3/4" U-matic

Sony U-matic VTR BVU-800
Media type	Magnetic Tape
Encoding	NTSC, PAL
Developed by	Sony
Usage	Video production

A U-matic tape

U-matic is an analog recording videocassette format first shown by Sony in prototype in October 1969, and introduced to the market in September 1971. It was among the first video formats to contain the videotape inside a cassette, as opposed to the various Reel-to-Reel or open-reel formats of the time. Unlike most other cassette-based tape formats, the supply and take-up reels in the cassette turn in opposite directions during playback, fast-forward, and rewind: one reel would run clockwise while the other would run counter-clockwise. A locking mechanism integral to each cassette secures the tape hubs during transportation to keep the tape wound tightly on the hubs. When the cassette is loaded into the videocassette recorder (VCR) or player, the mechanism releases the hubs, permitting the hubs to spin. A spring-loaded tape cover door protects the tape from damage; when the cassette is inserted into the VCR, the door is released and is opened, enabling the VCR mechanism to spool the tape around the spinning video drum. Accidental recording is prevented by the presence of a red plastic button fitted to a hole on the bottom surface of the tape; removal of the button disabled recording.

U-Matic VCRs and cassettes may be seen as props in the television program Lost (TV series) and movies Broadcast News, Blue Thunder, and Electric Horseman.

Development[link]

As part of its development, in March 1970, Sony, Matsushita Electric Industrial Co. (Panasonic), Victor Co. of Japan (JVC), and five non-Japanese companies reached agreement on unified standards.

The videotape was ³⁄₄ in (1.9 cm) wide, so the format is often known as 'three-quarter-inch' or simply 'three-quarter', comparing to other open reel videotape formats of the same vintage, such as 1 in (2.5 cm) type C videotape and 2 in (5.1 cm) quadruplex videotape.

The first generation of U-matic VCRs were large devices, approximately 30 in (76 cm) wide, 24 in (61 cm) deep, and 12 in (30 cm) high, requiring special shelving, and had mechanical controls limited to Record, Play, Rewind, Fast-Forward, Stop and Pause. Later models sported improvements such as chassis sized for EIA 19-inch rack mounting, with sliding rack rails for compressed storage in broadcast environments, solenoid control mechanics, jog-shuttle knob, remote controls, Vertical Interval Time Code (VITC), longitudinal time code, internal cuts-only editing controls, "Slo-Mo" slow-motion playback, and Dolby audio noise reduction.

U-matic was named after the shape of the tape path when it was threaded around the helical scan video head drum, which resembled the letter U.^[1] Betamax used this same type of "U-load" as well.

The total potential lines of horizontal resolution for standard U-matic is 280 lines per picture height.^[2] Vertical resolution is the NTSC standard of 486 visible scan lines, and recording time was limited to one hour.

Introduction[link]

At the 1971 introduction of U-Matic, Sony originally intended it to be a videocassette format oriented at the consumer market. This proved to be something of a failure, because of the high manufacturing cost and resulting retail price of the format's first VCRs.^[3] But the cost was affordable enough for industrial and institutional customers, where the format was very successful for such applications as business communication and educational television. As a result, Sony shifted U-Matic's marketing to the industrial, professional, and educational sectors.

U-Matic saw even more success from the television broadcast industry in the mid-1970s, when a number of local TV stations and national TV networks utilized the format when its first portable model, the Sony VO-3800, was released in 1974. This model ushered in the era of ENG, or Electronic News Gathering, which made obsolete the previous 16mm film cameras normally used for on-location television news gathering. Film required developing which took time, compared to the instantly available playback of videotape, making faster breaking news possible.

Models[link]

U-matic is also available in a smaller cassette size, officially known as U-Matic S. Much like VHS-C, U-Matic S was developed as a more portable version of U-Matic, to be used in smaller-sized S-format recorders such as the aforementioned Sony VO-3800, as well as the later VO-4800, VO-6800, VO-8800, BVU-50, BVU-100 and BVU-150 models from Sony, among others from Sony, Panasonic, JVC and other manufacturers. To minimize weight and bulk in the field, portable recorders had an external AC power supply, or could be operated from rechargeable nickel-cadmium batteries.

The price point of the VO series was oriented toward educational, corporate and industrial fields, featured unbalanced audio connectors, and did not typically include SMPTE time code (although one or two companies offered after-market modification services to install longitudinal time code). The VO-3800 was largely metal, which made the unit heavy, but still technically portable. The VO-4800 had the same functionality as the VO-3800, but at a greatly reduced weight and size, by replacing many components with plastic. The VO-6800 added the improvement of a long, thin battery standard ("candy bars") that permitted storage of the batteries in a trouser pocket. Common model numbers for these batteries were NP-1, NP-1A and NP-1B. The VO-8800 was the last of the portable VO series to be produced by Sony, and featured solenoid-controlled transport.

The Sony BVU series added longitudinal and vertical interval SMPTE time code, balanced audio XLR connectors, and heavier-duty transport features. The BVU-50 enabled recording in the field but not playback, and the BVU-100 permitted both recording and playback in the field. Portable recorders were connected to the camera with a multi-conductor cable terminated with multi-pin connectors on each end. The cable carried bi-directional audio, video, synchronization, record on/off control, and power. Early studio and all portable U-Matic VCRs had a drawer-type mechanism which required the tape to be inserted, followed by manual closure of the drawer (a "top-loading" mechanism). Later studio VCRs accepted the cassette from a port opening and the cassette was pulled into and seated in the transport (a "front-loading" mechanism).

S-format tapes could be played back in older top-loading standard U-Matic decks with the aid of an adapter (the KCA-1 from Sony) which fitted around an S-sized tape; newer front-loading machines can accept S-format tapes directly, as the tapes have a slot on the underside that rides along a tab. U-Matic S tapes had a maximum recording time of 20 minutes, although some tape manufacturers such as 3M came out with 30-minute tapes by loading the cassette with a thinner tape. It was the U-Matic S-format decks that ushered in the beginning of ENG, or Electronic News Gathering.

Some U-Matic VCRs could be controlled by external video editing controllers, such as the cuts-only Sony RM-440 for linear video editing systems. Sony and other manufacturers such as Convergence, Calaway, and CMX Systems produced A/B roll systems, which permitted two or more VCRs to be controlled and synchronized for video dissolves and other motion effects, integration of the character generator, audio controllers and digital video effects (DVE).

In the early 1980s, Sony introduced the semi backwards-compatible high-band or BVU (Broadcast Video U-matic) format, and the 'original' U-matic format became known as low-band. This high-band format had an improved colour recording system and lower noise levels. BVU gained immense popularity in ENG and location programme-making, spelling the end of 16 mm film in everyday production. By the early 1990s, Sony's ¹⁄₂ in (1.3 cm) Betacam SP format had all but replaced BVU outside of corporate and 'budget' programme making. Sony made a final improvement to BVU by further improving the recording system and giving it the same 'SP' suffix as Betacam. SP had a horizontal resolution of 330 lines.^[2] First-generation BVU-SP and Beta-SP recordings were hard to tell apart, but despite this the writing was on the wall for the U-matic family, due to intrinsic problems with the format.

Problems[link]

A recurring problem with the format was damage to the videotape caused by prolonged friction of the spinning video drum heads against a paused videotape. The drum would rub oxide off the tape or the tape would wrinkle; when the damaged tape was played back, a horizontal line of distorted visual image would ascend in the frame, and audio would drop out. Manufacturers attempted to minimize this issue with schemes in which the tape would loosen around the spinning head or the head would stop spinning after resting in pause mode for a pre-determined period of time.

The format video image also suffered from head-switching noise, a distortion of the image in which a section of video at the bottom of the video frame would be horizontally askew from the larger portion.

The format also had difficulty reproducing the color red, and red images would be noisier than other colors in the spectrum. For this reason, on-camera talent was discouraged from wearing red clothing that would call attention to the technical shortcoming.

Copying video from one VCR to another VCR displayed compromised playback reliability, and exponential levels of head-switching noise, chroma smearing and noise, compounded with every generation. These technical challenges motivated videotape editors and engineers to plan work around minimizing generational degradation. Use of a time-base corrector (TBC) or "dub" cable were methods of minimizing multi-generational quality loss. The TBC regenerates the sync tip portion of the video signal, improving playback reliability. The dub, demodulated (or "demod") cable was a multi-conductor cable that circumvented a portion of video circuitry, minimizing amplification noise.

Broadcast use[link]

For synchronization to broadcast or post-production editing house genlock systems, U-Matic VCRs required a Time Base Corrector (TBC). Some TBCs had a drop-out compensation (DOC) circuit which would hold lines of video in temporary digital memory to compensate for oxide drop-out or wrinkle flaws in the videotape, however the DOC circuits required several cables and expert calibration for use.

U-matic tapes were also used for easy transport of filmed scenes for dailies in the days before VHS, DVD, and portable hard drives. Several movies have surviving copies in this form. The first rough cut of Apocalypse Now, for example (the raw version of what became Apocalypse Now Redux), survived on three U-Matic cassettes.^[4]

Audio quality was compromised due the use of longitudinal audio tape heads in combination with slow tape speed. Sony eventually implemented Dolby noise reduction circuitry to improve audio fidelity.

U-matic would also see use for the storage of digital audio data. Most digital audio recordings from the 1980s were digitally mastered to U-matic tape. The Sony PCM-1600 PCM adaptor used a U-matic recorder as a transport. The PCM-1600 output standard "pseudo video" in 525/60 format, which appeared to be a video image of vibrating checkerboard patterns that could be recorded on a video recorder. The PCM-1600 was the first system used for mastering audio compact discs in the early 1980s, with the famous Compact Disc 44.1 kHz sampling rate based on a best-fit calculation for the U-matic's video horizontal-sync rate. The later PCM-1610 and 1630 units also used U-matic cassettes as a storage medium.

Decline of use[link]

U-matic is no longer used as a mainstream television production format, but it has found lasting appeal as a cheap, well specified, and hard-wearing format. The format permitted many broadcast and non-broadcast institutions to produce television programming on an accessible budget, spawning programming distribution, classroom playback, etc. At its peak popularity, U-matic recording and playback equipment was manufactured by Sony, Panasonic, JVC and Sharp, with many spin-off product manufacturers, such as video edit controllers, time base correctors, video production furniture, playback monitors and carts, etc.

Many television facilities the world over still have a U-matic recorder for archive playback of material recorded in the 1980s. For example, the Library of Congress facility in Culpeper, VA, holds thousands of its titles on U-matic video, as a means of providing access copies and proof for copyright deposit of old television broadcasts and films.

Four decades after it was developed, the format is still used for the menial tasks of the industry, being more highly specialized and suited to the needs of production staff than the domestic VHS, although as time passes it has been replaced at the bottom of the tree of tape-based production formats by Betacam and Betacam SP as these in turn are replaced by Digital Betacam and HDCAM.

References[link]

External links[link]

• Sony.com Sony History
• Sony.com Sony History timeline
• Total Rewind, Umatic VCRs, Photos and comparison of various Sony U-matic decks
• Sony U.S. patent for U-matic videotape cassette, filed 1971.
• Sony U.S. patent for design of U-matic deck, filed 1971.
• Umatic Pal site Type 2 U-matic
• Umatic Pal site, History
• encyclopediapro.com U-matic page
• experimental tv center U-matic page
• R-VCR, History of Videotape U-matic page
• Rewind Museum Sony VO-1600. The worlds first VCR. 1971
• Texas Commission on the Arts, 3/4" Umatic
• Fundamentals of television production, By Ralph Donald and Thomas Spann, Page 188, Ch 9.
• The History of Television, 1942 to 2000, By Albert Abramson and Christopher H. Sterling, Page 153, Ch 9.
• U-matic PALsite information about the U-matic video format.
• Lab Guy's World Three Quarter Inch Umatic VCR's
• Trans Diffusion, Tech Mark, From Baird to MPEG, By Martin Fenton
• tvhistory.tv VCR and Home Video History

v t e Sony Corporation Primary businesses Sony Corporation (electronics & holding of the Sony group) · Sony Music Entertainment (music) · Sony Pictures Entertainment (motion pictures and television) · Sony Computer Entertainment (video games) · Sony Financial Holdings (financial services; 60%) · Sony Digital Audio Disc Corporation Technologies and brands α · Betacam · Blu-ray · BRAVIA · CD · Cyber-shot · Dash · Dream Machine · DVD · Handycam · HDCAM/HDCAM-SR · LocationFree · Memory Stick · MiniDisc · MiniDV · mylo · Reader · S/PDIF · SDDS · SXRD · Sony Tablet · UMD · VAIO · Video8/Hi8/Digital8 · Walkman · Walkman Phones · XDCAM · Xplōd · HMZ-T1 Historical products AIBO · CV-2000 · DAT · Betamax · Sony CLIÉ · Discman · JumboTron · Lissa · Mavica · NEWS · Qualia · Rolly · TR-55 · Trinitron · U-matic · Watchman · WEGA Electronics Sony EMCS · Sony Electronics (subsidiary in the US) · Sony Creative Software · Sony Mobile Communications  · S-LCD (50% minus 1 share) · Sony Mobile Display · Sony Optiarc · Sharp Display Products (7%) · Aiwa (former) Sony Music Entertainment Sony/ATV Music Publishing (50%) · Columbia Records · Epic Records · RCA Records · Sony Music Nashville (Arista Nashville, BNA Records, Columbia Nashville, RCA Records Nashville) · Provident Label Group · Verity Gospel Music Group · Sony Music Latin · Sony Masterworks  · Legacy Recordings  · RED Distribution  · IODA  · Syco Music  · Syco TV  · Syco Film  · Sony Music Australia · Sony Music Japan  · Gracenote · Aniplex · A-1 Pictures Sony Pictures Entertainment Columbia TriStar Motion Picture Group (Columbia Pictures · Sony Pictures Classics · Screen Gems · TriStar Pictures · Triumph Films) · Sony Pictures Worldwide Acquisitions (Destination Films · Stage 6 Films · Affirm Films) · Sony Pictures Television Group (Adelaide Productions · Culver Entertainment · Embassy Row · 2waytraffic · Lean-M  · Gogglebox Entertainment · Victory Television · Silver River Productions · Starling · Huaso · Floresta · Teleset) Sony Pictures Home Entertainment · Sony Wonder · Sony Pictures Family Entertainment Group · Sony Pictures Digital (Sony Pictures Imageworks · Sony Pictures Animation · Sony Pictures Mobile) · Sony Pictures Studios · Sony Pictures Consumer Marketing (Sony Pictures Consumer Products · Sony Pictures Loot) U.S. networks Sony Movie Channel · GSN (40%), joint venture with DirecTV · FEARnet HD (joint venture with Comcast and Lionsgate) · 3net (joint venture with Discovery Communications and IMAX) International networks Sony Entertainment Television (Asia, South East Asia, India, Latin America, South Africa, Portugal, Russia, Spain, Baltic and United Kingdom) · AXN · AXN HD · AXN HD+1 · AXN Asia · AXN India · AXN Pakistan · AXN White · AXN Crime · AXN Black · AXN Mystery · AXN Sci Fi · AXN Spin · Sony Aath · Multi Screen Media · Animax · Animax Asia · Animax India · Animax Pakistan · Animax Korea · Animax Eastern Europe · BeTV · Sony Spin · SET One · SET Max · Sony SIX · Sony MIX · SET PIX · SAB TV · Men&Movies · Movies4Men Sony Computer Entertainment Sony Online Entertainment · PlayStation · PSP · PlayStation Vita · Cellius (49%) · Square Enix (8.25%) · Sony Imagesoft (defunct) Online distribution platforms Sony Entertainment Network (Music Unlimited · Video Unlimited · PlayStation Network) · FEARnet · The Minisode Network · Crackle Financial services Sony Financial Holdings · Sony Life Insurance · Sony Assurance · Sony Bank · Sony Bank Securities Other businesses So-net Entertainment · Sony Broadcast & Professional Research Laboratories · Sony Sendai Other assets Sony Corporation of America (umbrella company in the US) · Other subsidiaries Joint ventures Sony/ATV · FeliCa Networks · Vevo · Cellius (49%) · Sharp Display Products (7.04%) Key personnel Kazuo Hirai · Masaru Ibuka · Nobuyuki Idei · Yasuo Kuroki · Ken Kutaragi · Michael Lynton · Akio Morita · Norio Ohga · Amy Pascal · Howard Stringer  · Nicole Seligman Category ·  Commons ·  Wikinews

This biographical article needs additional citations for verification. Please help by adding reliable sources. Contentious material about living persons that is unsourced or poorly sourced must be removed immediately, especially if potentially libelous or harmful. (July 2011)

For the cutting tool, see scissors.

Safety Scissors is Matthew Patterson Curry, a minimal techno artist born in Minneapolis, Minnesota.^[1] He moved to the San Francisco Bay Area for a short while in order to attend San Francisco Art Institute. Curry then decided to focus more on music and eventually joined Belief Systems/Context Records where he began working with Kit Clayton, Sutekh, and Twerk.^[1] Curry also performs with Seth Horvitz (aka Sutekh) under the name Moron.^[1] In 2000, he moved to Berlin.

Curry has released three full length albums, Parts Water in 2001, Tainted Lunch (released on Stefan Behnke's ~scape label) in 2005, and Pigeon Funk Presents!!! with Sutekh. Parts Water was described by CMJ New Music Monthly as "a perfect headphone record", including what reviewer Tim Haslett called "possibly the first attempts by a techno artist to write pop tunes".^[2]

He also collaborated with Kit Clayton on an EP entitled Ping Pong, which sped through three dozen tracks in less than twenty minutes. Ping Pong was part of Carpark Records' sports-FAN series, so named because each release was pressed on a Fan CD.

From 2001 until 2006, Curry ran his own label Proptronix which was dedicated to fake electronics.

Discography[link]

Albums[link]

• Parts Water (2001), Plug Research

1. "Two Letter U's"
2. "A Wash"
3. "Stormy Weather"
4. "7 Glasses a Day/7 Days a Week"
5. "Your Beautiful Feet"
6. "Esperanto"
7. "Before (Less)"
8. "(Water)phone"
9. "Sailor Stripes"
10. "Dipsy Daisy"
11. "Sipper"
12. "Mirror (Wet)"

• Tainted Lunch (2005), Scape

1. "I Am the Cheese"
2. "Sunlight's on the Other Side"
3. "Breastbone"
4. "Amnesia, I Need You to Remind Me"
5. "A Fly in My Soup"
6. "After Disaster"
7. "Love Lately"
8. "L'Amour D'Cuisine"
9. "Here Come the Housewives"
10. "Where Is Germany and How Do I Get There?"

Singles, EPs[link]

• Rubber Stamp EP (1999), Context
• Pigeon Funk Presents!!! EP (2002), Onitor - with Sutekh
• "Sunlight's on the Other Side" (2005), Scape
• Camping 01 (2007), BPitch Control - single split with Ben Klock, includes Ellen Allien's remix of "Where Is Germany and How Do I Get There?"

References[link]

This article on an American electronic musician is a stub. You can help Wikipedia by expanding it. v t e

Low frequency or low freq or LF refers to radio frequencies (RF) in the range of 30 kHz–300 kHz. In Europe, and parts of Northern Africa and of 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 (LORAN), information, and weather systems. Time signal stations MSF, HBG, DCF77, JJY and WWVB are found in this band. Also known as the kilometre band or kilometre wave as the wavelengths range from one to ten kilometres.

Propagation of LF signals[link]

Because of their long wavelength, low frequency radio signals can refract over obstacles like mountain ranges and follow the curvature of the Earth. Radio waves reaching the receiver by this route are called ground waves. Their strength is not reduced by absorption as much as in higher frequencies. Ground wave can cover an area with a radius of 2000 km about the transmitting antenna.

Propagation by reflection (the actual mechanism is one of refraction) from the ionosphere is also possible. The refraction can take place at the E layer or F layers. These waves, called skywaves, can be detected at distances exceeding 300 km from the transmitting antenna.^[1]

Standard time signals[link]

An LF Radio clock

In the frequency range 40 kHz–80 kHz, there are several standard time and frequency stations, such as

• JJY in Japan (40 kHz and 60 kHz)
• MSF in Anthorn, England (60 kHz)
• WWVB in Fort Collins, Colorado, US (60 kHz)
• DCF77 in Mainflingen near Frankfurt am Main, Germany (77.5 kHz)
• HBG in Prangins, Switzerland (75 kHz) (closed down on 1 January 2012)

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.

Military[link]

Radio signals below 50 kHz are capable of penetrating ocean depths to approximately 200 metres, the longer the wavelength, the deeper. The British, German, Indian, Russian, Swedish, United States ^[2] and possibly other navies communicate with submarines on these frequencies.

In addition, Royal Navy nuclear submarines carrying ballistic missiles are allegedly 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, particularly of the morning news programme Today, as an indicator that the UK is under attack, whereafter their sealed orders take effect.^[3]

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 even in the case of a nuclear attack.

Experimental and amateur[link]

An international 2.1 kHz allocation, the 2200-meter band (135.7 kHz to 137.8 kHz), is available to amateur radio operators in several countries in Europe,^[4] New Zealand, Canada and French overseas dependencies. The world record distance for a two-way contact is over 10,000 km from near Vladivostok to New Zealand.^[5] As well as conventional Morse code many operators use very slow computer controlled Morse code (QRSS) or specialized digital communications modes. The 2007 World Radiocommunication Conference (WRC-07) made this band a worldwide amateur radio allocation.

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 W ERP (effective radiated power). This was withdrawn on 30 June 2003 after a number of extensions in favor of the European-harmonized 136 kHz band.^[6] A 1-watt transmission of very slow Morse Code between G3AQC (in the UK) and W1TAG (in the US) spanned the Atlantic Ocean for 3,275 miles (5,271 km) on November 21–22, 2001.

In the United States, there is a special license free allocation in the longwave range called LowFER. This experimental allocation between 160 kHz and 190 kHz is sometimes called the "Lost Band". Unlicensed operation by the public is permitted south of 60 degrees north latitude,^{[citation needed]} except where interference would occur to ten licensed location service stations located along the coasts.^{[citation needed]} Regulations for use include a power output of no more than 1 watt, a combined antenna/ground-lead length of no more than 15 meters, and a field strength of no more than 4.9 microvolts/meter.^{[citation needed]} Also, emissions outside of the 160 kHz–190 kHz band must be attenuated by at least 20 dB below the level of the unmodulated carrier. Many experimenters in this band are amateur radio operators.

Meteorological information broadcasts[link]

This section requires expansion.

A regular service transmitting RTTY marine meteorological information on LF is the German Meteorological Service (Deutscher Wetterdienst or DWD). 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.^[7]

Radio navigation signals[link]

This section requires expansion.

In parts of the world where there is no longwave broadcasting service, Non-directional beacons or NDB's used for aeronavigation operate on 190–300 kHz (and beyond into the MW band). In Europe, Asia and Africa, the NDB allocation starts on 283.5 kHz.

The LORAN-C radio navigation system operates on 100 kHz.

In the past, the Decca Navigator System operated between 70 kHz and 129 kHz. The last Decca chains were closed down in 2000.

Differential GPS telemetry transmitters operate between 283.5 and 325  kHz.^[8]

The commercial "DATATRAK" radio navigation system operates on a number of frequencies, varying by country, between 120 and 148 kHz.

Radio broadcasting[link]

The longwave radio broadcasting service operates on frequencies between 148.5 and 283.5 kHz in Europe and parts of Asia.

Other applications[link]

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.

Antennas[link]

Low cost LF time signal receiver

Transmitting antennas (aerials) used at these low frequencies are usually mast radiators, which are fed at the bottom and which are insulated from ground, or mast antennas fed by the guy ropes (such masts are usually grounded). T-antennas and L-antennas are used when antenna height is an issue. Long wire antennas are also used in rare cases. Nearly all LF antennas are electrically short, shorter than one quarter of the radiated wavelength. The only longwave transmission antenna realized with a height corresponding to a half radiated wavelength was the Warsaw Radio Mast. These electrically short antennas need loading coils of high inductance to bring them into resonance. These coils have high power losses due to ohmic heating of the coil wire, making the antenna inefficient. Many antenna types, such as the umbrella antenna, use capacitive top-loading (a "top hat"), in the form of a network of horizontal wires attached to the top of the vertical radiator. The capacitance improves the efficiency of electrically short LF antennas without increasing the height of the antenna or its supporting structures.

The height of antennas differ by usage.

For some non-directional beacons (NDBs) the height can be as low as 10 meters, while for more powerful navigation transmitters such as DECCA, masts with a height around 100 meters are used. T-antennas have a height between 50 and 200 meters, while mast aerials are usually taller than 150 meters.

The height of mast antennas for LORAN-C is around 190 meters for transmitters with radiated power below 500 kW, and around 400 meters for transmitters greater than 1000 kilowatts. The main type of LORAN-C antenna is insulated from ground.

LF (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.

For broadcasting stations, directional antennas are often required. They consist of multiple masts, which often have the same height. Some longwave antennas consist of multiple mast antennas arranged in a circle with or without a mast antenna in the center. Such antennas focus the transmitted power toward ground and give a large zone of fade-free reception. This type of antenna is rarely used, because they are very expensive and require much space and because fading occurs on longwave much more rarely than in the medium wave range. One antenna of this kind was used by transmitter Orlunda in Sweden.

For reception, long wire antennas are used, or more often ferrite loop antennas because of their small size.

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 health hazards associated with exposure to high-power radio waves.

See also[link]

• High frequency
• Long wave
• LowFER
• 2200-meter band
• Time signal
• WGU-20
• LowFID passive RFID tags

References[link]

Further reading[link]

• Tomislav Stimac, "Definition of frequency bands (VLF, ELF... etc.)".
• IK1QFK Home Page.
• Klawitter, G.; Oexner, M., Herold, K. (2000) (in German). Langwelle und Längstwelle. Meckenheim: Siebel Verlag GmbH. ISBN 3-89632-043-2. 
• Marten, M. (2007) (in German). Spezial-Frequenzliste 2007/08. Meckenheim: Siebel Verlag GmbH. pp. 36–39. ISBN 978-3-88180-665-7. 
• Mike Dennison, G3XDV and Jim Moritz, M0BMU (2007). LF Today. Radio Society of Great Britain. ISBN 978-1-905086-36-8. 

v t e Time Major concepts Time Eternity Arguments for eternity Immortality History Past Present Future Futures studies Deep time Time Portal Measurement and standards Chronometry UTC UT TAI Second Minute Hour Sidereal time Solar time Time zone Metric time Decimal time Hexadecimal time Clock Astrarium History of timekeeping devices Horology Marine chronometer Sundial Water clock Calendar Day Week Month Year Tropical year Gregorian Islamic Julian Intercalation Leap second Leap year Chronology Astronomical chronology Calendar era Chronicle Dating methodologies Geochronology Geologic Time Geological history Periodization Regnal year Timeline Religion and mythology Dreamtime Kāla Kalachakra Prophecy Time and fate deities Wheel of time Philosophy A-series and B-series B-Theory of time Causality Endurantism Eternal return Eternalism Event Perdurantism Presentism Temporal finitism Temporal parts The Unreality of Time Physical sciences Time in physics Absolute time and space Arrow of time Chronon Coordinate time Planck epoch Planck time Proper time Spacetime Theory of relativity Time dilation Gravitational time dilation Time domain T-symmetry Biology Chronobiology Circadian rhythms Psychology Mental chronometry Sense of time Specious present Sociology and anthropology Long Now Foundation Time discipline Time use research Economics Time value of money Time-based currency Time Banking Related topics Carpe diem Duration Space System time Tempus fugit Time capsule Time signature Time travel