|Known counterpart stations||V30|
M97 was transmitted from Vietnam. Morse code counterpart to V30.
The transmission format is given below. The speed is 20 words per minute. Standard five dashes are used for zero.
|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 is increased each time a new message is sent. The given "SN" number is 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 repeats the same message over extended periods of time.
M97 was noted on 10375kHz around 15:00 UTC. Its transmissions are irregular, and can be sent out daily for some time, then remain silent. Note that M97's time reference drifts back over time, and is usually put back at 15:00 by station's operators when it reaches 14:55. M97's presence is usually a foreshadowing for an upcoming V30 transmission, though V30 has been noted appearing without preceding M97, and M97 has been 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.