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11672Re: [softrock40] Re: softrock with dds -tell me more

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  • RAY
    Jun 2, 2007
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      I guess I was doing a little day-dreaming here - It looks like the XTAL is
      still the most cost effective way to go. So I will just switch in what I
      want when I need it - the DDS is nice but I agree it may be a little
      overkill and is frequency limited. I just thought it would be nice to use
      the SOFROCK as tuneable radio.

      73, Ray, N0FY

      ----- Original Message -----
      From: k5nwa
      To: softrock40@yahoogroups.com
      Sent: Saturday, June 02, 2007 10:27 PM
      Subject: Re: [softrock40] Re: softrock with dds -tell me more

      At 08:27 PM 6/2/2007, you wrote:

      >I think the DDS-60 is over kill. The SR40 wants only a square wave LO
      >You can do this with TTL. Simple use a fast clock that drives a
      >counter and
      >a magnitude comparitor that resets the counter. Use the reset line as
      >the LO.
      >Costa about $5 to make but you'd need to set the freq. with dip
      >switches or
      >again use a PIC as a fancy dip switch.
      >Chris Albertson
      >Home: 310-376-1029
      >Office: 310-336-5189

      Just out of curiosity, have you actually tried this? Usually
      Fractional N Synthesizers start off with GHz clocks to get the
      resolution and that is not cheap compared to a DDS.

      You want to listen to 7.050MHz at the center of the pass-band that
      requires a clock of 28.200MHz(35.5 ns period), but then you want to
      listen to 7.220MHz that requires a clock of around 28.880MHz(34.5 ns

      So how fast is the main clock that you count down with enough
      resolution to be able to put out these and other in between frequencies?

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