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Almost a year old now (October 2009), but in the interest of adding content,
here is something I wrote. I originally sent it to the ENIGMA2000 group, so
that's why you'll see references to "e2kfiles."
Information on V2a/M8a/SK01/Radio Habana Cuba ringing sound
I use a Ten-Tec RX320D and an indoor antenna that is a few feet longer than 100
feet (30.48 meters) and used Baudline ( http://www.baudline .com/) for analysis
of the frequencies and tone length.
Ringing:
Ring high tone : 777.10 Hz
Ring low tone : 621.83 Hz
Ring tone length : 0.0700 Seconds
Ring tone High-Low cycle length : 0.1400 Seconds
Ring High-Low rate : 7.1428571 Hz
Unknown low tone : 466.55 Hz
[Note: Frequencies and times were measured with a cheap internal sound card.
They are probably not totally accurate.]
With this information, I've made a simulation of the ringing. It is available
here: http://eepromeagle.dyndns.org/e2kfiles/ringsimulation.wav
The ringing will sometimes be longer or shorter than usual. However, I have not
checked the length of each ring to see if a certain ring length corresponds to
a certain number (like the XP stations, but with time instead of frequency).
By ear, the tones themselves seem to stay pretty much constant in length
somewhere near the measured 0.0700 second length, and it's the number of times
the high-low (or low-high) cycles repeat that changes. Listening to my
recordings, in one of the rings, the length of the first tone in the ring
sounds like it is shorter. I'm not sure if this was an error when I was
recording or if it really was shorter.
There is often a really low tone (the "Unknown low tone" as specified above)
that is sometimes present with the ringing and will sometimes stop and start.
This could be just RFI, but I thought it'd be worth mentioning.
I saw something about this on the list, but on 2009-10-21 at 04:48UTC on
6000kHz, I heard the same ringing sound on Radio Habana Cuba. I made two
recordings of that:
http://eepromeagle.dyndns.org/e2kfiles/RHCwRing-6000kHzAM-20091021-0448UTC.wav
and
http://eepromeagle.dyndns.org/e2kfiles/RHCwRing-6000kHzAM-20091021-0455UTC.wav .
I also made a good recording of SK01 with very loud ringing (some QRM though)
on 2009-10-13 at 09:33UTC on 5930kHz AM, which you can find here:
http://eepromeagle.dyndns.org/e2kfiles/SK01-5930kHzAM-20091013-0933UTC.wav
(warning : it is almost 150MB. I recorded it with a sample rate of 48000 kHz
even though I was using a filter that appears to filter off anything above
4.5kHz)
I might have recorded it in SSB and forgot to change the filename (my radio is
around 53Hz off frequency in SSB without correction). I think I had the radio
tuned somewhere around 53Hz below 5930kHz to correct for inaccuracy though.
Here is another one with loud ringing as well as the low tone (you can hear it
make a "dah-dit-dah" noise near the middle) 2009-10-13 at 09:32UTC on 5947kHz
LSB:
http://eepromeagle.dyndns.org/e2kfiles/SK01-5947kHzLSBaAM-20091013-0932UTC.wav
I did switch modes near the middle of the recording, so there are some loud
beeps. It was recorded in LSB, not sure if I corrected it or not.
I may have written down the frequencies and times incorrectly for the
recordings since I probably mistyped some of the filenames. I normally keep
logs with accurate data that are separate from the recordings, but when trying
to switch frequencies and start more recordings fast, it was kind of easy to
make mistakes.
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