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Re: ISCAT Internals

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  • booz2m
    Hi Andy et al An single ISCATmessage is encoded in this way C-style, modified for general purposes. For multiple purposes it is repeated. SYMBOLS ... int
    Message 1 of 3 , Oct 18, 2012
      Hi Andy et al

      An "single" ISCATmessage is encoded in this way C-style, modified for general purposes. For "multiple" purposes it is repeated.

      SYMBOLS
      -------

      int ISCATMakeMessage()
      {
      char ISCATChars[]="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ .?@-";
      char Msg[MaxMessageLength+3]="@"; // add @, " " and sz
      unsigned char I,MsgLen;

      strcat(Msg,TheMessage);
      MsgLen=strlen(Msg);

      Symbol[0]=0;
      Symbol[1]=1;
      Symbol[2]=3;
      Symbol[3]=2;

      Symbol[4]=MsgLen;
      Symbol[5]=MsgLen+5;

      for (I=0;I<MsgLen;I++)
      {
      Symbol[I+6]=GetCharNo_P(ISCATChars,Msg[I]);
      Symbol[I+6+MsgLen]=MGMSymCar[0][I+6];
      }

      return(2*MsgLen+6);
      }

      ISCAT is using 11025 Hz sampling rate and ISCAT-A uses 512 samples and ~B 256.

      Details in geniscat.f90 (classic ISCAT = ISCAT-B) and WSJT home page for ISCAT-A.

      73
      Bo, OZ2M
    • booz2m
      Hi The shown implementation applies only to messages less than 18 characters, excluding the @. The is not needed so the array is only +2. It is a leftover
      Message 2 of 3 , Oct 18, 2012
        Hi

        The shown implementation applies only to messages less than 18 characters, excluding the @.

        The " " is not needed so the array is only +2. It is a leftover from initial tests I carried out. The ISCAT carriers the message length so no " " needed to separate two decoded messages.

        73
        Bo, OZ2M
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