S03 – Okno

S03 was not actually a numbers station but a military test.  This station was likely used to test transmissions to an air force base called Jasan.  Okno translates to “Window” so this transmission means “Window for Jasan.”  This station was last heard in 1998.

S03 could have possibly been operated by Czech military intelligence using callsign “Okno” as spoken from the message.  This was a callsign used at Military installation 5847, Horoměřice.  An air-force installation near Hradec Králové also used the callsign “JASAN” in 1986, but this was before the station’s first activity was observed.

Recording Sample

There seems to be some discrepancies in Enigma 2000’s description of S03.  Recordings from the Conet Project and Simon Mason’s website conclude the station’s format shown below.  However Enigma 2000 describes a completely different station that has other words, endings, and possibly numbers being used.

Since there’s less information on Enigma 2000’s description and designation of this station, we should assume their ID of S03 is incorrect and the station they described should have another ID.

Enigma 2000 Description

Unid Russian/Slavic words, possibly “Adim Yadeliet Sim”, “Shest Sim Adim” “Shest Adim Vosim” or similar.  Messages were rarely sent, maybe it had a null format as well?  Possibly ended with (“Nula” / “Nul” / “Zero?”) repeated 3x. 

This station was very busy in March 1995 and May 1997, and was last observed on January 20th, 2018.  It operates on a random schedule, and was heard from 1994 – 1998 in 5/6 MHz frequencies.  Also used S&R 5680 kHz schedule before.  S03 has been confused with S18 and S19 before, but has a much different voice.  

Station Structure

Okno Okno Okno Zde Jasan Zde Jasan Konec
“Window, window, window” “This is Ash Tree, This is Ash Tree” “End”
Repeats 3x Repeats 2x
Repeats for 5 minutes


Station Summary

Nickname: Okno
Inactive, since 1998
Emission mode:
Voice Summary:
Female voice.  Possibly read live, but could be pre-recorded, or automated announcer.
Believed Country of Origin:
Czech Republic/Czechoslovakia



The Conet Project S03 Recording
Enigma 2000 Active Stations List V1.3