Letter beacon

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"Letter beacons" are mysterious radio broadcasts of unknown origin, which consist of only a single repeating Morse Code letter.^[1]

They are also often referred to as:

• SLB, or "Single Letter Beacons"
• SLHFB, or "Single Letter High Frequency Beacons"
• SLHFM, or "Single Letter High Frequency Markers"
• Channel markers
• Cluster beacons
• FSK markers
• MX - an Enigma designation^{[citation needed]}

Many of the letter beacons are thought to originate from either locations used by the Russian military or the United States Navy, but some originate from other places. The so-called "phantom fishnet beacons" are thought to be located in the South Atlantic Ocean. One beacon was found originating from a transmitter tied between two palm trees on a remote beach in Florida.^{[citation needed]}

These broadcasts were discovered in the late 1960s; their purpose is not known. They have been postulated to be channel markers, or used in tracking satellites, or used for civil defense purposes.^[1] Some stations, such as the 'U' marker station, have been implicated in deliberate jamming.^{[citation needed]} The frequencies they broadcast on have often changed since their discovery. Occasionally, RTTY or voice traffic has been heard on these stations,^[1] which were sometimes weather reports or encrypted information.^{[citation needed]}

The high cost of maintaining these stations makes a simple hoax unlikely.^{[citation needed]}

[edit] See also

• Numbers station
• Secret broadcast

[edit] References

1. ^ ^{a b c} Poundstone, Willian (1983). Big Secrets. New York: Quill, 191-193. ISBN 0688048307