Editing Very low frequency (section)

=== Military communications ===
Powerful VLF transmitters are used by the military to communicate with their forces worldwide. The advantage of VLF frequencies is their long range, high reliability, and the prediction that in a [[nuclear war]] VLF communications will be less disrupted by nuclear explosions than higher frequencies. Since it can penetrate seawater VLF is used by the military to [[Communication with submarines|communicate with submarines]] near the surface, while [[Extremely low frequency|ELF]] frequencies are used for deeply submerged subs.

Examples of naval VLF transmitters are
* Britain's [[Skelton Transmitting Station]] in Skelton, Cumbria
* Germany's [[VLF transmitter DHO38|DHO38]] in [[Rhauderfehn]], which transmits on 23.4&nbsp;kHz with a power of 800&nbsp;kW
* U.S. [[Jim Creek Naval Radio Station]] in [[Oso, Washington]] state, which transmits on 24.8&nbsp;kHz with a power of 1.2&nbsp;MW
* U.S. [[VLF Transmitter Cutler|Cutler Naval Radio Station]] at [[Cutler, Maine]] which transmits on 24&nbsp;kHz with 1.8&nbsp;MW.

Since 2004 the [[US Navy]] has stopped using ELF transmissions, with the statement that improvements in VLF communication has made them unnecessary, so it may have developed technology to allow submarines to receive VLF transmissions while at operating depth.

High power land-based and aircraft transmitters in countries that operate submarines send signals that can be received thousands of miles away. Transmitter sites typically cover great areas (many [[acres]] or square kilometers), with transmitted power anywhere from 20&nbsp;kW to 2,000&nbsp;kW. Submarines receive signals from land based and aircraft transmitters using some form of towed antenna that floats just under the surface of the water – for example a [[Buoyant Cable Array Antenna]] (BCAA).

Modern receivers use sophisticated [[digital signal processing]] techniques to remove the effects of atmospheric noise (largely caused by lightning strikes around the world) and adjacent channel signals, extending the useful reception range. Strategic nuclear bombers of the United States Air Force receive VLF signals as part of hardened nuclear resilient operations.

Two alternative character sets may be used: 5&nbsp;bit [[ITA2]] or 8&nbsp;bit [[ASCII]]. Because these are military transmissions they are almost always [[encrypted]] for security reasons. Although it is relatively easy to receive the transmissions and convert them into a string of characters, enemies cannot decode the encrypted messages; military communications usually use unbreakable [[one-time pad]] [[cipher]]s since the amount of text is so small.