China Suppliers
Management
Vendors at the San Jose Flea Market
The San Jose Flea Market is still family owned and operated. Although there is now a staff of 500 service employees and controlled by Ogden Entertainment Services, the Bumb family oversees all management of the market. Brian Bumb Sr., son of George Bumb Sr., now supervises and is part owner (15.7%) of the San Jose Flea market among his other brothers, George Bumb Jr., and Timothy Bumb, who each have 14.1% ownership. Other members of the Bumb family own vendor stalls, work at food carts, and have managerial positions within the flea market. Joe Bumb, cousin of Brian Bumb, owns American Precious Metals, an open-air store within the flea market that now sells mostly jewelry. Joe Bumb store revenue totals approximately $100,000 a month. On any given Sunday, a visitor can find Joe and a handful of his children helping their father at the family store. vpl cx70
On Site mr16 light bulb
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A Mariachi band performing at San Jose Flea Market
The eight miles (13 km) worth of aisles allows for over 2000 vendors to sell an array of goods. With a population and land mass larger than some small towns, the flea market is a major contributor to the income of many Silicon Valley families. Some of the treasures found at the landmark include jewelry, furniture, clothing, fruits, vegetables, shoes, collectables, toys, books, lamps, batteries, car stereo equipment, paintings, power drills, lamp shades, lipstick, and forks.
Along with the material items sold at the flea market, there are twenty five food vendors. Restaurants sell delicacies from burritos to French fries and freshly cooked meats on the outdoor barbecue in order to satisfy the tastes of the large clientele the Flea Market serves daily. There are also snack carts for shoppers on the run that offer delicious treats. Some of those include mango and pineapple spears on a stick, cold sodas, and churros. The largest section of the Flea Market is Produce Row which stretches a quarter of a mile through the market and contains vegetables and fruit from California farmers.
The atmosphere is like none other. To accompany the sweet and savory smells of the food, there is the sound of constant music playing. Since the Flea Market attracts people from a wide range of backgrounds and ethnicities, the songs played from vendor stands reflect the Market varying tastes. So, it is no surprise that an authentic Mexican mariachi band will be playing as a Beach Boys song is heard a few minutes later. There are also a carrousel, arcade, and three playgrounds for children.
The diversity of people, food, and music at the San Jose Flea Market epitomizes the melting pot on which California Bay Area prides itself.
School
To keep his family tradition of education in the Roman Catholic Church, George Bumb Sr. established Saint Thomas More School on the flea market property in 1978 . His grandchildren were the first to attend the school, but when St. Thomas More was relocated in 2004 to 1590 South White Road in San Jose, CA, the attendance increased to include students outside the Bumb family. Although it no longer remains on the Flea Market grounds, Saint Thomas More School resided on the site for twenty six years; a majority of the Flea Market's life.
Setbacks
Fraud and Theft
On Sunday, October 29, 1986, eight vendors at the San Jose Flea Market were arrested by undercover officers for selling counterfeit cassette tapes. The officers also confiscated 14,000 tapes from the stands. Sellers of these tapes were investigated after a 1984 study showed that the recording industry had lost over $300 million in fake tapes. Tapes at a record store sell for about $8 a tape; tapes at the flea market were being sold for two for $5 or three for $6.
In January 1990, five men were arrested for stealing 38 Ford pickup trucks from the parking lot of the San Jose Flea Market. The Fresno native men stole the cars to send them south to the San Joaquin Valley where they could be sold. The parking lot of the Flea Market is so big that security did not notice that nearly three cars were being stolen daily. But surveillance of the lot allowed authorities to catch the five suspects stealing the cars.
In December 1990, ten vendors were arrested for selling fake designer watches, athletic shoes, and clothing. 7,000 bogus items at an estimated worth of $150,000 were confiscated by a San Francisco investigator who was working with the San Jose police. In the beginning of this investigation, authorities bought 100 (Chanel, Fendi, Nike, Rolex, Adidas) counterfeit items from 42 vendors. On the day of the arrest, however, only 10 phony vendors were out due to the rain.
In May 1993, eight vendors were arrested for selling phony major league sports wear and $46,000 worth of clothing was confiscated. Imitation hats, t-shirts, and jackets were being sold and over $4,000 items were carried away.
Child Labor
In June 1992, Flea Market Inc. was fined $68,700 for alleged child labor at the San Jose Flea Market. Investigators of child labor laws in San Jose, claimed the Flea Market employed 71 children ages 1415 in a Flea Market restaurant for more than the federal standard time of 18 hours per week. The United States Department of Labor also regards this job as unsafe. Although the San Jose Flea Market did not appeal the facts of the case, they did dispute the fines received. The Flea Market claimed that since they are not involved in inter-state commerce, they abide by less limiting state laws and are not a part of the Federal Labor Department jurisdiction.
Family Feud
In the late 1970, problems began when George Bumb Sr.'s wife began having an affair with a man she met at a square dancing class. Felony charges faced George Bumb Sr. when he and an accomplice beat the man for 90 minutes. He offered him $100,000 to leave town. Bumb pleaded guilty to misdemeanors.
Throughout his career George Bumb Sr. included his eight children in the family business. He managed his businesses and family similarly with strict policies and fired his family members frequently. A more secretive family feud began when one of his sons, Brian Bumb Sr., did not send his children to the family school, St. Thomas More. Brian told his father the world was bigger than the Flea Market, and his children would explore it.
The Bumbs continue to have business and family difficulties. In the late 1990, George Bumb Sr.'s son Jeff spent $11.5 million to open up Bay 101, a card room in San Jose. But Jeff was unsuccessful in getting a gaming license from the state because of a loan that he never paid off. His two brothers, George Jr. and Tim Bumb, never planned to get involved but obtained the gaming license for Bay 101. Therefore Jeff originally did not receive any money from the Bay 101 profits. As a result, he asked his father for a bigger share of the Flea Market so all of the Bumb brothers' profits would be equal. George Bumb Sr. refused and Jeff consequently sued his family. The case settled for $5.8 million in 1996. George Bumb Sr. died shortly after, never reconciling with his son Jeff.
Fire
On Tuesday, November 29, 2006, a fire burned down 24 stands of Produce Row at the San Jose Flea Market. At 6:02 p.m, a 911 call was made and dozens of fire crews and a helicopter arrived to put out the flames. Although the fire was contained at 7:15 p.m, $200,000 worth of merchandise was destroyed. Burnt nuts, fruit, plants, and plastic were strewn all over the ground. Teresa Bumb, daughter of Brian Bumb Sr., stated that they would do their best to help those who were affected by the fire by offering free or reduced rent.
Future Developments
On August 14, 2007, the San Jose City Council approved the proposal to reconstruct the 120-acre (0.49 km2) property on Berryessa Road to allow for a 2,800-home development. The Council took suggestions from the public and discussed it among themselves for about two hours that concluded in an approval of the motion by a 10 to 1 vote. The lone disapproving vote was cast because the Council member felt the requirements the city gave the Bumb family were excessive. The motion approved the Bumb Family plan to develop the 120-acre (0.49 km2) lot that is the current home of the San Jose Flea Market. The flea market will remain open until 2010, but in the meantime, a joint effort between the Bumb family and the city will take place to find a new venue to host the vendors. The approval of the project would have a few more benefits aside from an increase in housing. The Flea Market location is also a future BART, Bay Area Rapid Transit, station site. The upside to building 2,000+ low-income homes around that station would be a positive effect on San Jose commuters.
The challenge is to find a replacement site for the Flea Market. Some potential sites are the Singleton Road landfill, the south end of Coyote Valley, the Santa Clara County Fairgrounds and Morgan Hill. Whichever site is chosen will need to be at least 80 acres (320,000 m2) to host the thousands of Flea Market vendors. With a recent increase in land value, finding such a spot will be an expensive task.
Notes
^ Vazquez, Daniel. "George Bumb Sr., Began Fleamarket". "San Jose Mercury News". 2000-8-21.
^ a b c *San Jose Flea Market History
^ Hendrickson, Steve. emorandum: Bay 101 Conditional Approval of Stock Transfer. 2007-9-13
^ Eunjung Cha, Ariana. nternet Threatens Old-Fashioned Sales Venues Washington Post. 2005-8-2.
^ Rodriguez, Joe. roduce Row Packs Them In. San Jose Mercury News. 2006-6-26.
^ *California Business Portal Corporations
^ Mercury News Staff Report. "San Jose Police Arrest 8 In Bogus Cassette Case." "San Jose Mercury News". 1986-11-6.
^ Barnacle, Betty. "5 Seized In Theft of Tucks Pickups Taken At Flea Market". "San Jose Mercury News". 1990-1-31.
^ Barnacle, Betty. "10 Arrested in Flea- Market Raid On Fakes". "San Jose Mercury News". 1990-12-18.
^ Barnacle, Betty. "Counterfeit Sports Wear Seized at Two S.J. FleaMarket Raids". "San Jose Mercury News". 1993-5-3.
^ Levander, Michelle. "Child Labor Exposed Employers Fined for Hours, Task Violation". "San Jose Mercury News". 1992-6-17.
^ Sulek, Julia. "Card Club Problems The Bay 101 Card Club in San Jose Has Been a Source of Controversy Within the Bumb Family". "San Jose Mercury News". 2000-12-31.
^ Gonzales, Sandra. ire Damages Flea Market. San Jose Mercury News. 2006-11-29.
^ Sherbert,Erin. he Waiting Game. The Metro Silicon Valley. 2007-9-12.
^ Gomez, Mark. lea-Market Future at Issue- ransit Village Planned for Property. San Jose Mercury News. 2007-8-13.
References
San Jose Flea Market History
ublic Eye The Metro Silicon Valley. 2000-8-24.
amily Feud The Metro Silicon Valley. 1999-7-1.
igh Class Joints The Metro Silicon Valley. 2000-9-7.
California Business Portal Corporations
Bailey, Brandon. airgrounds Floated as New Flea Market Site. San Jose Mercury News. 2007-4-15.
Bailey, Brandon. endors Rally to Save Flea Market. San Jose Mercury News. 2007-4-25.
Barnacle, Betty. "5 Seized In Theft of Tucks Pickups Taken At Flea Market". San Jose Mercury News. 1990-1-31.
Barnacle, Betty. "10 Arrested in Flea- Market Raid On Fakes". San Jose Mercury News. 1990-12-18.
Barnacle, Betty. "Counterfeit Sports Wear Seized at Two S.J. FleaMarket Raids". San Jose Mercury News. 1993-5-3.
Gomez, Mark. lea-Market Future at Issue- ransit Village Planned for Property. San Jose Mercury News. 2007-8-13.
Gonzales, Sandra. ire Damages Flea Market. San Jose Mercury News. 2006-11-29.
Gore, Robert J. he Bazaar Growth of Swap Meets. Los Angeles Times. 1982-6-18.
Eunjung Cha, Ariana. nternet Threatens Old-Fashioned Sales Venues Washington Post. 2005-8-2.
Hall, Christopher. hat Doing In San Jose. New York Times. 1998-4-12.
Hendrickson, Steve. emorandum: Bay 101 Conditional Approval of Stock Transfer. 2007-9-13
Levander, Michelle. "Child Labor Exposed Employers Fined for Hours, Task Violation". San Jose Mercury News. 1992-6-17.
Mercury News Staff Report. "San Jose Police Arrest 8 In Bogus Cassette Case." San Jose Mercury News. 1986-11-6.
Rodriguez, Joe. iscovering a World of Fruits and Vegetables. San Jose Mercury News. 2007-5-24.
Rodriguez, Joe. roduce Row Packs Them In. San Jose Mercury News. 2006-6-26.
Sherbert,Erin. he Waiting Game. The Metro Silicon Valley. 2007-9-12.
Sherbert,Erin. wilight Zoning. The Metro Silicon Valley. 2007-11-14.
Stein, Loren. ave Goodbye To the Train. The Metro Silicon Valley. 2002-12-26.
Sulek, Julia. "Card Club Problems The Bay 101 Card Club in San Jose Has Been a Source of Controversy Within the Bumb Family". San Jose Mercury News. 2000-12-31.
Vazquez, Daniel. "George Bumb Sr., Began Fleamarket". San Jose Mercury News. 2000-8-21.
Witt, Barry. lea-Market Rezoning Approved- Venue to be Open Until Early 2010. San Jose Mercury News. 2007-8-16.
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San Jose and Silicon Valley attractions
Arboreta/Gardens
Arizona Cactus Garden Chinese Cultural Garden Emma Prusch Farm Park Hakone Gardens Japanese Friendship Garden Overfelt Gardens SJ Municipal Rose Garden Stanford Arboretum Villa Montalvo Arboretum
Cultural
American Musical Theatre of SJ Ballet San Jose Cathedral Basilica of St. Joseph Choral Project De Saisset Museum MLK Library Gurdwara Sahib Ira F. Brilliant Center for Beethoven Studies Mexican Heritage Plaza Opera San Jose SJ City Hall SJ Flea Market SJ Improv SJ Museum of Art SJ Rep Theatre Viet Museum Villa Montalvo Vivace Youth Chorus
Event venues
Buck Shaw Stadium HP Pavilion at San Jose PAL Stadium SC Convention Center SJ Civic Auditorium SJ Convention Center SJ Municipal Stadium SJSU Event Center Arena Shoreline Amphitheatre Spartan Stadium
Events
BayCon Cinequest Film Festival FanimeCon FurCon Gilroy Garlic Festival LiveStrong Challenge SJ Holiday Parade SJ Jazz Festival Stanford Jazz Festival
Historical
Circle of Palms De Anza Hotel Hangar One History Park at Kelley Park HP Garage Peralta Adobe Portuguese Historical Museum Rengstorff House Rosicrucian Egyptian Museum SJ Museum of Quilts & Textiles Winchester Mystery House
Parks/Trails
Almaden Quicksilver County Park Alum Rock Park Bay Area Ridge Trail Castle Rock State Park Ed Levin Park Grant Ranch Park Guadalupe River Trail Henry W. Coe State Park Kelley Park Lake Cunningham Los Alamitos Creek Trail Los Gatos Creek Trail Plaza de Csar Chvez Rancho San Antonio Rosicrucian Park Sanborn Park SF Bay Trail Shoreline Park Stevens Creek Trail Vasona Park
Science/Tech/Education
Children's Discovery Museum Computer History Museum Googleplex Intel Museum Laser Quest Lick Observatory NASA Ames Research Center SJSU SCU Stanford The Tech Museum of Innovation
Shopping
Eastridge Great Mall Pruneyard San Antonio Santana Row Stanford Vallco Oakridge Valley Fair Westgate
Theme parks & Tours
Airship Ventures Billy Jones Wildcat Railroad Gilroy Gardens Great America Happy Hollow Park & Zoo Raging Waters
Vineyards/Wineries
Byington Vineyard J Lohr Vineyards and Wines Mountain Winery Picchetti Brothers Winery Savannah-Chanelle Vineyards
Categories: Visitor attractions in Silicon Valley | Retail markets in the United States | Economy of San Jose, California | Culture of San Jose, CaliforniaHidden categories: Santa Clara County, California articles missing geocoordinate data | All articles needing coordinates
Saturday, April 24, 2010
San Jose Flea Market
Swan Electronics
China Suppliers
History
Swan Electronics, then Swan Engineering, began as a one man operation with Herbert G. Johnson, W6QKI, building the first ten single sideband (SSB) transceivers in a garage in Benson, Arizona during the winter of 1960-1961. At that time, the only other SSB transceiver on the market was the well known Collins KWM-2, selling for considerably more money. Production continued into the 1970s with thousands of units being produced in Oceanside California. At its peak Swan produced as many as 400 radios per month.
Needing more capital and engineering resources for Swan's rapid expansion, the company merged with Cubic Corporation in 1967 and Johnson continued managing the Swan subsidiary until 1973. Johnson founded his second company, Atlas Radio, in 1974. Atlas produced a line of compact, rugged radios that became popular for mobile communications from cars and boats. The Swan line of equipment was mostly vacuum tube type design, and through the years more than 80,000 transceivers were sold. wilson cell phone antenna
Many Swan radios remain in service today, restored and operated by vintage amateur radio enthusiasts. treo antenna
Amateur Radio Products cb mobile antenna
Swan entry into the amateur radio equipment market consisted of transceivers primarily designed for the newly popular single sideband (SSB) mode of voice transmission, and covered only those portions of the amateur radio bands where SSB could be used.
The first ten transceivers Swan produced were serial numbered from 101-1 to 110-1, with the first nine being model SW-120 operating on 20 meters (14 MHz), and the tenth, 110-1, being the first SW-140, operating on 40 meters (7 MHz). The SW-175 then covered the 75 meter band (3.8 MHz).
Following the single band transceivers, Swan introduced the model 240, which covered all three bands in one unit, and then the model 400, which covered five bands (adding 21 and 28 MHz) and had a VFO in a separate unit.
Later, in the mid 1960s, Swan introduced the more full-featured models 350 and 500 transceivers. The Swan 500 was a more costly version of the 350, with higher output power and more operating features. Although they lacked the higher selectivity and tuning accuracy of higher priced transceivers, each performed solidly as a basic SSB station. They both used an outboard AC power supply with a built-in speaker, the model 117C and its variants. Improved versions of the 350 and 500 continued to be released into the early 1970s and were Swan best selling models.
One of the distinguishing design features of that generation of Swan transceivers was their dual rate, gear-driven tuning dial. A front knob provided slow rate tuning while a metal, outer collar tuned much faster enabling rapid frequency changes across a band. Improved models of the two transceivers were periodically introduced well into the 1970s along with accessories, including a remote VFO (for separate control of receiver and transmitter frequency) and the Mark-I and Mark-II linear amplifiers.
Magazine ad circa 1970s featuring Swan 600T/600R
Two additional single band transceivers were also made to operate on bands not included in the 350 and 500 but with similar styling and features. A 6 meter (50 MHz) transceiver, the Swan 250, was introduced in 1965, and the Swan 160X was built to cover (not surprisingly) the 160 meter (1.8 MHz) band. They were high and low frequency bookends to the mainstay, five-band 350 and 500.
In 1969 Swan brought out the slightly smaller model 260 transceiver which could be operated from either 110V AC or 12V DC permitting either fixed or mobile operation in one unit. Also named the ygnet, it resembled the earlier Swan 240 but with a different color scheme. It was followed by an improved model 270 which could only operate from AC power and required an accessory power supply for DC operation.
In the 1970s, the Swan 500 was upgraded again and became the model 700 and 750, and underwent a styling change in later versions after the merge with Cubic.
Swan also designed a matched, separate receiver and transmitter pair, the 600R and 600T, which together offered better performance, higher output power and many more features than the tranceivers could. They were produced in far fewer numbers, however, and are therefore harder for collectors to find today.
References
^ http://www.pcs.mb.ca/~standard/ Swan Virtual Museum
^ http://www.qsl.net/on6ab/History.html Swan History
^ he Swan Virtual Museum
See also
Collins radio
E.F. Johnson
Eico
Hallicrafters
Hammarlund
National radio
R. L. Drake Company
Signal/One
Vintage amateur radio
External links
ARRL News: Swan, Atlas Radio Founder Herbert G. Johnson
Swan rigs
Categories: Amateur radio companies | Defunct companies based in California
Handbell
China Suppliers
History
See also: Change Ringing and Bell (instrument)
The first tuned handbells were developed by brothers Robert and William Cor in Aldbourne, Wiltshire, England between 1696 and 1724. The Cor brothers originally made latten bells for hame boxes, but for reasons unknown, they began tuning their bells more finely to have an accurate fundamental tone, and fitted them with hinged clappers that only moved in one plane. reading wall lamp
Originally, tuned sets of handbells, such as the ones made by the Cor brothers, were used by change ringers to rehearse outside their towers. Rather than standing for hours in a draughty tower, they could sit comfortably indoors while they practiced the complicated algorithms of change ringing. The handbell sets used by change ringers had the same number of bells as in the towers generally six or 12 tuned to a diatonic scale. brass candle lamp
Handbells were first brought to the United States from England by Margaret Shurcliff in 1902. She was presented with a set of 10 handbells in London by Arthur Hughes, the general manager of the Whitechapel Bell Foundry after completing two separate two-and-a-half-hour change ringing peals in one day. antique bronze lamp
Terminology
Two English Handbells, manufactured by Whitechapel Bell Foundry.
The bells used in American handbell choirs are almost always English handbells. "English handbells" is a reference to a specific type of handbells, not to the country of origin. While some American handbell choirs do use bells made in England, the majority play bells made either by Malmark Bellcraftsmen or by Schulmerich Carillons, both based in Pennsylvania.
In the United Kingdom, there is a distinction between "American handbells" and "English handbells" "English handbells" are traditional, with leather clapper heads and handles (such as the bells Whitechapel makes), while "American handbells" use modern materials, such as plastic and rubber, to produce the same effect (such as those produced by Malmark and Schulmerich). In America, however, they are all called English handbells.
Characteristics
The two major defining characteristics of English handbells are their clappers and ability to produce overtones. The clapper on an English handbell is on a hinge and moves back and forth in a single direction, unlike a school bell in which the clapper swings freely in any direction. It also has a spring that holds the clapper away from the casting after the strike to allow the bell to ring freely. Furthermore, the shaft of the clapper is rigid, such that the bell may be held with its mouth facing upward. The overtones on an English handbell are a 12th (an octave and a perfect fifth) above the fundamental, while Dutch handbells such as Petit & Fritsen focus on the overtone a minor 10th (an octave and a minor third) or a major 10th (an octave and a major third) above the fundamental. Manufacturers give their attention to each bell's overtones, being especially careful to give all the bells in a set a consistent harmonic profile. Each of the foundries has a unique formula for emphasizing or de-emphasizing certain harmonic overtones to produce that bellmaker's unique sound.
Handbells can weigh as little as 7 oz (200 g) or upwards of 18 lb (8.2 kg).
Handbell performance
A girl's handbell choir during a performance.
A handbell choir or handbell ensemble [in the US] or handbell team [in England] is a group that rings recognizable music with melodies and harmony, as opposed to the mathematical permutations used in change ringing. The bells used generally include all notes of the chromatic scale within the range of the bell set. While a smaller group uses only 25 bells (two octaves), the sets are often larger, ranging up to a seven-and-a-half-octave set. The bells are typically arranged chromatically on foam-covered tables; these tables protect the bronze surface of the bell, as well as keep the bells from rolling when placed on their sides. Unlike an orchestra or choir in which each musician is responsible for one line of the texture, a bell ensemble acts as one instrument, with each musician responsible for particular notes, sounding his or her assigned bells whenever that note appears in the music.
Handbell music
Handbell choirs generally ring music composed or arranged specifically for the instruments because of their highly resonant sound, the limited note range of a handbell set, and the unique pitch-by-pitch division of the staff among the ringers.[citation needed]
The coordination of the bell ringers requires a different approach than other ensembles. All the ringers read from a complete score. This score is similar to a piano score, but with an additional convention: The C# above middle C and all notes below are always written in the bass clef, and the Db above middle C and all notes above are always written in the treble clef. (This formatting is not always the convention for solo and small-ensemble handbell music.) Handbell music is written one octave lower than the actual sound the bells make, so a "middle C bell" or bell is actually playing a note with a high C frequency. (For simplicity, the bell would still always be referred to as middle C or as C5.)
There are also a number of abbreviations and notations used exclusively or almost exclusively in handbell music: LV ("laissez vibrer" or "let vibrate," similar to a piano's sustain pedal); R ("ring," regular ringing or meaning to end the LV); SK ("shake," i.e. shaking the bell continuously during the duration of the note); TD ("thumb damp" ringing the bell with a thumb on the casting to create a staccato note); PL ("pluck," which means to throw down the clapper while the bell lies on the table); a small, solid triangle ("martellato" to strike bell against padding of the table, pushing the casting firmly against padding as to quickly dampen sound); SW ("swing" to play the bell in a normal position, swing it down to the waist, then bring it and back up); BD ("brush damp," brushing the rim of the bell against the ringer's chest to cause a quick diminuendo); and an upward arrow, usually with a curve at the bottom ("echo," ringing the bell and then touching it very briefly to the table, creating an echo effect).
Due to handbells' relative rarity outside of the confines of church serviceslthough less so now than in the 1980s and early 1990she majority of pieces composed and arranged for handbells last approximately four minutes. A few composers and arrangers write longer and more intricate works for handbells; generally these pieces use handbells in combination with other instruments.
Ringing techniques
To ring a handbell, the ringer moves it in such a way that the clapper strikes the inside surface of the bell, usually holding it against his or her shoulder, bell-upwards, and then swinging the bell through an elliptical shape to cause the clapper to strike the casting of the bell. The tone of the bell will continue to resonate, decaying naturally until it stops completely, or until the ringer stops the tone by damping the bell with a hand, on the body, or on a padded surface.
Handbell techniques have changed very much over the years. Donald Allured, founding director of Westminster Concert Bell Choir, is credited with fully realizing an American "off the table" style of ringing that includes many non-ringing sound effects including stopped techniques such as plucking the clapper with the bell on the table. He is also credited for promoting precise damping or stopping of the bell sound by touching the bell casting to a soft surface, in the service of more musical results.[citation needed]
Multiple bell techniques
Traditional ringing technique only allows one ringer to ring two bells at a time (one in each hand). Depending on the number of bells needed for a particular piece of music and the number of ringers in a choir, it may be necessary for each ringer to ring more than two bells at a time or in short succession. There are also many techniques that change the sound of the bell as it is rung.
Four bells
There are two main ways of ringing two handbells with one hand: four-in-hand and Shelley. In the four-in-hand technique, ringers hold two bells in one hand with the clappers at right angles to each other. This allows the ringer to either move the hand normally ("ring" - Primary Bell) or ring knuckles-first ("knock" - Secondary Bell) to ring two different bells independently with the same hand (for a total of four bells when ringing with both hands). The two bells can also be played together by holding the wrist at a 45 degree angle. Two opposing viewpoints exist regarding the merits of this technique: while some believe that Shelley ringing is rendered obsolete when four-in-hand is perfected, others believe that the control, balance and precision offered by Shelley ringing makes the technique more applicable in certain ringing situations (particularly those involving other techniques, such as shaking and martellato, which are nearly impossible to "perfect" with four-in-hand ringing).
In large ensembles, Four-in-hand is typically used to ring multiple positions or pick up accidentals.
Shelley ringing is similar, except that the clappers are each positioned the same direction. Using this technique, a ringer can then ring two bells simultaneously with one movement. Shelley is typically used to ring two notes, an octave apart. The motion of the clappers in the same plane makes feasible techniques which generally require this, such as martellato, vibrato and shake, all of which are difficult (if not impossible) to achieve with four-in-hand ringing. The Shelley technique can also be used to ring two notes separately by striking the primary bell sideways and the secondary bell forward in an action like tapping your fingers.
Six bells
There are several ways to play six bells at a time (i.e., to ring three bells in each hand). One way is to pick two bells up as if you were Shelly ringing, then pick the third up between your pinky and ring fingers (a 'triple shelly'). All three bells ring together when ringing in a knocking motion. A second way is to pick up the third bell sideways so that the clapper swings outward. Ringers with good control can then ring the first bell without ringing the third bell, allowing the ringer to play three different notes in one hand.
Weaving
Weaving is the technique of playing a succession of bells by changing which bell is in each hand as required. This is used by bass bell ringers and solo/small ensemble ringers. The large size and weight of bass bells makes four-in-hand ringing impractical and often a solo or small ensemble ringer will need to move up and down a range of bells, possibly sharing them with others. This technique means that more than two bells can be rung in short succession, using the table to damp the bell and free the hand to pick up the next bell. If the ringing sequence requires bells to be rung in tonal order, this technique often results in a weaving pattern as the ringer must often reach across their body for the next bell in the sequence. Weaving can also be used in combination with the four-in-hand in a technique called "traveling four-in-hand". By combining the ability to hold two bells in each hand, with the ability to quickly drop and pick up the secondary bell of a Four-in-hand, a ringer has quick access to several bells.
Other techniques
All kinds of mallets by Malmark
There are other ways to play music with handbells besides traditional ringing. Other techniques include plucking, shaking (or trilling), table damping (or martellato), and malleting bells (both on the table and suspended).
Plucking is accomplished by using the thumb and forefinger to force the clapper head into the casting while the bell is on the table, producing a staccato tone.
Shaking is accomplished by rapidly ringing the bell back and forth so that the clapper strikes both the front and back of the bell casting in quick succession. This technique created a continuous tone, as opposed to normal ringing in which the tone decays rapidly after being rung. Because of their size, bass bells are rarely shaken.
Martellato also creates a staccato tone and is accomplished by striking the bell into the foam-covered table in such a way that the clapper strikes the casting immediately after the bell strikes the foam. A variation, called a "Mart Lift" is accomplished by lifting the bell casting off the table very soon after the clapper strikes. This creates a staccato tone followed by a softened sounding of the bell.[citation needed]
Malleting bells involves using one of several types of rubber, plastic or yarn-wrapped mallet to strike the casting of the bell. This can create a staccato tone when the casing is pressed into foam, a normal ringing tone when the bell is suspended or even a drum-roll effect when multiple mallets are used. Suspended malleting can be employed to create a bell tree which allows many bells to be played by one ringer.
Echo technique adds a brief pulse of increased volume to a sustained handbell note. This is accomplished by gently touching the rim of a vibrating bell to the padded table.[citation needed]
The sound of the Singing Bell technique is similar to the sound a wine glass makes as its rim is stroked with a wet fingertip, and is accomplished in much the same way. A short wooden dowel or stick is touched to the outside of the rim of a handbell, which is being held in the other hand. The dowel is then used to stroke the rim of the bell in a circular or "stirring" motion.[citation needed]
See also
Wikimedia Commons has media related to: Hand bell
Belleplates
Handchime
Dead bell
External links
American Guild of English Handbell Ringers
Notes
^ a b Markey, Willard H. (May/June, 1997), "More History?: From Hame Boxes to Handbells", Overtones: the Official Journal of the American Guild of English Handbell Ringers 43 (3): 3637
^ A hame box is a device that attaches to the top of a horse collar and contains several bells that ring when the horse moves. For more information about the Cor brothers and a picture of a hame box, see A Brief History of The Aldbourne Bell Foundries.
^ Theile, Ron. "The History of Handbell Ringing". http://handbellringers.com/handbell_history.html. Retrieved 2009-08-13.
^ Bullen, Nigel (March/April, 1998), "Researching the History of Handbells: In the Beginning", Overtones: the Official Journal of the American Guild of English Handbell Ringers 44 (2): 3738
^ http://www.olypen.com/nwbell/handbell/sidenote/bell_weights.html, accessed 10/09/09
^ Schmidt-Jones, Catherine. "Transposing Instruments". http://cnx.org/content/m10672/latest/. Retrieved 2008-03-08.
^ http://www.ling.upenn.edu/~kingsbur/articulations.html, accessed 10/09/09
^ Moore, Daniel K. (May/June, 1998), "Technique-ly Speaking: The Basic Ringing Stroke/Shoulder Damp", Overtones: the Official Journal of the American Guild of English Handbell Ringers 44 (3): 1011
^ Leonard, Karen E. (September/October, 2000), "Technique-ly Speaking: Shelley Ringing", Overtones: the Official Journal of the American Guild of English Handbell Ringers 46 (5): 1314
^ Anderson, Christine (2000-01-14). "Multiple Bells In-Hand". http://www.knology.net/~jkearns/faqtechniques.htm#Four-in-hand/Shelley. Retrieved 2009-08-13.
^ Allured, Don (May/June, 1999), "Technique-ly Speaking: The Weave and Other Multiple Bell Doings", Overtones: the Official Journal of the American Guild of English Handbell Ringers 45 (3): 4144
^ http://www.ling.upenn.edu/~kingsbur/articulations.html. Retrieved 2009-10-09.
^ Ebling-Thorne, Kathy (September/October, 1998), "Technique-ly Speaking: The Shake and The Trill - What a Thrill!", Overtones: the Official Journal of the American Guild of English Handbell Ringers 44 (5): 910
^ Frier, Louise (September/October, 1999), "Technique-ly Speaking: Malleting Suspended Handbells", Overtones: the Official Journal of the American Guild of English Handbell Ringers 45 (5): 1416
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SIG Sauer P220
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History
The SIG P220 was developed for the Swiss Army as a replacement for the SIG P210, which had been developed during World War II; in service it is known as "Pistole 75" (P75). For development of the P220, SIG collaborated with J.P. Sauer & Sohn of Germany, thus, the P220 and all subsequent pistols from SIG are properly known as SIG Sauer pistols.
In 1975, Switzerland became the first nation to officially adopt the P220 as the "Pistole 75" (P75) chambered in 9 mm Parabellum. Other nations to adopt it for military use include Japan and Denmark though only to special forces. It was succeeded by the SIG Sauer P226. hms1 2
Upon completion of their military service, the officiers of the Swiss armed forces can obtain ownership of their P220 service pistols by paying an administrative fee of thirty Swiss francs. hms2
Design scrap stainless
The P220 operates by the locked breech short-recoil method pioneered by John Browning. On firing the slide and barrel are locked together until, after a few millimetres of rearward movement, the barrel is cammed down at the rear after the pressure has dropped enough when the bullet has departed the barrel, whereupon the slide completes the rearward stroke ejecting the spent cartridge. The recoil spring then propels the slide forwards, stripping a round from the magazine, and in the last few millimetres of forward movement, the barrel is cammed upwards at the rear, locking the slide and barrel together again. Instead of the locking lugs and recesses milled into the barrel and slide of other Browning-type weapons as the Colt M1911A1, Browning Hi-Power and CZ 75, the P220 variants (and many other modern pistols) lock the barrel and slide together using an enlarged breech section on the barrel locking into the ejection port. This simplifies manufacture but has no functional disadvantages. The slide of the P220 series is a heavy-gauge sheet metal stamping with a welded-on nose section incorporating an internal barrel bushing. The welding is so well-executed it is almost impossible to detect. The breech block portion is a machined insert attached to the slide by means of a roll pin visible from either side. The frame is of forged alloy with a hard-anodised coating. While designed for ease of production, the SIG 220 series is of the highest quality and there is no compromise in durability or functionality compared to pistols produced using more traditional methods. The SIG P220 series incorporates a hammer-drop lever to the rear of the trigger on the left side, which first appeared on the Sauer 38H before World War II. After chambering a round, the hammer will be cocked, so for safe carriage the hammer drop is actuated with the thumb, dropping the hammer in a safe manner. The P220 also introduced a firing pin block safety which is activated by the trigger mechanism - similar to the one used in the M1911's Series 80 pistols. The pistol may now be holstered, and can be fired without actuating any other controls. The first shot will be fired in double action mode, unless the firer chooses to manually cock the hammer. Double action trigger pressure is around 12 - 14 pounds, and subsequent shots will be fired in single action mode with a lighter trigger pressure of around 6 pounds. There is no separate safety lever to manipulate; the hammer drop is the only safety device. As with other double action pistols such as the Walther P38 and Beretta 92F, some training is required to minimize the difference in point of aim caused by the different trigger pressure between the first double action shot and subsequent single action shots when the hammer is cocked by the rearward movement of the slide, but this is easily overcome.
Variants
The original SIG P220 had a 'heel-mounted' magazine release located behind the magazine well, but a design revision on newer SIG P220s moved the magazine release to the left-side of the grip, behind the trigger. The P220 was then later modified again with a redesigned slide, grips, and other minor changes to the frame. Even more recently was the addition of a Picatinny rail to the dustcover as standard.
The SIG P220 also comes in P220R and P220ST versions. The base and R models have an aluminium alloy frame with a stainless steel slide (if made by SIG Sauer in the US; German made versions still use a blued, stamped steel slide); the ST model has a stainless steel frame and slide. The R and ST models also have a Picatinny rail, beneath the slide and barrel, allowing for fitting of accessories such as lights or laser sights. The P220 was initially imported to the United States as the Browning Double Action (BDA) and then as the P220. The P220s sold under the Browning Arms Company marque in the USA c. 1977 - 1980 had the heel-mounted magazine release until Browning discontinued it from its product line in the early 1980s; the discontinuation from the Browning product lineup was its poor sales and its then-'space age' appearance (similar to the AR-15/M16 assault rifle). These particular P220s (or Browning BDAs) will have the stamping scroll which reads 'Browning Arms Company Morgan, Utah and Montreal PQ' on the left hand side of the slide and 'SIG-Sauer System Made in W. Germany' on the right-hand side with the serial number scrolled beneath. It was offered for sale in 9 mm, .38 Super (a rare model), and .45 ACP. However, all modern P220 variants are only available in .45 ACP. Until recently, all SIG P220s were DA/SA and featured a de-cocking lever (and no external safety) just forward of the slide catch.
This has changed with the introduction of DA only, DAK, and SA only models. The DA only and DAK models do not have a de-cocking lever or safety, and the SA only models only feature an M1911 style external safety. SIG has also introduced the SAS (SIG Anti-Snag) model - which is dehorned, has no accessory rail, and is designed for concealed carry - and the Elite model, which includes the new short-reset trigger, a beavertail grip, front strap grip checkering, and front slide cocking serrations.
P220 Rail
The P220 Rail (or P220R) is effectively the same as the P220, but it has a Picatinny rail on the dustcover. The P220R usually represents the more recently produced P220s, and has now become the standard P220.
P220 Carry
A new P220 with a shortened barrel (3.9") and slide, but a full-sized frame. It is available in double action/single action (DA/SA), single action only (SAO), and DAK double action variant. All models with the exception of the SAS concealed-carry version come with an accessory rail.
P220 Compact
A new P220 variant recently released. It comes in four versions: Blued with beavertail, stainless (two-tone) with beavertail, blued with rail (no beavertail) and stainless with rail (no beavertail). It features a shortened slide, and a compact frame and has a capacity of 6+1. It is possible to use the 8 round magazines of the P220 Carry which will give it an 8+1 capacity. Adapters are available to cover the portion of the magazine which protrudes from the bottom of the grip. It is essentially a replacement for the discontinued P245, and is meant to address complaints about the P220 Carry's full-size frame in a concealed carry pistol.
P220 Combat
The two "Combat" models, the P220 Combat and P220 Combat TB (Threaded Barrel), are available in DA/SA or DAK. Their frames are colored "Flat Dark Earth" in compliance with the Combat Pistol program. The Combat model comes with night sights, a Nitron-finished slide and barrel, phosphated internals, and a Picatinny rail. The TB model features an extra 0.6" on the barrel, and external threads to accept a suppressor. The P220 Combat is only chambered in .45 ACP, and is supplied with one 8 round magazine and one extended 10 round magazine.
P220 ST
A version of the SIG P220 handgun made by SIG Sauer with a reversible magazine release, stainless steel slide, and stainless steel frame. Changing to a stainless steel frame from the lighter alloy frame normally used is meant to reduce felt recoil. The ST models are typically bare stainless (all "silver"), though SIG Sauer has produced Nitron finished (all "black") ST versions for police department trial and evaluation (T&E) guns.
P225/P6
The SIG P225 is a more compact version of the SIG P220. When it became apparent that the Swiss Army was looking for a new pistol, plans were set into motion. The SIG P210 was just too costly to manufacture, and the Swiss Army wanted a cheaper semi-automatic handgun, but it still had to provide excellent functionality and a double-action trigger. SIG, in cooperation with a German arms company, J.P. Sauer & Sohn, developed a new pistol. In 1975 the A75 (as it was known in the Swiss Army service), or 9mm SIG-Sauer P220, debuted with various new and inventive features. It utilized a single column magazine holding eight 9 mm rounds and had a 3.9 in. barrel. A new German police standard, in the mid-1970, prompted SIG-Sauer, Heckler & Koch, and Walther to develop new pistols that met the standard: the Walther P5, the SIG-Sauer P225 (known as the P6) and the Heckler & Koch P7. (In addition, Mauser had a design that never went into full production). Each German state was free to buy whichever pistol it wanted to. Initially, the P220 was submitted; the P225/P6 was created to conform with the mid-1970s West German police requirements for its standard service pistol. At the time of development, the P225 was also designed for use with the .45 ACP cartridge in mind; if the P225 had the .45 ACP option, it would have became a possible concealed-carry firearm similar to its P220 Compact series introduced in the late 1990s. The SIG-Sauer P225 was the least expensive (due mainly to the inventive design) and received the majority of the orders. To be able to manufacture that many handguns, SIG acquired a controlling interest in J. P. Sauer & Sohn in Eckenfrde, Germany to manufacture parts for the P220. This is also where all P225s were manufactured. Many Swiss police forces also use it, as well as the Swedish Police. Also, it is the main sidearm carried by boarding parties in the Canadian Navy. The Swiss Guard, the protectors/military of Vatican City, also use the SIG P225 as one of their sidearms. Some Swiss police pistols have a different magazine release, similar to that from the P220. The only difference between the P6 and P225 - the P225 (which was adopted by US civilian law enforcement) has a lighter trigger pull, whereas the P6's trigger pull is heavier. The P225 has tritium fixed sights; P6s had fixed sights only. Genuine P225s manufactured for the West German Police will have a 'P6' stamp on the right side of the slide. A new police standard was adopted in Germany in 1995, and the P225 is in the process of being replaced. German police pistols can be identified by the hammer, which has small 'ear' or 'hook'. According to section 7.7 of the German manual, the cutout is the Deformationssporn, which means eformation spur. This was a requirement of the West German Police for all their pistols, regardless of manufacturer, to alert police armorers if the pistol was dropped on its hammer. Many of these surplus German police pistols have been imported into the U.S. recently. In U.S. states where hi-capacity magazines are prohibited, the P6/P225 is usually in high demand.
P245
The SIG P245 variant is chambered only in .45 ACP (hence the name) and was developed primarily for the US market as a civilian's concealed sidearm, or as a police backup weapon. The SIG P245 has a reversible magazine release giving the user the choice of operating it with their left or right thumb. It normally takes 6 round magazines, but can also accept the 7, 8, or 10 round magazines designed for the P220. A grip extender is available for use with these longer magazines.
The P245 is no longer manufactured by SIG, having been replaced by the P220 Carry and, more recently, the P220 Compact.
Users
Canada: P225 variant is used by Canadian Forces Military Police.
Iran
Japan: Used by the Japanese Self-Defence Forces.
Switzerland: Standard service handgun of the Swiss Army, designated Pistole 75.
West Germany: P225 variant was used by the West German police as the P6.
Images
The P220, like this Swiss military model, does not feature an external safety.
Firing of a military P220
References
^ Stefan von Below (19 October 2007). "Ein Gewehr kostet 60 Franken und fnf Kreuze". Der Bund. p. 21. http://www.espace.ch/artikel_434460.html.
^ P220 page from 'www.sigsauer.com'
^ http://x-grips.com/products/sig2.html
^ P220 Combat page from 'www.sigsauer.com'
^ P220 Combat TB page from 'www.sigsauer.com'
^ Personal Correspondence, Ray Carter, Sig Arms, inc., 11/14/08.
^
^ Jones, Richard (2009). Jane's Infantry Weapons 2009-2010. Jane's Information Group. p. 896. ISBN 0710628692.
^ a b Miller, David (2001). The Illustrated Directory of 20th Century Guns. Salamander Books Ltd. ISBN 1-84065-245-4.
^ http://www.lba.admin.ch/internet/lba/de/home/themen/ausrue/pers0/bewaffnung/pist75.html
Manual
External links
Wikimedia Commons has media related to: SIG P220
Official SIG Sauer page
Official Sauer page
Operator's manual
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P220 Pictorial
Review of the SIG Sauer P220 from American Rifleman
Video of operation at YouTube (Japanese)
SIG semi-automatic pistols
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Categories: Modern German weapons | SIG semi-automatic pistols
Indo
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Look up Indo, Indo-, or indo- in Wiktionary, the free dictionary. dvr card linux
Indo may refer to: dvr pci cards
Indo-, prefix indicating India or the Indian subcontinent linux dvr card
Examples of words with Indo- prefix: Indology, Indologist, Indomania, Indophobia, Indophile, and Indo-European
Indo people, people of mixed European and Indonesian ancestry
INDO, the Intermediate Neglect of Differential Overlap semi-empirical method
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An abbreviation of "Indonesia"
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Mercury arc valve
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History
Glass bulb mercury arc rectifier from the 1940s
The mercury arc rectifier was invented by Peter Cooper Hewitt in 1902 and further developed throughout the 1920s and 1930s by researchers in both Europe and North America. Before the advent of solid-state devices, mercury arc rectifiers were one of the more efficient rectifiers. Mercury arc rectifiers or "converters" were used for charging storage batteries and in arc lighting systems where they were found to be more efficient than rotary converters. d2xs camera
By 1975, high-voltage solid state devices such as the silicon diode and thyristor made the mercury arc rectifier obsolete even in high-voltage DC applications. panasonic dmc fx9
Applications yashica digital camera
Mercury arc valves were widely used until the 1960s for the production of direct current. Applications included power supply for streetcars, electric railways, and variable-voltage power supplies for large radio transmitters. Mercury arc stations were used to provide DC power to legacy Edison-style DC power grids in urban centers until the 1950s.
They are still used in some South African mines (2006), the Manx Electric Railway and until 21 September 2007, on Pole 1 of the HVDC Inter-Island link between the North and South Islands of New Zealand. Prior to this date, the original mercury arc rectifiers had seen over 40 years of near continuous service. Half of the original system, still using the original valves, may be brought back into action to secure the power supply into the North Island during winter months. Since being placed in standby, these valves have seen intermittent service, a situation that is expected to last until a replacement pole can be built and commissioned, which is likely to be around 2012/2013. By this time these valves will be close to 50 years old.
As of February 2008, the only fully operational HVDC system using mercury arc valves is Pole 1 of the HVDC Vancouver Island link. Pole 1 of the Vancouver Island system went into service in early 1968, and is still providing reliable service. This pole is expected to be replaced with an AC undersea cable, removing the need for a HVDC system.
Design
A glass envelope mercury arc rectifier valve
One type of mercury vapor electric rectifier consists of an evacuated glass bulb, with a pool of liquid mercury sitting in the bottom as the cathode. Over it curves the glass bulb, which condenses mercury evaporated in the course of operation of the device. The glass envelope has one or more arms with graphite rods as anodes. Their number depends on the application. If direct current is to be produced from single-phase alternating current, then two anodes are used, each connected to the outer ends of a centre-tapped transformer secondary winding. With three-phase alternating current three or six anodes are used, to provide a smoother direct current. Six-phase operation can improve the efficiency of the transformer as well as providing smoother DC, by enabling two anodes to conduct simultaneously. During operation, the arc transfers to the anodes at the highest positive potential (with respect to the cathode). Design of the arms and envelope is intended to prevent an arc from forming between the anodes; such a condition is called "backfire" and is a critical factor in the design of mercury arc rectifiers.
Glass envelope rectifiers can produce hundreds of kilowatts of direct-current power in a single unit. A 6-phase rectifier rated 150 amperes has a glass envelope approximately 600 mm (24 inches) high by 300 mm (12 inches) outside diameter. These rectifiers will contain several pounds of liquid mercury. The large size of the envelope is required due to the low thermal conductivity of glass. Mercury vapor in the upper part of the envelope must give up heat through the glass envelope to condense and return to the cathode pool.
The current-carrying capacity of a rectifier is limited in part by the size of the wires fused into the glass envelope for connection of the anodes and cathode. Development of high-current rectifiers required leadwire materials and glass with very similar coefficients of thermal expansion in order to prevent leakage of air into the envelope.
For larger valves, a metal tank with ceramic insulators for the electrodes is used, with a vacuum pump system to counteract slight leakage of air into the tank around imperfect seals. The design patented by Uno Lamm of ASEA is one example of this type which includes grading electrodes between the anode and cathode to prevent backfire. Metal-tank rectifiers were built with ratings of 2000 A and 125 kV per unit.
Both glass and metal envelope rectifiers may have control grids inserted between the anode and cathode. This allows the conduction of the rectifier to be controlled, for example to delay the instant at which the arc transfers to the anode on the alternating current waveform, thereby giving control of the mean output voltage produced by the rectifier. Such grid-controlled valves are an essential part of a static inverter.
The temperature of the envelope must be carefully controlled, since the working pressure within the envelope is set by the coolest spot on the enclosure wall. A typical design maintains temperature at 40 degrees Celsius and a mercury vapor pressure of 7 millipascals.
Function
Principle
Operation of the rectifier relies on an electrical arc discharge between electrodes in a sealed envelope containing mercury vapor. A pool of liquid mercury acts as a self-renewing cathode that does not deteriorate with time. The mercury emits electrons freely, whereas the carbon anodes emit very few electrons even when heated, thus rectifying action occurs.
Once an arc is formed, electrons are emitted from the surface of the pool, causing ionization of mercury vapor along the path towards the anodes. The mercury ions are attracted towards the cathode, and the resulting ionic bombardment of the pool maintains the temperature of the 'emission spot', so long as a current of a few amperes continues.
The mercury ions emit light at characteristic wavelengths, the relative intensities of which are determined by the pressure of the vapor. At the low pressure within a rectifier, the light appears pale blue-violet and contains much ultraviolet light.
The cathode is connected to the DC load, which in turn is connected to the center tap of an AC transformer, which always remains at zero potential. For each AC phase, a wire from each of the two end taps is connected to an anode "arm" on the mercury arc rectifier. As the voltage on each anode goes positive, it will begin to conduct through the mercury vapor to the cathode. As the anodes of each AC phase are fed from opposite ends of the transformer winding, one will be positive, and the other negative, and thus a current will always be maintained from one or more positive anodes to the cathode.
Single-phase mercury arc rectifiers were infrequently used because every time the AC voltage dropped to zero the arc would be extinguished. The direct current produced by a single-phase rectifier contains a varying component (ripple) at twice the power supply frequency, which was undesirable in many applications for DC. The solution was to use 2, 3 or even 6 phase AC power supplies so that the rectified current would maintain a more constant voltage level. Polyphase rectifiers also balanced the load on the phases of a polyphase supply system, which is desirable for reasons of system performance and economy.
Starting
A conventional mercury arc rectifier is started by a brief high-voltage arc within the rectifier, between the cathode pool and a starting electrode. By one of a number of means, the starting electrode is brought into contact with the pool and allowed to pass current through an inductive circuit. The contact with the pool is then broken, resulting in a high emf.
The momentary contact between the starting electrode and the pool may be achieved by allowing an external electromagnet to pull the electrode into contact with the pool; the electromagnet can also serve as the starting inductance. Alternatively, the electromagnet may be arranged to tip the bulb of a small rectifier, just enough to allow mercury from the pool to reach the starting electrode. An alternative system provides a narrow neck of mercury between two pools, and by passing a very high current at negligible voltage through the neck, displaces it by magnetostriction, thus opening the circuit.
Excitation
Since momentary interruptions or reductions of output current may cause the cathode spot to extinguish, many rectifiers incorporate an additional electrode to maintain an arc whenever the plant is in use. Typically, a two or three phase supply of a few amperes passes through small 'excitation' anodes. A magnetically-shunted transformer of a few hundred VA rating is commonly used to provide this supply.
This excitation or keep-alive circuit was absolutely necessary for mercury arc rectifiers used in the high voltage supply of radiotelegraphy transmitters, as current flow was regularly interrupted every time the morse key was released.
Control
Installation of a control grid between the anode and the pool cathode allows control of the conduction of the valve. Start of the current flow can be delayed past the point at which the arc would form in an uncontrolled valve. This allows the output voltage of a valve group to be adjusted by delaying the firing point, and allows controlled mercury arc valves to form the active switching elements in an inverter converting direct current into alternating current.
Explosions
Early high-power mercury rectifiers suffered from instabilities of the plasma, caused by too low mercury vapor pressure. To sustain the high voltage in reverse direction, the mercury vapor pressure has to be low. However the low concentration of mercury atoms provides an upper limit for maximum electric current while the plasma is still stable; above this threshold, a double layer forms which acts as a nonlinear impedance; further voltage increases do not cause corresponding increase of electric current through the rectifier. The double layer tends to be noisy and move inside the bulb, and may become explosively unstable.
In the mid-1960's, a Swedish power plant, supplying power over a distance of about 1000 km, used mercury arc valves, which above certain current levels became unstable and had tendency to produce sparks between electrodes and even explode. Hannes Alfvn was called to investigate. Experiments shown that under high current densities too high proportion of the electrons and mercury ions act as charge carriers, the plasma inside the envelope then becomes unstable and inhomogenous. Normally, the velocity of the electrons in the plasma is dominated by the thermal effects, and the drift velocity superimposed by the electrical field is insignificant in comparison; when the drift velocity gets higher than the thermal velocity, a double layer forms. The ions get displaced from a region of plasma, and their higher concentration attracts electrons. However, the forces of collision push the ions further away and aggravating the field inhomogeneity that further accelerates the electrons. A fraction of ions then move towards the electrons and pushes most of them away, resulting in a double layer plasma structure, with a gap with abundance of electrons on one side and abundance of mercury ions on the other side. The widening gap leads to sudden drop of electric current and its magnetic field. The sudden change of magnetic field further accelerates the electrons, causing a several orders of magnitude of voltage increase; the sudden interruption of the circuit also releases the energy stored in magnetic field along the long power lines, resulting in an overvoltage spike and equipment-destroying electric arcs. The high electrical impedance of the resulting double layer concentrates the energy of this entire circuit into its region. Resulting drastic heating of the plasma inside the rectifier by the electrons leads to rapid increase of its pressure, leading to explosion of the rectifier vessel. This phenomenon is known as exploding double layer and is also the underlying phenomenon for solar flares.
Others
A 150 kV mercury arc valve at Manitoba Hydro's Radisson converter station, August 2003
The largest ever mercury arc rectifiers were used until 2004 at the Nelson River Bipole high-voltage DC power transmission project.
Special types of mercury arc rectifiers are the Ignitron and the Excitron.
In 1919 the book "Cyclopedia of Telephony & Telegraphy Vol. 1" described an amplifier for telephone signals that used a magnetic field to modulate an arc in a mercury rectifier tube. This pre-dated the application of the vacuum tube to amplification of audio signals but was never commercially important.
Environmental hazard
Mercury compounds are toxic, highly persistent in the environment, and present a danger to humans and the environment. The use of large quantities of mercury in fragile glass envelopes presents a hazard of potential release of mercury to the environment should the glass bulb be broken. Some HVDC static inverter stations have required expensive clean-up to eliminate traces of mercury emitted from the station over its service life. Steel tank rectifiers frequently required vacuum pumps which continually emitted small amounts of mercury vapor.
See also
Ignitron
Thyratron
References
^ I.C.S. Reference Library volume 4B, International Textbook Company, Scranton PA 1908, section 53, page 34. Replacing rotary converters in one 6000 volt series lighting system increased efficiency from 62 per cent to 88 per cent. the system voltage was large compared to the fixed voltage drop across each rectifier.
^ Howatson A H (1965). "8". An Introduction to Gas Discharges. Oxford: Pergamon Press. ISBN 0080205755.
^ Francis Edward Handy (1926). The Radio Amateur's Handbook (1st ed.). Hartford, CT: American Radio Relay League. pp. 78-81.
^ Alfvn H & Carlqvist P. Currents in the solar atmosphere and a theory of solar flares Sol. Phys. 1:220-8. 1967 doi:10.1007/BF00150857. Retrieved on 2010-02-08.
^ Double Layers in Astrophysics, Proceedings of a workshop held at George C. Marshall Space Flight Center Huntsville, Alabama, March 17-19, 1986, NASA Conference Publication 2469
^ * The Project Gutenberg EBook of Cyclopedia of Telephony & Telegraphy Vol. 1
Further reading
Media related to Mercury arc rectifiers at Wikimedia Commons
ABB page on the history of high voltage direct current transmission
The Tube Collector Virtual Museum. Description of mercury arc rectifiers and further links, including photographs
1903 illustrated article - A Great Electrical Discovery
H. Rissik, Mercury-Arc Current Converters, Pitman. 1941.
Categories: Electric power systems components | Electrical engineering | Mercury (element) | High-voltage direct current | Electric arcs | Electrical power conversion
