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SW number station

D

dc2rf

Guest
Jan 15, 2014
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Noticed a spanish language AM "numbers station" on 11.435mhz at 16:00utc today. I've heard them many times in the past, but it seems they are using a different format. At least this one is.

First, the usual voice number readoff, but then a two-tone followed by a transmission in some digital format. Of course, it's encrypted, but I was curious as to the mode of the digital transmission. This format is repeated for the duration.

Anyone have any interest in monitoring this activity on this forum? Know what mode/format the digital transmission is made?
 

Personally I have never found number stations interesting and can only tolerate to listen a few seconds. but can you post an audio clip to help ID the mode?
 
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IMD262 said:
...but can you post an audio clip to help ID the mode?
Click to expand...

I'm not sure how to post an audio clip on this board. As far as identifying the mode, a lot of the digital audio sounds similar... just "hissing" noise. I think viewing the audio spectrum might be more productive. Could you use a screen capture photo?

I think the stations are interesting simply because they're clandestine, and don't want to be indentified.
 
there are a few videos posted on you tube,,,does it sound like this one?




at one time i think they were possibly the spy thingy....but in the end i have no idea!
 
dc2rf said:
Noticed a spanish language AM "numbers station" on 11.435mhz at 16:00utc today. I've heard them many times in the past, but it seems they are using a different format. At least this one is.

First, the usual voice number readoff, but then a two-tone followed by a transmission in some digital format. Of course, it's encrypted, but I was curious as to the mode of the digital transmission. This format is repeated for the duration.

Anyone have any interest in monitoring this activity on this forum? Know what mode/format the digital transmission is made?
Click to expand...

the history surrounding these number stations is interesting. the mystery of their purpose is probably the most interesting part of the transmissions . keep us posted
 
Ok... I managed to set up a temporary video on the 'net taken of my sdr screen (recorded) during a numbers station transmission. Yes, I know the video isn't in perfect focus, and the sounds dynamic range isn't great. The sound of the digital data is far stronger than the S/S female voice.

The idea is, now you can see the digital "footprint" and audio waveforms for yourself. Note the very strong signal on the S-meter. I use an Elad FDM-S2 sdr with an un-amplified tuned 26" indoor loop to receive this signal. If you look close, you can also see the date and time of the transmission. Here's the link:

https://plus.google.com/107267961424748476379/videos

I'm not sure how long I'll leave the link up... probably just a couple weeks.

Let's hear from some digi experts. No, I don't expect the message decoded... just want to know the format used. Are there two types of digi used after the voice? Watch the vid carefully.
 
dc2rf said:
Ok... I managed to set up a temporary video on the 'net taken of my sdr screen (recorded) during a numbers station transmission. Yes, I know the video isn't in perfect focus, and the sounds dynamic range isn't great. The sound of the digital data is far stronger than the S/S female voice.

The idea is, now you can see the digital "footprint" and audio waveforms for yourself. Note the very strong signal on the S-meter. I use an Elad FDM-S2 sdr with an un-amplified tuned 26" indoor loop to receive this signal. If you look close, you can also see the date and time of the transmission. Here's the link:

https://plus.google.com/107267961424748476379/videos

I'm not sure how long I'll leave the link up... probably just a couple weeks.

Let's hear from some digi experts. No, I don't expect the message decoded... just want to know the format used. Are there two types of digi used after the voice? Watch the vid carefully.
Click to expand...
Sounds like a SelCal jammer on top of Cuba's usual number station....

73 mechanic
 
Does sound like Selcal...

Wonder if someone else will run across this transmission at another time and see if they get the same audio I got.
 
Well yeah; it is very interesting thing IMO. . .

Consider that the numbers are meaningless unless a key word is used. Even then, what is left is encrypted still. At one time in the past a 'one time pad' would be used with the code of the day/time to unravel the message.

The nature of it is to pass on directives to operatives/gov't agents in the field. Of course, this mode of communique still has a place; but also requires someone listening at the recieving end because they are operating in less than ideal conditions - ie outside of other means available to make a secure communincation.

There was a recent movie made on the subject that is a great explination of what it is and what they do for those that don't understand:

http://www.imdb.com/title/tt1659338/

 
Tones seem too long for SELCAL. Remember the old show EMERGENCY? Those were SELCAL tones sent when they were dispatched. Just listened t some transoceanic airline flights doing a SELCAL check and the tones were not that long.
 
dc2rf said:
Ok... I managed to set up a temporary video on the 'net taken of my sdr screen.... I use an Elad FDM-S2 sdr ....
Click to expand...

not to hijack your thread, but,...... how long have you had the Elad? and what do you think about it?

I am thinking about getting one, the price is right ( about $1200) and you can also operate it without a computer if you have to.
 
Yea, I don't believe it's Selcal. It's indeed a mystery.

On the sdr, it's not the $1200 Elad Duo. It's the S2 (no transmit... rx only) for about half that price.

After a lifetime (decades) of using radio "boxes" for SW-LW-HF reception, I took the plunge and bought the sdr, not knowing the "outcome". After a week or so, I sold the boxes and I won't go back. It does so much more than a box radio. I'm hooked on sdr. Not preaching... just MHO.
 
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