Carrier current

 ( Broadcast Engineering ) 

In Germany, the carrier current service was called Drahtfunk, and in Switzerland Telefonrundspruch. In the Soviet Union, this approach was very common beginning in the 1930s because of its low cost and accessibility, and because it made reception of uncensored over-the-air transmissions more difficult. In Norway radiation from power lines was used, provided by the Linjesender facility. In Britain such systems were used for a time in areas where reception from conventional BBC radio transmitters was poor.

In these systems programs were fed by special transformers into the lines. To prevent uncontrolled propagation, filters for the service's carrier frequencies were installed in substations and at line branches. Systems using telephone wires were incompatible with ISDN which required the same bandwidth to transmit digital data. Although the Swiss and German systems have been discontinued, the Italian Filodiffusione still has several hundred thousand subscribers.

Programs formerly carried by "wire broadcasting" in Switzerland included:

• 175 kHz Swissinfo
• 208 kHz RSR1 "la première" (French)
• 241 kHz "classical music"
• 274 kHz RSI1 "rete UNO" (Italian)
• 307 kHz DRS 1 (German)
• 340 kHz "easy music"

Carrier current broadcasting began in 1936, when students at Brown University in Providence, Rhode Island developed a carrier current station initially called WBRU. This station was founded by George Abraham "Dr. George Abraham, Ph.D" (collegebroadcasters.us) and David W. Borst, "David W. Borst" (collegebroadcasters.us) who had originally installed an intercom system between their dormitory rooms. The intercom links were first expanded to additional locations, and then the system was replaced by distributed low-powered radio transmitters, which fed their signals into various buildings' electrical wires, allowing nearby radio receivers to receive the transmissions. The Gas Pipe Networks: A History of College Radio 1936-1946 by Louis M. Bloch, Jr., 1980, pages 11-13.

The carrier current station idea soon spread to other college campuses, especially in the northeastern United States. The Intercollegiate Broadcasting System (IBS) was formed in February 1940, to coordinate activities between twelve college carrier current stations and to solicit advertisers interested in sponsoring programs geared toward their student audiences.Bloch (1980) pages 102-103. The innovation received a major publicity boost by a complimentary article that appeared in the May 24, 1941 issue of The Saturday Evening Post, "Radiator-Pipe Broadcasters" by Erik Barnouw, The Saturday Evening Post, May 24, 1941, pages 36, 79-80. and eventually hundreds of college stations were established. Responding to the growing phenomenon, a 1941 release issued by the U.S. Federal Communications Commission (FCC) stated that because of the stations' very limited ranges, it had "not promulgated any rule governing their operation."Bloch (1980) page 45. Therefore, to operate legally, U.S. carrier current station broadcast emissions must adhere to the FCC's Title 47 CFR Part 15 Rules for unlicensed transmissions. "Low Power Radio" (FCC.gov)

In the United States, unlike educational FM stations, carrier current stations can carry a full range of advertising. Due to their low power, these stations do not require an FCC license, and are not assigned an official call sign. However, in keeping with standard radio industry practice, they commonly adopt their own call sign-like identifiers.

• Bulls Radio () at the University of South Florida in Tampa, Florida; also heard on licensed WMNF
• KAMP () at the University of Arizona in Tucson, Arizona
• KANM () at Texas A&M University in College Station, Texas
• KASR () at Arizona State University in Tempe, Arizona
• KDUP () at the University of Portland in Portland, Oregon
• KJACK () at Northern Arizona University in Flagstaff, Arizonahttp://www.kjack.org/ http://www.kjackradio.com/
• KLBC () at Long Beach City College in Long Beach, California
• KMSC "Dragon Radio" () at Minnesota State University Moorhead in Moorhead, Minnesota KMSC Dragon Radio: About.
• KRFH-LP at Humboldt State University in Arcata, California
• "K-ROCKS RadioOne" ( / ) in Casper, Wyoming
• KSSU () at California State University, Sacramento in Sacramento, California
• KUR ( / ) at Kutztown University of Pennsylvania in Kutztown, Pennsylvania
• http://kuteradio.org/
• Radio Laurier Macdonald () at Laurier Macdonald High School in Saint-Leonard, Montreal, Quebec, Canada
• Radio SNHU () at Southern New Hampshire University
• Studio U () at the University of Oklahoma in Norman, Oklahoma
• UMSLRadio "The U" () at the University of Missouri–St. Louis in University City, Missouri
• WALT () at Davidson College in Davidson, North Carolina
• WERW () at Syracuse University in Syracuse, New York
• WGCC () at Genesee Community College in Batavia, New York
• Wolfpack Radio () at the University of Nevada in Reno, Nevada
• WPPJ () at Point Park University in Pittsburgh
• WPMD () at /ref>
• WQMC () at Queens College, City University of New York in Kew Gardens Hills, Queens
• WSIN () at Southern Connecticut State University in New Haven, Connecticut
• WSLU ( / ) at Saint Leo University in St. Leo, Florida
• WTBU ( / ) at Boston University in Boston

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• "Brown Student Radio" at Brown University in Providence, Rhode Island — now WBRU
• CBR/WVBR at Cornell University in Ithaca, New York — now WVBR-FM
• KAL at the University of California—Berkeley in Berkeley, California — now KALX
• KARL-AM at Carleton College in Northfield, Minnesota — now KRLX
• KASR at Arizona State University in Tempe, Arizona — now internet-only "Blaze Radio"
• "K.C. AM" at Colby College in Waterville, Maine — now WMHB
• KCAT at Central Washington State College in Ellensburg, Washington — now KCWU
• KCC at Chabot College in Hayward, California — now KCRH
• KCCS at the University of Missouri in Columbia, Missouri — supplanted by KCOU
• KCD at the University of California—Davis in Davis, California — now KDVS
• KCIZ at Mora High School in Mora, Minnesota
• KDSC/KDSU at North Dakota State University in Fargo, North Dakota — now KDSU
• KFRH at Washington University in St. Louis in St. Louis, Missouri — now KWUR
• KHSC at Humboldt State College in Arcata, California — now KHSU
• KMPS-AM at University of Alaska Fairbanks in Fairbanks, Alaska — now KSUA
• KNAB at Chapman University in Orange, California — now internet-only "ChapmanRadio.com"
• KNMA at New Mexico State University in Las Cruces, New Mexico
• KOWL at Rice University in Houston — later KHVU, now KTRU-LP
• KPCR-AM at Pomona College in Claremont, California – replaced by KSPC
• KRLK at Rio Linda High School in Rio Linda, California — now KRIO
• KRS at the Manhattan Project at Los Alamos, New Mexico — later KRSN
• KBIL/KSLU at Saint Louis University in St. Louis, Missouri — now internet-only "KSLU"
• KSU at Stanford University in Stanford, California – now KZSU
• KSUB at Seattle University in http://www.seattleu.edu/ksub/default.aspx?id=42100
• KSWC at Southwestern College in Winfield, Kansas — now KSWC-LP
• KUCB at University of Colorado Boulder in Boulder, Colorado — now KVCU
• MD2/KTTC at Texas Tech College in Lubbock, Texas — now KTXT-FM
• KUOK at University of Kansas in Lawrence, Kansas — now KJHK
• KVUC at Union College in Lincoln, Nebraska — now KUCV
• "Radio Western" at the University of Western Ontario in London, Ontario, Canada — now CHRW-FM
• WAMU at American University in Washington, D.C. — now WAMU
• WBAU at Adelphi University in Garden City, New York — became now-defunct station WBAU
• WBMB at Baruch College/City University of New York in New York City
• WBSC at Bloomsburg State College in Bloomsburg, Pennsylvania — now WHSK
• WCAR at University of North Carolina at Chapel Hill — now WXYC
• WCCT/WNTC at Clarkson College of Technology/SUNY Potsdam in Potsdam, New York — now WTSC-FM
• WCHP and WINO/WRFX at Central Michigan University in Mount Pleasant, Michigan
• WCXQ in Isabela, Puerto Rico — now WCXQ-LP
• WDBS at Duke University in Durham, North Carolina — now WXDU
• WDCR/WESB at the University of Dayton in Dayton, Ohio — now WUDR
• WDGN at Downers Grove North High School in Downers Grove, Illinois — now WDGC-FM
• WERC at The University of Toledo in Toledo, Ohio — now WXUT
• WERU at Embry–Riddle Aeronautical University in Daytona Beach, Florida — now WIKD-LP
• WEXP at La Salle University in Philadelphia — now internet-only
• WFAL at Bowling Green State University in Bowling Green, Ohio — now WFAL Falcon Radio
• WFIB at the University of Cincinnati in Cincinnati
• WFRS at Ferris State College in Big Rapids, Michigan
• WFVS at Fort Valley State University in Fort Valley, Georgia — later WFVS-LP, now WFVS-FM
• WGBC at State University of New York at Geneseo in Geneseo, New York
• WHAT at Johns Hopkins University in Baltimore — later WHSR, now WJHU
• WHEN/WDRB at the University of Delaware in Newark, Delaware — now WVUD
• WHEN at Western Illinois University in Macomb, Illinois — now WIUS
• WHRM at Hiram College in Hiram, Ohio — now internet-only "The Bark"
• WHUS at University of Connecticut in Storrs, Connecticut — now WHUS
• WJHU at Johns Hopkins University in Baltimore — now WJHU
• WJJC at the John Jay College of Criminal Justice/City University of New York in New York City
• WCBN/WJJX at the University of Michigan in Ann Arbor, Michigan — now WCBN-FM
• WJPZ at Syracuse University in Syracuse, New York — now WJPZ-FM
• WJRH at Lafayette College in Easton, Pennsylvania — now WJRH
• WKC at Knox College in Galesburg, Illinois — now WVKC
• WKCO at Kenyon College in Gambier, Ohio — now WKCO
• WKDT at United States Military Academy in West Point, New York — now internet-only
• WMAX/WXDT at Drexel University in Philadelphia — now WKDU
• WKSR at Kent State University in Kent, Ohio — now internet-only "Black Squirrel Radio"
• WCDW/WLCR at Camp Shaw-Mi-Del-Eca in Lewisburg, West Virginia, operated by summer camp attendees
• WHMA/WLHA at University of Wisconsin–Madison in Madison, Wisconsin — now internet-only "Lakeshore 64 WLHA"
• WLHD (East Green) and WSGR (South Green) at Ohio University in Athens, Ohio — supplanted by "ACRN: The Rock Lobster", now internet-only
• WLKR at Lake Superior State University in Sault Ste. Marie, Michigan — now WLSO
• WLRN at Lehigh University in Bethlehem, Pennsylvania
• WMAX at Mount Washington College in Manchester, New Hampshire
• WMCR at Monmouth College in Monmouth, Illinois
• WMIT at the Massachusetts Institute of Technology in Cambridge, Massachusetts — now WMBR
• WMSN at Michigan State University in East Lansing, Michigan; networked with WBRS (Brody Hall), WKME (Shaw Hall), WEAK (Wonders Hall), WMCD (McDonnell Hall), and WFEE (Fee Hall) — supplanted by WDBM
• WMUC at University of Maryland, College Park in College Park, Maryland — now WMUC-FM
• WNYU at New York University in Lower Manhattan — now WNYU-FM
• WOBC at Otterbein College/Otterbein University in Westerville, Ohio - Now WOBN-FM
• WOCR, a "Pirate radio" carrier current station in Ocean City, Maryland
• WOLF at North Carolina State University in Raleigh, North Carolina — now WKNC-FM
• WOMB at Franconia College (closed 1978) in Franconia, New Hampshire
• WPSM at Penn State—McKeesport in McKeesport, Pennsylvania — now internet-only "WMKP"
• WQAD/WFQR/WIN/WIUS at Indiana University in Bloomington, Indiana — now WIUX-LP
• WRAF at Binghamton University in Binghamton, New York — now WHRW
• WRCC at Rockland Community College in Ramapo, New York
• WRCK at Slippery Rock University of Pennsylvania in Slippery Rock, Pennsylvania - later WRSK, then WSRU
• WRCR at Rockford College in Rockford, Illinois — revived as internet-only in 2011, ceased operations in 2017
• WRCT at Carnegie Mellon University in Pittsburgh — now WRCT
• WRFX at Central Michigan University in Mount Pleasant, Michigan
• WRGW at George Washington University in Washington, D.C. — now internet-only
• "WRIU Studio B" at University of Rhode Island in Kingston, Rhode Island — now internet-only
• WRLC at Rutgers University—Livingston in Piscataway, New Jersey — now WVPH
• WRPS at SUNY Potsdam in Potsdam, New York — later WAIH
• WRSU at Rutgers University in New Brunswick, New Jersey — now WRSU-FM
• WRUB at State University of New York at Buffalo — defunded and closed in 2019
• WRUC at Union College in Schenectady, New York — now WRUC
• WRUR at University of Rochester in Rochester, New York — now WRUR-FM
• WSAC at Saint Anselm College in Goffstown, New Hampshire
• WSCS/WCUR at West Chester University in West Chester, Pennsylvania — now WCUR
• WSMC at St. Mary's College in St. Mary's, Maryland
• WSND at the University of Notre Dame in Notre Dame, Indiana — now WSND-FM
• WSOE at Milwaukee School of Engineering in Milwaukee — now WMSE
• WSUA at State University of New York at Albany-now WCDB.
• WTAS at Hope College in Holland, Michigan — now WTHS
• WTGR at Memphis State University in Memphis, Tennessee — now WYXR
• WTMC at the Boston Housing Authority's Bromley-Heath Housing Project in Jamaica Plain
• WUCB at the University of Chicago in Chicago, Illinois, now WHPK
• WUFI at Florida International University in Miami —now WRGP
• WUSB at Stony Brook University in Stony Brook, New York — now WUSB (FM)
• WUVA at University of Virginia in Charlottesville, Virginia — now WCVL-FM
• WUVT at Virginia Tech in Blacksburg, Virginia — now WUVT-FM
• WVAT at SUNY Alfred State in Alfred, New York — later WETD
• WVAU at American University in Washington, D.C. — now internet-only
• WVBU at Bucknell University in Lewisburg, Pennsylvania — now WVBU-FM
• WVCW at Virginia Commonwealth University in Richmond, Virginia — now WVCW
• WVOF at Fairfield University in Fairfield, Connecticut — now WVOF
• WVRW at Michigan Technological University in Houghton, Michigan — now WMTU-FM
• WVYC at York College of Pennsylvania in York, Pennsylvania — now WVYC
• WWRC at Rider University in Lawrenceville, New Jersey — now WRRC
• WWSU at Wright State University in Dayton, Ohio
• WVW/WOUX/WOU at Oakland University in Rochester Hills, Michigan — now WXOU
• WXPN and WQHS at the University of Pennsylvania in Philadelphia — now WXPN and internet-only "WQHS Radio"
• WYBC at Yale University in New Haven, Connecticut — supplanted by an unrelated WYBC (AM) in 1998

• Power-line communication
• Leaky feeder

• Carrier Current Broadcasting Theory by LPB