Editing Numbers station

{{Short description|Shortwave radio stations broadcasting only numbers}}
{{For|the 2013 film|The Numbers Station}}
{{Use dmy dates|date=March 2016}}
{{Listen |filename=Poacher.ogg |title="Lincolnshire Poacher" |description=Recording of the E03 "[[Lincolnshire Poacher (numbers station)|Lincolnshire Poacher]]" interval signal, followed by a coded transmission of five numbers: 0–2–5–8–8. |format=[[Ogg]] |alt=Recording of the Lincolnshire Poacher interval signal and five-number voice transmission}}
[[File:Estacion de números HM01.ogg|thumb|alt=Audio recording of a voice transmission from a Cuban numbers station|Cuban numbers station HM01]]
[[File:Gong numbers station.ogg|thumb|alt=Audio recording of the Gong numbers station used by East German military|A recording of ''The Gong'' numbers station, operated by the [[National People's Army]] of the German Democratic Republic in 1988]]

A '''numbers station''' is a [[shortwave]] [[radio station]] characterized by broadcasts of formatted numbers, which are believed to be addressed to [[intelligence officer]]s operating in foreign countries.<ref>{{cite news |url=https://www.bbc.co.uk/news/magazine-24910397 |title=The spooky world of the 'numbers stations' |last=Sorrel-Dejerine |first=Olivia |date=16 April 2014 |work=BBC News}}</ref> Most identified stations use [[speech synthesis]] to vocalize numbers, although digital modes such as [[phase-shift keying]] and [[frequency-shift keying]], as well as [[Morse code]] transmissions, are not uncommon. Most stations have set time schedules or schedule patterns; however, some appear to have no discernible pattern and broadcast at random times. Stations may have set frequencies in the [[high frequency|high-frequency]] band.<ref name="Number stations basic">{{cite web |url=http://priyom.org/number-stations |title=Number stations |website=Priyom}}</ref>

Numbers stations have been reported since at least the start of [[World War I]] and continue in use today. Amongst amateur radio enthusiasts, there is an interest in monitoring and classifying numbers stations, with many being given nicknames to represent their quirks or origins.

==History==
According to the notes of ''[[The Conet Project]]'',<ref>{{cite news |first=David |last=Segal |date=3 August 2004 |title=The shortwave and the calling: For Akin Fernandez, cryptic messages became music to his ears |newspaper=[[The Washington Post]] |page=C01 |url=https://www.washingtonpost.com/wp-dyn/articles/A35647-2004Aug2.html}}</ref><ref>{{harvnb|Mason|1991|pages=5–6}}</ref> which has compiled recordings of these transmissions, number stations have been reported since {{nobr|[[World War I]]}} with the numbers transmitted in Morse code. It is reported that [[Archduke Anton of Austria]] in his youth during World War I used to listen in to their transmissions, writing them down and passing them on to the Austrian military intelligence.<ref name="first-stations">{{cite web |url=https://www.numbers-stations.com/articles/the-first-numbers-stations/ |title=The First Numbers Stations |date=30 November 2014 |publisher=NSRIC |first=Ryan |last=Schaum |df=dmy-all }}</ref>

Numbers stations were most abundant during the [[Cold War]] era. According to an internal Cold War-era report of the Polish Ministry of the Interior, numbers stations DCF37 (3.370&nbsp;MHz) and DFD21 (4.010&nbsp;MHz) were transmitted from [[West Germany]] beginning in the early 1950s.<ref>{{cite journal |last=Bury |first=Jan |date=October 2007 |title=From the archives: The U.S. and West German agent radio ciphers |url=http://www.swldxer.co.uk/polish.mht |archive-url=https://web.archive.org/web/20121223120639/http://www.swldxer.co.uk/polish.mht |url-status=usurped |archive-date=23 December 2012 |journal=Cryptologia |volume=31 |issue=4 |pages=343–357 |doi=10.1080/01611190701578104 |issn=0161-1194 |s2cid=205487634|url-access=subscription }}</ref>

Many stations from this era continue to broadcast and some long-time stations may have been taken over by different operators.<ref>{{Cite news|date=2014-04-16|title=The spooky world of the 'numbers stations'|language=en-GB|work=BBC News|url=https://www.bbc.com/news/magazine-24910397|access-date=2021-07-12}}</ref><ref>{{cite web|url=https://www.numbers-stations.com|title=Numbers Stations Research|website=Numbers Stations Research}}</ref> The [[Ministry of the Interior (Czech Republic)|Czech Ministry of the Interior]] and the [[Swedish Security Service]] have both acknowledged the use of numbers stations by [[Czechoslovakia]] for espionage,<ref name="Säkerhetspolisen2015">{{cite web |title=Lyssna på ett hemligt telegram |url=http://www.sakerhetspolisen.se/ovrigt/pressrum/aktuellt/aktuellt/2015-01-23-lyssna-pa-ett-hemligt-telegram.html |publisher=[[Säkerhetspolisen]] |access-date=12 March 2016 |language=sv |date=23 January 2015 |archive-url=https://web.archive.org/web/20160308174151/http://sakerhetspolisen.se/ovrigt/pressrum/aktuellt/aktuellt/2015-01-23-lyssna-pa-ett-hemligt-telegram.html |archive-date=8 March 2016 |url-status=live |trans-title=Listen to a secret telegram |df=dmy-all }}</ref><ref name="Swedish Security Service">{{cite web |url=https://www.numbers-stations.com/articles/the-swedish-security-service-releases-info-on-a-numbers-station/ |title=The Swedish Security Service Releases Info on a Numbers Station |date=24 July 2015 |access-date=12 March 2016 |publisher=NSRIC |df=dmy-all }}</ref><ref>{{cite news |author1=Catinka Mannerfelt Agneskog |title=Säpos hemliga radiotelegram |url=http://www.svd.se/nyheter/inrikes/sapos-hemliga-radiotelegram_4273023.svd |access-date=23 January 2015 |publisher=SvD Nyheter |language=sv}}</ref> with declassified documents proving the same. Few [[QSL card|QSL]] responses have been received from numbers stations<ref>stations KKN44, BFBX and OLX {{cite web |url=http://www.simonmason.karoo.net/page30.html |title=Shortwave Espionage |last=Mason |first=Simon |access-date=28 October 2011 |archive-url=https://web.archive.org/web/20111203183625/http://www.simonmason.karoo.net/page30.html |archive-date=3 December 2011 |url-status=dead}}</ref> by [[shortwave listening|shortwave listeners]]<ref>{{Cite book|last=AMARAL|first=Cristiano Torres|title=Guia Moderno do Radioescuta|publisher=Amazon|year=2021|isbn=978-65-00-20800-9|location=Brasília|pages=333}}</ref> who sent reception reports to stations that identified themselves or to entities the listeners believed responsible for the broadcasts, which is the expected behaviour of a non-clandestine station.<ref>{{Cite web|date=2015-01-24|title=OLX|url=http://www.simonmason.karoo.net/page61.html|url-status=dead|archive-url=https://web.archive.org/web/20150124031223/http://www.simonmason.karoo.net/page61.html|archive-date=2015-01-24|access-date=2020-09-23}}</ref><ref>{{cite book |last=Helms |first=Harry L. |title=How to Tune the Secret Shortwave Spectrum |year=1981 |publisher=TAB Books|location=Blue Ridge Summit, Pennsylvania |isbn=0-8306-1185-1 |page=52 |chapter=Espionage Radio Activity}}</ref>

One well-known numbers station was the E03 "[[Lincolnshire Poacher (numbers station)|Lincolnshire Poacher]]",<ref name="E03 › Priyom.org">{{Cite web|url=http://priyom.org/number-stations/english/e03|title=E03|website=Priyom.org|language=en|access-date=2017-06-17}}</ref> which is thought to have been run by the British [[Secret Intelligence Service]].<ref>{{cite web |url=https://www.numbers-stations.com/E03 |title=E03 The LincolnShire Poacher |access-date=6 September 2014}}</ref> It was first broadcast from [[Bletchley Park]] in the mid-1970s but later was broadcast from [[RAF Akrotiri]] in [[Cyprus]]. It ceased broadcasting in 2008.<ref name=":0">{{Cite web|last=Gorvett|first=Zaria|title=The ghostly radio station that no one claims to run|url=https://www.bbc.com/future/article/20170801-the-ghostly-radio-station-that-no-one-claims-to-run |date=15 July 2020 |access-date=2021-07-12|website=BBC Future |language=en}}</ref>

In 2001, the United States tried the [[Cuban Five]] on the charge of spying for Cuba. The group had received and decoded messages that had been broadcast from the "Atención" number station in Cuba.<ref name="MNT">{{cite news|last=Sokol|first=Brett|date=8 February 2001|title=Espionage Is in the Air|work=Miami New Times|url=http://www.miaminewtimes.com/issues/2001-02-08/kulchur.html|archive-url=https://web.archive.org/web/20010221161138/http://www.miaminewtimes.com/issues/2001-02-08/kulchur.html|archive-date=21 February 2001}}</ref>

=== Atención spy case ===
The "Atención" station of Cuba became the world's first numbers station to be officially and publicly accused of transmitting to spies. It was the centerpiece of a United States federal court espionage trial, following the arrest of the [[Wasp Network]] of Cuban spies in 1998. The U.S. prosecutors claimed the accused were writing down number codes received from Atención, using Sony hand-held shortwave receivers, and typing the numbers into [[laptop]] computers to decode spying instructions. The FBI testified that they had entered a spy's apartment in 1995, and copied the computer decryption program for the Atención numbers code. They used it to decode Atención spy messages, which the prosecutors unveiled in court.<ref name="MNT" />

The United States government's evidence included the following three examples of decoded Atención messages.<ref name="MNT" />
* "prioritize and continue to strengthen friendship with Joe and Dennis"
* "Under no circumstances should [agents] German nor Castor fly with BTTR or another organization on days 24, 25, 26 and 27." (BTTR is the anti-Castro airborne group [[Brothers to the Rescue]])
* "Congratulate all the female comrades for International Day of the Woman."

The moderator of an e-mail list for global numbers station hobbyists claimed that "Someone on the Spooks list had already cracked the code for a repeated transmission [from Havana to Miami] if it was received garbled." Such code-breaking may be possible if a [[one-time pad]] decoding key is used more than once.<ref name="MNT" /> If used properly, however, the code [[One-time pad#Perfect secrecy|cannot be broken]].

=== Recent cases ===
In 2001, [[Ana Belén Montes]], a senior US [[Defense Intelligence Agency]] analyst, was arrested and charged with espionage. The federal prosecutors alleged that Montes was able to communicate with the Cuban [[Intelligence Directorate]] through encoded messages, with instructions being received through "encrypted shortwave transmissions from Cuba".

In 2006, [[Carlos Alvarez (professor)|Carlos Alvarez]] and his wife, [[Elsa Alvarez|Elsa]], were arrested and charged with espionage. The U.S. District Court for the Southern District of Florida<ref>''United States v. Alvarez'', 506 F. Supp. 2d 1285 (S.D. Fla. 2007)</ref>{{which|date=January 2020}} stated that "defendants would receive assignments via shortwave radio transmissions".{{citation needed|date=January 2020}}

In June 2009, the United States similarly charged [[Walter Kendall Myers]] with conspiracy to spy for Cuba, and receiving and decoding messages broadcast from a numbers station operated by the Cuban Intelligence Directorate to further that conspiracy.<ref>{{cite web |first=Dirk |last=Rijmenants |url=https://www.ciphermachinesandcryptology.com/papers/cuban_agent_communications.pdf |title=Cuban Agent Communications |year=2013 |type=PDF |website=Cipher Machines & Cryptology |access-date=30 December 2013}}</ref><ref>{{cite web |url=http://i.cdn.turner.com/cnn/2009/images/06/05/myers.indictment.pdf |title=United States v. Walter Kendall Myers, United States District Court, District of Columbia, no. xxx. |access-date=26 August 2010}}</ref> As discovered by the FBI up to 2010, one way that Russian agents of the [[Illegals Program]] were receiving instructions was via coded messages on shortwave radio.<ref name=":0" />
It has been reported that the United States has used number stations to communicate encoded information to persons in other countries.<ref name="MNT" /> There are also claims that [[State Department]]-operated stations, such as KKN50 and KKN44, used to broadcast similar "numbers" messages or related traffic, although these radio stations have been off the air for many years.<ref>{{cite book |last=Helms |first=Harry L. |title=How to Tune the Secret Shortwave Spectrum |year=1981 |publisher=TAB Books] |location=Blue Ridge Summit, Pennsylvania |isbn=0-8306-1185-1 |page=58 |chapter=Government and Military Communications}}</ref><ref>{{cite book |last=Schimmel |first=Donald W. |title=The Underground Frequency Guide: A Directory of Unusual, Illegal, and Covert Radio Communications |edition=3 |location=Solana Beach, California |publisher=High Text Publications |year=1994 |isbn=1-878707-17-5 |pages=88–95}}</ref>

[[North Korea]] revived number broadcasts in July&nbsp;2016 after a hiatus of sixteen years, a move which some analysts speculated was [[psychological war]];<ref name="Choe-2016-07-21-NYT">{{cite news |last=Choe |first=Sang-Hun |date=2016-07-21 |title=North Korea revives coded spy broadcasts after 16&nbsp;year silence |newspaper=[[The New York Times]] |url=https://www.nytimes.com/2016/07/22/world/asia/north-korea-spy-radio-broadcasts.html |access-date=2016-07-30}}</ref> sixteen such broadcasts occurred in 2017, including unusually timed transmissions in April.<ref name="Osbourne-2017-05-12-DExp">{{cite news |last=Osbourne |first=Simon |date=2017-05-12 |title=North Korea sends chilling coded radio messages to South Korea amid fears of WW3 |newspaper=[[Daily Express]] |url=http://www.express.co.uk/news/world/803845/North-Korea-broadcasts-coded-radio-messages-South-Korea-Kim-Jong-un-World-War-3}}</ref>

== Suspected use for espionage ==

It has long been speculated, and was argued in one court case, that these stations operate as a simple and fool-proof method for government agencies to communicate with spies working undercover.<ref>{{cite book |last=Wagner |first=Thomas |year=2004 |title=If it had Not Been for Fifteen Minutes: A true account of espionage and hair-raising adventure |chapter=Chapter&nbsp;6 – So here she was, with a pillow over her head and over the radio&nbsp;... |chapter-url=http://radio-weblogs.com/0101986/stories/2002/04/24/ifItHadNotBeenFor15MinutesChapter6.html |access-date=30 October 2013}}</ref> According to this hypothesis, the messages must have been encrypted with a [[one-time pad]] to avoid any risk of decryption by the enemy. Writing in 2008, Wallace & [[H. Keith Melton|Melton]] described how numbers stations could be used in this way for espionage:<ref name="Wallace-Melton-2008">{{harvnb|Wallace|Melton|2008|p=438}}</ref>

:The [[one-way voice link]] (OWVL) described a covert communications system that transmitted messages to an agent's unmodified shortwave radio using the high-frequency shortwave bands between {{nobr|3 and 30 MHz}} at a predetermined time, date, and frequency contained in their communications plan.<ref name="Wallace-Melton-2008" />
: The transmissions were contained in a series of repeated random number sequences and could only be deciphered using the agent's one-time pad. If proper tradecraft was practised and instructions were precisely followed, an OWVL transmission was considered unbreakable. As long as the agent's cover could justify possessing a shortwave radio and he was not under technical surveillance, high-frequency OWVL was a secure and preferred system for the CIA during the Cold War.<ref name="Wallace-Melton-2008" />

Evidence to support this theory includes the fact that numbers stations have changed details of their broadcasts or produced special, nonscheduled broadcasts coincident with extraordinary political events, such as the [[1991 Soviet coup d'état attempt|attempted coup of August&nbsp;1991]] in the [[Soviet Union]].<ref>{{cite report |title=Irdial-Discs, included booklet |series=[[The Conet Project]] |website=hyperreal.org |page=59 |url=http://irdial.hyperreal.org/www/conet_project_booklet.pdf |archive-url=https://web.archive.org/web/20060425154733/http://irdial.hyperreal.org/www/conet_project_booklet.pdf |url-status=dead |archive-date=25 April 2006 }}</ref>

A 1998 article in ''[[The Daily Telegraph]]'' quoted a spokesperson for the [[Department of Trade and Industry (United Kingdom)|Department of Trade and Industry]] (the government department that, at that time, regulated radio broadcasting in the United Kingdom) as saying
: "These [numbers stations] are what you suppose they are. People shouldn't be mystified by them. They are not for, shall we say, public consumption."<ref name=Pescovitz1999>{{cite magazine |first=David |last=Pescovitz |date=16 September 1999 |title=Counting spies |magazine=Salon |url=http://www.salon.com/1999/09/16/numbers_2/ |url-status=live |access-date=12 March 2016 |archive-url=https://web.archive.org/web/20000119102137/http://salon.com/people/feature/1999/09/16/numbers/print.html |archive-date=19 January 2000 |df=dmy-all }}</ref>

== Formats ==
[[File:Russian Man signoff 2013-04-23.ogg|thumb|The "Russian Man" station signing off. The numbers read: 83912 83912 10080 10080 46543 46543{{spnd}}257 257 143 143{{spnd}}000 00]]
Generally, numbers stations follow a basic format, although there are many differences in details between stations. Transmissions usually begin on the hour or half-hour.{{citation needed|date=December 2015}}

The prelude, introduction, or call-up of a transmission (from which stations' informal nicknames are often derived) includes some kind of identifier,<ref name="Numbers Stations">{{cite web |url=https://www.numbers-stations.com/ns/ |title=Intro to Numbers Stations |date=8 February 2016 |access-date=12 March 2016 |publisher=NSRIC |df=dmy-all}}</ref> for the station itself, the intended recipient, or both. This can take the form of numeric or [[spelling alphabet|radio-alphabet]] "code names" (e.g. "Charlie India Oscar", "250 250 250", "Six-Niner-Zero-Oblique-Five-Four"), characteristic phrases (e.g. "¡Atención!", "Achtung!", "Ready? Ready?", "1234567890"), and sometimes musical or electronic sounds (e.g. "The Lincolnshire Poacher", "Magnetic Fields"). Sometimes, as in the case of radio-alphabet stations, the prelude can also signify the nature or priority of the message to follow (e.g., it may indicate that no message follows). Often the prelude repeats for a period before the body of the message begins.{{citation needed|date=December 2015}}

After the prelude, there is usually an announcement of the number of number-groups in the message,<ref name="Numbers Stations" /> the page to be used from the one-time pad, or other pertinent information. The groups are then recited. Groups are usually either four or five digits or radio-alphabet letters. The groups are typically repeated, either by reading each group twice or by repeating the entire message as a whole.{{citation needed|date=December 2015}}

Some stations send more than one message during a transmission. In this case, some or all of the above process is repeated, with different contents.{{citation needed|date=December 2015}}

Finally, after all the messages have been sent, the station will sign off in some characteristic fashion. Usually, it will simply be some form of the word "end" in whatever language the station uses (e.g., "End of message; End of transmission", "Ende", "Fini", "Final", "конец"). Some stations, especially those thought to originate from the former Soviet Union, end with a series of zeros, e.g., "00000" "000 000"; others end with music or other sounds.<ref name="Numbers Stations" />

Because of the secretive nature of the messages, the [[cryptography|cryptographic function]] employed by particular stations is not publicly known, except in one (or possibly two){{efn|In the possible case, the underlying type of encryption might have been stated in the court record of the Atención case when the secretly copied decryption software was introduced into evidence.}}) cases. It is assumed that most stations use a one-time pad that would make the contents of these number groups indistinguishable from randomly generated numbers or digits. In one confirmed case, West Germany did use a one-time pad for numbers transmissions.<ref>{{cite web |last1=Wagner |first1=Thomas |title=If it had not been for 15 Minutes, Chapter 7 |url=http://radio-weblogs.com/0101986/stories/2002/12/08/ifItHadNotBeenFor15MinutesChapter7.html |website=Radio Weblogs |access-date=18 March 2022 |archive-url=https://web.archive.org/web/20131102124519/http://radio-weblogs.com/0101986/stories/2002/12/08/ifItHadNotBeenFor15MinutesChapter7.html |archive-date=2 November 2013 |date=8 December 2012 |url-status=live}}</ref>

== Transmission technology ==
[[High-frequency]] radio signals transmitted at relatively low power can travel around the world under ideal [[Radio propagation|propagation]] conditions – which are affected by local [[electromagnetic interference|RF noise]] levels, weather, season, and [[sunspot]]s – and can then be best received with a properly tuned antenna (of adequate, possibly conspicuous size) and a good receiver.<ref name="MNT" />

Although few numbers stations have been tracked down by location, the technology used to transmit the numbers has historically been clear—stock shortwave [[transmitter]]s using powers from 10{{nbsp}}kW to 100{{nbsp}}kW.{{citation needed|date=December 2015}}

[[Amplitude modulation|Amplitude modulated]] (AM) transmitters with optionally–variable frequency, using [[Class-C amplifier|class-C]] power output stages with [[radio transmitter design#Plate AM modulators|plate modulation]], are the workhorses of international shortwave broadcasting, including numbers stations.{{citation needed|date=December 2015}}

Application of [[Spectrum analyzer|spectrum analysis]] to numbers station signals has revealed the presence of data bursts, [[radioteletype]]-modulated [[subcarrier]]s, [[Phase-shift keying|phase-shifted carriers]], and other unusual transmitter modulations like [[Multiple frequency-shift keying|polytones]].<ref>{{cite book |last=Schimmel |first=Donald W. |title=The Underground Frequency Guide: A Directory of Unusual, Illegal, and Covert Radio Communications |edition=3 |location=Solana Beach, California |publisher=High Text Publications, Inc. |year=1994 |isbn=1-878707-17-5 |pages=27–28}}</ref> (RTTY-modulated subcarriers were also present on some U.S. commercial radio transmissions during the Cold War.<ref>{{cite journal |last=Collins |first=Barry W. |title=The day the U.S. Army invaded W4TLV |journal=QST |volume=81 |pages=48–49 |date=July 1997 |issn=0033-4812}}</ref>)
[[File:Sprach-Morse-Generator.jpg|thumb|The Speech/Morse generator (pictured here) is a machine that has been used for many well-known numbers stations]]

The frequently reported use of high-tech modulations like [[burst transmission|data bursts]], in combination or in sequence with spoken numbers, suggests varying transmissions for differing intelligence operations.<ref>{{cite web |url=http://www.cvni.net/radio/nsnl/nsnl015/nsnl15vs.html |title=NSNL 15: Voice stations |publisher=Cvni.net |date=3 July 1999 |access-date=26 August 2010 |archive-date=26 January 2021 |archive-url=https://web.archive.org/web/20210126030846/http://www.cvni.net/radio/nsnl/nsnl015/nsnl15vs.html |url-status=dead }}</ref>

Those receiving the signals often have to work only with available hand-held receivers, sometimes under difficult local conditions, and in all reception conditions (such as sunspot cycles and seasonal static).<ref name="MNT" /> However, in the field low-tech spoken number transmissions continue to have advantages even in the 21st century. High-tech data-receiving equipment can be difficult to obtain and even a non-standard civilian shortwave radio can be difficult to obtain in a totalitarian state.<ref>{{cite web |last1=Wagner |first1=Thomas |title=If it had not been for 15 Minutes, Chapter 6 |url=http://radio-weblogs.com/0101986/stories/2002/04/24/ifItHadNotBeenFor15MinutesChapter6.html |website=Radio Weblogs |access-date=18 March 2022 |archive-url=https://web.archive.org/web/20141101065629/http://radio-weblogs.com/0101986/stories/2002/04/24/ifItHadNotBeenFor15MinutesChapter6.html |archive-date=1 November 2014 |date=24 April 2002 |url-status=live}}</ref> Being caught with just a shortwave radio has a degree of [[plausible deniability]], for example, that no spying is being conducted.{{citation needed|date=December 2015}}

== Interference ==

=== Interfering with other broadcasts ===
The North Korean foreign language service [[Voice of Korea]] began to broadcast on the E03 [[Lincolnshire Poacher (numbers station)|Lincolnshire Poacher]]'s former frequency, 11545&nbsp;kHz, in 2006, possibly to deliberately interfere with its propagation.{{citation needed|date=October 2017}} However, Lincolnshire Poacher broadcasts on three different frequencies, and the remaining two, have not been interfered with. The apparent target zone for the Lincolnshire Poacher signals originating in Cyprus was the Middle East, not the Far East, which is covered by its sister station, E03a [[Cherry Ripe (numbers station)|Cherry Ripe]].<ref>{{Cite web|url=http://priyom.org/number-stations/english/e03a|title=E03a|website=Priyom.org|language=en|access-date=2017-06-17}}</ref><ref name="karoo514">{{cite web |url=http://www.simonmason.karoo.net/page514.htm |title=Secret Signals |publisher=Simonmason.karoo.net |access-date=7 November 2015 |archive-date=10 February 2016 |archive-url=https://web.archive.org/web/20160210010724/http://www.simonmason.karoo.net/page514.htm |url-status=dead }}</ref>

On 27 September 2006, amateur radio transmissions in the 30&nbsp;m band were affected by an S06 "Russian Man"<ref>{{cite web |url=http://priyom.org/number-stations/slavic/s06 |title=S06|website=Priyom.org |language=en |access-date=2017-06-17}}</ref> numbers station at 17:40 UTC.<ref name="karoo514" />

In October 1990, it was reported that a numbers station had been interfering with communications on 6577&nbsp;kHz, a frequency used by air traffic in the Caribbean. The interference was such that on at least one monitored transmission, it blocked the channel entirely and forced the air traffic controller to switch the pilot to an alternative frequency.<ref name="karoo514" />

A [[BBC]] frequency, 7325&nbsp;kHz, has also been used. This prompted a letter to the BBC from a listener in [[Andorra]]. She wrote to the [[BBC World Service|World Service]] ''[[Waveguide]]'' programme in 1983 complaining that her listening had been spoiled by a female voice reading out numbers in English and asked the announcer what this interference was. The BBC presenter laughed at the suggestion of spy activity. He had consulted the experts at [[Bush House]] (BBC World Service headquarters), who declared that the voice was reading out nothing more sinister than snowfall figures for the ski slopes near the listener's home. After more research into this case, shortwave enthusiasts are fairly certain that this was a numbers station being broadcast on a random frequency.<ref>{{cite web |url=http://www.simonmason.karoo.net/page34.html |title=Secret Signals |publisher=Simonmason.karoo.net |access-date=26 August 2010 |archive-url=https://web.archive.org/web/20070220145145/http://www.simonmason.karoo.net/page34.html |archive-date=20 February 2007 |url-status=dead }}</ref>

The Cuban numbers station "HM01" has been known to interfere with shortwave broadcaster Voice of Welt on 11530&nbsp;kHz.<ref>{{Citation|last=Anthony Spinelli|title=HM01 and Voice of Welt 11530 AM 10 18 2018 1743z|date=2018-10-18|url=https://www.youtube.com/watch?v=JgzyVNGdbzM |archive-url=https://ghostarchive.org/varchive/youtube/20211211/JgzyVNGdbzM| archive-date=2021-12-11 |url-status=live|access-date=2018-11-26}}{{cbignore}}</ref>

=== Attempted jamming ===
Numbers station transmissions have often been the target of intentional jamming attempts. Despite this targeting, many numbers stations continue to broadcast unhindered. Historical examples of jamming include the E10 (a station thought to originate from Israel's [[Mossad]] intelligence agency) being jammed by the "Chinese Music Station" (thought to originate from the [[People's Republic of China]] and usually used to jam "[[Sound of Hope]]" radio broadcasts which are anti-CCP in nature).<ref>{{cite web |url=http://www.swldxer.co.uk/yhf-dec06.wma |title=Chinese Music Station |format=Windows Media Audio |access-date=16 July 2012 |archive-url=https://web.archive.org/web/20120308232621/http://www.swldxer.co.uk/yhf-dec06.wma |archive-date=8 March 2012 |url-status=usurped }}</ref>

== Identification and classification ==
Monitoring and chronicling transmissions from numbers stations has been a hobby for shortwave and [[ham radio]] enthusiasts from as early as the 1970s.<ref>Māris Goldmanis, [https://www.numbers-stations.com/articles/before-enigma-the-early-numbers-stations-monitors/ Before enigma; the early numbers stations, monitors] NSRIC; retrieved 13 December 2019</ref> Numbers stations are often given nicknames by enthusiasts, often reflecting some distinctive element of the station such as the [[interval signal]]. For example, the "Lincolnshire Poacher" station played the first two bars of the folk song "[[The Lincolnshire Poacher]]" before each string of numbers.<ref>{{harvnb|Mason|1991|pages=20–21}}</ref> Sometimes these traits have helped to uncover the broadcast location of a station.  The "Atención" station was thought to be from [[Cuba]], because a supposed error allowed [[Radio Havana Cuba]] to be carried on the frequency.<ref>{{cite book |last=Poundstone |first=William |title=Big Secrets |page=197}}</ref>{{full citation needed|date=December 2022}}

{{Undue weight|date=January 2023}}

Although many numbers stations have nicknames which usually describe some aspect of the station itself, these nicknames have sometimes led to confusion among listeners, particularly when discussing stations with similar traits. M. Gauffman of the ENIGMA numbers stations monitoring group originally assigned a code to each known station.<ref name="NSRIC">{{cite news |title=ENIGMA: The European Numbers Information Gathering and Monitoring Association |url=https://www.numbers-stations.com/enigma |publisher=NSRIC |access-date=24 February 2015}}</ref>

Portions of the original [[ENIGMA group]] moved on to other interests in 2000 and the classification of numbers stations was continued by the follow-on group ENIGMA 2000.<ref>{{cite web |title=ENIGMA 2000 |url=http://apul64.dsl.pipex.com/enigma2000/ |access-date=1 March 2015 |archive-date=15 September 2009 |archive-url=https://web.archive.org/web/20090915175228/http://www.apul64.dsl.pipex.com/enigma2000/ |url-status=dead }}</ref> The document containing the description of each station and its code designation was called the "ENIGMA Control List" until 2016, after which it was incorporated into the "ENIGMA 2000 Active Station List"; the latest edition of the list was published in September 2017.<ref>{{cite web|date=September 2017|title=ENIGMA 2000 Active Station List|url=http://www.signalshed.com/docs/ENIGMA%202000%20Active%20Stations%20List%20V1.3.pdf|access-date=2020-08-25|website=signalshed.com|publisher=ENIGMA 2000|type=Booklet|version=1.3}}</ref> This classification scheme takes the form of a letter followed by a number (or, in the case of some "X" stations, more numbers).<ref>{{cite journal |journal=[[Radio World]] |year=2014 |pages=14 |last=Friesen |first=Christopher |title=Spy 'Numbers Stations' still enthrall |issn=0274-8541 |volume=38 |issue=2}}</ref> The letter indicates the language used by the station in question:
* E indicates a station broadcasting in English.
* G indicates a station broadcasting in German.
* S indicates a station broadcasting in a [[Slavic languages|Slavic language]].
* V indicates all other languages.
* M is a station broadcasting in [[Morse code]].
* X indicates all other transmissions, such as polytones, in addition to some unexplained broadcasts which may not actually be numbers stations.

There are also a few other stations<ref name="Numbers Stations" /> with a specific classification:
* SK: Digital mode
* HM: Hybrid mode
* DP: Digital-pseudo polytone

Some stations have also been stripped of their designation when they were discovered not to be a numbers station. This was the case for E22, which was discovered in 2005 to be test transmissions for [[All India Radio]].<ref>{{Cite web|url=http://www.cvni.net/radio/e2k/e2k032/e2k32e22.html|title=E2K 32 – E22 is not what it seems|website=www.cvni.net|archive-url=https://web.archive.org/web/20071117095441/http://www.cvni.net/radio/e2k/e2k032/e2k32e22.html|access-date=2016-04-05|archive-date=17 November 2007}}</ref>

== Recordings ==
* ''[[The Conet Project]]: Recordings of Shortwave Numbers Stations'' is a four-[[compact disc|CD]] set of recordings of numbers stations. It was first released in 1997 by the Irdial-Discs record label.

== In popular culture ==
{{Primary sources |section|date=December 2023}}

=== Film ===
* The British–American action thriller ''[[The Numbers Station]]'', released in 2013 and starring [[John Cusack]] and [[Malin Åkerman]], features a [[Central Intelligence Agency|CIA]]‑run numbers station in the British countryside.<ref name="Dowd2013">{{cite web |url=http://www.avclub.com/review/the-numbers-station-96938 |title=Movie Review: The Numbers Station |work=The A.V. Club |date=25 April 2013 |archive-url=https://web.archive.org/web/20160312201645/http://www.avclub.com/review/the-numbers-station-96938 |archive-date=12 March 2016 |url-status=live |first=A.&nbsp;A. |last=Dowd |location=Chicago |df=dmy-all }}</ref>
* The 2013 American horror film ''[[Banshee Chapter]]'', starring [[Ted Levine]] and [[Katia Winter]], features a numbers station transmitting from the [[Black Rock Desert]] in [[Nevada]].<ref>{{cite web |url=https://variety.com/2014/film/reviews/film-review-banshee-chapter-1201037926/ |title=Film Review: 'Banshee Chapter' |first=Dennis |last=Harvey |website=[[Variety (magazine)|Variety]] |date=8 January 2014 |access-date=28 December 2023}}</ref>

=== Television ===
* In the British television spy drama ''[[Spooks (TV series)|Spooks]]'' episode "[[Nuclear Strike (Spooks)|Nuclear Strike]]", a Russian [[sleeper agent]] is awoken by a numbers station broadcast to detonate a nuclear suitcase bomb in central [[London]]. The radio broadcast states in Russian, "2.5.0.0.2.5, Finland Red, Egypt White, It is twice blest, It is twice blest, rain from heaven, rain from heaven."{{citation needed|date=September 2023}}
* The American science fiction series ''[[Fringe (TV series)|Fringe]]'' has an episode, "[[6955 kHz]]", featuring a numbers station that induces amnesia.<ref>{{cite web |url=https://www.avclub.com/fringe-6995-khz-1798166505 |title=''Fringe'': '6995&nbsp;kHz' |first=Noel |last=Murray |work=The A.V. Club |date=12 November 2010 |access-date=1 October 2012}}</ref>
* In the British mystery series ''[[Endeavour (TV series)|Endeavour]]'' episode "[[List of Endeavour episodes#Series 5 (2018)|Quartet]]", a spy ring in [[Oxford]] communicates using a numbers station, which has a female voice that speaks German and uses "[[London Bridge Is Falling Down]]" as an interval signal.<ref>{{cite episode |title=Quartet |series=Endeavour |series-number=5 |number=5 |url=https://www.pbs.org/wgbh/masterpiece/episodes/endeavour-s5-e5/ |network=[[PBS]] |time=1:09:00 |time-caption=At}}</ref>
* In the 2020 British show ''[[Truth Seekers]]'', the protagonists listen to a parody of the [[Lincolnshire Poacher (numbers station)|Lincolnshire Poacher]].<ref>{{cite web |title=The truth is way, way out there: how Cold War radio signals inspired new series Truth Seekers |url=https://www.theguardian.com/amazon-prime-video-truth-seekers/2020/oct/30/the-truth-is-way-way-out-there-how-cold-war-radio-signals-inspired-new-series-truth-seekers |archive-url=https://web.archive.org/web/20221025074155/https://www.theguardian.com/amazon-prime-video-truth-seekers/2020/oct/30/the-truth-is-way-way-out-there-how-cold-war-radio-signals-inspired-new-series-truth-seekers |archive-date=25 October 2022 |url-status=dead |website=[[The Guardian]] |date=29 October 2020 |access-date=1 November 2020 }}</ref> <!-- Primary source (sponsored content) -->

=== Literature ===
* The first section of ''In the Dark'', a Chinese novel by [[Mai Jia]], focuses on a [[Cryptography|cryptographer]] in Special Unit 701, part of China's effort to track down and decode enemy number stations. The novel has been adapted into a TV series and a movie.<ref name="Forbes2016">{{cite web |url=http://www.pressreader.com/uae/the-national-news-the-review/20150829/281547994649041/TextView |title=Book review: Mai Jia's In the Dark shines a light on China's secret world |access-date=12 March 2016 |work=[[The National (Abu Dhabi)|The National]] |date=27 August 2015 |archive-url=https://web.archive.org/web/20160303153738/http://www.thenational.ae/arts-lifestyle/the-review/book-review-mai-jias-in-the-dark-shines-a-light-on-chinas-secret-world |archive-date=3 March 2016 |url-status=live |first=Malcolm |last=Forbes |df=dmy-all }}</ref>

=== Music ===
* American band [[Wilco]] named its 2001 album ''[[Yankee Hotel Foxtrot]]'' after a segment of a recorded numbers station transmission. Samples from E10, an Israeli numbers station, appear in the album's song "Poor Places".<ref name="Shachtman2004">{{cite magazine |url=http://archive.wired.com/entertainment/music/news/2004/06/63952 |magazine=Wired |date=23 June 2004 |title=Wilco Pays Up for Spycasts |access-date=12 March 2016 |archive-url=https://web.archive.org/web/20080421131324/http://www.wired.com/entertainment/music/news/2004/06/63952 |archive-date=21 April 2008 |first=Noah |last=Shachtman |url-status=dead |df=dmy-all }}</ref>
* American musician [[Neil Cicierega]]'s 2014 [[mashup (music)|mashup]] album ''[[Mouth Silence]]'' includes the track "Transmission", which rearranges samples of the [[David Bowie]] song "[[Space Oddity]]" to resemble a numbers station broadcast.<ref>{{cite web |title=Neil Cicierega – Transmission Lyrics |url=https://genius.com/Neil-cicierega-transmission-lyrics |access-date=30 November 2017 |website=[[Genius (company)|Genius]]}}</ref> <!-- Better source? -->
* Icelandic composer [[Jóhann Jóhannsson]] sampled tape recordings of German numbers station broadcasts in the track "A Song for Europa" on his 2016 album ''[[Orphée (album)|Orphée]]''.<ref>{{cite web |last=Robertson |first=Derek |title=Jóhann Jóhannsson's Track By <!--sic--> Track Guide to Orphée |url=http://drownedinsound.com/in_depth/4150386-j-hann-j-hannssons-track-by-track-guide-to-orph-e |website=[[Drowned in Sound]] |date=15 September 2016 |access-date=28 December 2023 |language=en |archive-date=15 February 2018 |archive-url=https://web.archive.org/web/20180215143940/http://drownedinsound.com/in_depth/4150386-j-hann-j-hannssons-track-by-track-guide-to-orph-e |url-status=live}}</ref>
* American [[metalcore]] band [[Norma Jean (band)|Norma Jean]]'s 2016 album ''[[Polar Similar]]'' includes a track titled "II.  The People" that samples a recording of the Lincolnshire Poacher.<ref>{{Cite news |last=Zorgdrager |first=Bradley |date=7 September 2016 |title=Norma Jean: Polar Similar |website=[[Exclaim!]] |url=http://exclaim.ca/music/article/norma_jean-polar_similar |access-date=1 November 2020}}</ref>

=== Radio and podcasts ===
* Several [[BBC Radio 4]] dramas have incorporated numbers stations:
** The standalone 2015 drama ''Fugue State'', written by [[Julian Simpson]], focuses on a British government agent investigating a numbers station in a remote village, and features recordings of numbers stations.<ref>{{cite web |title=Fugue State |url=http://www.bbc.co.uk/programmes/b06kgvc4 |website=BBC Radio 4 |access-date=26 February 2016}}</ref> <!-- Primary source -->
** Numbers stations, including the Lincolnshire Poacher, feature in Simpson's 2019 adaptation of [[H. P. Lovecraft]]'s ''[[The Whisperer in Darkness]]'', the second series of ''[[The Lovecraft Investigations]]''.<ref>{{cite web |title=The Whisperer in Darkness |url=https://www.bbc.co.uk/programmes/p06spb8w/episodes/downloads |website=BBC Radio 4 Podcasts |access-date=5 December 2019}}</ref> <!-- Primary source -->
** The 5-part 2022 drama ''Dead Hand'' by Stuart Drennan features a numbers station in [[Northern Ireland]] broadcasting the voices of individuals who have mysteriously disappeared.<ref>{{cite web|title=Dead Hand|url=https://www.bbc.co.uk/programmes/m0015vls|website=BBC Radio 4 Limelight|access-date=1 April 2022}}</ref> <!-- Primary source -->
* In a 2015 episode of ''[[Welcome to Night Vale]]'', a numbers station called WZZZ begins broadcasting words along with its numbers.<ref>{{cite web |title=Welcome to Night Vale Recap: Numbers |url=https://www.themarysue.com/welcome-to-night-vale-recap-42/ |website=[[The Mary Sue]] |date=4 December 2015 |access-date=20 November 2020}}</ref>
* ''[[The Magnus Archives]]''' 2019 episode "Decrypted" features a numbers station that appears on an iPod, attached to the entity The Extinction.<ref>{{cite web |title=Magnus 144: Decrypted |url=https://play.acast.com/s/themagnusarchives/mag144-decrypted/ |website=Acast |date=11 July 2019 |access-date=1 July 2021}}</ref> <!-- Primary source -->
* A 2008 episode of ''[[Skeptoid]]'' discusses numbers stations.<ref>{{cite web |title=Skeptoid: Spy Radio: Numbers Stations |url=https://skeptoid.com/episodes/4107 |website=Skeptoid |access-date=12 February 2022}}</ref> <!-- Primary source -->

=== Visual art ===
* In 2005 at the [[Mattress Factory]], Noah Lang, in conjunction with- and invited by Akin Fernandez, presented several stand-alone sculptures based on numbers stations broadcasting antennas including [[the Buzzer]], [[the Lincolnshire Poacher]], and [[Cherry Ripe (numbers station)|Cherry Ripe]]. <ref>{{cite web |title=(secret) Messages and (cryptic) Communications |url=https://wavefarm.org/wf/calendar/yddpq8 |website=Wave Farm}}</ref>

=== Video games ===
* In ''[[Signalis]]'', the player uses in-game radio signals transmitting numbers to solve puzzles. Some frequencies feature samples from historical German number stations.<ref>{{cite web |title=Signalis Review: Numbers Stations and Numbing Dread |url=https://www.fanbyte.com/games/reviews/signalis-review-numbers-stations-and-numbing-dread/ |website=Fanbyte |date=26 October 2022 |access-date= 17 April 2023}}</ref>
* In ''[[Call of Duty: Black Ops]]'', the main character Alex Mason is brainwashed in the Soviet Gulag of [[Vorkutlag]], and receives orders from a numbers station broadcast in Cuba.<ref>{{Cite web |last=Milzarski |first=Eric |date=2018-06-27 |title=How numbers stations like the ones in 'Black Ops' worked |url=https://www.wearethemighty.com/mighty-gaming/numbers-stations-cod-black-ops/ |access-date=2024-02-20 |website=We Are The Mighty |language=en}}</ref>

== See also ==
{{portal|Radio}}
* [[Secret broadcast]]
* [[Letter beacon]]
* [[Yosemite Sam (shortwave)]]
* [[UVB-76]]
* [[Warrenton Training Center]]
* [[Radio Londres]]
* [[Markovian Parallax Denigrate]]

== Notes ==
{{Notelist}}

== References ==
{{reflist}}

== Bibliography ==
{{refbegin|small=yes}}
* {{cite book |last=Mason |first=Simon |year=1991 |title=Secret Signals: The Euronumbers Mystery |publisher=Tiare Publications |location=Lake Geneva, WI |isbn=0-936653-28-0 |url=http://www.simonmason.karoo.net/page32.html |access-date=24 December 2013 |url-status=dead |archive-url=https://web.archive.org/web/20060613195836/http://www.simonmason.karoo.net/page32.html |archive-date=13 June 2006}}
* {{cite journal |first1=Robert |last1=Wallace |first2=H. Keith |last2=Melton |author2-link=H. Keith Melton |date=June 2008 |title=Spycraft: The Secret History of the CIA's Spytechs, from Communism to al-Qaeda |journal=Intelligence Studies |series=Studies in Computational Intelligence |volume=52 |issue=2 |doi=10.1007/978-3-540-76361-1 |isbn=978-3-540-76359-8 |url=https://www.cia.gov/static/66a33964c68ff18076cee58bf68b2c68/Review-Spycraft-Secret-History.pdf |via=The U.S. [[Central Intelligence Agency]]}} {{cite web |title=Alternate Source |date=7 October 2016 |website=[[The Internet Archive]] (archive.org) |url=https://archive.org/details/SPYCRAFTTHESECRETHISTORYOFTHECIASSPYTECHSFROMCOMMUNISMTOALQAEDA2008}}
* {{cite book |first1=Robert |last1=Wallace |first2=H. Keith |last2=Melton |author2-link=H. Keith Melton |date=26 May 2009 |title=Spycraft: The Secret History of the CIA's Spytechs, from Communism to al-Qaeda |location=New York, NY |publisher=Plume |isbn=978-0-452-29547-6 |edition=Illustrated, print}}
{{refend}}

== Further reading ==
{{refbegin}}
* {{cite journal |last=Beaumont |first=Paul |journal=Radio User |date=November 2012 |title=Numbers Stations: A Modern Perspective (Part&nbsp;1) |pages=50–53 |publisher=PW Publishing |location=Poole, UK |issn=1748-8117}}
* {{cite journal |last=Beaumont |first=Paul |journal=Radio User |date=January 2013 |title=Numbers Stations: A Modern Perspective (Part&nbsp;2) |pages=50–55 |publisher=PW Publishing |location=Poole, UK |issn=1748-8117}}
* {{cite journal |last=Bury |first=Jan |journal=Cryptologia |volume=31 |issue=4 |date=October 2007 |title=From the Archives: The U.S. and West German Agent Radio Ciphers |pages=343–57 |doi=10.1080/01611190701578104 |s2cid=205487634 |url=http://www.swldxer.co.uk/polish.mht |archive-url=https://web.archive.org/web/20121223120639/http://www.swldxer.co.uk/polish.mht |url-status=usurped |archive-date=23 December 2012 |issn=0161-1194|url-access=subscription }}
* {{cite journal |last=Friesen |first=Christopher |journal=[[Radio World]] |volume=38 |issue=2 |date=15 January 2014 |pages=12, 14 |title=Spy 'Numbers Stations' Still Enthrall |url=https://www.researchgate.net/publication/340451591_Spy_Numbers_Stations_Still_Enthrall |issn=0274-8541}}
* {{cite book |last=Moon |first=Havana |title=Uno, Dos, Cuatro: A Guide to the Numbers Stations |publisher=Tiare Publications |location=Lake Geneva, WI |year=1987 |isbn=0-936653-06-X |url=http://www.numbersoddities.nl/unodoscuatro.pdf |access-date=24 December 2013}}
* {{cite book |last=Pierce |first=Langley |title=Intercepting Numbers Stations |publisher=Interproducts |location=Perth, UK |year=1994 |isbn=0-9519783-4-9}}
* {{cite book |last=Schimmel |first=Donald W. |title=The Underground Frequency Guide: A Directory of Unusual, Illegal, and Covert Radio Communications |edition=3rd |chapter=1. Numbers Stations |pages=1–28 |publisher=High Text Publications |location=Solana Beach, California |year=1994 |isbn=1-878707-17-5}}
* {{cite journal |last=Smolinski |first=Chris |journal=[[Popular Communications]] |date=February 1998 |pages=8–10 |title=Spy Numbers Stations: Have You Heard Them? |publisher=CQ Communications |location=Hicksville, NY |issn=0733-3315}}
{{refend}}

== External links ==
{{Commons category|Numbers stations}}
* [https://www.numbers-stations.com/ Numbers Stations Research and Information Center]

{{Espionage}}

{{intelligence cycle management}}

[[Category:Cold War broadcasting]]
[[Category:Numbers stations| ]]
[[Category:Secret broadcasting]]
[[Category:Radio stations]]
[[Category:Cold War terminology]]