Numbers station
A shortwave station that reads out groups of numbers or letters, by voice, Morse or a data mode, often on a fixed schedule.
What does it sound like?
A synthetic or recorded voice reading numbers, sometimes with a tune or tone beforehand; or Morse or data.
Who uses it?
Operators are officially unacknowledged; hobbyists track their schedules and formats.
Where and when can I hear it?
Shortwave, on regular schedules that hobbyist groups document.
Hear it live
- University of Twente WebSDR (Enschede, the Netherlands)
Times and frequencies change often. Check the Priyom schedule for a station due soon, then enter its frequency in the receiver (most use USB).
These are free public receivers run by other people; we only link to them. You'll hear the signal only if it's on the air right now and conditions carry it to that receiver, so if it's quiet, try another time. Links last reviewed 2026-09-28.
The science
Numbers stations send groups of digits, read by a voice that is often synthesized, sent in Morse code, or sent in a data mode; the station hobbyists call E11, which they attribute to Poland, uses upper sideband and a female voice reading five-digit groups. The messages are generally believed to be encrypted with one-time pads, sheets of random numbers shared only by sender and recipient, which cannot be broken without the matching pad. Hobbyists catalog the stations with letter-and-number designations: E for English, S for Slavic languages, and so on.
Why they use shortwave
Shortwave bounces off the ionosphere and can reach a continent away from a single transmitter. The broadcast is one-way, so the intended recipient needs only an ordinary shortwave receiver and never has to transmit or reveal a location.
Lore
A documented example of their use came to light in 2001, when the FBI arrested U.S. defense analyst Ana Montes. According to the FBI, she received instructions from Cuba in code via shortwave radio; she pleaded guilty in March 2002 to conspiracy to commit espionage for Cuba.
Easily confused with
- Time signal station: time stations tick every second