Editing Low frequency (section)

===Military===
{{further|Communication with submarines}}
Radio signals below 50&nbsp;kHz are capable of penetrating ocean depths to approximately {{convert|200|metres|feet}}; the longer the wavelength, the deeper they go. The British, German, Indian, Russian, Swedish, United States,<ref>
{{cite web
 | title=Very Low Frequency (VLF)
 | year = 1998
 | department = United States Nuclear Forces
 | website = fas.org
 | url=http://www.fas.org/nuke/guide/usa/c3i/vlf.htm
 | access-date = 2008-01-09  | url-status=live
 | archive-url=https://web.archive.org/web/20071227165518/http://www.fas.org/nuke/guide/usa/c3i/vlf.htm
 | archive-date = 2007-12-27
}}
</ref>
and possibly other [[navy|navies]] communicate with [[submarine]]s on these frequencies.

In addition, [[Royal Navy]] nuclear submarines carrying ballistic missiles are allegedly under standing orders to monitor the [[BBC Radio 4]] transmission on 198&nbsp;kHz in waters near the UK. It is rumoured that they are to construe a sudden halt in transmission, particularly of the morning news programme [[Today (BBC Radio 4)|''Today'']], as an indicator that the UK is under attack, whereafter their [[Letters of last resort|sealed orders]] take effect.<ref>
{{cite episode
 | title=The Human Button
 | series = [[Today (BBC Radio 4)|Today]]
 | air-date=2008-12-02
 | network=[[BBC]]
 | station=[[BBC Radio 4]]
 | url=http://www.bbc.co.uk/programmes/b00fq2sy
 | access-date=2011-08-06 | url-status=live
 | archive-url=https://web.archive.org/web/20110203232901/http://www.bbc.co.uk/programmes/b00fq2sy
 | archive-date=2011-02-03 | df = dmy-all
}}
</ref>

The United States has four LF stations maintaining contact with its submarine force: [[Aguada, Puerto Rico]], [[Naval Air Station Keflavik|Keflavik, Iceland]], [[Awase Airfield|Awase, Okinawa]], and [[Naval Air Station Sigonella|Sigonella, Italy]], using AN/FRT-95 solid state transmitters.

In the U.S., the [[Ground Wave Emergency Network]] or GWEN operated between 150 and 175&nbsp;kHz, until replaced by satellite communications systems in 1999. GWEN was a land based military radio communications system which could survive and continue to operate even in the case of a nuclear attack.