M40 was transmitted from North Korea. Very frequent transmissions while it was active. Regular transmissions ceased in October 2003.
The transmission format is given below. The speed was 20 words per minute. One dash was used for zero.
|VVV||CQ 747.343||HR||46||BT BT||71841 80146 47834 ...||AR AR||RPT RPT||VVV||CQ 343||HR||46||BT BT||71841 80146 47834 ...||AR AR||SK SK|
|3-figure station ID + 3-figure recipient ID||Amount of 5-figure groups in the message||5-figure single groups||3-figure recipient ID||Amount of 5-figure groups in the message||5-figure single groups|
|Repeated thrice||Repeated thrice||Repeated twice||Repeated twice||Repeated thrice||Repeated thrice||Repeated twice||Repeated twice|
|Repeated for 5 minutes|
In 1999, M40 operated on the following schedule. First transmissions were made on the full hour, then repeated 30 minutes later. The frequencies were changed seasonally. All schedules were daily, except where noted.
|5150||4700||Nov, Dec, Jan, Feb|
|5590||6630||Mar, Apr, Sep, Oct|
|5810||8210||May, Jun, Jul, Aug|
|4660||5650||Nov, Dec, Jan, Feb|
|5150||5810||Mar, Apr, Sep, Oct|
|5650||6870||May, Jun, Jul, Aug|
|CQ 466||06:30||Tue/Wed/Thu only|
|8110||Mar, Apr, Sep, Oct|
|8620||May, Jun, Jul, Aug|
|5535||4600||Nov, Dec, Jan, Feb|
|5535||6750||Mar, Apr, Sep, Oct|
|5535||7400||May, Jun, Jul, Aug|
|5190||5900||May, Jun, Jul, Aug|
|4670||5200||Mar, Apr, Sep, Oct|
|5670||6425||May, Jun, Jul, Aug|
|CQ 616||23:00||23:30||4th, 5th, 20th, 21st day of the month only|
And also "CQ 747" at 09:00, 10:00 and 20:00 on 10620kHz, and at 09:30, 10:30 and 20:30 on 12948kHz. "747" and "515" were the only ID's audible in Europe.
In Now, as a Woman, the Japanese version of her memoir, Kim Hyon-hui describes her use of M40 as a North Korean agent.