Editing Carrier current

{{short description|Transmission of low-power radio signals through electrical conductors}}
'''Carrier current''' transmission, originally called '''wired wireless''', employs guided low-power [[Radio frequency|radio-frequency]] signals, which are transmitted along electrical conductors. The transmissions are picked up by receivers that are either connected to the conductors, or a short distance from them. Carrier current transmission is used to send audio and [[telemetry]] to selected locations, and also for [[low-power broadcasting]] that covers a small geographical area, such as a college campus. The most common form of carrier current uses [[longwave]] or [[medium wave]] [[Amplitude modulation|AM]] radio signals that are sent through existing electrical wiring, although other conductors can be used, such as telephone lines.

== Technology ==
Carrier current generally uses low-power transmissions. In cases where the signals are being carried over electrical wires, special preparations must be made for distant transmissions, as the signals cannot pass through standard utility [[transformer]]s. Signals can bridge transformers if the utility company has installed [[high-pass filter]]s, which typically has already been done when carrier current-based data systems are in operation. Signals can also be impressed onto the neutral leg of the [[three-phase electric power]] system, a practice known as "neutral loading", in order to reduce or eliminate [[mains hum]] (60 [[hertz]] in North American installations), and to extend effective transmission line distance.

For a broadcasting installation, a typical carrier current transmitter has an output in the range 5 to 30 watts. However, electrical wiring is a very inefficient antenna, and this results in a transmitted [[effective radiated power]] of less than one watt, and the distance over which signals can be picked up is usually less than 60 meters (200 feet) from the wires. Transmission sound quality can be good, although it sometimes includes the low-frequency mains hum interference produced by the alternating current. However, not all listeners notice this hum, nor is it reproduced well by all receivers.

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.

==Initial development==
The ability for electrical conductors to act as waveguides for radio signals was noted in the earliest days of radio experimentation, and [[Heinrich Hertz]] published the first review of the phenomenon in 1889.<ref>[https://books.google.com/books?id=EYRNAAAAYAAJ&dq=%22On+the+Propagation+of+Electric+Waves+along+Wires%22&pg=PA334 "Heinrich Hertz"], ''The Electrician'', July 20, 1894, page 333. Hertz's paper was titled "On the Propagation of Electric Waves along Wires".</ref> By 1911, Major General [[George Owen Squier]] was conducting some of the earliest studies designed to put carrier current transmissions, which he called "wired wireless", to practical use.<ref>[https://babel.hathitrust.org/cgi/pt?id=umn.31951d00118867a&view=1up&seq=1151 "Multiplex Telephony and Telegraphy by Means of Electric Waves Guided by Wires"] by George O. Squier, ''Proceedings of the American Institute of American Engineers'', May, 1911, pages 857-862. Squier assigned ownership of his U.S. patents to "the American People". He later unsuccessfully tried to claim that this had not exempted commercial concerns from paying royalties on his patents.</ref> To be effective, the radio transmitter must be capable of generating pure continuous-wave AM transmissions. Thus, the technology needed to set up carrier current transmissions would not be readily available until the late 1910s, with the development of [[vacuum tube]] transmitters and amplifiers.

==Long-distance communication==
{{Main|Power-line communication}}
The first commercial applications of carrier current technology included the setting up of long-distance telegraph, telemetry, and telephone communication by electrical companies over their high-voltage distribution lines. This approach had a major advantage over standard telegraph and telephone lines, because radio signals can readily jump over any small gaps in cases when there is a line break. In May 1918, the Imperial Japanese Electro-Technical Laboratory of Tokyo successfully tested "wave telephony" over the Kinogawa Hydro-Electric Company's 144-kilometer (90-mile) long power line.<ref name="schwartz">[https://ethw.org/Telephony_over_Power_Lines_%28Early_History%29 "Telephony over Power Lines (Early History)"] by Mischa Schwartz, "Presented IEEE History Conference, Newark, New Jersey, August 2007 and annotated since". (ethw.org)</ref> In the summer of 1920, a successful test transmission over 19.2 kilometers (12 miles) of high-tension wires was reported from New Jersey,<ref>[https://babel.hathitrust.org/cgi/pt?id=mdp.39015080024006&view=1up&seq=169 "Interplant Telephonic Communications Established Over High-Tension Lines"], ''Electrical World'', July 17, 1920, page 141.</ref> and by 1929, 1,000 installations had been made in the United States and Europe.<ref name="schwartz" /> The majority of power line communication installations use transmissions in the longwave band, to avoid interference to and from standard AM stations.

==Home entertainment services==
{{Main article|cable radio}}
===United States===
In 1923, the Wired Radio Service Company, a subsidiary of the local electric company, set up a subscription news and entertainment service at Staten Island, New York that used carrier current transmissions over the electrical power lines. To receive the transmissions, subscribers had to lease a receiver costing between two and five dollars a month.<ref>[https://babel.hathitrust.org/cgi/pt?id=mdp.39015013717379&view=1up&seq=493 "Giving the Public a Light-Socket Broadcasting Service"] by William Harris, Jr., ''Radio Broadcast'', October 1923, pages 465-470.</ref> However, despite the power company's optimism that the system would eventually be installed nationally, the effort proved unable to compete with the free offerings provided by standard radio stations. General Squier continued to unsuccessfully promote the technology for home entertainment, until 1934, when he helped found the [[Muzak]] company, which focused on the business market.

===Europe===
{{More citations needed section|date=December 2011}}
Carrier current home entertainment services would prove to be more popular in Europe. Previously, there had been a few successful [[telephone newspaper]] services, which sent entertainment to subscribers over standard telephone lines. However, carrier current transmissions had the ability to provide programs over telephone lines without affecting the regular telephone service, and could also send multiple programs simultaneously.

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 [[Integrated Services Digital Network|ISDN]] which required the same bandwidth to transmit digital data. Although the Swiss and German systems have been discontinued, the Italian ''[[:it:Filodiffusione]]'' still has several hundred thousand subscribers.

Programs formerly carried by "wire broadcasting" in Switzerland included:
* 175&nbsp;kHz [[Swissinfo|Swiss Radio International]]
* 208&nbsp;kHz RSR1 "la première" (French)
* 241&nbsp;kHz "classical music"
* 274&nbsp;kHz [[Radiotelevisione svizzera|RSI1]] "rete UNO" (Italian)
* 307&nbsp;kHz [[Radio SRF 1|DRS 1]] (German)
* 340&nbsp;kHz "easy music"

==Low-power broadcasting stations==
{{See also|Low-power broadcasting}}
Carrier current technology is also used for broadcasting radio programs that can be received over a small area by standard AM radios. This is most often associated with [[Campus radio|college radio]] and [[high school radio]], but also has applications for [[hospital radio]] stations and at military bases, sports stadiums, convention halls, mental and penal institutions, trailer parks, summer camps, office buildings, and drive-in movie theaters. Transmitters that use carrier current are very simple, making them an effective option for students interested in radio.

Carrier current broadcasting began in 1936, when students at [[Brown University]] in Providence, Rhode Island developed a carrier current station initially called [[WBRU|"The Brown Network"]]. This station was founded by George Abraham<ref>[https://web.archive.org/web/20170204141707/http://www.collegebroadcasters.us/content/about/gabraham.html "Dr. George Abraham, Ph.D"] (collegebroadcasters.us)</ref> and David W. Borst,<ref>[https://web.archive.org/web/20170313042328/http://www.collegebroadcasters.us/content/about/dborst.html "David W. Borst"] (collegebroadcasters.us)</ref> 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.<ref>''The Gas Pipe Networks: A History of College Radio 1936-1946'' by Louis M. Bloch, Jr., 1980, pages 11-13.</ref>

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.<ref>Bloch (1980) pages 102-103.</ref> The innovation received a major publicity boost by a complimentary article that appeared in the May 24, 1941 issue of ''[[The Saturday Evening Post]]'',<ref>[https://archive.org/details/the-saturday-evening-post-1941-05-24/page/n37/mode/1up "Radiator-Pipe Broadcasters"] by Erik Barnouw, ''The Saturday Evening Post'', May 24, 1941, pages 36, 79-80.</ref> 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."<ref>Bloch (1980) page 45.</ref> 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.<ref>[https://www.fcc.gov/media/radio/low-power-radio-general-information "Low Power Radio"] (FCC.gov)</ref>

===Educational institution carrier current and cablecast stations===
Many [[campus radio|college stations]] that went on to obtain FM broadcasting licenses started out as carrier current stations because of the low cost and relative ease of starting one. Although college-based carrier current stations have existed for over 80 years, their numbers are steadily declining, becoming supplemented, or replaced, by other transmission methods, including low-power FM ([[Low-power broadcasting|LPFM]]), [[closed-circuit radio|closed circuit]] over cable TV channels, and Internet [[Streaming media#Consumerization of streaming|streaming audio and video]], along with simple [[Microsoft PowerPoint|PowerPoint]] presentations of college campus news and information being streamed using low-cost consumer televisions and monitors. As with most other student-run facilities, these stations often operate on sporadic schedules.

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.

====Existing stations====
{{Incomplete list|date=February 2017}}
*Bulls Radio ({{Frequency|1620|AM}}) at the [[University of South Florida]] in [[Tampa, Florida]]; also heard on licensed [[WMNF|WMNF-HD2]]<ref>{{Cite web|url=http://bullsradio.org/|title=Welcome to BullsRadio.org|website=Bullsradio.org|access-date=2009-10-25|archive-date=2009-09-28|archive-url=https://web.archive.org/web/20090928034936/http://bullsradio.org/|url-status=dead}}</ref>
*KAMP ({{Frequency|1570|AM}}) at the [[University of Arizona]] in [[Tucson, Arizona]]<ref>{{Cite web|url=http://kamp.arizona.edu/|title=Kamp Student Radio|website=kamp.arizona.edu|access-date=2009-10-16|archive-url=https://web.archive.org/web/20091002221103/http://kamp.arizona.edu/|archive-date=2009-10-02|url-status=dead}}</ref>
*KANM ({{Frequency|1580|AM}}) at [[Texas A&M University]] in [[College Station, Texas]]<ref>{{Cite web|url=http://kanm.tamu.edu/|archive-url=https://web.archive.org/web/19981205055656/http://kanm.tamu.edu/|url-status=dead|archive-date=5 December 1998|title=KANM 99.9 FM Cable - 1600 AM|date=5 December 1998}}</ref>
*KASR ({{Frequency|1330|AM}}) at [[Arizona State University]] in [[Tempe, Arizona]]<ref name="theblaze1260.com">{{Cite web | url=http://www.theblaze1260.com/ | archive-url=https://web.archive.org/web/20100619040107/http://www.theblaze1260.com/ | url-status=dead | archive-date=2010-06-19 |title = Kasc - arizona state's original alternative}}</ref>
*KDUP ({{Frequency|1580|AM}}) at the [[University of Portland]] in [[Portland, Oregon]]<ref>{{Cite web|url=http://kdup.up.edu/|title=KDUP – Bluff Radio|website=kdup.up.edu}}</ref>
*KJACK ({{Frequency|1680|AM}}) at [[Northern Arizona University]] in [[Flagstaff, Arizona]]<ref>http://www.kjack.org/ http://www.kjackradio.com/</ref>
*KLBC ({{Frequency|1610|AM}}) at [[Long Beach City College]] in [[Long Beach, California]]<ref>{{Cite web|url=http://www.klbc.org/|title=KLBC 1610AM - "Truly Underground Radio"|website=www.klbc.org}}</ref>
*[[Minnesota State University Moorhead#Dragon Radio|KMSC]] "Dragon Radio" ({{Frequency|1500|AM}}) at [[Minnesota State University Moorhead]] in [[Moorhead, Minnesota]]<ref>[http://dragonradio.org/about/ KMSC Dragon Radio:] About.</ref>
*[[KRFH-LP|KRFH]] at [[Humboldt State University]] in [[Arcata, California]]
*"K-ROCKS RadioOne" ({{Frequency|1670|AM}} / {{Frequency|710|AM}}) in [[Casper, Wyoming]]<ref>{{Cite web|url=http://krocksradioone.com/|title=K-ROCKS Radio One - We Don't Do Cute at KROCKS!|website=krocksradioone.com|access-date=2012-06-15|archive-url=https://web.archive.org/web/20120620003716/http://www.krocksradioone.com/|archive-date=2012-06-20|url-status=dead}}</ref>
*[[California State University, Sacramento#KSSU 1580 AM|KSSU]] ({{Frequency|1580|AM}}) at [[California State University, Sacramento]] in [[Sacramento, California]]
*KUR ({{Frequency|1670|AM}} / {{Frequency|88.3|FM}}) at [[Kutztown University of Pennsylvania]] in [[Kutztown, Pennsylvania]]<ref>{{Cite web |url=http://www.kutztown.edu/divisions/studentservices/departments/radioservices/ |title=Kutztown University Radio Services |access-date=2009-10-16 |archive-url=https://web.archive.org/web/20090926042941/http://www.kutztown.edu/divisions/studentservices/departments/radioservices/ |archive-date=2009-09-26 |url-status=dead }}</ref>
*KUTE ({{Frequency|1620|AM}}) at the [[University of Utah]]<ref>https://web.archive.org/web/20111121074604/http://www.kute.utah.edu/ http://kuteradio.org/</ref>
*Radio Laurier Macdonald ({{Frequency|560|AM}}) at [[Laurier Macdonald High School]] in [[Saint-Leonard, Quebec|Saint-Leonard, Montreal, Quebec]], Canada
*Radio SNHU ({{Frequency|1620|AM}}) at [[Southern New Hampshire University]]<ref>{{Cite web|url=http://radio.snhu.edu/|title=RadioSNHU|last=RadioSNHU|website=radio.snhu.edu}}</ref>
*[[Gaylord College of Journalism and Mass Communication#Student media|Studio U]] ({{Frequency|1710|AM}}) at the [[University of Oklahoma]] in [[Norman, Oklahoma]]
*UMSLRadio "The U" ({{Frequency|1620|AM}}) at the [[University of Missouri–St. Louis]] in [[University City, Missouri]]<ref>{{Cite web|url=http://umslradio.com/|title=The U|website=umslradio.com}}</ref>
*WALT ({{Frequency|1610|AM}}) at [[Davidson College]] in [[Davidson, North Carolina]]<ref>{{cite web |url=http://listentowalt.com/ |title=Archived copy |website=listentowalt.com |access-date=12 January 2022 |archive-url=https://web.archive.org/web/20140518040339/http://listentowalt.com/ |archive-date=18 May 2014 |url-status=dead}}</ref>
*[[WERW (student radio)|WERW]] ({{Frequency|1670|AM}}) at [[Syracuse University]] in [[Syracuse, New York]]
*WGCC ({{Frequency|650|AM}}) at [[Genesee Community College]] in [[Batavia, New York]]
*Wolfpack Radio ({{Frequency|1700|AM}}) at the [[University of Nevada, Reno|University of Nevada]] in [[Reno, Nevada]]<ref>{{Cite web | url=http://www.wpr.wolfpackradio.org/ | title=WPR – UNR Student-Run Radio Station}}</ref>
*WPPJ ({{Frequency|670|AM}}) at [[Point Park University]] in [[Pittsburgh|Pittsburgh, Pennsylvania]]<ref>{{Cite web|url=http://www.pointpark.edu/Academics/Schools/SchoolofCommunication/StudentMedia/WPPJ|title=WPPJ - Point Park University|website=www.pointpark.edu}}</ref>
*WPMD ({{Frequency|1700|AM}}) at [[Cerritos College]] in [[Norwalk, California]]<ref>https://web.archive.org/web/20170922094625/http://wpmd.org/ https://web.archive.org/web/20161211110723/http://www.wpmdonthenet.com/about/</ref>
*WQMC ({{Frequency|1290|AM}}) at [[Queens College, City University of New York]] in [[Kew Gardens Hills, Queens]]
*WSIN ({{Frequency|1590|AM}}) at [[Southern Connecticut State University]] in [[New Haven, Connecticut]]<ref>{{Cite web|url=http://radio.southernct.edu/|title=WSIN - SCSU Independent Radio|website=radio.southernct.edu}}</ref>
*WSLU ({{Frequency|1620|AM}} / {{Frequency|100.1|FM}}) at [[Saint Leo University]] in [[St. Leo, Florida]]<ref>{{Cite web |url=http://www.wsluradio.webs.com/ |title=Home - |access-date=2014-05-03 |archive-url=https://web.archive.org/web/20140503032156/http://www.wsluradio.webs.com/ |archive-date=2014-05-03 |url-status=dead }}</ref>
*[[WTBU (Boston University)|WTBU]] ({{Frequency|640|AM}} / {{Frequency|89.3|FM}}) at [[Boston University]] in [[Boston|Boston, Massachusetts]]

====Former stations====
{{Incomplete list|date=February 2017}}

*WCPR-AM 740 at [[Stevens Institute of Technology]] in [[Hoboken, New Jersey]] https://wcpr.org
*"Brown Student Radio" at [[Brown University]] in [[Providence, Rhode Island]]&nbsp;— now [[WBRU]]
*CBR/WVBR at [[Cornell University]] in [[Ithaca, New York]]&nbsp;— now [[WVBR-FM]]
*KAL at the [[University of California, Berkeley|University of California—Berkeley]] in [[Berkeley, California]]&nbsp;— now [[KALX]]
*KARL-AM at [[Carleton College]] in [[Northfield, Minnesota]]&nbsp;— now [[KRLX]]
*KASR at [[Arizona State University]] in [[Tempe, Arizona]]&nbsp;— now internet-only "Blaze Radio"<ref name="theblaze1260.com"/>
*"K.C. AM" at [[Colby College]] in [[Waterville, Maine]]&nbsp;— now [[WMHB]]
*KCAT at [[Central Washington University|Central Washington State College]] in [[Ellensburg, Washington]]&nbsp;— now [[KCWU]]
*KCC at [[Chabot College]] in [[Hayward, California]]&nbsp;— now [[KCRH]]
*KCCS at the [[University of Missouri]] in [[Columbia, Missouri]]&nbsp;— supplanted by [[KCOU]]<ref>{{Cite web |title=The great 58 // Show Me Mizzou // University of Missouri |url=https://showme.missouri.edu/2021/the-great-58/ |access-date=2022-06-01 |website=showme.missouri.edu |language=en-US}}</ref>
*KCD at the [[University of California, Davis|University of California—Davis]] in [[Davis, California]]&nbsp;— now [[KDVS]]
*KCIZ at Mora High School in [[Mora, Minnesota]]<ref name="Archived copy">{{Cite web |title=16/KCIZ :: KCIZ-AM 1650, Mora, Minnesota |url=http://www.morarocks.com/ |url-status=dead |archive-url=https://web.archive.org/web/20080929153608/http://www.morarocks.com/ |archive-date=2008-09-29 |access-date=2008-09-29}}</ref>
*KDSC/KDSU at [[North Dakota State University]] in [[Fargo, North Dakota]]&nbsp;— now [[KDSU]]
*KFRH at [[Washington University in St. Louis]] in [[St. Louis|St. Louis, Missouri]]&nbsp;— now [[KWUR]]
*KHSC at [[California State Polytechnic University, Humboldt|Humboldt State College]] in [[Arcata, California]]&nbsp;— now [[KHSU]]
*KMPS-AM at [[University of Alaska Fairbanks]] in [[Fairbanks, Alaska]]&nbsp;— now [[KSUA]]
*KNAB at [[Chapman University]] in [[Orange, California|Orange, California&nbsp;—]] now internet-only "ChapmanRadio.com"
*KNMA at [[New Mexico State University]] in [[Las Cruces, New Mexico]]<ref>{{Cite web|url=http://www.jpeek.com/krwg/|title=KRWG Radio, Las Cruces, NM -- History and FM's 10th Anniversary|first=Jerry|last=Peek|website=jpeek.com}}</ref>
*KOWL at [[Rice University]] in [[Houston|Houston, Texas]]&nbsp;— later [[KHVU]], now [[KTRU-LP]]
*KPCR-AM at [[Pomona College]] in [[Claremont, California]]&nbsp;– replaced by [[KSPC]]<ref>{{cite news |title=Pomona College's KSPC-FM: real pro station |url=https://www.newspapers.com/article/progress-bulletin-pomona-colleges-kspc/129788187/ |access-date=10 August 2023 |work=[[Progress Bulletin]] |date=17 December 1977 |pages=28 |via=[[Newspapers.com]]}}</ref>
*KRLK at [[Rio Linda High School]] in [[Rio Linda, California]]&nbsp;— now KRIO
*KRS at the [[Manhattan Project]] at [[Los Alamos, New Mexico]] — later [[KRSN]]
*KBIL/KSLU at [[Saint Louis University]] in [[St. Louis|St. Louis, Missouri]]&nbsp;— now internet-only "[[KSLU (Saint Louis University)|KSLU]]"
*KSU at [[Stanford University]] in [[Stanford, California]]&nbsp;– now [[KZSU]]
*KSUB at [[Seattle University]] in [[Seattle|Seattle, Washington]]&nbsp;— now KXSU-LP<ref>https://kxsuseattle.wordpress.com/ https://web.archive.org/web/20160323002125/http://www.ksubseattle.org/ http://www.seattlespectator.com/2015/10/21/seattle-u-student-radio-entering-a-new-era/ https://www.seattleu.edu/alumni/su-voice-alumni-blog/from-ksub-to-kxsu---big-changes-for-seattle-university-student-radio.html {{Webarchive|url=https://web.archive.org/web/20171115083412/https://www.seattleu.edu/alumni/su-voice-alumni-blog/from-ksub-to-kxsu---big-changes-for-seattle-university-student-radio.html|date=2017-11-15}} http://www.seattleu.edu/ksub/default.aspx?id=42100 {{Webarchive|url=https://web.archive.org/web/20100601173119/http://www.seattleu.edu/ksub/default.aspx?id=42100|date=2010-06-01}}</ref>
*KSWC at [[Southwestern College (Kansas)|Southwestern College]] in [[Winfield, Kansas]]&nbsp;— now [[KSWC-LP]]
*KUCB at [[University of Colorado Boulder]] in [[Boulder, Colorado]]&nbsp;— now [[KVCU]]
*MD2/KTTC at [[Texas Tech University|Texas Tech College]] in [[Lubbock, Texas]]&nbsp;— now [[KTXT-FM]]
*KUOK at [[University of Kansas]] in [[Lawrence, Kansas]]&nbsp;— now [[KJHK]]
*KVUC at [[Union College (Nebraska)|Union College]] in [[Lincoln, Nebraska]]&nbsp;— now [[KUCV]]
*"Radio Western" at the [[University of Western Ontario]] in [[London, Ontario]], Canada&nbsp;— now [[CHRW-FM]]
*WAMU at [[American University]] in [[Washington, D.C.]]&nbsp;— now [[WAMU]]
*WBAU at [[Adelphi University]] in [[Garden City, New York]]&nbsp;— became now-defunct station [[WBAU]]
*WBMB at [[Baruch College]]/[[City University of New York]] in [[New York City]]
*WBSC at [[Bloomsburg University of Pennsylvania|Bloomsburg State College]] in [[Bloomsburg, Pennsylvania]]&nbsp;— now [[WHSK]]
*WCAR at [[University of North Carolina at Chapel Hill]]&nbsp;— now [[WXYC]]
*WCCT/WNTC at [[Clarkson University|Clarkson College of Technology]]/[[State University of New York at Potsdam|SUNY Potsdam]] in [[Potsdam, New York]]&nbsp;— now [[WTSC-FM]]
*WCHP and WINO/WRFX at [[Central Michigan University]] in [[Mount Pleasant, Michigan]]
*WCXQ in [[Isabela, Puerto Rico]]&nbsp;— now [[WCXQ-LP]]
*WDBS at [[Duke University]] in [[Durham, North Carolina]]&nbsp;— now [[WXDU]]
*WDCR/WESB at the [[University of Dayton]] in [[Dayton, Ohio]]&nbsp;— now [[WUDR]]
*WDGN at [[North High School (Downers Grove, Illinois)|Downers Grove North High School]] in [[Downers Grove, Illinois]]&nbsp;— now [[WDGC-FM]]
*WERC at [[The University of Toledo]] in [[Toledo, Ohio]]&nbsp;— now [[WXUT]]
*WERU at [[Embry–Riddle Aeronautical University]] in [[Daytona Beach, Florida]]&nbsp;— now [[WIKD-LP]]
*[[WEXP (La Salle University)|WEXP]] at [[La Salle University]] in [[Philadelphia|Philadelphia, Pennsylvania]]&nbsp;— now internet-only
*WFAL at [[Bowling Green State University]] in [[Bowling Green, Ohio]]&nbsp;— now [[WFAL Falcon Radio]]
*WFIB at the [[University of Cincinnati]] in [[Cincinnati|Cincinnati, Ohio]]
*WFRS at [[Ferris State University|Ferris State College]] in [[Big Rapids, Michigan]]
*WFVS at [[Fort Valley State University]] in [[Fort Valley, Georgia]]&nbsp;— 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|Baltimore, Maryland]]&nbsp;— later WHSR, now [[WJHU]]
*WHEN/WDRB at the [[University of Delaware]] in [[Newark, Delaware]]&nbsp;— now [[WVUD]]
*WHEN at [[Western Illinois University]] in [[Macomb, Illinois]]&nbsp;— now [[WIUS]]
*WHRM at [[Hiram College]] in [[Hiram, Ohio]]&nbsp;— now internet-only "The Bark"
*WHUS at [[University of Connecticut]] in [[Storrs, Connecticut]]&nbsp;— now [[WHUS]]
*WJHU at [[Johns Hopkins University]] in [[Baltimore|Baltimore, Maryland]]&nbsp;— 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]]&nbsp;— now [[WCBN-FM]]<ref name="WCBN1">{{Cite web | url = http://arborwiki.org/city/Category:WCBN#History | title = Category:WCBN - Ann Arbor - ArborWiki | access-date = 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 | access-date = 2011-09-27}}</ref>
*WJPZ at [[Syracuse University]] in [[Syracuse, New York]]&nbsp;— now [[WJPZ-FM]]
*WJRH at [[Lafayette College]] in [[Easton, Pennsylvania]]&nbsp;— now [[WJRH]]
*WKC at [[Knox College (Illinois)|Knox College]] in [[Galesburg, Illinois]]&nbsp;— now [[WVKC]]
*WKCO at [[Kenyon College]] in [[Gambier, Ohio]]&nbsp;— now [[WKCO]]
*WKDT at [[United States Military Academy]] in [[West Point, New York]]&nbsp;— now internet-only<ref>{{Cite web |date=2019-04-29 |title=WKDT "Voice of the Long Gray Line" Now Online |url=https://www.radioworld.com/news-and-business/programming-and-sales/wkdt-voice-of-the-long-gray-line |access-date=2022-06-01 |website=Radio World |language=en-US}}</ref>
*WMAX/WXDT at [[Drexel University]] in [[Philadelphia|Philadelphia, Pennsylvania]]&nbsp;— now [[WKDU]]<ref>{{Cite web |url=http://www.wkdu.org/node/5 |title=Station History &#124; WKDU 91.7 Philadelphia |access-date=2008-08-07 |archive-url=https://web.archive.org/web/20081004193636/http://www.wkdu.org/node/5 |archive-date=2008-10-04 |url-status=dead }}</ref>
*WKSR at [[Kent State University]] in [[Kent, Ohio]]&nbsp;— now internet-only "[[Black Squirrel Radio]]"<ref>{{Cite news |last=Sharma |first=Rekha |date=November 18, 1999 |title=WKSR uses Internet broadcasting to pass competition |page=6 |work=The Daily Kent Stater |location=Kent, Ohio |url=https://dks.library.kent.edu/?a=d&d=dks19991118-01.2.26&srpos=24&dliv=none&e=------199-en-20--21-byDA-txt-txIN-WKSR----1999-- |url-status=live |access-date=May 20, 2022 |archive-url=https://web.archive.org/web/20220521003704/https://dks.library.kent.edu/?a=d&d=dks19991118-01.2.26&srpos=24&dliv=none&e=------199-en-20--21-byDA-txt-txIN-WKSR----1999-- |archive-date=May 21, 2022}}</ref><ref>{{Cite news |last=Peris |first=Kenny |date=September 12, 2005 |title=Black squirrels take over the radio |page=6 |work=The Daily Kent Stater |location=Kent, Ohio |url=https://dks.library.kent.edu/?a=d&d=dks20050913-01.2.35&srpos=62&dliv=none&e=-------en-20--61-byDA-txt-txIN-WKSR----2005-- |url-status=live |access-date=May 20, 2022 |archive-url=https://web.archive.org/web/20220521003710/https://dks.library.kent.edu/?a=d&d=dks20050913-01.2.35&srpos=62&dliv=none&e=-------en-20--61-byDA-txt-txIN-WKSR----2005-- |archive-date=May 21, 2022}}</ref>
* WCDW/WLCR at Camp Shaw-Mi-Del-Eca in [[Lewisburg, West Virginia]], operated by summer camp attendees<ref>{{Cite web |last=Walsh |first=Glenn A. |title=History of Radio Station WLCR-AM: Carrier Current, Lewisburg/White Sulphur Springs, West Virginia and The Radio Group |url=https://johnbrashear.tripod.com/wlcr.html |access-date=2022-06-01 |website=johnbrashear.tripod.com}}</ref>
*WHMA/WLHA at [[University of Wisconsin–Madison]] in [[Madison, Wisconsin]]&nbsp;— now internet-only "Lakeshore 64 WLHA"
*WLHD (East Green) and WSGR (South Green) at [[Ohio University]] in [[Athens, Ohio]]&nbsp;— supplanted by "ACRN: The Rock Lobster", now internet-only<ref>{{Cite web |last=Grisez |first=Abby |date=March 29, 2018 |title=Queer Eye Creator On Time At Ohio University |url=https://woub.org/2018/03/29/queer-eye-creator-time-ohio-university/ |access-date=2022-06-01 |website=WOUB Public Media |language=en-US}}</ref><ref>{{cite web |date=1971-04-04 |title=The Rock Lobster |url=http://acrn.com/about/history/ |url-status=dead |archive-url=https://archive.today/20120701144834/http://acrn.com/about/history/ |archive-date=July 1, 2012 |access-date=2011-10-06 |publisher=ACRN |df=mdy-all}}</ref>
*WLKR at [[Lake Superior State University]] in [[Sault Ste. Marie, Michigan]]&nbsp;— 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]]&nbsp;— 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)&nbsp;— supplanted by [[WDBM]]
*WMUC at [[University of Maryland, College Park]] in [[College Park, Maryland]]&nbsp;— now [[WMUC-FM]]<ref>{{Cite web|url=http://www.wmuc.umd.edu/tech/index.html|archive-url=https://web.archive.org/web/20021009230234/http://www.wmuc.umd.edu/tech/index.html|url-status=dead|archive-date=9 October 2002|title=WMUC - The University of Maryland, College Park|date=9 October 2002}}</ref>
*WNYU at [[New York University]] in [[Lower Manhattan]]&nbsp;— now [[WNYU-FM]]
*WOBC at [[Otterbein College/Otterbein University]] in [[Westerville, Ohio]] - Now [[WOBN-FM]]
*WOCR, a "[[Pirate radio|pirate]]" carrier current station in [[Ocean City, Maryland]]
*WOLF at [[North Carolina State University]] in [[Raleigh, North Carolina]]&nbsp;— now [[WKNC-FM]]
*WOMB at Franconia College (closed 1978) in Franconia, New Hampshire
*WPSM at [[Penn State Greater Allegheny|Penn State—McKeesport]] in [[McKeesport, Pennsylvania]]&nbsp;— now internet-only "WMKP"<ref>{{Cite web|url=http://www.clubs.psu.edu/mk/wmkp/|title=Join a Student Organization - Penn State Student Affairs|website=www.clubs.psu.edu}}</ref>
*WQAD/WFQR/WIN/WIUS at [[Indiana University Bloomington|Indiana University]] in [[Bloomington, Indiana]]&nbsp;— now [[WIUX-LP]]
*WRAF at [[Binghamton University]] in [[Binghamton, New York]]&nbsp;— 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 (Illinois)|WRCR]] at [[Rockford University|Rockford College]] in [[Rockford, Illinois]]&nbsp;— revived as internet-only in 2011, ceased operations in 2017<ref>{{Citation|url=http://www.wrcr.radiohistory.net/|title=WRCR alumni site}}</ref>
*WRCT at [[Carnegie Mellon University]] in [[Pittsburgh|Pittsburgh, Pennsylvania]]&nbsp;— now [[WRCT]]
*WRFX at [[Central Michigan University]] in [[Mount Pleasant, Michigan]]
*[[WRGW (student radio)|WRGW]] at [[George Washington University]] in [[Washington, D.C.]]&nbsp;— now internet-only
*"[[WRIU]] Studio B" at [[University of Rhode Island]] in [[Kingston, Rhode Island]]&nbsp;— now internet-only
*WRLC at [[Rutgers University|Rutgers University—Livingston]] in [[Piscataway, New Jersey]]&nbsp;— now [[WVPH]]
*WRPS at [[State University of New York at Potsdam|SUNY Potsdam]] in [[Potsdam, New York]]&nbsp;— later [[WAIH (New York)|WAIH]]
*WRSU at [[Rutgers University]] in [[New Brunswick, New Jersey]]&nbsp;— now [[WRSU-FM]]
*[[WRUB (college radio)|WRUB]] at [[State University of New York at Buffalo]]&nbsp;— defunded and closed in 2019<ref>{{Cite web|last=O'Neil-White|first=Thomas|title=Protests over the elimination of student-owned services corporation|url=https://news.wbfo.org/post/protests-over-elimination-student-owned-services-corporation|access-date=2021-04-13|website=news.wbfo.org|date=May 14, 2019|language=en|archive-date=April 13, 2021|archive-url=https://web.archive.org/web/20210413001830/https://news.wbfo.org/post/protests-over-elimination-student-owned-services-corporation|url-status=live}}</ref>
*WRUC at [[Union College]] in [[Schenectady, New York]]&nbsp;— now [[WRUC]]
*WRUR at [[University of Rochester]] in [[Rochester, New York]]&nbsp;— now [[WRUR-FM]]
*WSAC at [[Saint Anselm College]] in [[Goffstown, New Hampshire]]
*WSCS/WCUR at [[West Chester University]] in [[West Chester, Pennsylvania]]&nbsp;— now [[WCUR]]
*WSMC at [[St. Mary's College of Maryland|St. Mary's College]] in [[St. Mary's City, Maryland|St. Mary's, Maryland]]
*WSND at the [[University of Notre Dame]] in [[Notre Dame, Indiana (CDP)|Notre Dame, Indiana]]&nbsp;— now [[WSND-FM]]
*WSOE at [[Milwaukee School of Engineering]] in [[Milwaukee|Milwaukee, Wisconsin]]&nbsp;— now [[WMSE]]
*WSUA at State University of New York at Albany-now WCDB.
*WTAS at [[Hope College]] in [[Holland, Michigan]]&nbsp;— now [[WTHS]]
*WTGR at [[University of Memphis|Memphis State University]] in [[Memphis, Tennessee]]&nbsp;— now [[WYXR]]
*WTMC at the [[Boston Housing Authority]]'s Bromley-Heath Housing Project in [[Jamaica Plain|Jamaica Plain, Massachusetts]]<ref>{{Cite news |date=November 1973 |title=Carrier Current Radio Used in Housing Project |volume=9 |page=55 |work=Broadcast Management Engineering |issue=11 |url=https://worldradiohistory.com/Archive-Broadcast-Engineering/BME/70s/BME-1973-11.pdf |access-date=June 1, 2022 |via=World Radio History}}</ref>
*WUCB at the [[University of Chicago]] in [[Chicago, Illinois]], now [[WHPK]]
*WUFI at [[Florida International University]] in [[Miami|Miami, Florida]]&nbsp;—now [[WRGP]]<ref>{{Cite web|url=http://www.wrgp.org/|title=88.1 - WRGP Radiate FM& - 95.3|website=www.wrgp.org}}</ref>
*WUSB at [[Stony Brook University]] in [[Stony Brook, New York]]&nbsp;— now [[WUSB (FM)]]<ref>{{Cite news |date=October 3, 1963 |title=W.U.S.B. |page=3 |work=The Statesman |url=https://ir.stonybrook.edu/xmlui/bitstream/handle/11401/62025/Statesman%2c%20V.7%2c%20n.%201.pdf}}</ref>
*WUVA at [[University of Virginia]] in [[Charlottesville, Virginia]]&nbsp;— now [[WCVL-FM]]
*WUVT at [[Virginia Tech]] in [[Blacksburg, Virginia]]&nbsp;— now [[WUVT-FM]]
*WVAT at [[Alfred State College|SUNY Alfred State]] in [[Alfred, New York]]&nbsp;— later [[WETD]]
*[[WVAU]] at [[American University]] in [[Washington, D.C.]]&nbsp;— now internet-only
*WVBU at [[Bucknell University]] in [[Lewisburg, Pennsylvania]]&nbsp;— now [[WVBU-FM]]
*WVCW at [[Virginia Commonwealth University]] in [[Richmond, Virginia]]&nbsp;— now [[WVCW (Virginia Commonwealth University)|WVCW]]
*WVOF at [[Fairfield University]] in [[Fairfield, Connecticut]]&nbsp;— now [[WVOF]]
*WVRW at [[Michigan Technological University]] in [[Houghton, Michigan]]&nbsp;— now [[WMTU-FM]]
* WVYC at [[York College of Pennsylvania]] in [[York, Pennsylvania]]&nbsp;— now [[WVYC]]
*WWRC at [[Rider University|Rider College]] in [[Lawrenceville, New Jersey]]&nbsp;— now [[WRRC]]
*[[WWSU]] at [[Wright State University]] in [[Dayton, Ohio|Dayton]], [[Ohio]]
*WVW/WOUX/WOU at [[Oakland University]] in [[Rochester Hills, Michigan]]&nbsp;— now [[WXOU]]
*WXPN and WQHS at the [[University of Pennsylvania]] in [[Philadelphia|Philadelphia, Pennsylvania]]&nbsp;— now [[WXPN]] and internet-only "[[WQHS Radio]]"
*WYBC at [[Yale University]] in [[New Haven, Connecticut]]&nbsp;— supplanted by an unrelated [[WYBC (AM)]] in 1998<ref>{{YouTube | id=gtliYu2lDQU | title=This Is College Radio (1956) - WYBC Yale Radio & the Ivy (Radio) Network}}</ref>

==See also==
*[[Power-line communication]]
*[[Leaky feeder]]

==References==
{{Reflist|30em}}

== Further reading ==

{{refbegin}}

* {{Cite encyclopedia |last1=Gutmacher |first1=Glenn |editor-last1=Labov |editor-first1=William |editor-last2=Browne |editor-first2=Ray Broadus |editor-last3=Browne |editor-first3=Pat |title=Carrier Current and Cable Radio |page=138 |date=2001 |url=https://books.google.com/books?id=U3rJxPYT32MC&pg=PA138 |language=en |isbn=978-0-87972-821-2 |publisher=Popular Press |encyclopedia=The Guide to United States Popular Culture |df=mdy-all }}

{{refend}}

==External links==
*[http://utopianetwork.home.comcast.net/carrier/cct.pdf Carrier Current Broadcasting Theory by LPB]{{Dead link|date=June 2019 |bot=InternetArchiveBot |fix-attempted=yes }}

{{DEFAULTSORT:Carrier Current}}
[[Category:Broadcast engineering]]
[[Category:Radio technology]]