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''''Carrier current''' is a method of [[low-power broadcasting|low power]] [[Amplitude modulation|AM]] radio transmission that uses AC electrical wiring to propagate a [[medium frequency]] AM signal to a relatively small area, such as a building or a group of buildings. In the [[United States]], carrier current stations do not require a [[broadcasting]] license from the [[Federal Communications Commission|FCC]], as long as the emissions adhere to the [[Part 15]] Rules for unlicensed transmissions.{{Citation needed|date=August 2013}} ==Predecessor== {{main article|Muzak (brand)}} In the 1920s, '''Wired Radio''''s subscription music service was delivered over electrical power lines, and billed for on the customer's electric bill. As [[AM broadcasting]] improved and grew, its business model, in which content is supported by advertising rather than subscriber fees, destroyed the home market for this service. In 1934, its owner created the Muzak company, focused on the business market. ==Application== Carrier current broadcasting has been used by many types of facilities that need to transmit radio to a small area. Carrier current is most often associated with [[college radio]] and [[high school radio]], but was formerly used for [[hospital radio]] stations and at [[military bases]], sports [[stadiums]], convention halls, mental and penal institutions, [[trailer park]]s, [[summer camp]]s, office buildings, and [[Drive-in theater|drive-in movie theaters]]. Many college stations that went on to obtain broadcasting licenses started out as carrier current stations because of the low cost and relative ease of starting up such a [[radio station]]. Carrier current stations generally operate with very low power. Though a typical carrier current transmitter's output might be 5 to 30 [[watt]]s, using AC wiring as an antenna is very inefficient and can result in an [[effective radiated power]] of less than one watt. The usable range of the signal is usually less than 200 feet (60 meters) from the wire. These signals cannot pass through utility [[transformer]]s, and are prone to [[electromagnetic interference]] from the [[alternating current]]. Transmitters that use carrier current are very simple, making them an effective option for students interested in radio. Transmissions can be of good quality, although there is a low frequency background [[Mains hum|hum]] (60 [[hertz]] in [[North America]]n installations) associated with carrier current, due to the alternating current. Not all listeners notice this hum, nor is it reproduced well by all receivers. ==European broadcasters== {{refimprove|section|date=December 2011}} In Germany, carrier current transmission was called ''Drahtfunk''. In Switzerland, ''Telefonrundspruch'' used telephone lines. In the [[Soviet Union]], PLC was very common for broadcasting since the 1930s because of its low cost and accessibility, and because it made reception of uncensored over-the-air transmissions more difficult. In Norway the radiation of [[Power line communication|PLC]] systems from powerlines was sometimes used for radio supply. These facilities were called ''[[Linjesender]]''. In Britain such systems were for a time used in areas where reception from conventional BBC transmitters was poor. In all cases the radio programme was fed by special transformers into the lines. To prevent uncontrolled propagation, filters for the carrier frequencies of the PLC systems were installed in substations and at line branches. An example of the programs formerly carried by "wire broadcasting" in Switzerland: * 175&nbsp;kHz [[Swiss Radio International]] * 208&nbsp;kHz RSR1 "la première" (French) * 241&nbsp;kHz "classical music" * 274&nbsp;kHz [[Radiotelevisione svizzera di lingua italiana|RSI]]1 "rete UNO" (Italian) * 307&nbsp;kHz [[DRS 1]] (German) * 340&nbsp;kHz "easy music" Systems using telephone wires were incompatible with [[ISDN]] use which required the same bandwidth for digital data. The Swiss and German systems have been discontinued, but in Italy Filodiffusione still has several hundred thousand subscribers. ==Community radio== There are many examples of [[community radio]] stations being operated in the United States using carrier current AM broadcasting. Signals ''may'' pass a transformer if the utility company has bypass lines installed (typically when non-conflicting carrier current-based data systems of their own are in operation). Signals may also be impressed onto the neutral leg of the [[three-phase electric power]] system, a practice known as "neutral loading", in an effort both to reduce (sometimes eliminate) 60&nbsp;Hz hum, and to extend effective transmission line distance. It has been successful in both ways in community and campus installations. Extensive systems can include multiple unit installations with [[linear amplifier]]s and splitters to increase the coupling points to a large electrical grid (whether a campus, a high-rise apartment or a community). These systems would typically require coaxial cable interconnection from a transmitter to the linear amplifiers. In the 1990s, [[LPB, Inc.]], possibly the largest manufacturer of these transmission systems, designed and supplied several extensive campus-based systems that included fiber-optic links between linear amplifiers to prevent heterodyne interference. ==Student-run carrier current or cable cast stations== {{Expand list|date=August 2008}} As with most other student-run stations, these stations often operate on sporadic schedules. Most of these stations are also supplemented by other broadcasting methods, such as [[LPFM]], [[closed-circuit radio|closed circuit]], and [[streaming audio]]. Many carrier current stations have been, and continue to be, replaced by these technologies as well. Though legal, these stations are not licensed by the [[Federal Communications Commission|FCC]] and their [[call sign|call letters]] are entirely self-styled. ===Existing stations=== *Bulls Radio 1620 - [[University of South Florida]], also heard on licensed [[WMNF]]-[[HD Radio|HD2]]<ref>[http://bullsradio.org/ Bulls Radio - Florida's No. 1 College Radio Station! | The University of South Florida's student radio station | Tampa's college station | 88.5 HD 2 | 1620 AM | Bullsradio.org<!-- Bot generated title -->]</ref> *KAMP-1570 at the [[University of Arizona]]<ref>[http://kamp.arizona.edu/ kamp.arizona.edu<!-- Bot generated title -->]</ref> *KANM-1580 at [[Texas A&M University]]<ref>[http://kanm.tamu.edu/ KANM Student Radio - The college station of College Station - 1580 AM - Campus Cable Channel 88<!-- Bot generated title -->]</ref> *KASR-1330 [[Arizona State University]]<ref>http://www.theblaze1260.com/</ref> *KDUP-1580 at University of Portland, (Portland, Oregon) http://kdup.up.edu/ *KCIZ 1650 at Mora High School, [[Mora, Minnesota]]<ref>[http://www.morarocks.com/ Tech Deck Skateboarding<!-- Bot generated title -->]</ref> *KJACK 1680 - [[Northern Arizona University]]<ref>[http://www.kjack.org/ KJACK 1680 AM · Flagstaff, AZ · Northern Arizona University's Student Run Radio<!-- Bot generated title -->]</ref> *KLBC-1610 at [[Long Beach City College]]<ref>[http://www.klbc.org/ KLBC 1610AM - "Truly Underground Radio"<!-- Bot generated title -->]</ref> *[[KMSC (AM)|KMSC-1500]] at [[Minnesota State University Moorhead]] *[[KRFH]] at [[Humboldt State University]] *[[KRIO 1660]] at [[Rio Linda High School]] *K-ROCKS RadioOne AM Stereo 1670 and AM Stereo 710 in Casper Wyoming <ref> http://krocksradioone.com/ </ref> *[[KSSU (AM)|KSSU]] 1580 AM at [[California State University, Sacramento]] *KUR-1670/88.3 at [[Kutztown University]]<ref>[http://www.kutztown.edu/divisions/studentservices/departments/radioservices/ Kutztown University Radio Services<!-- Bot generated title -->]</ref> *KUTE-1620 [[University of Utah]]<ref>[http://www.kute.utah.edu/ We Have Moved<!-- Bot generated title -->]</ref> *Radio SNHU 1620 at [[Southern New Hampshire University]]<ref>[http://radio.snhu.edu/ RadioSNHU<!-- Bot generated title -->]</ref> *WALT-1610 at [[Davidson College]]<ref>http://listentowalt.com/</ref> *[[WERW (student radio)|WERW 1570 AM]] at [[Syracuse University]] *[[WEXP (La Salle University)|WEXP]] at [[La Salle University]] *WGCC 650 AM at [[Genesee Community College]] *[[The WIRE]] - 1710 AM at the [[University of Oklahoma]] *WMAX 540 at [[Mount Washington College]] in [[Manchester, New Hampshire]] *WNEC 91.7 FM at [[New England College]] in [[Henniker, New Hampshire]]<ref> {{cite web |title=WNEC official Website |url=http://www.nec.edu/necradio}}</ref> *Wolfpack Radio-1700 at the [[University of Nevada, Reno|University of Nevada]]<ref>[http://www.wpr.wolfpackradio.org/ 1700 am | wolfpackradio.org<!-- Bot generated title -->]</ref> *WPPJ-670 [[Point Park College]]<ref>[http://www.pointpark.edu/Academics/Schools/SchoolofCommunication/StudentMedia/WPPJ WPPJ | Point Park University<!-- Bot generated title -->]</ref> *WPMD-1700 at [[Cerritos College]]<ref>[http://www.wpmd.org/ WPMD on the Internet<!-- Bot generated title -->]</ref> *WSIN-1590 at [[Southern Connecticut State University]]<ref>[http://radio.southernct.edu/ WSIN Radio : 1590 AM<!-- Bot generated title -->]</ref> *WSLU-1620/100.1] at [[Saint Leo University]], [[St. Leo, Florida]]<ref>[http://wsluradio.webs.com/ Home<!-- Bot generated title -->]</ref> *KSUB at [[Seattle University]] in conjunction with 8&nbsp;mW [[low-power broadcasting]] and [[Internet radio]]<ref>{{citation|url=http://www.seattleu.edu/ksub/default.aspx?id=42100|title=KSUB Seattle history|publisher=Seattle University|accessdate=2010-02-26}}</ref> *[[WTBU (college radio)|WTBU]] 640 AM/89.3 FM at [[Boston University]] *Radio Laurier Macdonald 560 AM at [[Laurier Macdonald High School]] in [[St. Leonard, Quebec|St. Leonard, Montreal, Quebec]], Canada ===Former stations=== *[[Brown Student Radio]] at [[Brown University]] in [[Providence, Rhode Island]], on A.M. 600. *[[CHRW-FM]] at the [[University of Western Ontario]] started as a carrier current station at 610&nbsp;kHz *K.C. AM at [[Colby College]], now [[WMHB]] *KARL-AM at [[Carleton College]], now [[KRLX]] *KAL at [[University of California, Berkeley]] - now [[KALX]] *KCC at [[Chabot College]], [[Hayward, California]] - now [[KCRH]] 89.9 *[[KCWS-AM]] at [[Central Washington State College]] - now [[KCWU-FM]] *[[KDVS|KDVS, originally KCD]] at [[University of California, Davis]] *KFRH at [[Washington University in St. Louis]] - now [[KWUR]]-FM *[[KSLU_(Saint Louis University)|KLSU]] at [[Saint Louis University]] in Saint Louis, Missouri - originally KBIL, now online *KMPS-AM at [[University of Alaska Fairbanks]] - now [[KSUA]]-FM *KNAB at [[Chapman University]], [[Orange, California]] - ceased carrier current in 1991, now internet-only station ChapmanRadio.com *KOWL at [[Rice University]] - now [[Rice Radio]] *KRLK 97.5 at [[Rio Linda High School]], California - now [[KRIO 1660]] *KSU at [[Stanford University]]&nbsp;– now [[KZSU]]-FM *[[KSWC (defunct)|KSWC]] at [[Southwestern College (Kansas)|Southwestern College]] in [[Winfield, Kansas]] - now at 100.3 FM *KUOK at the [[University of Kansas]] - now [[KJHK]] *WBMB at [[Baruch College]], [[CUNY]]; started as a carrier current station at 590AM *[[WBUQ|WBSC]] on 640 AM at Bloomsburg State College (now [[Bloomsburg University]]) in [[Bloomsburg, Pennsylvania]], but has merged with 91.1 FM [[WBUQ]] after that station signed on in 1985. For several years, both stations operated independent of one another prior to the merger. *WCAR 550 AM at the [[University of North Carolina at Chapel Hill]] - now [[WXYC]]-FM 89.3 *WCHP 650 AM at Central Michigan University at Mount Pleasant Michigan *[[WCUR]] as WSCS 640 AM, and WCUR 680 AM at [[West Chester University]] in [[West Chester, Pennsylvania]], but has since migrated to 91.7 FM, as well as online at wcur.org *WDBS 560 AM at [[Duke University]] - now [[WXDU-FM]] 88.7 *WDGN AM 600 at Downers Grove North High School, became [[WDGC-FM]], Downers Grove, Illinois *WERU 710 AM/104.7 FM at [[Embry–Riddle Aeronautical University]] - now [[WIKD-LP]] 102.5 *WFAL 1610 AM at [[Bowling Green State University]] *[[WFVS-LP]] 530 AM and recently LPFM at 100.5 at [[Fort Valley State University]] in [[Fort Valley, Georgia]] (fiber-optic linked carrier current system) *WHAT 530 AM at [[Johns Hopkins University]], later WHSR and now [[WJHU]] *WHEN 640 AM at the [[University of Delaware]] *WHEN 570 AM "The Rock of Macomb" at [[Western Illinois University]] *WHRM 580 and 620 AM at [[Hiram College]] *[[WJHU]] at Johns Hopkins University, Baltimore, Maryland. *WJJX 640AM at the [[University of Michigan]] from 1952 to mid-1990's, predecessor to (and previously using the call letters) [[WCBN]] now on FM 88.3<ref name='WCBN1'> {{cite web | url = http://arborwiki.org/city/Category:WCBN#History | title = Category:WCBN - Ann Arbor - ArborWiki: | accessdate = 2011-09-27 | date = 2011-01-07}}</ref> <ref name='WCBN2'> {{cite web | url = http://www.wcbn.org/history/history-1.html | title = CBN History Part I: Residence Hall Studios: | accessdate = 2011-09-27}}</ref> *[[WJPZ]] at [[Syracuse University]], now 89.1 FM *WKC at [[Knox College (Illinois)|Knox College]], [[Galesburg, Illinois]] - now [[WVKC]]-FM *[[WKCO]] at [[Kenyon College]], Gambier, OH - now [[WKCO-FM]] *[[WKDU| WKDU-FM 91.7]], the student-run radio station of [[Drexel University]] formally WMAX (1958)<ref>http://www.wkdu.org/node/5</ref> *WKDT 89.3 FM, the cadet radio station, [[United States Military Academy]], [[West Point, New York]] * [http://johnbrashear.tripod.com/wlcr.html WLCR-AM 640] (originally WCDW-AM 830) operated by Summer campers at Camp Shaw-Mi-Del-Eca in Lewisburg, West Virginia. *WLKR AM [[Lake Superior State University]], [[Sault Ste. Marie, Michigan]] - Now [[WLSO]] 90.1 FM "The Sounds of Lake State" *[[WMTU-FM]] at [[Michigan Technological University]]; started as a carrier-current AM station *[[WMUC-FM]] at the [[University of Maryland, College Park]]; started in 1937 on 650 AM<ref>[http://web.archive.org/web/20021009230234/www.wmuc.umd.edu/tech/index.html WMUC - The University of Maryland, College Park<!-- Bot generated title -->]</ref> *WNYU on 800 AM in [[New York University]]'s dorms at its [[Lower Manhattan]] campus *WOCR-650, a "pirate" carrier current station in [[Ocean City, Maryland]], in 1973 *WOLF at [[North Carolina State University]] in [[Raleigh, North Carolina]] - now [[WKNC]] *WPSM at Penn State's McKeesport campus (now [[Penn State Greater Allegheny]]) - now an internet station WMKP<ref>[http://www.clubs.psu.edu/mk/wmkp/ WMKP Radio - The Voice of Penn State Greater Allegheny<!-- Bot generated title -->]</ref> *[[WIUX-LP|WQAD/WFQR/WIN/WIUS]] at [[Indiana University Bloomington|Indiana University]] - now [[WIUX]]-LP *[[WHRW|WRAF]] on 590 AM at [[Binghamton University]] - now [[WHRW]] *WRCC-AM at 640 AM at Rockland Community College *WRCR-AM [[Rockford College]]<ref>{{citation|url=http://www.wrcr.radiohistory.net/|title=WRCR alumni site}}</ref> *[[WRCT]] on 900 AM at [[Carnegie Mellon University]] - now WRCT-FM *[[WRIU]] Studio B, now only online, at the [[University of Rhode Island]] and licensed to [[Kingston, Rhode Island]], on A.M. 580. *WRPS-730 AM at SUNY Potsdam (NY), now WAIH 90.3 *[[WVPH|WRLC-AM]] on 1110 and 1150 AM at [[Rutgers University]], now WVPH-FM *WRUR-AM 1090 at the [[University of Rochester]] in [[Rochester, New York]] - now WRUR-FM; see also [[campus radio]] * WSAC 710 AM at [[St. Anselm College]], [[Goffstown, New Hampshire]] *[[WSGR]] (South Green Radio) at [[Ohio University]] in [[Athens, Ohio]] *WSOE on 1200 AM at the [[Milwaukee School of Engineering]] in [[Milwaukee]], [[Wisconsin]] - now [[WMSE]] on 91.7 FM *WTGR 530 AM (1969) at [[Memphis State University]] in [[Memphis]], [[Tennessee]], now the [[University of Memphis]] - now [[WUMR]] on 91.7 FM *WUFI-540AM at [[Florida International University]], now WRGP 88.1 & 95.3 FM<ref>[http://www.wrgp.org/ FIU Student Media<!-- Bot generated title -->]</ref> *[[WUVA]] 640 AM at the [[University of Virginia]] in [[Charlottesville]] from 1947 until 1979, when it was licensed to 92.7&nbsp;MHz FM *WUVT 640 AM at [[Virginia Tech]] *WVAT (Voice of Alfred Tech) at [[Alfred State College|SUNY, Alfred, New York]] - started broadcasting January 1965, now WETD-FM *[[WVAU]] on 610 AM at [[American University]], Washington, D.C. (station is still present, but they no longer broadcast carrier current) *[[WVBU]] on 640 AM at [[Bucknell University]] later licensed to 90.5&nbsp;MHz FM, carrier current turned off several years later *[[WVOF]] on 620 AM at [[Fairfield University]], Connecticut * WVYC 640 AM at [[York College of Pennsylvania]], sister station to FCC-licensed WVYC FM 99.7, also on the Internet *[[WXOU]] 88.3 FM at [[Oakland University]] in [[Rochester Hills, Michigan]] (licensed to [[Auburn Hills, Michigan]]) *[[WXPN]] and [[WQHS Radio|WQHS-730]] at the [[University of Pennsylvania]] *[[WYBC (AM)|WYBC]]/640 at [[Yale University]]<ref>[https://www.youtube.com/watch?v=gtliYu2lDQU "This is College Radio" film about WYBC taken circa November 17, 1956.]</ref> ==See also== *[[Power line communication]] *[[Leaky feeder]] ==References== {{Reflist}} ==External links== *[http://utopianetwork.home.comcast.net/carrier/cct.pdf Carrier Current Broadcasting Theory by LPB] {{DEFAULTSORT:Carrier Current}} [[Category:Broadcast engineering]] [[Category:Radio technology]] [[de:Drahtfunk]]'