In radio, long wave or long-wave, abbreviated LW, refers to parts of the radio spectrum with wavelengths longer than what was called the medium-wave broadcasting band. The term is historic, dating from the early 20th century, when the radio spectrum was considered to consist of longwave, medium-wave, short-wave radio bands. Most modern radio systems and devices use wavelengths which would have been considered'ultra-short'. In contemporary usage, the term longwave is not defined and its intended meaning varies, it may be used for radio wavelengths longer than 1,000 m i.e. frequencies up to 300 kilohertz, including the International Telecommunications Union's low frequency and low frequency bands. Sometimes the upper limit is taken to be higher than 300 kHz, but not above the start of the medium wave broadcast band at 525 kHz. In Europe and large parts of Asia, where a range of frequencies between 148.5 and 283.5 kHz is used for AM broadcasting in addition to the medium-wave band, the term longwave refers to this broadcasting band, which falls wholly within the low frequency band of the radio spectrum.
The "Longwave Club of America" is interested in "frequencies below the AM broadcast band". Because of their long wavelength, radio waves in this frequency range can diffract over obstacles like mountain ranges and travel beyond the horizon, following the contour of the Earth; this mode of propagation, called ground wave, is the main mode in the longwave band. The attenuation of signal strength with distance by absorption in the ground is lower than at higher frequencies, falls with frequency. Low frequency ground waves can be received up to 2,000 kilometres from the transmitting antenna. Low frequency waves below 30 kHz can be used to communicate at transcontinental distances, can penetrate saltwater to depths of hundreds of feet, is used by the military to communicate with submerged submarines. Low frequency waves can occasionally travel long distances by reflecting from the ionosphere, although this method, called skywave or "skip" propagation, is not as common as at higher frequencies. Reflection occurs at F layers.
Skywave signals can be detected at distances exceeding 300 kilometres from the transmitting antenna. Non-directional beacons transmit continuously for the benefit of radio direction finders in marine and aeronautical navigation, they identify themselves by a callsign in Morse code. They can occupy any frequency in the range 190–1750 kHz. In North America, they occupy 190–535 kHz. In ITU Region 1 the lower limit is 280 kHz. There are institutional broadcast stations in the range that transmit coded time signals to radio clocks. For example: WWVB in Colorado, United States, on 60 kHz DCF77 in Frankfurt, Germany, on 77.5 kHz JJY in Japan, on 40 & 60 kHz 66.66 kHz in Taldom transmitter, Russia BPC in Lintong, China, 68.5 kHz MSF time and 60 kHz frequency standard transmitted from Anthorn in the UK. TDF from Allouis, France, on 162 kHzRadio-controlled clocks receive their time calibration signals with built-in long-wave receivers, they use long-wave, rather than short-wave or medium-wave, because long-wave signals from the transmitter to the receiver always travel along the same direct path across the surface of the Earth, so the time delay correction for the signal travel time from the transmitting station to the receiver is always the same for any one receiving location.
Longwaves travel by groundwaves that hug the surface of the earth, unlike mediumwaves and shortwaves. Those higher-frequency signals do not follow the surface of the Earth beyond a few kilometers, but can travel as skywaves, ‘bouncing’ off different layers of the ionosphere at different times of day; these different propagation paths can make the time lag different for every signal received. The delay between when the long-wave signal was sent from the transmitter and when the signal is received by the clock depends on the overland distance between the clock and the transmitter and the speed of light through the air, very nearly constant. Since the time lag is the same, a single constant shift forward from the time coded in the signal can compensate for all long-wave signals received at any one location from the same time signal station; the militaries of the United Kingdom, Russian Federation, United States, Germany and Sweden use frequencies below 50 kHz to communicate with submerged submarines.
In North America during the 1970s, the frequencies 167, 179 and 191 kHz were assigned to the short-lived Public Emergency Radio of the United States. Nowadays, in the United States, Part 15 of FCC regulations allows unlicensed use of 136 kHz and the 160–190 kHz band at output power up to 1 watt with up to a 15-meter antenna; this is called Low Frequency Experimental Radio. The 190–435 kHz band is used for navigational beacons. Swedish station SAQ, located at the Varberg Radio Station facility in Grimeton, is the last remaining operational Alexanderson alternator long-wave transmitter. Although the station ended regular service in 1996, it has been maintained as a World Heritage Site, makes at least two demonstration transmissions yearly, on 17.2 kHz. Longwave is used for broadcasting only within ITU Region 1; the long-wave broadcasters are located in western, northern and southeastern Europe, the former Soviet Union, Mongolia and Morocco. A larger geographic area can be covered by a long-w
Sirius XM Satellite Radio
Sirius XM Holdings, Inc. doing business as Sirius XM Satellite Radio, is a broadcasting company headquartered in Midtown Manhattan, New York City that provides three satellite radio and online radio services operating in the United States: Sirius Satellite Radio, XM Satellite Radio, Sirius XM Radio. The company has a minor interest in SiriusXM Canada, an affiliate company that provides Sirius and XM service in Canada. At the end of 2013, Sirius XM reorganized their corporate structure, which made Sirius XM Radio Inc. a direct, wholly owned subsidiary of Sirius XM Holdings, Inc. Sirius XM Radio was formed after the U. S. Federal Communications Commission approved the acquisition of XM Satellite Radio Holding, Inc. by Sirius Satellite Radio, Inc. on July 29, 2008, 17 months after the companies first proposed the merger. The merger brought the combined companies a total of more than 18.5 million subscribers based on current subscriber numbers on the date of merging. The deal was valued at $3.3 billion, not including debt.
Through Q2 2017, Sirius XM has more than 32 million subscribers. The proposed merger was opposed by those. Sirius and XM argued. In September 2018, the company agreed to purchase the competing streaming music service and this transaction was completed on the 1st of February 2019. Sirius Satellite Radio was founded by Martine Rothblatt, David Margolese, Robert Briskman. In 1990, Rothblatt founded Satellite CD Radio in Washington, DC; the company was the first to petition the FCC to assign unused frequencies for satellite radio broadcast, which "provoked a furor among owners of both large and small radio stations." In April 1992, Rothblatt resigned as CEO to start a medical research foundation. Former NASA engineer Briskman, who designed the company's satellite technology, was appointed chairman and CEO. Six months in November 1992, Rogers Wireless co-founder Margolese, who had provided financial backing for the venture, acquired control of the company and succeeded Briskman. Margolese renamed the company CD Radio, spent the next five years lobbying the FCC to allow satellite radio to be deployed, the following five years raising $1.6 billion, used to build and launch three satellites into elliptical orbit from Kazakhstan in July 2000.
In 1997, after Margolese had obtained regulatory clearance and "effectively created the industry," the FCC sold a license to XM Satellite Radio, which followed Sirius' example. In November 1999, marketing chief Ira Bahr convinced Margolese to again change the name of the company, this time to Sirius Satellite Radio, in order to avoid association with the soon-to-be-outdated CD technology. Having secured installation deals with automakers, including BMW, Chrysler and Ford, Sirius launched the initial phase of its service in four cities on February 14, 2002, expanding to the rest of the contiguous United States on July 1, 2002. In November 2001, Margolese stepped down as CEO, remaining as chairman until November 2003, with Sirius issuing a statement thanking him "for his great vision and dedication in creating both Sirius and the satellite radio industry." Joe Clayton, former CEO of Global Crossing, followed as CEO from November 2001 until November 2004. Mel Karmazin, former president of Viacom, became CEO in November 2004 and remained in that position through the merger, until December 2012.
The origin of XM Satellite Radio was a Petition for Rulemaking filed at the Federal Communications Commission by regulatory attorney and Founder of Satellite CD Radio Martine Rothblatt, to establish frequencies and licensing rules for the world's first-ever Satellite Digital Audio Radio Service. On May 18, 1990, Satellite CD Radio, Inc. filed a Petition for Rule Making in which it requested spectrum to offer Compact Disc quality digital audio radio service to be delivered by satellites and complementary radio transmitters. Following the Allocation NPRM, the FCC established a December 15, 1992 cut-off date for applications proposing satellite DARS to be considered in conjunction with CD Radio's application. One such application came from American Mobile Radio Corporation, the predecessor company to XM Satellite Radio. XM Satellite Radio was founded by Gary Parsons, it has its origins in the 1988 formation of the American Mobile Satellite Corporation, a consortium of several organizations dedicated to satellite broadcasting of telephone and data signals.
In 1992, AMSC established a unit called the American Mobile Radio Corporation, dedicated to developing a satellite-based digital radio service. Its planned financing was complete by July 2000, at which point XM had raised $1.26 billion and secured installation agreements with General Motors and Toyota. Scheduled for September 12, 2001, XM's service start date was postponed due to the September 11 terrorist attacks on the World Trade Center and The Pentagon. XM Satellite Radio's first broadcast was on September 2001, nearly four months before Sirius. Gary Parsons served as chairman of XM Satellite Radio from its inception through the merger, resigned from the position in November 2009. Hugh Panero served as XM's CEO from 1998 until July 2007, shortly after the merger with Sirius was proposed. Nate Davis was appointed interim CEO until the merger was completed, at which point Sirius CEO Mel Karmazin took over as CEO of the newly merged company, Sirius XM. After years of speculation and three months of serious negotiations, the $13 b
Shortwave radio is radio transmission using shortwave radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band, extends from 1.7–30 MHz. Radio waves in the shortwave band can be reflected or refracted from a layer of electrically charged atoms in the atmosphere called the ionosphere. Therefore, short waves directed at an angle into the sky can be reflected back to Earth at great distances, beyond the horizon; this is called skywave or "skip" propagation. Thus shortwave radio can be used for long distance communication, in contrast to radio waves of higher frequency which travel in straight lines and are limited by the visual horizon, about 64 km. Shortwave radio is used for broadcasting of voice and music to shortwave listeners over large areas, it is used for military over-the-horizon radar, diplomatic communication, two-way international communication by amateur radio enthusiasts for hobby and emergency purposes, as well as for long distance aviation and marine communications.
The widest popular definition of the shortwave frequency interval is the ITU Region 1 definition, is the span 1.6–30 MHz, just above the medium wave band, which ends at 1.6 MHz. There are other definitions of the shortwave frequency interval: 1.71 to 30 MHz in ITU Region 2 1.8 to 30 MHz 2.3 to 30 MHz 2.3 to 26.1 MHz In Germany and Austria the ITU Region 1 shortwave radio frequency interval can be subdivided in: de:Grenzwelle: 1.605–3.8 MHz In Germany these shortwave radio frequency intervals have been seen used: the above other definitions The name "shortwave" originated during the early days of radio in the early 20th century, when the radio spectrum was considered divided into long wave, medium wave and short wave bands based on the wavelength of the radio waves. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used for radio communications; the broadcast medium wave band now extends above the 200 m/1,500 kHz limit, the amateur radio 1.8 MHz – 2.0 MHz band is the lowest-frequency band considered to be'shortwave'.
Early long distance radio telegraphy used long waves, below 300 kilohertz. The drawbacks to this system included a limited spectrum available for long distance communication, the expensive transmitters and gigantic antennas that were required, it was difficult to beam the radio wave directionally with long wave, resulting in a major loss of power over long distances. Prior to the 1920s, the shortwave frequencies above 1.5 MHz were regarded as useless for long distance communication and were designated in many countries for amateur use. Guglielmo Marconi, pioneer of radio, commissioned his assistant Charles Samuel Franklin to carry out a large scale study into the transmission characteristics of short wavelength waves and to determine their suitability for long distance transmissions. Franklin rigged up a large antenna at Poldhu Wireless Station, running on 25 kW of power. In June and July 1923, wireless transmissions were completed during nights on 97 meters from Poldhu to Marconi's yacht Elettra in the Cape Verde Islands.
In September 1924, Marconi transmitted daytime and nighttime on 32 meters from Poldhu to his yacht in Beirut. Franklin went on to refine the directional transmission, by inventing the curtain array aerial system. In July 1924, Marconi entered into contracts with the British General Post Office to install high speed shortwave telegraphy circuits from London to Australia, South Africa and Canada as the main element of the Imperial Wireless Chain; the UK-to-Canada shortwave "Beam Wireless Service" went into commercial operation on 25 October 1926. Beam Wireless Services from the UK to Australia, South Africa and India went into service in 1927. Shortwave communications began to grow in the 1920s, similar to the internet in the late 20th century. By 1928, more than half of long distance communications had moved from transoceanic cables and longwave wireless services to shortwave and the overall volume of transoceanic shortwave communications had vastly increased. Shortwave stations had cost and efficiency advantages over massive longwave wireless installations, however some commercial longwave communications stations remained in use until the 1960s.
Long distance radio circuits reduced the load on the existing transoceanic telegraph cables and hence the need for new cables, although the cables maintained their advantages of high security and a much more reliable and better quality signal than shortwave. The cable companies began to lose large sums of money in 1927, a serious financial crisis threatened the viability of cable companies that were vital to strategic British interests; the British government convened the Imperial Wireless and Cable Conference in 1928 "to examine the situation that had arisen as a result of the competition of Beam Wireless with the Cable Services". It recommended and received Government approval for all overseas cable and wireless resources of the Empire to be merged into one system controlled by a newly formed company in 1929, Imperial and International Communications Ltd; the name of the company was changed to Cable and Wireless Ltd. in 1934. Long-distance cables had a
In signal processing, control theory and mathematics, overshoot is the occurrence of a signal or function exceeding its target. It arises in the step response of bandlimited systems such as low-pass filters, it is followed by ringing, at times conflated with the latter. Maximum overshoot is defined in Katsuhiko Ogata's Discrete-time control systems as "the maximum peak value of the response curve measured from the desired response of the system." In control theory, overshoot refers to an output exceeding its steady-state value. For a step input, the percentage overshoot is the maximum value minus the step value divided by the step value. In the case of the unit step, the overshoot is just the maximum value of the step response minus one. See the definition of overshoot in an electronics context. For second order systems, the percentage overshoot is a function of the damping ratio ζ and is given by P O = 100 ⋅ e The damping ratio can be found by ζ = 2 π 2 + 2 In electronics, overshoot refers to the transitory values of any parameter that exceeds its final value during its transition from one value to another.
An important application of the term is to the output signal of an amplifier. Usage: Overshoot occurs when the transitory values exceed final value; when they are lower than the final value, the phenomenon is called "undershoot". A circuit is designed to minimize risetime while containing distortion of the signal within acceptable limits. Overshoot represents a distortion of the signal. In circuit design, the goals of minimizing overshoot and of decreasing circuit risetime can conflict; the magnitude of overshoot depends on time through a phenomenon called "damping." See illustration under step response. Overshoot is associated with settling time, how long it takes for the output to reach steady state. See the definition of overshoot in a control theory context. In the approximation of functions, overshoot is one term describing quality of approximation; when a function such as a square wave is represented by a summation of terms, for example, a Fourier series or an expansion in orthogonal polynomials, the approximation of the function by a truncated number of terms in the series can exhibit overshoot and ringing.
The more terms retained in the series, the less pronounced the departure of the approximation from the function it represents. However, though the period of the oscillations decreases, their amplitude does not. For the Fourier transform, this can be modeled by approximating a step function by the integral up to a certain frequency, which yields the sine integral; this can be interpreted as convolution with the sinc function. In signal processing, overshoot is when the output of a filter has a higher maximum value than the input for the step response, yields the related phenomenon of ringing artifacts; this occurs for instance in using the sinc filter as an ideal low-pass filter. The step response can be interpreted as the convolution with the impulse response, a sinc function; the overshoot and undershoot can be understood in this way: kernels are normalized to have integral 1, so they send constant functions to constant functions – otherwise they have gain. The value of a convolution at a point is a linear combination of the input signal, with coefficients the values of the kernel.
If a kernel is non-negative, such as for a Gaussian kernel the value of the filtered signal will be a convex combination of the input values, will thus fall between the minimum and maximum of the input signal – it will not undershoot or overshoot. If, on the other hand, the kernel assumes negative values, such as the sinc function the value of the filtered signal will instead be an affine combination of the input values, may fall outside of the minimum and maximum of the input signal, resulting in undershoot and overshoot. Overshoot is undesirable if it causes clipping, but is sometimes desirable in image sharpening, due to increasing acutance. A related phenomenon is ringing, following overshoot, a signal falls below its steady-state value, may bounce back above, taking some time to settle close to its steady-state value. In ecology, overshoot is the analogous concept, where a population exceeds the carrying capacity of a system. Step response Ringing Settle time Damping Overmodulation Integral windup Percentage overshoot calculator
Medium wave is the part of the medium frequency radio band used for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz, using channels spaced every 9 kHz, in North America an extended MW broadcast band ranges from 525 kHz to 1705 kHz, using 10 kHz spaced channels. The term is a historic one, dating from the early 20th century, when the radio spectrum was divided on the basis of the wavelength of the waves into long wave, medium wave, short wave radio bands. Wavelengths in this band are long enough that radio waves are not blocked by buildings and hills and can propagate beyond the horizon following the curvature of the Earth. Practical groundwave reception extends to 200–300 miles, with greater distances over terrain with higher ground conductivity, greatest distances over salt water. Most broadcast stations use groundwave to cover their listening area. Medium waves can reflect off charged particle layers in the ionosphere and return to Earth at much greater distances.
At night in winter months and at times of low solar activity, the lower ionospheric D layer disappears. When this happens, MW radio waves can be received many hundreds or thousands of miles away as the signal will be reflected by the higher F layer; this can allow long-distance broadcasting, but can interfere with distant local stations. Due to the limited number of available channels in the MW broadcast band, the same frequencies are re-allocated to different broadcasting stations several hundred miles apart. On nights of good skywave propagation, the skywave signals of a distant station may interfere with the signals of local stations on the same frequency. In North America, the North American Regional Broadcasting Agreement sets aside certain channels for nighttime use over extended service areas via skywave by a few specially licensed AM broadcasting stations; these channels are called clear channels, they are required to broadcast at higher powers of 10 to 50 kW. Broadcasting in the United States was restricted to two wavelengths: "entertainment" was broadcast at 360 meters, with stations required to switch to 485 meters when broadcasting weather forecasts, crop price reports and other government reports.
This arrangement had numerous practical difficulties. Early transmitters were technically crude and impossible to set on their intended frequency and if two stations in the same part of the country broadcast the resultant interference meant that neither could be heard clearly; the Commerce Department intervened in such cases but left it up to stations to enter into voluntary timesharing agreements amongst themselves. The addition of a third "entertainment" wavelength, 400 meters, did little to solve this overcrowding. In 1923, the Commerce Department realized that as more and more stations were applying for commercial licenses, it was not practical to have every station broadcast on the same three wavelengths. On 15 May 1923, Commerce Secretary Herbert Hoover announced a new bandplan which set aside 81 frequencies, in 10 kHz steps, from 550 kHz to 1350 kHz; each station would be assigned one frequency, no longer having to broadcast weather and government reports on a different frequency than entertainment.
Class A and B stations were segregated into sub-bands. Today in most of the Americas, mediumwave broadcast stations are separated by 10 kHz and have two sidebands of up to ±5 kHz in theory. In the rest of the world, the separation is 9 kHz, with sidebands of ±4.5 kHz. Both provide adequate audio quality for voice, but are insufficient for high-fidelity broadcasting, common on the VHF FM bands. In the US and Canada the maximum transmitter power is restricted to 50 kilowatts, while in Europe there are medium wave stations with transmitter power up to 2 megawatts daytime. Most United States AM radio stations are required by the Federal Communications Commission to shut down, reduce power, or employ a directional antenna array at night in order to avoid interference with each other due to night-time only long-distance skywave propagation; those stations which shut down at night are known as "daytimers". Similar regulations are in force for Canadian stations, administered by Industry Canada. In Europe, each country is allocated a number of frequencies.
In most cases there are two power limits: a lower one for omnidirectional and a higher one for directional radiation with minima in certain directions. The power limit can be depending on daytime and it is possible, that a station may not work at nighttime, because it would produce too much interference. Other countries may only operate low-powered transmitters on the same frequency, again subject to agreement. For example, Russia operates a high-powered transmitter, located in its Kaliningrad exclave and used for external broadcasting, on 1386 kHz; the same frequency is used by low-powered local radio stations in the United Kingdom, which has 250 medium-wave transmitters of 1 kW and over. International mediumwave broadcasting in Europe has decreased markedly with
Low frequency or LF is the ITU designation for radio frequencies in the range of 30 kilohertz to 300 kHz. As its wavelengths range from ten kilometres to one kilometre it is known as the kilometre band or kilometre wave. LF radio waves exhibit low signal attenuation, making them suitable for long-distance communications. In Europe and areas of Northern Africa and Asia, part of the LF spectrum is used for AM broadcasting as the "longwave" band. In the western hemisphere, its main use is for aircraft beacon, navigation and weather systems. A number of time signal broadcasts are broadcast in this band; because of their long wavelength, low frequency radio waves can diffract over obstacles like mountain ranges and travel beyond the horizon, following the contour of the Earth. This mode of propagation, called ground wave, is the main mode in the LF band. Ground waves must be vertically polarized, so vertical monopole antennas are used for transmitting; the attenuation of signal strength with distance by absorption in the ground is lower than at higher frequencies.
Low frequency ground waves can be received up to 2,000 kilometres from the transmitting antenna. Low frequency waves can occasionally travel long distances by reflecting from the ionosphere, although this method, called skywave or "skip" propagation, is not as common as at higher frequencies. Reflection occurs at F layers. Skywave signals can be detected at distances exceeding 300 kilometres from the transmitting antenna. In Europe and Japan, many low-cost consumer devices have since the late 1980s contained radio clocks with an LF receiver for these signals. Since these frequencies propagate by ground wave only, the precision of time signals is not affected by varying propagation paths between the transmitter, the ionosphere, the receiver. In the United States, such devices became feasible for the mass market only after the output power of WWVB was increased in 1997 and 1999. Radio signals below 50 kHz are capable of penetrating ocean depths to 200 metres, the longer the wavelength, the deeper.
The British, Indian, Swedish, United States and other navies communicate with submarines on these frequencies. In addition, Royal Navy nuclear submarines carrying ballistic missiles are under standing orders to monitor the BBC Radio 4 transmission on 198 kHz in waters near the UK, it is rumoured that they are to construe a sudden halt in transmission of the morning news programme Today, as an indicator that the UK is under attack, whereafter their sealed orders take effect. In the US, the Ground Wave Emergency Network or GWEN operated between 150 and 175 kHz, until replaced by satellite communications systems in 1999. GWEN was a land based military radio communications system which could survive and continue to operate in the case of a nuclear attack; the 2007 World Radiocommunication Conference made this band a worldwide amateur radio allocation. An international 2.1 kHz allocation, the 2200 meter band, is available to amateur radio operators in several countries in Europe, New Zealand and French overseas dependencies.
The world record distance for a two-way contact is over 10,000 km from near Vladivostok to New Zealand. As well as conventional Morse code many operators use slow computer-controlled Morse code or specialized digital communications modes; the UK allocated a 2.8 kHz sliver of spectrum from 71.6 kHz to 74.4 kHz beginning in April 1996 to UK amateurs who applied for a Notice of Variation to use the band on a noninterference basis with a maximum output power of 1 Watt ERP. This was withdrawn on 30 June 2003 after a number of extensions in favor of the European-harmonized 136 kHz band. Slow Morse Code from G3AQC in the UK was received 3,275 miles away, across the Atlantic Ocean, by W1TAG in the US on 21-22 November 2001 on 72.401 kHz. In the United States, there is a exemption within FCC Part 15 regulations permitting unlicensed transmissions in the frequency range of 160 to 190 kHz. Longwave radio hobbyists refer to this as the' LowFER' band, experimenters, their transmitters are called'LowFERs'.
This frequency range between 160 kHz and 190 kHz is referred to as the 1750 Meter band. Requirements from 47CFR15.217 and 47CFR15.206 include: The total input power to the final radio frequency stage shall not exceed one watt. The total length of the transmission line and ground lead shall not exceed 15 meters. All emissions below 160 kHz or above 190 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier; as an alternative to these requirements, a field strength of 2400/F microvolts/meter may be used. In all cases, operation may not cause harmful interference to licensed services. Many experimenters in this band are amateur radio operators. A regular service transmitting RTTY marine meteorological information in SYNOP code on LF is the German Meteorological Service; the DWD operates station DDH47 on 147.3 kHz using standard ITA-2 alphabet with a transmission speed of 50 baud and FSK modulation with 85 Hz shift. In parts of the world where there is no longwave broadcasting service, Non-directional beacons used for aeronavigation operate on 190–300 kHz.
In Europe and Africa, the NDB allocation starts on 283.5 kHz. The LORAN-C radio navigation system operated on 100 kHz. In the past, the Decca Navigator System operated betw