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Spy Numbers / Re: 5883 kHz Spanish numbers station 07:06 utc
« on: October 06, 2009, 1314 UTC »Sounds somewhat like OTH Radar,but to my limited knowledge Over The Horizon Radar is more continuous.
Observed up an down the HF Spectrum;However, seems to be fond of these Cuban/Spanish numbers stations.
Very interested in ID'ing this signal. At times, it is quite prevalent.
OTHR can run the gamut from continuous to sub second burst on a specific frequency depending on the type and mission. Along with varying frequency, different swept bandwidths, PRFs (Pulse Repetition Frequency), PWs (Pulse Widths, and thus instantaneous bandwidth), and sweep rates are used to detect different kinds of targets and targets moving at different speeds. It can also consist of FMCW transmissions that are not pulsed at all, but simply swept. On a narrow bandwidth receiver, such as most people use for HF monitoring, this can sound like pulses, but with a chirp or sweep to them.
The description of a digital signal lasting for 20 seconds or more does not sound prototypical of OTHR to me unless there are dropouts of just under a second ever 3 to 7 seconds during that time period. They typically have very long dwell times or sub 5 second dwell times. Yes, it could be one, it is not impossible at all, but there is another answer that might be valid also and in this case is more likely.
Associated with V02a (the Spanish language numbers station the OP is probably reporting, 5883 is a known and very common freq for it) and M08 (its CW companion), is a digital signal, SK01. This is digital data being sent in several modes, and if you use a program such as DIGTRX you can capture the data, of course, like the numbers themselves, the data is encrypted and will be gibberish, but a valid txt file. You will likely find that the transmissions in a given time period will all be the same gibberish. It is very common to hear SK01 alone, but it is also common to hear it after a V02a voice transmission or after a M08 transmission. The "every five minutes after the voice has stopped" description makes me strongly suspect SK01. If the same data burst continues after the carrier drops I would suspect a different source, but I bet this is SK01.
T!
Mohave Desert, California, USA
Edit: Of course, less than an hour after I wrote the above I watched an OTHR hit a V02a freq for exactly 24 seconds with no drops or breaks. I still think SK01 is the most probable player here though.
