"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[2]
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.[3] These beacons are a watertight floating transmitter with a floating insulated wire antenna that is attached to drift nets. 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.[4] 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. The high cost of maintaining these stations makes a simple hoax unlikely.
See also
References
- ^ a b c Poundstone, Willian (1983). Big Secrets. New York: Quill, 191-193. ISBN 0-688-04830-7
- ^ Enigma 2000 Group (May 2005). Enigma Control List (text). Enigma 2000. Retrieved on [[7 February 2007]].
- ^ Weiskopf, Myke (1994), "Mysteries of Radio", Radio! magazine (no. 3): 51-53
- ^ Pleikys, Rimantas (1998). Jamming. Vilnius Lithuania: Sigitas Zilionis.
- Spooks Newsletter Numbers and Oddities column
