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???
04/16/10 04:44
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#175082 - it's been a while ...
Responding to: ???'s previous message
IIRC, and that may not be the case, the way we did it back in the late '70's with our rather slow 8-bit micro's was to differentiate the signal coming to the receiver, and time the distance between the pulses. A pulse occurred at the positive and negative peaks, but, AC coupling (differentiating) the signal and biasing it to GND meant that one only got a positive spike when there was a positive edge, i.e. the slope of the incoming waveform had switched from negative to positive. This enables one to discriminate between the high and low frequency. Some reasonable wave shaping has to be done at the transmitter.

Keep in mind, too, that this was done for use with low-cost audio-cassette recorders with limited frequency response. One guy used a pretty good tape recorder and found that the higher quality actually made things more difficult.

RE


List of 17 messages in thread
TopicAuthorDate
FSK Modul            01/01/70 00:00      
   Incomplete question            01/01/70 00:00      
   Yes            01/01/70 00:00      
      Just Simple FSK            01/01/70 00:00      
         V.22?            01/01/70 00:00      
         Scenix and Cypress            01/01/70 00:00      
      Yes, here's an 80c51 that does it            01/01/70 00:00      
         ftp://ftp.embedded.com/pub/2002/09banks            01/01/70 00:00      
            it's been a while ...            01/01/70 00:00      
   with 80C51            01/01/70 00:00      
      Built FSK Modul            01/01/70 00:00      
         there's such info            01/01/70 00:00      
            I cannot find it            01/01/70 00:00      
               past info            01/01/70 00:00      
   Lots of unanswered questions, but probably yes            01/01/70 00:00      
      I was thinjing much the same thing            01/01/70 00:00      
         There are problems with some modulation schemes            01/01/70 00:00      

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