All,
I have been meaning to write up something on the MFSK Oddity that has been being reported by multiple people to this forum over the past year+. Unfortunately, real life has gotten in the way and I have not had time to do it.
So I am going to pull all (well, all I can find) the threads together under this one thread and include a couple recordings I have made.
(edit) Well, that did not work. I will link the other threads to this one, not merge the threads.
For those not familiar, the MFSK Oddity is a signal that has been showing up since at least mid 2020, and I suspect it was around a bit before that. Further, I think some of the phantom "1 PPS" signals before that time may be related.
Some listeners tie this signal to HFT (High Frequency Trading). I do not think that has been proven, but geolocation via TDOA and HFDF, searches of related frequency authorizations for HFT license, and similar frequency use / habits of other HFT tied signals make the HFT association very possible, if not probable. If not quite proven it is a best guess. 10Band LLC and related businesses are likely candidates.
The arguments against HFT are that the data rate is too slow to be useful for that service, and the data also appears static, unchanging, for very long periods of time. If you are leveraging RF vs fiber to gain microseconds of advantage, why use a data format that sends bits in 10's or 100's of millisecond intervals?
I have measured bandwidths of about 2.6, 4, and 10 kHz, I have seen other bandwidths but they have been too weak for me to get a decent estimate of the occupied bandwidth.
I have seen pulse rates of between 200 Hz (5 msec pulse interval) to 1 Hz (1 second pulse interval). I have seen repeating "bit patterns" (for lack of better term) of 8, 16, and 32 bits.
The signal appears to be MFSK like. Since late 2020 it has generally appeared to be 4 channels of data (prior to that it was 3 channels, or less), each channel with 4 FSK like steps. There may be some other modulation on each pulse, but if so I have not been able to confirm it. Arbitrarily, for my notes, I have called the lowest frequency channel of data Ch1, and moving up in freq Ch2, Ch3, and Ch4. Within each channel I have called the tones, again low freq to high, 1, 2, 3, and 4.
These signals move frequencies regularly, probably as needed for propagation.
Some videos below, sorry, they are not nicely annotated or explained, but at least they are recordings. The frequencies listed are center frequency.
4 kHz bandwidth, 4 Channel, 16 bit, 1000 msec interval, 15910 kHzhttps://www.youtube.com/watch?v=wdzHIOUuJ-c4 kHz bandwidth, 4 Channel, 16 bit, 100 msec interval, 14903 kHzhttps://www.youtube.com/watch?v=GTYZrmO6rxE4 kHz bandwidth, 4 Channel, 16 bit, 66.7 msec interval, 10160 kHzhttps://www.youtube.com/watch?v=gKb2Z5LOdlE4 kHz bandwidth, 4 Channel, 16 bit, 50 msec interval, 10170 kHzhttps://www.youtube.com/watch?v=T18rzFeMG044 kHz bandwidth, 4 Channel, 16 bit, 33.3 msec interval, 13909 kHzhttps://www.youtube.com/watch?v=sz2eRqMXVyk4 kHz bandwidth, 4 Channel, 16 bit, 20 msec interval, 13928 kHzhttps://www.youtube.com/watch?v=QM0o4jCjLHk4 kHz bandwidth, 4 Channel, 16 bit, 10 msec interval, 10807 kHzhttps://www.youtube.com/watch?v=_6Riik2BGJU4 kHz bandwidth, 4 Channel, 32 bit, 100 msec interval, 15905 kHzhttps://www.youtube.com/watch?v=7-Kqwf3PGFY4 kHz bandwidth, 4 Channel, 32 bit, 5 msec interval, 14500 kHzhttps://www.youtube.com/watch?v=HhwsXmk77uc2.6 kHz bandwidth, 4 Channel, 3 step, 16 bit, 100 msec, 6993 and 6988 kHzhttps://www.youtube.com/watch?v=V54EMvVuViI2.6 kHz bandwidth, 4 Channel, 3 step, 16 bit, 50 msec interval, 14480 kHzhttps://www.youtube.com/watch?v=oaoMYPot2koT!
Related threads:
UNID 9060 Digihttps://www.hfunderground.com/board/index.php/topic,93053.0.htmlUNID 6940.0 kHz (CF) 00:00 UTC 01 FEBRUARY 2022https://www.hfunderground.com/board/index.php/topic,92398.0.htmlUNID 6985 (CF) 1310 UTC 09 JAN 2022https://www.hfunderground.com/board/index.php/topic,91412.0.htmlUNID 6988 USB 2223 UTC 09 DEC 2021https://www.hfunderground.com/board/index.php/topic,90040.0.htmlUNID 6965 (CF) 2200 UTC 09 DEC 2021https://www.hfunderground.com/board/index.php/topic,90039.0.htmlUNID 6970 2019 UTC 19 NOV 2021--see waterfallhttps://www.hfunderground.com/board/index.php/topic,89284.0.html
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