M94

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M94, MCW, 5f, 4500, 5115, 5715 and 6330 kHz


Contents

Background

The MCW (1) Morse Code numbers station M94 is believed to originate from South Korea, although this has never been confirmed and the exact transmitter location is unknown. This is believed to be a sister station to the Korean Language voice numbers station V24 and possibly originates from the same studio, transmitter, or transmitters, as technical difficulties on one station (such as AC hum or low audio) have been noticed on the other when they share a frequency.

Recently a normally scheduled M94 transmission was made and the carrier never went off the air before a regularly scheduled V24 transmission was made on the same frequency half an hour later. I think that is pretty much proof they originate from the same source.

The ENIGMA 2000 originated designator “M94” was assigned to this station effective June 1, 2009. The station had been reported in a variety of ways prior to receiving this designation, often just being called “Unided CW”. How long it has been in operation is unknown, but the possibility is there that it has been in operation as long as V24. Initially this signal may have been confused with M40, and that might explain why it went unidentified for as long as it did. Of course, there is also the possibility that it is indeed the same signal as the old, not seen for some time, M40, but that it has had a major format change.

M94 transmissions have been reduced since 1 January, 2010. At this time (August 10, 2010) there are only a few transmissions each month, about 8 total. V24 transmissions have been increased, and probably some of the M94 slots have converted to V24.

Reporting history

M94, like V24, is not as often reported as some other numbers stations, such as E10, V02a, or M8a. This is likely caused by several factors.

While the station has been monitored World wide, some areas have a better chance of intercept than others. Many (but certainly not all) hobbiest who monitor numbers transmissions seem to be congregated in either Europe or North America. Given M94’s most well known transmission times and frequencies propagation is not favorable into either Europe or Eastern North America.

Western North America has a better probability of being able to hear the transmissions and the far West coast of North America has the best potential path of the mentioned locations. Japan and Australia have excellent paths and the station has been reported there with great success, however Australia seems to have only a few numbers station monitors and Japan may have a substantial number but because of the language barrier reports there may not often be shared outside of the country.

If you have read the above three paragraphs, and also read the entry on this Web Site concerning V24, they may look familiar. Yes, the above are a cut-and-paste right out of the V24 page.

Frequencies and Times

M94 has been observed on the frequencies of 4500, 5115, 5715 and 6330 kHz. As there are many holes in the combined schedule of M94 and V24 it is quite possible more frequencies are in use, but have yet to be correlated to this pair of emitters.

Transmission times as reported are between 1200 and 1600 UTC, with start times occurring on the half hour or the hour. Again, it is very possible M94 is using other time periods but propagation might be biasing the perceived schedule.

At this time (August 10, 2010) the only frequencies still in use are 5715 and 6330 kHz, all others ceased operation around January 1, 2010.

Schedule

The M94 transmission schedule is not fully understood at this time. On a given day there may be no transmissions or as many as five may be observed in the 1200-1600 UTC window.

Transmissions seem to be tied to calendar days and specific day/time/frequency slots and are repeated two days in a row.

For example if a transmission is observed on the first day of the month on 5715 kHz at 1300 UTC and there was not a transmission in the same time/freq slot the day before (last day of prior month), it is quite probable there will be one on 5715 kHz at 1300 UTC on the second day of the month. The transmissions on the first and second will contain the same message. There is a trend to also have the same time/freq slot filled about 15 days later, however this is a loose trend with many deviations.

Sched V2 Oct2010.jpg

Transmission format

M94 transmissions have a fairly rigid format. The following is a typical transmission:

VVV VVV VVV CQ CQ CQ de 1017 QRV QRK5 QTC K

VVV VVV VVV CQ CQ CQ de 1017 QRV QRK5 QTC K

VVV VVV VVV CQ CQ CQ de 1017 QRV QRK5 QTC K

HR W24 BT

57684 31687 96163 37824 18927 51667 95484
11274 17151 94152 71216 25267 89741 64298
38755 89422 73134 19870 21465 85410 07497
68165 64400

RPT BT

57684 31687 96163 37824 18927 51667 95484
11274 17151 94152 71216 25267 89741 64298
38755 89422 73134 19870 21465 85410 07497
68165 64400

BT AR K TU VA

In the first three lines of the above example the number following “de” (in this example 1017) is quite likely to be the ID of the recipient station. This number changes, but for a given time/date/freq it is always the same (except when there is a schedule change). For example, if this month on the first day of the month at 1300 UTC on 5715 kHz the ID used is “1017”, then next month on the first day of the month at 1300 UTC on 5715 kHz “1017” will also be the ID used.

The next line is “HR W24 BT” in this example. The number in “W24” is the number of five figure groups that will later be sent. This number varies with message length. There probably are no limits on this number, but as few as 12 or as many as 37 have been seen.

In this example 24 groups of five figures each are sent, this is the body of the message.

The line “RPT BT” indicates the group messages will be repeated.

The same groups are again sent, this will be identical to the first half of the message.

The line “BT AR K TU VA” indicates the end of the message.

Notes and references

  1. MCW stands for Modulated Continuous Wave, in this case meaning an A2A transmission. This consist of an AM modulated carrier. The carrier is modulated with a tone, and the tone is turned on and off to send the Morse Code characters. It has the advantage (over the more common CW or A1A transmission) of being able to be received on a simple AM radio receiver (assuming the correct frequency range). Of course, it requires roughly the same higher signal to noise ratio as any AM transmission, so the weak signal advantage of A1A CW is lost.

See also