Enigma ID M97
Frequencies 10375
Status Inactive
Voice N/A
Emission mode ICW
Location Vietnam
Activity pages

M97 was transmitted from Vietnam. Morse code counterpart to V30. Last heard in May 6, 2016.

The transmission format is given below. The speed was 20 words per minute. Standard five dashes were used for zero.

Intro Preamble Message Outro
A SD 61 HT SN 68 01349 88612 83023 ... K
  "SD" + Message serial number Sometimes "TK" instead "SN" + Amount of 5-figure groups in the message 5-figure single groups  
Repeated 29 times Repeated thrice Repeated thrice Repeated thrice   Repeated 29 times

"SD" and "SN" presumably stand for "So Dien" and "So Nhom", Vietnamese phrases used by V30's voice counterpart, which are used in the same manner over there. The "SD" number was increased each time a new message was sent. The given "SN" number was not always correct.

In November 2011, M97 was also observed with a 2-message format. The two messages were separated by "KKKKKKK AAAAAAA". It has not been seen in such a format ever since.

M97 repeated the same message over extended periods of time, just as its voice counterpart.

M97 was noted on 10375kHz around 15:00 UTC. Its transmissions were irregular, and could be sent out daily for some time, then remain silent. Note that M97's time reference drifted back over time, and was usually put back at 15:00 by station's operators when it reached 14:55. M97's presence was usually a foreshadowing for an upcoming V30 transmission, though V30 was noted appearing without preceding M97, and M97 was noted without following V30.

M97 was occasionally observed sending plaintext messages, believed to serve either test ot training purposes. They were transmitted at different times and frequencies than normal transmissions. They began and ended with the normal "AAAAAAAA..." and "KKKKKKKK..." intro/outro, but the messages were product advertisements in Vietnamese.