Subj : Numbers stations
To   : Angus McLeod
From : Spaceman Spiff
Date : Tue Aug 16 2005 07:34 pm

  Re: Numbers stations
  By: Angus McLeod to Digital Man on Sat Aug 13 2005 12:44 am

 >   Re: Numbers stations
 >   By: Digital Man to All on Fri Aug 12 2005 17:20:00
 > 
 >  > What experiences do any of you have with "Numbers stations"?
 > 
 > I've heard them.
 > 
 > They are obviously coded messages being passed for clandestine purposes.
 > Given the technology available today (like encrypted e-mail, or even
 > encrypted digital radio transmissions on various bands and even spread
 > spectrum) I'd have to assume that they are intended for reception by
 > operatives under deep cover, who can not have any incriminating hardware
 > lying about.  You can copy the numbers stations with a simple shortwave
 > receiver and a pencil, and then (providing you have the key) decrypt the
 > message.
 > 
 > I can see the system being used to send a message to a spy operating in a
 > foreign country, rather than, say, to an /embassy/ in a foreign country.
 > 
 >  > From http://en.wikipedia.org/wiki/Number_station:
 > 
 > I find some of the analysis here interesting.  For instance, they say that
 > Class-B, AM transmitters operating in the HF bands are the norm, and that
 > Polyphase and PDM modulators are not used because "energy costs were not
 > an issue", and then wanders off into a discussion of DRM.  Frankly, I
 > wouldn't consider the energy budget to be of much concern to these people,
 > and I am surprised that they (Wikipedia) do not consider the complexity of
 > the *receiving* station necessary to copy these transmissions.  An
 > amplitude modulated signal can be received with a single diode (a la
 > crystal-set), whereas Polyphase and PDM modulated signals are not so easy
 > to copy.  If, as I suspect, the point is to signal to someone in posession
 > of absolutely minimum suspicious hardware, an AM transmitter in the HF
 > band is about as easy as it gets.
 > 
 > Obviously, the transmitter would have to be class-B or class-A (less
 > efficient) since class-C transmitters are only good for FM (more complex
 > receiver) or CW (more training needed for the operator).  I can't imagine
 > why they thought the transmitter class was germane to the discussion.
 > 
 > I am interested in hearing any ideas other DOVE-Netters may have.
 > 
 > 
 > 
Remember the Movie "Phenomina" with John Travolta, and his HAM radio friend
copies a Morse code message with a cryptic message and John Travolta figures it
out and has the HAM send a reply message that gets them in deep trouble with
the military. Great movie!

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