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Re: Softrock sensitivity.

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  • grahamg3zod
    Martin, just to confirm that the recording I made was using 1 microvolt signal. 73 de Graham G3ZOD FISTS #8385 http://www.fists.co.uk
    Message 1 of 35 , Jun 1, 2011
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      Martin, just to confirm that the recording I made was using 1 microvolt signal.

      73 de Graham G3ZOD FISTS #8385
      http://www.fists.co.uk

      --- In softrock40@yahoogroups.com, "Martin Sole" <hs0zed@...> wrote:
      > I tried 4.7k for R7 and R8 but my opinion is that it is too much and
      > compromises the performance though the gain is about the same as the 20m 6.2
      > TXRX. With the 1k resistors and using Rocky I need to add about 18dB offset
      > to the S meter for S9 at -73dBm.
      >
      > The next bit of your message Alan got a bit confusing. You said 1mV, Graham
      > said 1 uV. Listening again t sounds like it could certainly be 1mV!
      >
      > 1mV is -47dBm. Adding 27dB attenuation would be -70dBm, still huge. If you
      > meant 1uV that's -107dBm adding 27dB attenuation would be -134dBm, that's
      > weak 0.045uV, way more than I need.
      >
      > 4.7k resistors give me about 6dB SINAD for a 1uV (-107dBm) input. Putting
      > them back to 1k drops that to about 4.5dB but with a flatter noise floor. A
      > resonant 40m antenna gives about a 7 to 10dB increase in noise over nothing
      > connected so now I'm starting to wonder if I really do have a problem. Think
      > I am going to have to rig something up using the Orion as a reference and
      > see what that sounds like in comparison. Could well be all for naught but
      > still my audio does not sound as strong as Grahams signal if that was 1uV.
      >
      > 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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