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Re: [softrock40] Re: Softrock sensitivity.

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  • Alan
    ... Subject: RE: [softrock40] Re: Softrock sensitivity. ... In that case, 1K. BUT this is to reduce the gain. Tony reduces gain on the lower bands by
    Message 1 of 35 , Jun 1, 2011
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      ----- Original Message -----
      Subject: RE: [softrock40] Re: Softrock sensitivity.


      > No, I'm building the Lite II for 40. The early version seems to show 1k
      > but
      > Tony's later drawing shows 4k99. I have 1k fitted as per Jan's kit,
      > sooooo,
      > what's it to be, 1k or 4k99?
      >

      In that case, 1K.
      BUT this is to reduce the gain.
      Tony reduces gain on the lower bands by increasing R5/6, effectively the
      same.
      Please try this with an antenna. See how it actually works. can you compare
      it with something else?
      I found my 1mV source, tested it with my AR7030 on 5MHz. It sounded like
      Graham's MP3.
      I could still hear it with 27dB attenuation of the 1mV.
      the 5MHz band at midday in the summer is at it's quietest. When I attached
      an antenna I reckoned the noise was about 6dB below the unattenuated 1mV
      source.
      Now his is not with a Softrock but it shows my AR7030 was far too sensitive
      as I had set it.
      Striving for the ultimate MDS is irrelevant on the lower frequencies. It
      just reduces dynamic range.
      If you do think you need more gain you could put 4K99s in and see what you
      think.

      73 Alan G4ZFQ
    • 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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