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Re: [softrock40] Does Ham Radio need a $15 two-band SDR receiver kit?

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  • Tony Parks
    Hi Art, Band switching is by changing the frequency of the QSD clocking by 2x. If the QSD is well balanced then its response to the 2nd harmonic is well down
    Message 1 of 2 , Mar 1 11:07 AM
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      Hi Art,

      Band switching is by changing the frequency of the QSD clocking by 2x. If
      the QSD is well balanced then its response to the 2nd harmonic is well down
      so one could listen to 80m signals and not be bothered by 40m signals at the
      same time. This should make it possible to switch between two bands with a
      wide BPF. On the other hand, what you say about having a narrow BPF for the
      desired band makes good sense for a number of reasons.

      Thanks and 73,
      Tony KB9YIG

      ----- Original Message -----
      From: "KY1K" <ky1k@...>
      To: <softrock40@yahoogroups.com>
      Sent: Wednesday, March 01, 2006 11:07 AM
      Subject: Re: [softrock40] Does Ham Radio need a $15 two-band SDR receiver
      kit?


      >
      >
      > Hi Tony,
      >
      > I'm late to respond, but I did read all the other responses before
      > sending this.
      >
      > Regarding the 2 band softrock-yes, of course we would like it.
      >
      > However, I have grave concerns regarding the wideband front end,
      > especially since the 2 bands chosen are harmonically related. No one
      > else has expressed concern over this, and I'm NOT quite sure why::>
      >
      > With a wideband front end, the softrock will hear 80 meters and 40
      > meters at the same time. Note that there is some attenuation if a
      > single band antenna is used, but that any 40 meter signal that makes
      > it to the antenna input will be heard with very little attenuation
      > due to the nature of the beast...WE AREN'T USING A SUPERHET TO LIMIT
      > THE RESPONSE TO UNDESIRED BANDS!
      >
      > I think that even relatively weak signals on 80 meters will be heard
      > on 40 meters.
      >
      > I know it's a low cost demonstration platform, but few users would
      > find it acceptable to wonder whether the signal they're listening to
      > is on 40 or 80 meters!!
      >
      > I'd use the narrowest filter I could and have 2 filters, one for each
      > band.
      >
      > I hope the beta testers evaluate this aspect of the new dual band
      > softrock.
      >
      > Art
      >
      >
      >
      >>I have a new single-board SoftRock design that provides two band
      >>coverage in a $15 kit. The kit will include the PCB and all
      >>components to provide coverage of a portion of the 80m (3.5 - 3.55
      >>MHz with 96kHz sampling) and 40m (7.0 - 7.062 MHz with 96 kHz
      >>sampling) bands. (With 48kHz sampling the band coverage will only be
      >>7.0 - 7.038 MHz and 3.5 - 3.531 MHz. Some coverage below the two
      >>bands also is part of the tuning range with each of the sampling
      >>rates. With the right 4x-8x crystal frequency the band coverage
      >>could be better placed.)
      >
      >
      >
      >
      > Yahoo! Groups Links
      >
      >
      >
      >
      >
      >
    • KY1K
      ... Tony, isn t the response to the second harmonic only 6 db down???? Even if the second harmonic was 30 db down, signals that are s9 +30db are not at all
      Message 2 of 2 , Mar 1 5:42 PM
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        At 02:07 PM 3/1/2006, you wrote:
        >Hi Art,
        >
        >Band switching is by changing the frequency of the QSD clocking by 2x. If
        >the QSD is well balanced then its response to the 2nd harmonic is well down
        >so one could listen to 80m signals and not be bothered by 40m signals at the
        >same time. This should make it possible to switch between two bands with a
        >wide BPF. On the other hand, what you say about having a narrow BPF for the
        >desired band makes good sense for a number of reasons.



        Tony, isn't the response to the second harmonic only 6 db down????

        Even if the second harmonic was 30 db down, signals that are s9 +30db
        are not at all uncommon, especially on 40 and 80 meters. That would
        leave the out of band signal at s9.

        Regards,

        Art
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