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New member intro; Coop, AA1WW

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  • aa1ww
    Hi PowerSDR-IQ, I m Coop, AA1WW and I ve been reading about SDR recently. Before becoming an instructor at a community college here in the states (stcc.edu), I
    Message 1 of 7 , Jul 3, 2012
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      Hi PowerSDR-IQ,

      I'm Coop, AA1WW and I've been reading about SDR recently. Before becoming an instructor at a community college here in the states (stcc.edu), I was an EE doing mostly digital FPGA stuff and some contract work that got me into very basic analog electronics along with the embedded digital stuff.

      I've read through the classic Software-for-the-Masses articles and a few others and am learning as I go. I hoping to build an direct-conversion SDR front-end along those lines. I found a deal on a used Creative Labs Audigy 2 card for my PC. I know a little DSP and have written some VB and C# apps and have some experience on Linux.

      Currently I'm trying to understand offset and THD demands on the front-end operational amplifiers and gain distribution in general (to RF preamp or not to RF premap).

      Hopefully I can successfully search and avoid asking the well-known FAQs. Thanks for providing and participating in this group.

      Coop,
      AA1WW

      PS: This is the same intro I gave on the Soft_Radio Yahoo group.
    • Gary Greene
      Hi Coop, The Tayloe detector (an RF Mux used to send RF to two storage caps for audio decode, see W2ZV.COM) has a best case NF of 1db, and so (for HF, 30 MHz
      Message 2 of 7 , Jul 4, 2012
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        Hi Coop,

        The Tayloe detector (an RF Mux used to send RF to two storage caps for audio decode, see W2ZV.COM) has a best case NF of 1db, and so (for HF, 30 MHz or lower) with a low noise op-amp, 2 to 3 db is well below band noise, and no RF preamp is needed. The king of the hill of op-amps is the AD797 at +/- 15 volts, but you will not find many in use, the  LT6231 is nearly as good, runs at 12.6 V max (an 78L08 works well) and is used a lot, often at just 5 votls. Input is about 200 ohms, so a lot of audio op-amps are not as good at this low impedance. I use it as a IF tap off my Icom radios.

        I will be gone till sunday, so 73's and have fun,

        Gary Greene, W2ZV

        aa1ww wrote:
        Hi PowerSDR-IQ,
        
        I'm Coop, AA1WW and I've been reading about SDR recently. Before becoming an instructor at a community college here in the states (stcc.edu), I was an EE doing mostly digital FPGA stuff and some contract work that got me into very basic analog electronics along with the embedded digital stuff.
        
        I've read through the classic Software-for-the-Masses articles and a few others and am learning as I go. I hoping to build an direct-conversion SDR front-end along those lines. I found a deal on a used Creative Labs Audigy 2 card for my PC. I know a little DSP and have written some VB and C# apps and have some experience on Linux.
        
        Currently I'm trying to understand offset and THD demands on the front-end operational amplifiers and gain distribution in general (to RF preamp or not to RF premap).
        
        Hopefully I can successfully search and avoid asking the well-known FAQs.  Thanks for providing and participating in this group.
        
        Coop,
        AA1WW
        
        PS:  This is the same intro I gave on the Soft_Radio Yahoo group.
        
        
        
        ------------------------------------
        
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      • Jeff Cooper
        Gary, W2ZV, Thanks for your reply. I m used to omitting RF preamps at HF but it s less intuitive when looking at the overall signal path gain outside the PC.
        Message 3 of 7 , Jul 4, 2012
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          Gary, W2ZV,

          Thanks for your reply.  I'm used to omitting RF preamps at HF but it's less intuitive when looking at the overall signal path gain outside the PC.
          I've been wondering about opamp choice especially for 24-bit PC sound cards.  So I've been comparing some opamp data (apart from specific application circuits).
           
          OpAmp     Noise(nV/rootHz)    THD                                   Comments
          --------  ------------------  ------------------------------------  -----------
          LT6231    1.1                              -90   dB THD @ <100 KHz
          AD797     0.9 typ; 1.2 max                -120   dB THD @   20 KHz
          AD8597    1.1 @ 1 KHz                     -120   dB THD @    1 KHz
          OPA1611   1.1 @ 1 KHz         0.000015% = -136.5 dB THD @    1 KHz
          OPA1632   1.3                 0.000022% =  -93.2 dB THD            (Fully Diff)
          OPA211    1.1 @ 1 KHz                     -136.5 dB THD @    1 KHz (Av = 1)
          LME49990  0.9 typ; 1.3 max    0.000010% = -140   dB THD @    1 KHz (Av = 1)
           
          It's really quite impressive to thinking about 100+ dB dynamic range.
           
          Coop, AA1WW

          To: powersdr-iq@yahoogroups.com
          From: w2zv@...
          Date: Wed, 4 Jul 2012 04:17:32 -0400
          Subject: Re: SPAM -> [powersdr-iq] New member intro; Coop, AA1WW

           
          Hi Coop,

          The Tayloe detector (an RF Mux used to send RF to two storage caps for audio decode, see W2ZV.COM) has a best case NF of 1db, and so (for HF, 30 MHz or lower) with a low noise op-amp, 2 to 3 db is well below band noise, and no RF preamp is needed. The king of the hill of op-amps is the AD797 at +/- 15 volts, but you will not find many in use, the  LT6231 is nearly as good, runs at 12.6 V max (an 78L08 works well) and is used a lot, often at just 5 votls. Input is about 200 ohms, so a lot of audio op-amps are not as good at this low impedance. I use it as a IF tap off my Icom radios.

          I will be gone till sunday, so 73's and have fun,

          Gary Greene, W2ZV

          aa1ww wrote:
          Hi PowerSDR-IQ,
          
          I'm Coop, AA1WW and I've been reading about SDR recently. Before becoming an instructor at a community college here in the states (stcc.edu), I was an EE doing mostly digital FPGA stuff and some contract work that got me into very basic analog electronics along with the embedded digital stuff.
          
          I've read through the classic Software-for-the-Masses articles and a few others and am learning as I go. I hoping to build an direct-conversion SDR front-end along those lines. I found a deal on a used Creative Labs Audigy 2 card for my PC. I know a little DSP and have written some VB and C# apps and have some experience on Linux.
          
          Currently I'm trying to understand offset and THD demands on the front-end operational amplifiers and gain distribution in general (to RF preamp or not to RF premap).
          
          Hopefully I can successfully search and avoid asking the well-known FAQs.  Thanks for providing and participating in this group.
          
          Coop,
          AA1WW
          
          PS:  This is the same intro I gave on the Soft_Radio Yahoo group.
          
          
          
          ------------------------------------
          
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              http://groups.yahoo.com/group/powersdr-iq/
          
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        • Marciniak, Ed
          Most of the better op amps have a pair of back to back diodes (or two in series back to back), which limits the differential input voltage range to something
          Message 4 of 7 , Jul 4, 2012
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            Most of the better op amps have a pair of back to back diodes (or two in series back to back), which limits the differential input voltage range to something like 0.7V or 1.4V. This wouldn't normally be such a big deal but at low voltage gains used as a buffer, it may be the limiting factor.

            The stated noise densities are also usually input referred noise for a voltage gain of 100. The are not that good at say x10 voltage gain.

            I have a creative emu 1820m with AK5394A ADCs, on my softrock, and I lowered the voltage gain by changing the 5k resistors to 499 ohms. The noise floor increased by a few db for 20 db increase in strong signal handling capability. Since I intended to use transverters with a 10m IF, and my rf preamps have fractional db noise figures it was a good trade.

            With that said, I'd really like to build a I2S ADC interface to the radio and use a fully differential op amp out of the tayloe detector.

            I do recall Leif or Luis (sorry don't recall which) used bipolair transistors in front of a CA3140, but that topology had more gain than I wanted.

            There is room for improvement over the basic LT6231 but it won't come cheap...it might add 40 or more to cost overall.

            I'd be interested in chatting/emailing if someone in interested. I hate reinventing the wheel.

            Vy 73,
            Ed Marciniak
            NB0M

             
            From: Jeff Cooper [mailto:aa1ww@...]
            Sent: Wednesday, July 04, 2012 11:47 AM
            To: powersdr-iq@yahoogroups.com <powersdr-iq@yahoogroups.com>; w2zv@... <w2zv@...>
            Subject: RE: SPAM -> [powersdr-iq] New member intro; Coop, AA1WW
             
             

            Gary, W2ZV,

            Thanks for your reply.  I'm used to omitting RF preamps at HF but it's less intuitive when looking at the overall signal path gain outside the PC.
            I've been wondering about opamp choice especially for 24-bit PC sound cards.  So I've been comparing some opamp data (apart from specific application circuits).
             
            OpAmp     Noise(nV/rootHz)    THD                                   Comments
            --------  ------------------  ------------------------------------  -----------
            LT6231    1.1                              -90   dB THD @ <100 KHz
            AD797     0.9 typ; 1.2 max                -120   dB THD @   20 KHz
            AD8597    1.1 @ 1 KHz                     -120   dB THD @    1 KHz
            OPA1611   1.1 @ 1 KHz         0.000015% = -136.5 dB THD @    1 KHz
            OPA1632   1.3                 0.000022% =  -93.2 dB THD            (Fully Diff)
            OPA211    1.1 @ 1 KHz                     -136.5 dB THD @    1 KHz (Av = 1)
            LME49990  0.9 typ; 1.3 max    0.000010% = -140   dB THD @    1 KHz (Av = 1)
             
            It's really quite impressive to thinking about 100+ dB dynamic range.
             
            Coop, AA1WW

            To: powersdr-iq@yahoogroups.com
            From: w2zv@...
            Date: Wed, 4 Jul 2012 04:17:32 -0400
            Subject: Re: SPAM -> [powersdr-iq] New member intro; Coop, AA1WW

             
            Hi Coop,

            The Tayloe detector (an RF Mux used to send RF to two storage caps for audio decode, see W2ZV.COM) has a best case NF of 1db, and so (for HF, 30 MHz or lower) with a low noise op-amp, 2 to 3 db is well below band noise, and no RF preamp is needed. The king of the hill of op-amps is the AD797 at +/- 15 volts, but you will not find many in use, the  LT6231 is nearly as good, runs at 12.6 V max (an 78L08 works well) and is used a lot, often at just 5 votls. Input is about 200 ohms, so a lot of audio op-amps are not as good at this low impedance. I use it as a IF tap off my Icom radios.

            I will be gone till sunday, so 73's and have fun,

            Gary Greene, W2ZV

            aa1ww wrote:
            Hi PowerSDR-IQ,
            
            I'm Coop, AA1WW and I've been reading about SDR recently. Before becoming an instructor at a community college here in the states (stcc.edu), I was an EE doing mostly digital FPGA stuff and some contract work that got me into very basic analog electronics along with the embedded digital stuff.
            
            I've read through the classic Software-for-the-Masses articles and a few others and am learning as I go. I hoping to build an direct-conversion SDR front-end along those lines. I found a deal on a used Creative Labs Audigy 2 card for my PC. I know a little DSP and have written some VB and C# apps and have some experience on Linux.
            
            Currently I'm trying to understand offset and THD demands on the front-end operational amplifiers and gain distribution in general (to RF preamp or not to RF premap).
            
            Hopefully I can successfully search and avoid asking the well-known FAQs.  Thanks for providing and participating in this group.
            
            Coop,
            AA1WW
            
            PS:  This is the same intro I gave on the Soft_Radio Yahoo group.
            
            
            
            ------------------------------------
            
            Yahoo! Groups Links
            
            <*> To visit your group on the web, go to:
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          • Marciniak, Ed
            If the op amp is low enough noise, even perhaps 60db of common mode rejection won t eliminate all of the supply noise. Something better than a 7808 will be
            Message 5 of 7 , Jul 4, 2012
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              If the op amp is low enough noise, even perhaps 60db of common mode rejection won't eliminate all of the supply noise. Something better than a 7808 will be needed.

              73,
              Ed
              NB0M

               
              From: Gary Greene [mailto:w2zv@...]
              Sent: Wednesday, July 04, 2012 03:17 AM
              To: powersdr-iq@yahoogroups.com <powersdr-iq@yahoogroups.com>
              Subject: Re: SPAM -> [powersdr-iq] New member intro; Coop, AA1WW
               
               

              Hi Coop,

              The Tayloe detector (an RF Mux used to send RF to two storage caps for audio decode, see W2ZV.COM) has a best case NF of 1db, and so (for HF, 30 MHz or lower) with a low noise op-amp, 2 to 3 db is well below band noise, and no RF preamp is needed. The king of the hill of op-amps is the AD797 at +/- 15 volts, but you will not find many in use, the  LT6231 is nearly as good, runs at 12.6 V max (an 78L08 works well) and is used a lot, often at just 5 votls. Input is about 200 ohms, so a lot of audio op-amps are not as good at this low impedance. I use it as a IF tap off my Icom radios.

              I will be gone till sunday, so 73's and have fun,

              Gary Greene, W2ZV

              aa1ww wrote:

              Hi PowerSDR-IQ,
              
              I'm Coop, AA1WW and I've been reading about SDR recently. Before becoming an instructor at a community college here in the states (stcc.edu), I was an EE doing mostly digital FPGA stuff and some contract work that got me into very basic analog electronics along with the embedded digital stuff.
              
              I've read through the classic Software-for-the-Masses articles and a few others and am learning as I go. I hoping to build an direct-conversion SDR front-end along those lines. I found a deal on a used Creative Labs Audigy 2 card for my PC. I know a little DSP and have written some VB and C# apps and have some experience on Linux.
              
              Currently I'm trying to understand offset and THD demands on the front-end operational amplifiers and gain distribution in general (to RF preamp or not to RF premap).
              
              Hopefully I can successfully search and avoid asking the well-known FAQs.  Thanks for providing and participating in this group.
              
              Coop,
              AA1WW
              
              PS:  This is the same intro I gave on the Soft_Radio Yahoo group.
              
              
              
              ------------------------------------
              
              Yahoo! Groups Links
              
              <*> To visit your group on the web, go to:
                  http://groups.yahoo.com/group/powersdr-iq/
              
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                  Individual Email | Traditional
              
              <*> To change settings online go to:
                  http://groups.yahoo.com/group/powersdr-iq/join
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            • Ambro_IW2FVO
              Hi to all of you, I have an home made SDR based on the Avala_01 project. I would ask if there would be an improvement using the MAX412 in place of the NE5532.
              Message 6 of 7 , Jul 5, 2012
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                Hi to all of you,
                I have an home made SDR based on the Avala_01 project.
                I would ask if there would be an improvement using the MAX412 in place of the NE5532.
                ( they are pin to pin equivalent an DIP package ! )
                Thanks
                Ambrogio


                From: "Marciniak, Ed" <elmarciniak@...>
                To: "'powersdr-iq@yahoogroups.com'" <powersdr-iq@yahoogroups.com>
                Sent: Thursday, July 5, 2012 3:49 AM
                Subject: Re: SPAM -> [powersdr-iq] New member intro; Coop, AA1WW

                 
                Most of the better op amps have a pair of back to back diodes (or two in series back to back), which limits the differential input voltage range to something like 0.7V or 1.4V. This wouldn't normally be such a big deal but at low voltage gains used as a buffer, it may be the limiting factor.

                The stated noise densities are also usually input referred noise for a voltage gain of 100. The are not that good at say x10 voltage gain.

                I have a creative emu 1820m with AK5394A ADCs, on my softrock, and I lowered the voltage gain by changing the 5k resistors to 499 ohms. The noise floor increased by a few db for 20 db increase in strong signal handling capability. Since I intended to use transverters with a 10m IF, and my rf preamps have fractional db noise figures it was a good trade.

                With that said, I'd really like to build a I2S ADC interface to the radio and use a fully differential op amp out of the tayloe detector.

                I do recall Leif or Luis (sorry don't recall which) used bipolair transistors in front of a CA3140, but that topology had more gain than I wanted.

                There is room for improvement over the basic LT6231 but it won't come cheap...it might add 40 or more to cost overall.

                I'd be interested in chatting/emailing if someone in interested. I hate reinventing the wheel.

                Vy 73,
                Ed Marciniak
                NB0M

                 
                From: Jeff Cooper [mailto:aa1ww@...]
                Sent: Wednesday, July 04, 2012 11:47 AM
                To: powersdr-iq@yahoogroups.com <powersdr-iq@yahoogroups.com>; w2zv@... <w2zv@...>
                Subject: RE: SPAM -> [powersdr-iq] New member intro; Coop, AA1WW
                 
                 
                Gary, W2ZV,

                Thanks for your reply.  I'm used to omitting RF preamps at HF but it's less intuitive when looking at the overall signal path gain outside the PC.
                I've been wondering about opamp choice especially for 24-bit PC sound cards.  So I've been comparing some opamp data (apart from specific application circuits).
                 
                OpAmp     Noise(nV/rootHz)    THD                                   Comments
                --------  ------------------  ------------------------------------  -----------
                LT6231    1.1                              -90   dB THD @ <100 KHz
                AD797     0.9 typ; 1.2 max                -120   dB THD @   20 KHz
                AD8597    1.1 @ 1 KHz                     -120   dB THD @    1 KHz
                OPA1611   1.1 @ 1 KHz         0.000015% = -136.5 dB THD @    1 KHz
                OPA1632   1.3                 0.000022% =  -93.2 dB THD            (Fully Diff)
                OPA211    1.1 @ 1 KHz                     -136.5 dB THD @    1 KHz (Av = 1)
                LME49990  0.9 typ; 1.3 max    0.000010% = -140   dB THD @    1 KHz (Av = 1)
                 
                It's really quite impressive to thinking about 100+ dB dynamic range.
                 
                Coop, AA1WW

                To: powersdr-iq@yahoogroups.com
                From: w2zv@...
                Date: Wed, 4 Jul 2012 04:17:32 -0400
                Subject: Re: SPAM -> [powersdr-iq] New member intro; Coop, AA1WW

                 
                Hi Coop,

                The Tayloe detector (an RF Mux used to send RF to two storage caps for audio decode, see W2ZV.COM) has a best case NF of 1db, and so (for HF, 30 MHz or lower) with a low noise op-amp, 2 to 3 db is well below band noise, and no RF preamp is needed. The king of the hill of op-amps is the AD797 at +/- 15 volts, but you will not find many in use, the  LT6231 is nearly as good, runs at 12.6 V max (an 78L08 works well) and is used a lot, often at just 5 votls. Input is about 200 ohms, so a lot of audio op-amps are not as good at this low impedance. I use it as a IF tap off my Icom radios.

                I will be gone till sunday, so 73's and have fun,

                Gary Greene, W2ZV

                aa1ww wrote:
                Hi PowerSDR-IQ,
                
                I'm Coop, AA1WW and I've been reading about SDR recently. Before becoming an instructor at a community college here in the states (stcc.edu), I was an EE doing mostly digital FPGA stuff and some contract work that got me into very basic analog electronics along with the embedded digital stuff.
                
                I've read through the classic Software-for-the-Masses articles and a few others and am learning as I go. I hoping to build an direct-conversion SDR front-end along those lines. I found a deal on a used Creative Labs Audigy 2 card for my PC. I know a little DSP and have written some VB and C# apps and have some experience on Linux.
                
                Currently I'm trying to understand offset and THD demands on the front-end operational amplifiers and gain distribution in general (to RF preamp or not to RF premap).
                
                Hopefully I can successfully search and avoid asking the well-known FAQs.  Thanks for providing and participating in this group.
                
                Coop,
                AA1WW
                
                PS:  This is the same intro I gave on the Soft_Radio Yahoo group.
                
                
                
                ------------------------------------
                
                Yahoo! Groups Links
                
                <*> To visit your group on the web, go to:
                    http://groups.yahoo.com/group/powersdr-iq/
                
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              • applewiz2000
                Thread title changed to remove the word spam!!! NE5532 was introduced in 1979 and if you pay more money there are many better chips. Be careful to allow for
                Message 7 of 7 , Jul 5, 2012
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                  Thread title changed to remove the word spam!!!

                  NE5532 was introduced in 1979 and if you pay more money there are many better chips. Be careful to allow for the 12V supply.

                  MAX412 may well perform better, worth a try. The Avala circuit uses a differential configuration. There are some very descriptive datasheets from Texas Instruments on their differential amplifiers. In particular they give equations for calculating noise.

                  For general gain distribution see here:
                  https://sites.google.com/site/lofturj/comparison_of_sdr_vs_superhet

                  Most circuits, including the Avala do not utilise the 24 bit soundcards fully.

                  73s, Rob
                  (M0RZF)

                  --- In powersdr-iq@yahoogroups.com, Ambro_IW2FVO <iw2fvo@...> wrote:
                  > Hi to all of you,
                  > I have an home made SDR based on the Avala_01 project.
                  > I would ask if there would be an improvement using the MAX412 in place of the NE5532.
                  > ( they are pin to pin equivalent an DIP package ! )
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