View source for Allouis longwave transmitter

{{Short description|French longwave broadcast transmitter}}
{{Use dmy dates|date=November 2018}}

The '''Allouis longwave transmitter''' has been [[France]]'s central [[longwave]] [[broadcast]] [[transmitter]] since 1939.  It is located near the village of [[Allouis]].

[[File:emetteur-allouis3.jpg|300px|thumb|Allouis transmitter]]
It broadcast the [[France Inter]]  public radio station from October 1952<ref name=chronology/> until 31 December 2016.  Since 2017, it broadcasts only the [[TDF time signal]], which has been renamed ALS162 since 2017. 

The first transmitter, built in 1939 during the [[Phoney War]], used an aerial with four masts and a transmitter rated at 500 [[kilowatt]]s.<ref name=chronology>{{in lang|fr}}[http://pagesperso-orange.fr/tvignaud/am/allouis/allouis-chrono.htm Chronologie des radios françaises en ondes longues 1921–2000] ("Chronology of french long-wave transmitters 1921–2000")</ref>  It was destroyed in 1944 during the [[scorched earth]] retreat by German forces.

On 19 October 1952 a new 250&nbsp;kW transmitter came into service. This used a special [[cage aerial]], mounted on a {{convert|308|m|ft|0|abbr=on}} high earthed mast. In 1957 the transmission power was increased to 600&nbsp;kW, in 1974 to 1,000&nbsp;kW, and in 1981 to 2,000&nbsp;kW. Transmission power was reduced to 1,000&nbsp;kW during the hours of darkness. In 2011 the transmission power was reduced to 1,500&nbsp;kW for cost savings. For the same reason the transmission power was reduced to 1,100&nbsp;kW in 2017 and subsequently in February 2020 to 800&nbsp;kW.<ref name=anfr>[https://www.anfr.fr/gestion-des-frequences-sites/signal-horaire/quest-ce-que-le-signal-horaire/ ANFR website (in French)]</ref><ref>[http://pa3fwm.nl/signals/tdf162kHz-power/ TDF 162 kHz power test, November 2019 Pieter-Tjerk de Boer, PA3FWM]</ref><ref>[http://pa3fwm.nl/signals/tdf162kHz-antennatest/ TDF 162 kHz antenna test, February 2020 Pieter-Tjerk de Boer, PA3FWM]</ref> In 2024, tests were performed at a reduced transmission power of 675 kW.<ref>{{Cite web |title=Diffusion du signal horaire : l'ANFR lance une expérimentation à partir d'aujourd'hui {{!}} Maire-Info, quotidien d'information destiné aux élus locaux |url=https://www.maire-info.com/am%C3%A9nagement-num%C3%A9rique-du-territoire/diffusion-du-signal-horaire-l'anfr-lance-une-experimentation-%EF%BF%BD-partir-d'aujourd'hui-article-29034 |access-date=2024-10-27 |website=www.maire-info.com}}</ref>

In 1974 the aerial was renewed. The cage aerials were removed and the mast height was increased to {{convert|350|m|ft|0|abbr=on}}. A second mast of the same height was constructed at the same time.

In 1977, the current [[phase modulation|phase modulated]] time signal was added to the transmissions.  The broadcast frequency, formerly 164&nbsp;kHz, was changed to 163.840&nbsp;kHz (the 5th harmonic of the common 32,768&nbsp;Hz timekeeping frequency used by most [[quartz clock]]s) to be a more convenient frequency standard.<ref name=reorient/>

In 1980, the first [[atomic clock]] was installed to regulate the [[carrier frequency]].<ref name=reorient>{{in lang|fr}}[http://pagesperso-orange.fr/tvignaud/am/allouis/allouis4.htm Les ré-orientations]</ref>

On 1 February 1986, the frequency was changed to its current value of 162&nbsp;kHz (still an accurately controlled frequency standard) to bring it to a multiple of 9&nbsp;kHz in accordance with the [[Geneva Frequency Plan of 1975]].

The radio channel [[France Inter]] announced during 2016 that the channel would discontinue transmitting on the 162&nbsp;kHz frequency on 31 December 2016, seeking cost savings of approximately 6 million Euros per year. The transmission of the [[ALS162 time signal]] was and will be continued after this date, as this time signal is critical for over 300,000 devices, which are deployed within French enterprises and state entities, like the French railways SNCF, the electricity distributor ENEDIS, airports, hospitals, municipalities, et cetera.<ref>{{in lang|fr}}[http://www.lalettre.pro/Le-signal-horaire-restera-sur-le-162-kHz-de-France-Inter_a12354.html Le signal horaire restera sur le 162 kHz de France Inter]</ref><ref>{{in lang|fr}}[https://www.leberry.fr/allouis-18500/actualites/l-emetteur-d-allouis-passe-aussi-a-l-heure-d-ete-cette-nuit_13529170/ L'émetteur d'Allouis passe aussi à l'heure d'été cette nuit]</ref>
The transmitter is owned by [[TDF Group|TéléDiffusion de France]] and the dissemination of the Metropolitan French national legal time to the public is a joint responsibility of ANFR (state body for radio frequencies), the trade body France Horlogerie and the [[Paris Observatory|LNE-SYRTE]] and LNE-LTFB time laboratories.<ref>[https://syrte.obspm.fr/spip/services/ref-temps/article/mise-a-disposition-du-temps-legal-par-le-signal-als162 Provision of the legal time by ALS162 signal]</ref> 

==References==
{{Reflist}}

==External links==
* {{Structurae|id=20010738|title=France Inter Radio Masts}}
* {{in lang|fr}} http://perso.wanadoo.fr/tvignaud/am/allouis/fr-allouis.htm
* http://www.skyscraperpage.com/diagrams/?b44247
* http://skyscraperpage.com/diagrams/?b58020

{{coord|47|10|10.5|N|2|12|16.5|E|type:landmark|display=title}}

{{Radio France}}
{{TimeSig}}
{{Time Topics}}
{{Time measurement and standards}}

[[Category:Radio masts and towers in Europe]]
[[Category:Buildings and structures in Cher (department)]]
[[Category:Transmitter sites in France]]
[[Category:Time signal radio stations]]
[[Category:1939 establishments in France]]