or oceans. At worst, when a band is `` dead '', no communication beyond the limited groundwave paths is possible no matter what powers, antennas or other technologies are brought to bear. When a transcontinental or worldwide path is open on a particular frequency, digital, SSB and Morse code communication is possible using surprisingly low transmission powers, often of the order of milliwatts, provided suitable antennas are in use at both ends and that there is little or no man - made or natural interference. On such an open band, interference originating over a wide area affects many potential users. These issues are significant to military, safety and amateur radio users of the HF bands. Uses An amateur radio station incorporating two HF transceivers. A typical Yagi antenna used by a Canadian radio amateur for long distance communication Boeing 707 used a HF antenna mounted on top of the tail fin The main users of the high frequency spectrum are : Military and governmental communication systems Aviation air - to - ground communications Amateur radio Shortwave international and regional broadcasting Maritime sea - to - shore services Over-the - horizon radar systems Global Maritime Distress and Safety System ( GMDSS ) communication The high frequency band is very popular with amateur radio operators, who can take advantage of direct, long - distance ( often inter-continental ) communications and the `` thrill factor '' resulting from making contacts in variable conditions. International shortwave broadcasting utilizes this set of frequencies, as well as a seemingly declining number of `` utility '' users ( marine, aviation, military, and diplomatic interests ), who have, in recent years, been swayed over to less volatile means of communication ( for example, via satellites ), but may maintain HF stations after switch - over for back - up purposes. However, the development of Automatic Link Establishment technology based on MIL - STD - 188 - 141 for automated connectivity and frequency selection, along with the high costs of satellite usage, have led to a renaissance in HF usage in government networks. The development of higher speed modems such as those conforming to MIL - STD - 188 - 110C which support data rates up to 120 kilobit / s has also increased the usability of HF for data communications and video transmission. Other standards development such as STANAG 5066 provides for error free data communications through the use of ARQ protocols. Some modes of communication, such as continuous wave Morse code transmissions ( especially by amateur radio operators ) and single sideband voice transmissions are more common in the HF range than on other frequencies, because of their bandwidth - conserving nature, but broadband modes, such as TV transmissions, are generally prohibited by HF 's relatively small chunk of electromagnetic spectrum space. Noise, especially man - made interference from electronic devices, tends to have a great effect on the HF bands. In recent years, concerns have risen among certain users of the HF spectrum over `` broadband over power lines '' ( BPL ) Internet access, which has an almost destructive effect on HF communications. This is due to the frequencies on which BPL operates ( typically corresponding with the HF band ) and the tendency for the BPL signal to leak from power lines. Some BPL providers have installed notch filters to block out certain portions of the spectrum ( namely the amateur radio bands ), but a great amount of controversy over the deployment of this access method remains. Other electronic devices including plasma televisions can also have a detrimental effect on the HF spectrum. In aviation, HF communication systems are required for all trans - oceanic flights. These systems incorporate frequencies down to 2 MHz to include the 2182 kHz international distress and calling channel. The upper section of HF ( 26.5 - 30 MHz ) shares many characteristics with the lower part of VHF. The parts of this section not allocated to amateur radio are used for local communications. These include CB radios around 27 MHz, studio - to - transmitter ( STL ) radio links, radio control devices for models and radio paging transmitters. Some radio frequency identification ( RFID ) tags utilize HF. These tags are commonly known as HFID 's or HighFID 's ( High Frequency Identification ). Antennas Since horizontally polarized radio waves work better for skywave propagation ( due to the greater ground absorption of vertically polarized waves ), antennas based on horizontal dipoles are typically used. The most common antennas in this band are wire antennas such as wire dipoles and the rhombic antenna ; in the upper frequencies, multielement dipole antennas such as the Yagi, quad, and reflective array antennas. Powerful shortwave broadcasting stations often use large wire curtain arrays. For receiving, random wire antennas are often used. See also High Frequency Active Auroral Research Program High Frequency Internet Protocol Low frequency Very high frequency Radio propagation Space weather Critical frequency References Jump up ^ `` Rec. ITU - R V. 431 - 7, Nomenclature of the frequency and wavelength bands used in telecommunications '' ( PDF ). ITU. Archived from the original ( PDF ) on 31 October 2013. Retrieved 28 January 2015. Jump up ^ Seybold, John S. ( 2005 ). Introduction to RF Propagation. John Wiley and Sons. pp. 55 -- 58. ISBN 0471743682. Jump up ^ Paul Harden ( 2005 ). `` Solar Activity & HF Propagation ''. QRP Amateur Radio Club International. Retrieved 2009 - 02 - 22. Jump up ^ `` Amateur Radio Emergency Communication ''. American Radio Relay League, Inc. 2008. Archived from the original on January 29, 2009. Retrieved 2009 - 02 - 22. Jump up ^ http://vipclubmn.org/couplers.html The Antenna Coupler Program. Marc Shoquist, Project Engineer in Engineering Research Associates Further reading Maslin, N.M. `` HF Communications - A Systems Approach ''. ISBN 0 - 273 - 02675 - 5, Taylor & Francis Ltd, 1987 Johnson, E.E., et al., `` Advanced High - Frequency Radio Communications ''. ISBN 0 - 89006 - 815 - 1, Artech House, 1997 V. Narayanamurti, et al., `` Selective Transmission of High - Frequency Phonons by a Superlattice : The `` Dielectric '' Phonon Filter ``. Phys. Rev. Lett. 43, 2012 -- 2016 ( Issue 27 -- 31 December 1979 ). Boulos - Paul Bejjani, et al., `` Transient Acute Depression Induced by High - Frequency Deep - Brain Stimulation ''. New England Journal of Medicine, Volume 340 : 1476 - 1480 May 13, 1999 Number 19. Massachusetts Medical Society. H.C. Liu, `` Analytical model of high - frequency resonant tunneling : The first - order ac current response ''. Phys. Rev. B 43, 12538 -- 12548 ( Issue 15 -- 15 May 1991 ). Sipila, M., et al., `` High - frequency periodic time - domain waveform measurement system ''. IEEE Transactions on Microwave Theory and Techniques, Volume 36, Issue 10, pg. 1397 - 1405, Oct 1988. ISSN 0018 - 9480 INSPEC 3291255 DOI 10.1109 / 22.6087 Morched, A., et al., `` A high frequency transformer model for the EMTP ''. IEEE Transactions on Power Delivery, Volume 8, Issue 3, pg. 1615 - 1626, Jul 1993. ISSN 0885 - 8977 INSPEC 4581865 DOI 10.1109 / 61.252688 External links Tomislav Stimac, `` Definition of frequency bands ( VLF, ELF... etc. ) ''. IK1QFK Home Page ( vlf.it ). Douglas C. Smith, High Frequency Measurements Web Page ; Index and Technical Tidbits. D.C. Smith Consultants, Los Gatos, CA. High Frequency Propagation Models, its.bldrdoc.gov. High Frequency Wave Propagation, cscamm.umd.edu. `` High frequency noise '' ( PDF ) `` Advantages of HF Radio '' Codan Solar conditions for HF - radio Time signal stations Longwave BPC BPL BSF DCF77 JJY RBU RJH66 ( Beta ) RTZ MSF TDF WWVB Shortwave BPM BSF CHU HD2IOA HLA JN53DV RWM ROA WWV WWVH ( Hawaii, USA ) YVTO VHF / FM / UHF RDS CT Satellite GPS BeiDou Galileo GLONASS IRNSS QZSS Defunct HBG NAA WWVL OMA OLB5 VNG Y3S Radio spectrum ( ITU ) ELF 3 Hz / 100 Mm 30 Hz / 10 Mm SLF 30 Hz / 10 Mm 300 Hz / 1 Mm ULF 300 Hz / 1 Mm 3 kHz / 100 km VLF 3 kHz / 100 km 30 kHz / 10 km LF 30 kHz / 10 km 300 kHz / 1 km MF 300 kHz / 1 km 3 MHz / 100 m HF 3 MHz / 100 m 30 MHz / 10 m VHF 30 MHz / 10 m 300 MHz / 1 m UHF 300 MHz / 1 m 3 GHz / 100 mm SHF 3 GHz / 100 mm 30 GHz / 10 mm EHF 30 GHz / 10 mm 300 GHz / 1 mm THF 300 GHz / 1 mm 3 THz / 0.1 mm Electromagnetic spectrum ← higher frequencies longer wavelengths → Gamma rays X-rays Ultraviolet Visible Infrared Terahertz radiation Microwave Radio Visible ( optical ) Violet Blue Green Yellow Orange Red Microwaves W band V band Q band K band K band K band X band S band C band L band Radio EHF SHF UHF VHF HF MF LF VLF ULF SLF ELF Wavelength types Microwave Shortwave Medium wave Longwave Analog and digital audio broadcasting Terrestrial Radio modulation AM FM COFDM Frequency allocations LW ( LF ) MW ( MF ) SW ( HF ) VHF ( low / mid / high ) L band ( UHF ) Digital systems CAM - D DAB / DAB+ DRM / DRM+ FMeXtra HD Radio CDR DVB - T2 Lite Satellite Frequency allocations C band K band L band S band Digital systems ADR DAB - S DVB - SH S - DMB SDR Commercial radio providers 1worldspace Sirius XM Holdings SiriusXM Canada Codecs AAC AMR - WB+ HDC HE - AAC MPEG - 1 Audio Layer II Subcarrier signals AMSS DirectBand PAD RDS / RBDS SCA / SCMO DARC Related topics Technical ( audio ) Audio data compression Audio signal processing Technical ( AM stereo formats ) Belar C - QUAM Harris Kahn - Hazeltine Magnavox Technical ( emission ) AM broadcasting AM expanded band Cable radio Digital radio Error detection and correction FM broadcast band FM broadcasting Multipath propagation Shortwave relay station Cultural History of radio International broadcasting Comparison of radio systems GND : 4129005 - 7 Retrieved from `` https://en.wikipedia.org/w/index.php?title=High_frequency&oldid=817624119 '' Categories : Radio spectrum Wireless Hidden categories : All articles with unsourced statements Articles with unsourced statements from January 2012 Wikipedia articles with GND identifiers Talk Contents About Wikipedia Asturianu Dansk Deutsch Español Français हिन्दी Bahasa Indonesia Italiano עברית Magyar Bahasa Melayu Nederlands Suomi Svenska Türkçe 中文 Edit links This page was last edited on 29 December 2017, at 15 : 28. 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Question: hf frequency bands used for aviation are between
Answer: (2.31–25.82 MHz)