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• Low Frequency https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency Utility companies use special coupling capacitors to connect radio transmitters to the power-frequency AC conductors 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency 1 On some powerlines in the former Soviet Union, PLC-signals are not fed into the high voltage line, but in the ground conductors, which are mounted on insulators at the pylons. https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency While utility companies use microwave and now, increasingly, fiber optic cables for their primary system communication needs, the power-line carrier apparatus may still be useful as a backup channel or for very simple low-cost installations that do not warrant installing fiber optic lines. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency 1 Power line carrier communication (PLCC) is mainly used for telecommunication, teleprotection and tele-monitoring between electrical substations through power lines at high voltages, such as 110 kV, 220 kV, 400 kV. The major benefit is the union of two applications in a single system, which is particularly useful for monitoring electric equipment and advanced energy management techniques (such as OpenADR and OpenHAN). https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency The modulation generally used in these system is amplitude modulation. The carrier frequency range is used for audio signals, protection and a pilot frequency. The pilot frequency is a signal in the audio range that is transmitted continuously for failure detection. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency 1 The voice signal is compressed and filtered into the 300 Hz to 4000 Hz range, and this audio frequency is mixed with the carrier frequency. The carrier frequency is again filtered, amplified and transmitted. The transmission power of these HF carrier frequencies will be in the range of 0 to +32 dbW. This range is set according to the distance between substations. PLCC can be used for interconnecting private branch exchanges (PBXs). https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency To sectionalize the transmission network and protect against failures, a "wave trap" is connected in series with the power (transmission) line 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency 1 A coupling capacitor is used to connect the transmitters and receivers to the high voltage line. This provides low impedance path for carrier energy to HV line but blocks the power frequency circuit by being a high impedance path. The coupling capacitor may be part of a capacitor voltage transformer used for voltage measurement. https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency Power line carriers may change its transmission system from analog to digital to enable Internet Protocol devices. Digital power line carrier (DPLC) was developed for digital transmission via power lines. DPLC has the required quality of bit error rate characteristics and transmission ability such as transmitting information from monitored electric-supply stations and images. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency 1 Power line carrier systems have long been a favorite at many utilities because it allows them to reliably move data over an infrastructure that they control. Many technologies have multiple applications. For example, a communication system bought initially for automatic meter reading can sometimes also be used for load control or for demand response applications. https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency 1 A PLC carrier repeating station is a facility, at which a power line communication (PLC) signal on a powerline is refreshed. Therefore the signal is filtered out from the powerline, demodulated and modulated on a new carrier frequency, and then reinjected onto the powerline again. As PLC signals can carry long distances (several 100 kilometres), such facilities only exist on very long power lines using PLC equipment. https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency PLC is one of the technologies used for automatic meter reading 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency In a one-way (inbound only) system, readings "bubble up" from end devices (such as meters), through the communication infrastructure, to a "master station" which publishes the readings. A one-way system might be lower-cost than a two-way system, but also is difficult to reconfigure should the operating environment change. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Power line communication - Long haul, low frequency In a two-way system (supporting both outbound and inbound), commands can be broadcast out from the master station to end devices (meters) -- allowing for reconfiguration of the network, or to obtain readings, or to convey messages, etc 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Powerline Digital Subscriber Line - Long haul, low frequency Utility companies use special coupling capacitors to connect radio transmitters to the power-frequency AC conductors 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Powerline Digital Subscriber Line - Long haul, low frequency power-line carrier communication (PLCC) is mainly used for telecommunication, tele-protection and tele-monitoring between electrical substations through power lines at high voltages, such as 110 kV, 220 kV, 400 kV. The major benefit is the union of two applications in a single system, which is particularly useful for monitoring electric 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Powerline Digital Subscriber Line - Long haul, low frequency The voice signal is compressed and filtered into the 300Hz to 4000Hz range, and this audio frequency is mixed with the carrier frequency. The carrier frequency is again filtered, amplified and transmitted. The transmission power of these HF carrier frequencies will be in the range of 0 to +32 Decibel|dbW. This range is set according to the distance between substations. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Powerline Digital Subscriber Line - Long haul, low frequency To sectionalize the transmission network and protect against failures, a wave trap is connected in series with the power (transmission) line 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Powerline Digital Subscriber Line - Long haul, low frequency power-line carriers may change its transmission system from analog to digital to enable Internet Protocol devices. Digital power-line carrier (DPLC) was developed for digital transmission via power lines. DPLC has the required quality of bit error rate characteristics and transmission ability such as transmitting information from monitored electric-supply stations and 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Powerline Digital Subscriber Line - Long haul, low frequency 1 power-line carrier systems have long been a favorite at many utilities because it allows them to reliably move data over an infrastructure that they control. Many technologies have multiple applications. For example, a communication system bought initially for automatic meter reading can sometimes also be used for load control or for demand response https://store.theartofservice.com/the-low-frequency-toolkit.html Powerline Digital Subscriber Line - Long haul, low frequency 1 A PLC carrier repeating station is a facility, at which a power-line communication (PLC) signal on a Electric power transmission|powerline is refreshed. Therefore https://store.theartofservice.com/the-low-frequency-toolkit.html Powerline Digital Subscriber Line - Long haul, low frequency the signal is filtered out from the powerline, Demodulation|demodulated and Modulation|modulated on a new Carrier wave|carrier frequency, and then reinjected onto the powerline again. As PLC signals can carry long distances (several 100 kilometres), such facilities only exist on very long power lines using PLC equipment. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Powerline Digital Subscriber Line - Long haul, low frequency In a one-way (inbound only) system, readings bubble up from end devices (such as meters), through the communication infrastructure, to a master station which publishes the readings. A one-way system might be lower-cost than a two-way system, but also is difficult to reconfigure should the operating environment change. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Powerline Digital Subscriber Line - Long haul, low frequency 1 In a two-way system (supporting both outbound and inbound), commands can be broadcast out from the master station to end devices (meters) – allowing for reconfiguration of the network, or to obtain readings, or to convey messages, etc https://store.theartofservice.com/the-low-frequency-toolkit.html Super low frequency Another conflicting designation which includes this frequency range is Extremely Low Frequency (ELF), which in some contexts refers to all frequencies up to 300 hertz. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Super low frequency 1 It became operational in 1989 but was discontinued in 2004 due to advances in Very low frequency|VLF communication systems https://store.theartofservice.com/the-low-frequency-toolkit.html Super low frequency 1 The requirements for receivers at SLF frequencies is less stringent than transmitters, because the signal strength (set by atmospheric noise) is far above the noise floor of the receiver, so small, inefficient antenna (radio)|antennas can be used https://store.theartofservice.com/the-low-frequency-toolkit.html Surround sound - Low Frequency Effects (LFE) channel Because the low-frequency effects channel requires only a fraction of the bandwidth of the other audio channels, it is referred to as the .1 channel; for example 5.1 or 7.1. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Surround sound - Low Frequency Effects (LFE) channel The LFE is a source of some confusion in surround sound 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Surround sound - Low Frequency Effects (LFE) channel In the original movie theater implementation, the LFE was a separate channel fed to one or more subwoofers 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Surround sound - Low Frequency Effects (LFE) channel 1 Some record labels such as Telarc and Chesky have argued that LFE channels are not needed in a modern digital multichannel entertainment system https://store.theartofservice.com/the-low-frequency-toolkit.html Radio frequencies - Extremely Low frequency RF 1 High-power extremely Low frequency RF with electric field levels in the low kV/m range are known to induce perceivable currents within the human body that create an annoying tingling sensation https://store.theartofservice.com/the-low-frequency-toolkit.html Radio frequencies - Extremely Low frequency RF page 63[http://www.who.int/pehemf/publications/elf_ehc/en/index.html Extremely Low Frequency Fields Environmental Health Criteria Monograph No.238], chapter 5, page 121, WHO 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency 1 'Low frequency' or 'low freq' or 'LF' refers to Radio frequency|radio frequencies (RF) in the range of 30kHzndash;300kHz https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Propagation Because of their long wavelength, low frequency radio waves can Diffraction|diffract over obstacles like mountain ranges and follow the curvature of the Earth. This mode of propagation, called ground wave, is the main mode in the LF band. The attenuation of signal strength with distance by absorption in the ground is lower than at higher frequencies. Low frequency ground waves can be 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Propagation 1 Low frequency waves can also travel long distances by reflecting from the ionosphere (the actual mechanism is one of refraction), although this method, called skywave or skip propagation, is not as common as at higher frequencies. Reflection occurs at the Kennelly– Heaviside layer|E layer or F Region|F layers. Skywave signals can be detected at distances exceeding 300km from the transmitting antenna. https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Standard time signals 1 In the frequency range 40kHz–80kHz, there are several standard time and frequency stations, such as https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Standard time signals 1 * HBG Prangins|HBG in Prangins, Switzerland (75kHz) (closed down on 1 January 2012) https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Standard time signals 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, and 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. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Military 1 Radio signals below 50kHz are capable of penetrating ocean depths to approximately 200 metres, the longer the wavelength, the deeper. The British, German, Indian, Russian, Swedish, United States and possibly other navy|navies communicate with submarines on these frequencies. https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Military In addition, Royal Navy nuclear submarines carrying ballistic missiles are allegedly under standing orders to monitor the BBC Radio 4 transmission on 198kHz in waters near the UK. It is rumoured that they are to construe a sudden halt in transmission, particularly of the morning news programme Today Programme|Today, as an indicator that the UK is under attack, whereafter their sealed 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Military 1 In the US, the Ground Wave Emergency Network or GWEN operated between 150 and 175kHz, until replaced by satellite communications systems in 1999. GWEN was a land based military radio communications system which could survive and continue to operate even in the case of a nuclear attack. https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Experimental and amateur An international 2.1kHz allocation, the 2200-meterband (135.7kHz to 137.8kHz), is available to amateur radio operators in several countries in Europe,European Conference of Postal and Telecommunications Administrations|CEPT/ERC Recommendation 62-01 E (Mainz 1997): Use of the band 135.7-137.8 kHz by the Amateur Service 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Experimental and amateur 1 The UK allocated a 2.8kHz sliver of spectrum from 71.6kHz to 74.4kHz 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 W ERP (effective radiated power) https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Experimental and amateur 1 In the United States, there is a special license free allocation in the longwave range called LowFER https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Meteorological information broadcasts A regular service transmitting radioteletype|RTTY marine meteorological information in SYNOP code on LF is the German Meteorological Service (Deutscher Wetterdienst or [http://www.dwd.de DWD]). The DWD operates station DDH47 on 147.3kHz using standard ITA-2 alphabet with a transmission speed of 50 baud and FSK modulation with 85Hz shift. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Radio navigation signals 1 In parts of the world where there is no longwave broadcasting service, Nondirectional beacons or NDB's used for aeronavigation operate on 190–300kHz (and beyond into the MW band). In Europe, Asia and Africa, the NDB allocation starts on 283.5kHz. https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Radio navigation signals The commercial DATATRAK radio navigation system operates on a number of frequencies, varying by country, between 120 and 148kHz. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Radio broadcasting 1 The longwave radio broadcasting service operates on frequencies between 148.5 and 283.5kHz in Europe and parts of Asia. https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Other applications 1 Some radio frequency identification (RFID) tags utilize LF. These tags are commonly known as LFID's or LowFID's (Low Frequency Identification). The LF RFID tags are near field devices. https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Antennas 1 Since the ground waves used in this band require vertical polarization, vertical antennas are used for transmission, usually mast radiators, either insulated from the ground and fed at the bottom, or occasionally fed through guy-wires https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Antennas 1 The height of antennas differ by usage. https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Antennas For some non-directional beacons (NDBs) the height can be as low as 10 meters, while for more powerful navigation transmitters such as Decca Navigator System|DECCA, masts with a height around 100 meters are used. Tantennas have a height between 50 and 200 meters, while mast aerials are usually taller than 150 meters. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Antennas The height of mast antennas for LORAN-C is around 190 meters for transmitters with radiated power below 500kW, and around 400 meters for transmitters greater than 1000 kilowatts. The main type of LORAN-C antenna is insulated from ground. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Antennas LF Longwave|(longwave) broadcasting stations use mast antennas with heights of more than 150 meters or T-aerials. The mast antennas can be ground-fed insulated masts or upper-fed grounded masts. It is also possible to use cage antennas on grounded masts. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Antennas For broadcasting stations, directional antennas are often required 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Antennas 1 For reception, long wire antennas are used, or more often ferrite loop antennas because of their small size. Amateur radio operators have achieved good LF reception using active antennas with a short whip. https://store.theartofservice.com/the-low-frequency-toolkit.html Low frequency - Antennas LF transmitting antennas for high power transmitters require large amounts of space, and have been the cause of controversy in Europe and the United States due to concerns about possible electromagnetic radiation and health|health hazards associated with exposure to high-power radio waves. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Extremely low frequency 1 'Extremely low frequency' ('ELF') waves are electromagnetic radiation (radio waves) with frequencies from 3to30Hertz|Hz, and corresponding wavelengths from 100,000 to 10,000 kilometers. In atmosphere science, an alternative definition is usually given, from 3Hzto3kHz.Liemohn, Michael W. and A. A. CHAN, [http://lwstrt.gsfc.nasa.gov/trt_liemohn05eos.pdf https://store.theartofservice.com/the-low-frequency-toolkit.html Extremely low frequency 1 In the related magnetosphere science, the lower frequency electromagnetic oscillations (pulsations occurring below ~3Hz) are considered to lie in the ultra low frequency|ULF range, which is thus also defined differently from the ITU Radio Bands. https://store.theartofservice.com/the-low-frequency-toolkit.html Extremely low frequency ELF radio waves are generated by lightning and natural disturbances in Earth's magnetic field, so they are a subject of research by atmospheric scientists 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Radiation - Very low frequency (VLF) Very low frequency, or VLF, refers to a frequency range of 30 Hz to 3kHz which corresponds to wavelengths of 100,000 to 10,000 meters respectively. Since there is not much bandwidth in this range of the radio spectrum, only the very simplest signals can be transmitted, such as for radio navigation. Also known as the myriameter band or myriameter wave as the wavelengths range from ten to one myriameter (an obsolete metric unit equal to 10 kilometers). 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Radiation - Extremely low frequency (ELF) Extremely low frequency (ELF) is radiation frequencies from 3 to 30Hz (108 to 107 meters respectively). In atmosphere science, an alternative definition is usually given, from 3Hz to 3kHz. In the related magnetosphere science, the lower frequency electromagnetic oscillations (pulsations occurring below ~3Hz) are considered to lie in the ULF range, 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Inductive coupling - Low frequency induction Low frequency induction is an unwanted form of inductive coupling, which can occur when a metallic Pipeline transport|pipeline is installed parallel to a high-voltage power line. The pipeline, which is a conductor, and is insulated from the earth by its protective coating, can develop voltages which are hazardous to personnel operating valves or 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Radio navigation - Low frequency radio range 1 The low-frequency radio range (LFR, also other names) was the main navigation system used by aircraft for Instrument flight rules|instrument flying in the 1930s and 1940s in the U.S. and other countries, until the advent of the VOR in the late 1940s. It was used for both enroute navigation as well as instrument approaches. https://store.theartofservice.com/the-low-frequency-toolkit.html Radio navigation - Low frequency radio range 1 The ground stations consisted of a set of four antennas that projected Lorenz beams in four cardinal directions https://store.theartofservice.com/the-low-frequency-toolkit.html Radiological - Very low frequency (VLF) Very low frequency, or VLF, refers to a frequency range of 30Hz to 3kHz which corresponds to wavelengths of 100,000 to 10,000 meters respectively. Since there is not much bandwidth in this range of the radio spectrum, only the very simplest signals can be transmitted, such as for radio navigation. Also known as the myriameter band or myriameter wave as the wavelengths range from ten to one myriameter (an obsolete metric unit equal to 10 kilometers). 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Antenna height considerations - Longwave/low frequency antennas 1 At VLF, LF and Medium frequency|MF the Radio masts and towers|radio mast or tower is often used directly as an antenna https://store.theartofservice.com/the-low-frequency-toolkit.html Antenna height considerations - Longwave/low frequency antennas For high power transmitters, masts with heights of about half the radiated wavelength are preferred because they concentrate the radiated power toward the horizon. This enlarges the distance at which selective fading occurs. However, masts with heights of around half a wavelength are much more expensive than shorter ones and often too expensive for lower power 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Antenna height considerations - Longwave/low frequency antennas 1 For longwave transmitters, however, the construction of halfwave masts is infeasible in most cases, either for economic reasons or because of problems with flight safety https://store.theartofservice.com/the-low-frequency-toolkit.html Antenna height considerations - Longwave/low frequency antennas Use is not normally made of masts higher than five-eighths (5/8) of a wavelength, because such masts (except for some special constructions for high power mediumwave broadcasting) exhibit poor vertical radiation patterns. The heights of masts for mediumwave transmitters normally do not exceed the 300 metre (1000foot) level. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Antenna height considerations - Longwave/low frequency antennas Sometimes cage aerials or longwire aerials are used for LF and MF transmission. In this case the height of the tower may be greater than is usually the case. Because towers or masts used for cage or long wire aerials are grounded at the base, they are especially suitable for supporting antennas for Ultra high frequency|UHF or VHF broadcasting. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Ultra low frequency Gordeev, [http://www.nat-hazardsearth-syst-sci.net/3/203/2003/nhess3-203-2003.pdf Preseismic ULF electromagnetic effect from observation at Kamchatka], Natural Hazards and Earth System Sciences, Volume 3, Pages 203-209, 2003 Frequencies above 3Hz in atmosphere science are usually assigned to the extremely low frequency|ELF range. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Ultra low frequency Many types of waves in the ULF frequency band can be observed in the magnetosphere and on the ground. These waves represent important physical processes in the near-Earth plasma environment. The speed of the ULF waves is often associated with the Alfvén velocity that depends on the ambient magnetic field and plasma mass density. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Ultra low frequency 1 This band is used for communications in Mining|mines, as it can penetrate the earth.[http://www.weather.nps.navy.mil/~ps guest/EMEO_online/module3/module_3_1 .html HF and Lower Frequency Radiation Introduction] https://store.theartofservice.com/the-low-frequency-toolkit.html Ultra low frequency - Earthquakes 1 Some monitoring stations have reported that earthquakes are sometimes preceded by a spike in ULF activity https://store.theartofservice.com/the-low-frequency-toolkit.html Ultra low frequency - Earth mode communications 1 ULF has been used by the military for secure communications through the ground https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency 'Very low frequency' or 'VLF' is the International Telecommunications Union|ITU designation for radio frequency|radio frequencies (RF) in the range of 3 kHz to 30 kHz and wavelengths from 10 to 100 kilometres 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Propagation characteristics 1 Because of their large wavelengths, VLF radio waves can Diffraction|diffract around large obstacles and so are not blocked by mountain ranges, and can propagate as a ground wave following the curvature of the Earth https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Propagation characteristics VLF waves have very low path attenuation, 2-3 dB per 1000km, with little of the fading experienced at higher frequencies, This is because VLF waves are reflected from the bottom of the ionosphere, while higher frequency shortwave signals are returned to Earth from higher layers in the ionosphere, the F1 layer|F1 and F2 layer|F2 layers, by a refraction process, and spend most of their 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Propagation characteristics 1 VLF waves can penetrate seawater to a depth of at least 10 to 40 meters (30 to 130 feet), depending on the frequency employed and the salinity of the water, so they are used to communicate with submarines. https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Antennas 1 A major practical drawback to this band is that because of the length of the waves, full size resonant antennas (half wave dipole or monopole antenna|quarter wave monopole antennas) cannot be built because of their physical height https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Antennas 1 Transmitting antennas for VLF frequencies are very large wire antennas, up to a mile across https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Antennas 1 To minimize power dissipated in the ground, these antennas require extremely low resistance ground systems. Because of soil resistance, Counterpoise (ground system)|counterpoise systems are often used, consisting of radial networks of copper cables supported several feet above the ground under the antenna, extending out radially https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Antennas 1 The requirements for receiving antennas are less stringent, because the transmitter power is generally high to overcome atmospheric noise. Atmospheric noise and not Noise figure|receiver noise determines the receiver signal to noise ratio, so small inefficient receiving antennas can be used. Loop antennas are often used for reception. https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Applications 1 The frequency range below 9kHz is not allocated by the International Telecommunication Union and may be used in some nations license-free. https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Applications VLF is used to Communication with submarines|communicate with submarines near the surface (for example using the transmitter VLF transmitter DHO38|DHO38), while Extremely low frequency|ELF is used for deeply submerged vessels. VLF is also used for radio navigation beacons (alpha) and time signals (beta). VLF is also used in Electromagnetic 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Applications 1 In the USA, the time signal station WWVL began transmitting a 500W signal on 20kHz in August 1963. It used Frequency Shift Keying (Frequency-shift keying|FSK) to send data, shifting between 20kHz and 26kHz. The WWVL service was discontinued in July 1972. https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Applications 1 Historically, this band was used for transcontinental radio communication during the wireless telegraphy era between about 1900 and 1925 https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Applications 1 Naturally occurring signals in the VLF band are used for long range lightning location https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - Applications 1 and for research into phenomena such as Upper-atmospheric lightning|transient luminous events. Measurements of https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - VLF submarine communication methods 1 High power land-based transmitters in countries that operate submarines send signals that can be received thousands of miles away https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - VLF submarine communication methods 1 Because of the low bandwidth available it is not possible to transmit audio signals, therefore all messaging is done with alphanumeric data at very low bit rates. Three types of modulation are used: https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - VLF submarine communication methods * OOK / CWK: On-Off Keying / Continuous Wave Keying. Simple Morse code transmission mode where carrier on = mark and off = space. This is the simplest possible form of radio transmission, but it is difficult for transmitters to transmit high power levels, and the signal can easily be swamped by atmospheric noise, so this is only really used for 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - VLF submarine communication methods 1 * FSK: Frequency-shift keying. The oldest and simplest form of digital radio data modulation. Frequency is increased by 25Hz (for example) from the carrier to indicate a binary “1” and reduced by 25Hz to indicate binary “0”. FSK is used at rates of 50 bit/s and 75 bit/s. https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - VLF submarine communication methods 1 * MSK: Minimum-shift keying. A more sophisticated modulation method that uses less bandwidth for a given data rate than FSK. This is the normal mode for submarine communications today, and can be used at data rates up to 300 bit/s- or about 35 8-bit ASCII characters per second (or the equivalence of a sentence every two seconds) – a total of 450 words per https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - VLF submarine communication methods Two alternative character sets may be used: 5-bit ITA2 or 8-bit ASCII. Because these are military transmissions they are almost always encrypted for security reasons. Although it is relatively easy to receive the transmissions and convert them into a string of characters, civilians cannot decode any encrypted messages because they most likely use one-time pads since the amount of text is so small. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - PC-based VLF reception 1 VLF signals are often monitored by radio amateurs using simple homemade VLF radio receivers based on personal computers (PCs) https://store.theartofservice.com/the-low-frequency-toolkit.html Very low frequency - PC-based VLF reception These spectrograms show many signals, which may include VLF transmitters and the horizontal electron beam deflection of TV sets. The strength of the signal received can vary with a Sudden Ionospheric Disturbance. These cause the ionization level to drop in the atmosphere. The result of this is that the VLF signal will reflect down to Earth 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Super-low frequency 1 Another conflicting designation which includes this frequency range is Extremely Low Frequency (ELF), which in some contexts refers to all frequencies up to 300 hertz. https://store.theartofservice.com/the-low-frequency-toolkit.html Super-low frequency 1 It became operational in 1989 but was discontinued in 2004 due to advances in Very low frequency|VLF communication systems https://store.theartofservice.com/the-low-frequency-toolkit.html Non-ionizing radiation - Very low frequency (VLF) Very low frequency or VLF is the radio frequencies (RF) in the range of 3 to 30kHz. Since there is not much bandwidth in this band of the radio spectrum, only the very simplest signals are used, such as for radio navigation. Also known as the myriameter band or myriameter wave as the wavelengths range from ten to one myriameter (an obsolete metric unit equal to 10 kilometers) 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Non-ionizing radiation - Extremely low frequency (ELF) Extremely low frequency (ELF) is the range of radiation frequencies from 3 to 30Hz. In atmosphere science, an alternative definition is usually given, from 3Hz to 3kHz. In the related magnetosphere science, the lower frequency electromagnetic oscillations (pulsations occurring below ~3Hz) are considered to be in the ULF range, which is thus also defined differently from the ITU Radio Bands. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Genome instability - Low frequency of mutations without cancer The protein coding regions of the human genome, collectively called the exome, constitutes only 1.5% of the total genome. As pointed out above, ordinarily there are only an average of 0.35 mutations in the exome per generation (parent to child) in humans. In the entire genome (including non-protein coding regions) there are only about 70 new 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Planck (spacecraft) - Low Frequency Instrument The LFI has three frequency bands, covering the range of 30–70GHz, covering the microwave to infra-red regions of the electromagnetic spectrum. The detectors use high-electron-mobility transistors. 1 https://store.theartofservice.com/the-low-frequency-toolkit.html Common-emitter amplifier - Low frequency voltage amplifier 1 A typical example of the use of a common-emitter amplifier is shown in Figure 3. https://store.theartofservice.com/the-low-frequency-toolkit.html Common-emitter amplifier - Low frequency voltage amplifier The input capacitor C removes any constant component of the input, and the resistors R1 and R2 bias the transistor so that it will remain in active mode for the entire range of the input 1 https://store.theartofservice.com/the-low-frequency-toolkit.html For More Information, Visit: • https://store.theartofservice.co m/the-low-frequencytoolkit.html The Art of Service https://store.theartofservice.com