Loading ...
Sorry, an error occurred while loading the content.

Re: [softrock40] SSB demod, was Re: carrirer oscillator

Expand Messages
  • w keith griffith
    Thanks,,, very fun following the list. I m not likely to get involved with this type project at the hardware level, my current interests are mostly tube gear,
    Message 1 of 31 , Sep 29, 2005
    • 0 Attachment
      Thanks,,, very fun following the list. I'm not likely to get involved with
      this type project at the hardware level, my current interests are mostly
      tube gear, but current interests do change over time ;-)


      At 09:26 AM 9/29/2005, you wrote:
      >--- In softrock40@yahoogroups.com, w keith griffith <kgriffit@w...>
      >wrote:
      > >
      > > I have,,, 'SomeWhere' a really good description of the Weaver ssb
      > > method.
      >
      >There's a decent description of the Weaver method in the DSP section
      >of all the recent ARRL Handbooks.
      >
      > > How, if at all, does that method compare with the
      > > softrock?
      >
      >The SoftRock itself does no demodulation. All it does is sample the
      >incoming signal in such a way as to mix down to 11250Hz. The
      >downconverted signal is then dumped to the computer's soundcard.
      >
      >In the subsequent software DSP on the digitized signal, the SSB
      >"demodulation" consists entirely of a bandpass filtering stage and
      >another mixing stage to spin the signal centered at 11025Hz down to
      >0Hz.
      >
      >CW is the same, except the mixing stage spins the signal down to the
      >CW offset frequency (700Hz or whatever) rather than 0Hz.
      >
      >73
      >Frank
      >AB2KT
    • Bill Tracey
      When tuning an SDR 1000, if spur reduction is turned off, the DDS is tuner 11025 khz below the frequency of interest and the software (DttSP) oscillator is set
      Message 31 of 31 , Oct 1, 2005
      • 0 Attachment
        When tuning an SDR 1000, if spur reduction is turned off, the DDS is tuner
        11025 khz below the frequency of interest and the software (DttSP)
        oscillator is set to -11025 khz to recover the frequency of interest. This
        works well but for the spurs from the DDS.

        If spur reduction is turned on (the normal case) the DDS is tuned to the
        nearest low spur point (as documented by some of the AD docs) and then
        DttSP oscillator is set to an appropriate value to recover the signal of
        interest. This generally results in a DttSP oscillator value between -9.5
        and -12.5 khz.

        On the SoftRock all the tuning is done with the DttSP oscillator and it
        ranges over +/- 24 khz - giving a tuning range of 48 khz.

        Regards,

        Bill (kd5tfd)
      Your message has been successfully submitted and would be delivered to recipients shortly.