The majority of the “new” numbers stations are not AM, most are USB, some are LSB. Some are USB with carrier but many are fully suppressed carrier. The power levels of many would suggest they are not using repurposed BC transmitters, but rather possibly military facilities. Possibly since digital readout portables with SSB are so easy to have today this has allowed the use of the more efficient mode.
Several numbers stations, but still small a minority, include digital data. With things like laptops and smart phones being so common, particularly in developed nations, these would not be “indicators” or unusual to have, and would not draw attention to the user. They would probably draw less attention to the user than a shortwave radio would in some cases.
SK01 was the first digital numbers station that Enigma 2000 recognized as part of a numbers station and assigned an identifier to. It uses RDFT, a ham digital mode, and can be demodulated using a shareware program (but still needs to be decrypted after demodulation). HM01 is the first “hybrid” (using both voice and digital) numbers station to be designated.
Of course, the Cuban numbers stations still use SW BC transmitters and AM modulation, even for the digital signals they send. They appear to be mixture of “old” and “new”.
From here on down laced heavily with my opinion, but I believe most of it is supportable opinion.
The thought of numbers stations being AM and using high powered repurposed broadcast transmitters is “old school” and less frequent now than it once was. Portables 30 or 40 years ago had poor frequency readout and most did not have a detector for SSB and relatively few had even a BFO for CW/SSB. This was probably a large driver behind most old style numbers stations being AM and using a recognizable interval signal (like many BC stations did/do) or very long repeating headers. The interval signal that came up before the message allowed the user to find the frequency before anything of importance was sent.
Today I see people trying to find “meaning”, maybe even data, in the lead-in music, but those people probably never used something like a Zenith Transoceanic or Hallicrafters TW1000 to listen, they have no idea how important that lead-in or interval signal was to determining you were on the right frequency before the program started.
Fewer numbers stations today have interval or lead-in music. More of them just pop up on frequency at XXXX time, right into a message.
There are other digital numbers stations out there besides SK01 or HM01, but they have never been given designators by Enigma 2000 and likely will not be given designators. I do not speak for E2K and do not pretend to have knowledge of how they decide to assign designators, the following is just observation.
As an example, the Chinese voice numbers station V26 has a Morse Code sister station called M97, and also an undesignated digital sister station. The sequence is almost always digital first, CW second, voice third, in variable length transmissions of each. Of mild interest is the fact that in this case the digital is normally sent in LSB, the CW is in honest CW (not MCW), and the voice is sent in USB. The digital signal was identified as part of the normal sequence before the CW station received the designator M97. The problem is the digital signal uses a format called “Chinese 4+4 modem”, and this format is used by many non-numbers transmissions. To assign an E2K ID to this modem would result in reports of “numbers” stations all over the place, the vast majority of which are not likely to be numbers type transmissions at all.
Similarly, V22 voice transmissions were replaced a few years ago by a digital mode, but little data was ever compiled on the specifics of this digital mode, because it was similar to other digital signals.
Last year, when V16 made a several month reappearance after several years of not being reported, it went to a digital mode after a few weeks of voice activity. Despite the fact that the digital signal unmistakably used the same times and frequencies as the former voice transmissions no E2K designator was assigned. The digital mode was determined to be similar to a 4FSK 200 bd mode used by Chinese Air Defense, and again assigning a designator would probably result in many false reports of numbers activity. This station switched from AM to USB during this period of operation, it started as AM with the voice transmissions for several weeks, stayed with AM after the switch to digital for about a month, switched to USB from then on, and when it ended operations it went back to voice for the last two weeks, but again stayed USB for that time period.
It is quite possible that a lot of the numbers stations that have disappeared over the years have gone to a digital format, it is almost certain we as hobbyist will never be able to confirm this activity.
T!
Topic: V2a 5855 10:00z 12/31/2012 (Read 3778 times)