View source for VLF transmitter DHO38

{{Short description|VLF radio transmitter operated by German Navy}}
[[File:Marinesender DHO38 Längstwellensender der Marine.jpg|thumb|VLF transmitter DHO38]]
The '''VLF transmitter DHO38''' (known as ''VLF/MSK Marinefunksendestelle Rhauderfehn'' or ''Marinefunksendestelle Saterland-Ramsloh'')<ref name="nwz">{{cite web |last1=Zur Brügge |first1=Jan |title=25 Jahre Arbeit zwischen den Türmen |url=https://www.nwzonline.de/wirtschaft/ramsloh-jubilaeum-25-jahre-arbeit-zwischen-den-tuermen_a_5,1,478844132.html# |website=www.nwzonline.de |access-date=9 April 2025 |language=de |date=13 December 2007}}</ref> is a very low frequency ([[VLF]]) transmitter used by the [[German Navy]] near [[Rhauderfehn]], [[Saterland]], [[Germany]]. It is used to transmit coded orders to [[submarine]]s of the [[German Navy]] and navies of other [[NATO]] countries.<ref>{{cite web |last1=Meredith |first1=Nigel P. |last2=Horne |first2=Richard B. |last3=Clilverd |first3=Mark A. |last4=Ross |first4=Johnathan P. J. |title=An Investigation of VLF Transmitter Wave Power in the Inner Radiation Belt and Slot Region |url=https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JA026715 |website=Journal of Geophysical Research: Space Physics |access-date=9 April 2025 |pages=5246–5259 |language=en |doi=10.1029/2019JA026715 |date=2019}}</ref>

DHO38 has transmitted since 1982 on 23.4 [[Hertz|kHz]] with a power of up to 800 [[Watt|kilowatts]], although other sources says 300kW is the usual power.<ref>{{cite journal |last1=Němec |first1=F. |last2=Santolík |first2=O. |last3=Albert |first3=J. M. |title=VLF Transmitter Signals Observed by the Cluster Spacecraft Over a Wide Range of Latitudes |journal=Journal of Geophysical Research: Space Physics |date=2025 |volume=130 |issue=2 |pages=e2024JA033621 |doi=10.1029/2024JA033621 |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024JA033621 |language=en |issn=2169-9402|doi-access=free }}</ref> Each mast is powered by 100kW transmitter but all masts operate at once.<ref name="esut">{{cite web |last1=Heiming |first1=Gerhard |title=Modernisierung der NATO VLF/MSK Marinefunksendestelle Rhauderfehn abgeschlossen |url=https://esut.de/2019/12/meldungen/ruestung2/17297/modernisierung-der-marinefunksendestelle-fuer-u-boote-abgeschlossen/ |website=esut.de |language=de-DE |date=10 December 2019}}</ref> The transmitter is able to transmit signals in a range from 14 to 50 kHz.<ref name="bundes">{{Cite web |date=2018-08-02 |title=U-Boot-Kommunikation: Der „Unterwasser“-Sender |url=https://www.bundeswehr.de/de/organisation/marine/aktuelles/u-boot-kommunikation-funksendestelle-ramsloh-89966 |access-date=2025-02-27 |website=www.bundeswehr.de |language=de}}</ref> DHO38 uses an [[umbrella antenna]] which is carried from eight steel tube masts each with a height of {{convert|352.8|metres}}. Each pylon stands on three-metre-tall [[ceramic]] cylinders, which serve as [[Electrical insulation|insulator]]s for voltages up to 300 [[Volt|kV]].<ref name="bundes" /> The masts are equipped with cylindrical [[oscillation]] [[Tuned mass damper|dampers]] for better protection against storms.<ref>{{cite web |title=Die NATO VLF / MSK Marinefunksendestelle Rhauderfehn |url=https://media.frag-den-staat.de/files/foi/470661/Info-Flyer.pdf |access-date=10 April 2025 |language=DE |format=pdf |date=n.d.}}</ref> 

Each mast has an [[antenna tuning hut]] and sits on a copper mat 30cm under the ground. The site is wet which helps improve the performance of the antenna.<ref name="nwz" /> The transmitter is capable of transmitting signals to submarines worldwide to depths of approx. 30 metres.<ref name="bundes" />

In 2016 the transmitters were updated to semi-conductor technology from the previous [[Vacuum tube|valve]] based ones.<ref name="esut" />

== Transmission ==
[[File:Marinesender DHO38 Längstwellensender der Marine - Abstimmmittel-Häuser.jpg|thumb|right|The masts and cables]]

The signal from DHO38 is an [[Minimum-shift keying|MSK]]-coded signal with 4 x 50 baud on all 4 channels on frequency 23.4 kHz.<ref>{{cite web |last1=Anselmi |first1=Antonio |title=STANAG-5030/MIL-188-140 VLF/LF multichannel broadcast to submarines (2) |url=https://i56578-swl.blogspot.com/2019/03/stanag-5030mil-188-140-vlflf.html |access-date=9 April 2025 |date=2 March 2019}}</ref> All transmissions from DHO38 are encrypted. The messages transmitted via DHO38 are processed at the naval telecommunications center [[Glücksburg]]. They are sent "by cable" from German and NATO offices to the protective structure there and are prepared for transmission by the responsible telecommunications operators.<ref name="bundes" />

== References ==
{{Reflist}}

==External links==
* {{Structurae|id=20012017|title=Sendemasten Marinefunkstelle Saterland-Ramsloh}}
* http://skyscraperpage.com/diagrams/?b45289

{{Radio spectrum}}
{{EMSpectrum}}
{{Authority control}}
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[[Category:Radio masts and towers in Germany]]
[[Category:Military radio systems]]
[[Category:1982 establishments in West Germany]]
[[Category:Towers completed in 1982]]
[[Category:Buildings and structures in Leer (district)]]