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Softrock sensitivity.

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  • Martin Sole
    I just completed a Lite II and a QRP 2000 synth from SDR kits. Both working well it seems though I am not sure about the receiver sensitivity. Are there
    Message 1 of 35 , May 31, 2011
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      I just completed a Lite II and a QRP 2000 synth from SDR kits. Both working well it seems though I am not sure about the receiver sensitivity. Are there specifications or measurements that indicate what to expect in terms of S+N:N or MDS? I can hear a signal at 1uV but nothing much really below that although the signal is visible. I have about a -125dBm noise level with no antenna (or the generator) connected and can easily distinguish a signal close(ish) to that but cannot hear it. Similar results in Rocky and psdr.

       

      Seems to me it might be more sound card or software than receiver. But not sure how to determine what a typical set of input and output values might be.

       

      P4 2.8GHz

      2MB RAM

      Delta 44

       

       

      Thanks

      Martin, HS0ZED

    • R. R. (Robby) Robson
      http://www.wb5rvz.com/sdr/sr_lite_ii/04_opamp.htm ... -- Cheers, Robby Richard R. (Robby) Robson Amateur Radio Station WB5RVZ www.wb5rvz.com
      Message 35 of 35 , Jun 2, 2011
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        http://www.wb5rvz.com/sdr/sr_lite_ii/04_opamp.htm

        On Wed, Jun 1, 2011 at 5:35 AM, Tony Parks <kb9yig@...> wrote:
         
        [Attachment(s) from Tony Parks included below]

        Hi Martin,

        The feedback resistors are supposed to be 4.99k resistors.  The schematic page for the Lite II kit is included with this note. 

        73,

        --
        Tony Parks
        kb9yig@...
        http://www.kb9yig.com
        
        


        On Wed, 2011-06-01 at 17:04 +0700, Martin Sole wrote:
         
        Okay, well I’m not convinced it’s working right yet. Here’s another thing I have just noted. In addition to the Lite I that  am referring to I also have a TXRX 6.2 partially built for 20 and 30 metres. The receiver seems noticeably livelier. Connecting an antenna makes the noise jump up a good 10dB on 30 or 20 but has no obvious effect on the noise with the Lite II. About the only thing I can figure is a difference with the op-amp. The 6.2 and 6.3 have LT6231 op amps with 4.99k resistors in the feedback but the Lite II has the same LT6231 op-amp (changed from a TLV2462) but with 1k resistors in the feedback. It also has 1 resistors in the op –amp output. Just wondering about that.

         

        Regards

        Martin, HS0ZED

         

         

        From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On Behalf Of Alan
        Sent: 01 June 2011 15:41
        To: softrock40@yahoogroups.com
        Subject: Re: [softrock40] Re: Softrock sensitivity.


         

         


        ----- Original Message -----
        Subject: RE: [softrock40] Re: Softrock sensitivity.

        >
        > I'm still left with not being able to hear much below 1uV and that seems
        > to
        > me to be about 20dB deafer than I would expect.
        >

        Martin,
        Sorry but I'm not familiar with how the figures compare with actual
        audibility.
        If you search the messages you will find what others have said.
        for example <http://groups.yahoo.com/group/softrock40/message/53438>

        73 Alan G4ZFQ






        --
        Cheers,
        Robby
         
        Richard R. (Robby) Robson
        Amateur Radio Station WB5RVZ

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