Enigma ID M04

Frequencies 5748, 7250, 8188
Status Inactive
Voice N/A
Emission mode MCW
Location Poland
Activity pages

Download audio sample

Known counterpart stations G02, E23

M04 was ran by Polish Office for State Protection (UOP). Morse code counterpart to G02, and later E23. Last heard on 14 September 2000.[1]

The traffic format is given below. The speed was 19 words per minute. Standard five dashes were used for zero.

Preamble Message Outro
U LOLO LOLO LOLO / 01723 LOLO / 01723 BT BT 89261 12616 ... 31657 AR SK
Tuning signal 5-figure message header 5-figure message header   Fixed-length message of 100 5-figure single groups  
Repeated for 3 minutes Repeated for 5 minutes Repeated twice Repeated twice

Full transmissions always took roughly 26 minutes.


Prior to April 1998, M04 ran on the following schedule.[2] The counting of the weeks started on the first Saturday of the month.

Day UTC Freq Week 1 Week 2 Week 3 Week 4 Week 5
Monday 20:00 5340     x    
Tuesday 18:00 4195 x        
Tuesday 20:00 4195 x x      
Wednesday 09:00 4195   x      
Thursday 20:00 5340     x    
Thursday 21:00 5340     x    
Friday 00:00 5340       x  

The U's at the beginning were initially repeated for 10 minutes. In April 1998, it was shortened to 3 minutes.

On 1 April 1998, the schedules above were replaced, and the following schedules came into use.[3] The transmissions from now on only took place on the second Monday, Wednesday and Thursday, with the same message repeated throughout all the transmissions during the week.[4] The counting of the weeks still started on the first Saturday of the month.

Monday, Wednesday, Thursday
Week 09:57 11:57 12:57
2nd 7250 8188 5748

The final M04 transmission was on 14 September 2000, however, blank carriers were transmitted for the length of E23 transmissions on its former schedules until 2002.[1]


  1. Numbers & Oddities #32 (December 2000) [accessed September 13th, 2014]
  2. ENIGMA Newsletter #10 (January 1996), p. 7-8 - read a scanned version here
  3. Simon Mason, G2/E23 [accessed September 13th, 2014]
  4. Numbers & Oddities #8 (December 1998) [accessed September 13th, 2014]

Recording courtesy of Numbers & Oddities

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