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Coaxial Cavity Filter

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  • Scotty
    Hi All, With so many comments about the Coaxial Cavity Filter, I could explain the history behind the development of the MSA and why the Coaxial Cavity Filter
    Message 1 of 17 , Jan 24, 2009
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      Hi All,
      With so many comments about the Coaxial Cavity Filter, I could
      explain the history behind the development of the MSA and why the
      Coaxial Cavity Filter became necessary. However, the history is
      involved and somewhat boring. So, I will keep the history short.
      My intention was to create a spectrum analyzer with only two
      frequency conversions. This dual conversion scheme minimizes
      Intermodulation Distortion and Multiple Conversion Harmonic Products.
      Both, undesireable in a spectrum analyzer.
      Before even thinking much about the first I.F., I mandated that the
      second I.F. (Final I.F) would be 10.7 MHz. Why, you ask? Because, so
      many components are commercially available for this "industry standard
      frequency". More so than any of the other "standards", such as 21
      MHz, 45 MHz, and 70 MHz.
      With VCO restrictions, and many other factors, this necessitated the
      first I.F. to be 1013.3 MHz and the second local oscillator to be 1024
      MHz.
      As with any receiver (and a spectrum analyzer is a receiver), the
      first I.F. must be the only frequency allowed to enter the second
      mixer. One signal is most important to keep from entering the second
      mixer. It is called the image frequency. It is also the most
      difficult to keep out. The image frequency, when mixed with the local
      oscillator of the second mixer will create 10.7 MHz. This would be
      1034.7 MHz. (1034.7 - 1024 = 10.7). Image frequencies are created
      when signals enter the spectrum analyzer (first mixer) and are mixed
      with the first mixer's local oscillator to create 1034.7 MHz. This
      occurs often, and special attention must be made to prevent the image
      from reaching the second mixer.
      In the MSA, with the first I.F. at 1013.3 MHz, attenuating the image
      frequency at 1034.7 MHz is difficult. There are several methods to do
      this. Some are expensive, and some are very complicated. And, other
      methods require special building practices, which I can't expect the
      average home builder to duplicate. Therefore, I created the Coaxial
      Cavity Filter which is a compromise of expense, complication and
      duplicateability (is that a real word?). Even if the Coaxial Cavity
      Filter is not constructed perfectly, it should still work quite well
      in the MSA.
      For those who would like to experiment with replacing the Coaxial
      Cavity Filter with something else, keep the following in mind:
      1. You would like the image frequency to be attenuated as much as
      possible. A minimum ratio of image frequency/real frequency is about
      70 dB. 70 dB is quite noticeable on the graph, but if you know it is
      there, you can live with it. I would prefer it to be -90 dB or
      better. The Coaxial Cavity Filter should get you somewhere between
      -90 dB and -110 dB. More, if it is perfectly constructed.
      2. For a Basic Spectrum Analyzer, the filter bandwidth is not
      terribly, important. Neither is insertion loss. Maximum attenuation
      of the image frequency is most important.
      3. For a Spectrum Analyzer with Tracking Generator, or a Spectrum
      Analyzer/Vector Network Analyzer, the filter bandwidth does become a
      factor. Due to the topology of my design for creating the TG, the
      narrower the bandwidth, the better.
      I have yet to experiment with these, but there are several options
      I'd really like to play with, to replace the Coaxial Cavity Filter.
      A. Hairpin and "racetrack" printed wiring board filters.
      B. Discrete component filters combined with stubs to "suck out" the
      image frequency.
      C. SAW filters and "hocky puck" resonators.
      D. Commercial Helical filters, likely in cascade.
      E. Dielectric and ceramic filters (common in cell phones), also in
      cascade.
      F. Perhaps, even amplification between cascaded filters

      The bottom line: The Coaxial Cavity Filter is the best I have for
      now. Stay tuned for future developments.
      Scotty
    • Phil Harman
      Hi Scotty, I ve been experimenting with a version of your SSA that uses dielectric filters for the first IF filter. I m using a higher second IF (96MHz) so my
      Message 2 of 17 , Jan 24, 2009
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        Hi Scotty,
         
        I've been experimenting with a version of your SSA that uses dielectric filters for the first IF filter.
         
        I'm using a higher second IF (96MHz) so my image rejection requirements are somewhat relaxed.
         
        I find the filters work very well but they need to be individually well screened to avoid blow-round.
         
        Overall design ideas are here
         
         
         
        and the dielectric filters are here
         
         
         
        Regards
         
        Phil...VK6APH
         
         
      • changwonson
        Hi Phil! I just went your site. The CYCLOPS looks good for me as a digital engineer my self(not RF). My current plan include dedicated Display and touch pannel
        Message 3 of 17 , Jan 25, 2009
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          Hi Phil!
          I just went your site.
          The CYCLOPS looks good for me as a digital engineer my self(not RF).
          My current plan include dedicated Display and touch pannel for the SA
          under Arm-9 processor control without PC attachment.

          However, the CYCLOPS does not have any further information except
          block diagram.



          --- In spectrumanalyzer@yahoogroups.com, "Phil Harman" <phil@...>
          wrote:
          >
          > Hi Scotty,
          >
          > I've been experimenting with a version of your SSA that uses
          dielectric filters for the first IF filter.
          >
          > I'm using a higher second IF (96MHz) so my image rejection
          requirements are somewhat relaxed.
          >
          > I find the filters work very well but they need to be individually
          well screened to avoid blow-round.
          >
          > Overall design ideas are here
          >
          > < http://hpsdr.org/wiki/index.php?title=CYCLOPS >
          >
          >
          > and the dielectric filters are here
          >
          > < http://www.toko.co.jp/products/en/filters_dielectric/6dfa_e.html>
          >
          >
          > Regards
          >
          > Phil...VK6APH
          >
        • Phil Harman
          Hi, I do have a working prototype and can send you schematics if you like. It s still very much experimental but I expect to go to prototype PCBs very shortly.
          Message 4 of 17 , Jan 25, 2009
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            Hi,
             
            I do have a working prototype and can send you schematics if you like. It's still very much experimental but I expect to go to prototype PCBs very shortly.
             
            Phil....
             
             
            ----- Original Message -----
            Sent: Sunday, January 25, 2009 6:28 PM
            Subject: [spectrumanalyzer] Re: Coaxial Cavity Filter

            Hi Phil!
            I just went your site.
            The CYCLOPS looks good for me as a digital engineer my self(not RF).
            My current plan include dedicated Display and touch pannel for the SA
            under Arm-9 processor control without PC attachment.

            However, the CYCLOPS does not have any further information except
            block diagram.

            --- In spectrumanalyzer@ yahoogroups. com, "Phil Harman" <phil@...>
            wrote:
            >
            > Hi Scotty,
            >
            > I've been experimenting with a version of your SSA that uses
            dielectric filters for the first IF filter.
            >
            > I'm using a higher second IF (96MHz) so my image rejection
            requirements are somewhat relaxed.
            >
            > I find the filters work very well but they need to be individually
            well screened to avoid blow-round.
            >
            > Overall design ideas are here
            >
            > < http://hpsdr. org/wiki/ index.php? title=CYCLOPS >
            >
            >
            > and the dielectric filters are here
            >
            > < http://www.toko. co.jp/products/ en/filters_ dielectric/ 6dfa_e.html>
            >
            >
            > Regards
            >
            > Phil...VK6APH
            >



            No virus found in this incoming message.
            Checked by AVG - http://www.avg.com
            Version: 8.0.176 / Virus Database: 270.10.13/1914 - Release Date: 1/24/2009 8:40 PM
          • changwonson
            YES. I will be delighted if you share the schematic with me. I may Interested in your prototype PCB. I can produce a copy of PCB from your schematic. But,
            Message 5 of 17 , Jan 25, 2009
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              YES.

              I will be delighted if you share the schematic with me.

              I may Interested in your prototype PCB.

              I can produce a copy of PCB from your schematic.
              But, without RF knowledge, the layout can not finished without the
              assistance by the RF engineer like you.


              --- In spectrumanalyzer@yahoogroups.com, "Phil Harman" <phil@...>
              wrote:
              >
              > Hi,
              >
              > I do have a working prototype and can send you schematics if you
              like. It's still very much experimental but I expect to go to
              prototype PCBs very shortly.
              >
              > Phil....
              >
              >
              > ----- Original Message -----
              > From: changwonson
              > To: spectrumanalyzer@yahoogroups.com
              > Sent: Sunday, January 25, 2009 6:28 PM
              > Subject: [spectrumanalyzer] Re: Coaxial Cavity Filter
              >
              >
              > Hi Phil!
              > I just went your site.
              > The CYCLOPS looks good for me as a digital engineer my self(not
              RF).
              > My current plan include dedicated Display and touch pannel for
              the SA
              > under Arm-9 processor control without PC attachment.
              >
              > However, the CYCLOPS does not have any further information
              except
              > block diagram.
              >
              > --- In spectrumanalyzer@yahoogroups.com, "Phil Harman" <phil@>
              > wrote:
              > >
              > > Hi Scotty,
              > >
              > > I've been experimenting with a version of your SSA that uses
              > dielectric filters for the first IF filter.
              > >
              > > I'm using a higher second IF (96MHz) so my image rejection
              > requirements are somewhat relaxed.
              > >
              > > I find the filters work very well but they need to be
              individually
              > well screened to avoid blow-round.
              > >
              > > Overall design ideas are here
              > >
              > > < http://hpsdr.org/wiki/index.php?title=CYCLOPS >
              > >
              > >
              > > and the dielectric filters are here
              > >
              > > <
              http://www.toko.co.jp/products/en/filters_dielectric/6dfa_e.html>
              > >
              > >
              > > Regards
              > >
              > > Phil...VK6APH
              > >
              >
              >
              >
              >
              >
              >
              > -------------------------------------------------------------------
              -----------
              >
              >
              >
              > No virus found in this incoming message.
              > Checked by AVG - http://www.avg.com
              > Version: 8.0.176 / Virus Database: 270.10.13/1914 - Release
              Date: 1/24/2009 8:40 PM
              >
            • Derward Myrick
              ... From: Phil Harman To: spectrumanalyzer@yahoogroups.com Sent: Sunday, January 25, 2009 3:56 AM Subject: Re: [spectrumanalyzer] Re: Coaxial Cavity Filter Hi,
              Message 6 of 17 , Jan 25, 2009
              • 0 Attachment
                 
                ----- Original Message -----
                Sent: Sunday, January 25, 2009 3:56 AM
                Subject: Re: [spectrumanalyzer] Re: Coaxial Cavity Filter
                Hi,
                 
                I do have a working prototype and can send you schematics if you like. It's still
                very much experimental but I expect to go to prototype PCBs very shortly.
                 
                Phil....
                 
                 
                Phil,
                 
                I would like to receive the schematics if you don't mind.
                 
                Thanks
                 
                Derward Myrick  KD5WWI

                .

              • Phil Harman
                Hi, Please find attached a copy of the current Cyclops schematics. Regards Phil.... ... From: changwonson To: spectrumanalyzer@yahoogroups.com Sent: Sunday,
                Message 7 of 17 , Jan 25, 2009
                • 0 Attachment
                  Hi,
                   
                  Please find attached a copy of the current  Cyclops schematics.
                   
                  Regards
                   
                  Phil....
                   
                   
                   
                  ----- Original Message -----
                  Sent: Sunday, January 25, 2009 8:03 PM
                  Subject: [spectrumanalyzer] Re: Coaxial Cavity Filter

                  YES.

                  I am pleased if you can share the schematic with me.

                  I may also want to make a prototype PCB myself.

                  Some times international delivery is not much cost efective than
                  coining localy.

                  --- In spectrumanalyzer@ yahoogroups. com, "Phil Harman" <phil@...>
                  wrote:
                  >
                  > Hi,
                  >
                  > I do have a working prototype and can send you schematics if you
                  like. It's still very much experimental but I expect to go to
                  prototype PCBs very shortly.
                  >
                  > Phil....
                  >
                  >
                  > ----- Original Message -----
                  > From: changwonson
                  > To: spectrumanalyzer@ yahoogroups. com
                  > Sent: Sunday, January 25, 2009 6:28 PM
                  > Subject: [spectrumanalyzer] Re: Coaxial Cavity Filter
                  >
                  >
                  > Hi Phil!
                  > I just went your site.
                  > The CYCLOPS looks good for me as a digital engineer my self(not
                  RF).
                  > My current plan include dedicated Display and touch pannel for
                  the SA
                  > under Arm-9 processor control without PC attachment.
                  >
                  > However, the CYCLOPS does not have any further information
                  except
                  > block diagram.
                  >
                  > --- In spectrumanalyzer@ yahoogroups. com, "Phil Harman" <phil@>
                  > wrote:
                  > >
                  > > Hi Scotty,
                  > >
                  > > I've been experimenting with a version of your SSA that uses
                  > dielectric filters for the first IF filter.
                  > >
                  > > I'm using a higher second IF (96MHz) so my image rejection
                  > requirements are somewhat relaxed.
                  > >
                  > > I find the filters work very well but they need to be
                  individually
                  > well screened to avoid blow-round.
                  > >
                  > > Overall design ideas are here
                  > >
                  > > < http://hpsdr. org/wiki/ index.php? title=CYCLOPS >
                  > >
                  > >
                  > > and the dielectric filters are here
                  > >
                  > > <
                  http://www.toko. co.jp/products/ en/filters_ dielectric/ 6dfa_e.html>
                  > >
                  > >
                  > > Regards
                  > >
                  > > Phil...VK6APH
                  > >
                  >
                  >
                  >
                  >
                  >
                  >
                  > ------------ --------- --------- --------- --------- --------- -
                  -----------
                  >
                  >
                  >
                  > No virus found in this incoming message.
                  > Checked by AVG - http://www.avg. com
                  > Version: 8.0.176 / Virus Database: 270.10.13/1914 - Release
                  Date: 1/24/2009 8:40 PM
                  >



                  No virus found in this incoming message.
                  Checked by AVG - http://www.avg.com
                  Version: 8.0.176 / Virus Database: 270.10.13/1914 - Release Date: 1/24/2009 8:40 PM
                • Phil Harman
                  Hi, Please find attached a copy of the current Cyclops schematics. Regards Phil.... ... From: Derward Myrick To: spectrumanalyzer@yahoogroups.com Cc:
                  Message 8 of 17 , Jan 25, 2009
                  • 0 Attachment
                    Hi,
                     
                    Please find attached a copy of the current  Cyclops schematics.
                     
                    Regards
                     
                    Phil....
                     
                     
                     
                    ----- Original Message -----
                    Sent: Monday, January 26, 2009 12:08 AM
                    Subject: Re: [spectrumanalyzer] Re: Coaxial Cavity Filter

                     
                    ----- Original Message -----
                    Sent: Sunday, January 25, 2009 3:56 AM
                    Subject: Re: [spectrumanalyzer] Re: Coaxial Cavity Filter
                    Hi,
                     
                    I do have a working prototype and can send you schematics if you like. It's still
                    very much experimental but I expect to go to prototype PCBs very shortly.
                     
                    Phil....
                     
                     
                    Phil,
                     
                    I would like to receive the schematics if you don't mind.
                     
                    Thanks
                     
                    Derward Myrick  KD5WWI

                    .



                    No virus found in this incoming message.
                    Checked by AVG - http://www.avg.com
                    Version: 8.0.176 / Virus Database: 270.10.13/1914 - Release Date: 1/24/2009 8:40 PM
                  • changwonson
                    Attachment is not there. Would you check that again? ... you like. It s still ... very shortly. ... Date: 1/24/2009 8:40 PM
                    Message 9 of 17 , Jan 25, 2009
                    • 0 Attachment
                      Attachment is not there.
                      Would you check that again?

                      --- In spectrumanalyzer@yahoogroups.com, "Phil Harman" <phil@...>
                      wrote:
                      >
                      > Hi,
                      >
                      > Please find attached a copy of the current Cyclops schematics.
                      >
                      > Regards
                      >
                      > Phil....
                      >
                      >
                      >
                      > ----- Original Message -----
                      > From: Derward Myrick
                      > To: spectrumanalyzer@yahoogroups.com
                      > Cc: wdmyrick@...
                      > Sent: Monday, January 26, 2009 12:08 AM
                      > Subject: Re: [spectrumanalyzer] Re: Coaxial Cavity Filter
                      >
                      >
                      >
                      >
                      > ----- Original Message -----
                      > From: Phil Harman
                      > To: spectrumanalyzer@yahoogroups.com
                      > Sent: Sunday, January 25, 2009 3:56 AM
                      > Subject: Re: [spectrumanalyzer] Re: Coaxial Cavity Filter
                      > Hi,
                      >
                      > I do have a working prototype and can send you schematics if
                      you like. It's still
                      > very much experimental but I expect to go to prototype PCBs
                      very shortly.
                      >
                      > Phil....
                      >
                      >
                      > Phil,
                      >
                      > I would like to receive the schematics if you don't mind.
                      >
                      > Thanks
                      >
                      > Derward Myrick KD5WWI
                      >
                      >
                      > .
                      >
                      >
                      >
                      >
                      >
                      >
                      > -------------------------------------------------------------------
                      -----------
                      >
                      >
                      >
                      > No virus found in this incoming message.
                      > Checked by AVG - http://www.avg.com
                      > Version: 8.0.176 / Virus Database: 270.10.13/1914 - Release
                      Date: 1/24/2009 8:40 PM
                      >
                    • Phil Harman
                      I ll add the latest schematics to the Wiki since lots of folks seem to be interested and Yahoo appears to strip attachments. Phil... ... From: changwonson To:
                      Message 10 of 17 , Jan 25, 2009
                      • 0 Attachment
                        I'll add the latest schematics to the Wiki since lots of folks seem to be interested and Yahoo appears to strip attachments.
                         
                        Phil...
                         
                         
                        ----- Original Message -----
                        Sent: Monday, January 26, 2009 10:31 AM
                        Subject: [spectrumanalyzer] Re: Coaxial Cavity Filter

                        Attachment is not there.
                        Would you check that again?

                        --- In spectrumanalyzer@ yahoogroups. com, "Phil Harman" <phil@...>
                        wrote:
                        >
                        > Hi,
                        >
                        > Please find attached a copy of the current Cyclops schematics.
                        >
                        > Regards
                        >
                        > Phil....
                        >
                        >
                        >
                        > ----- Original Message -----
                        > From: Derward Myrick
                        > To: spectrumanalyzer@ yahoogroups. com
                        > Cc: wdmyrick@...
                        > Sent: Monday, January 26, 2009 12:08 AM
                        > Subject: Re: [spectrumanalyzer] Re: Coaxial Cavity Filter
                        >
                        >
                        >
                        >
                        > ----- Original Message -----
                        > From: Phil Harman
                        > To: spectrumanalyzer@ yahoogroups. com
                        > Sent: Sunday, January 25, 2009 3:56 AM
                        > Subject: Re: [spectrumanalyzer] Re: Coaxial Cavity Filter
                        > Hi,
                        >
                        > I do have a working prototype and can send you schematics if
                        you like. It's still
                        > very much experimental but I expect to go to prototype PCBs
                        very shortly.
                        >
                        > Phil....
                        >
                        >
                        > Phil,
                        >
                        > I would like to receive the schematics if you don't mind.
                        >
                        > Thanks
                        >
                        > Derward Myrick KD5WWI
                        >
                        >
                        > .
                        >
                        >
                        >
                        >
                        >
                        >
                        > ------------ --------- --------- --------- --------- --------- -
                        -----------
                        >
                        >
                        >
                        > No virus found in this incoming message.
                        > Checked by AVG - http://www.avg. com
                        > Version: 8.0.176 / Virus Database: 270.10.13/1914 - Release
                        Date: 1/24/2009 8:40 PM
                        >



                        No virus found in this incoming message.
                        Checked by AVG - http://www.avg.com
                        Version: 8.0.176 / Virus Database: 270.10.13/1915 - Release Date: 1/25/2009 6:13 PM
                      • changwonson
                        Thanks Phil, I got a copy. From that, I found you use BGA616 for filter loss recovery. I have a bunch of BGA5689 and BGA2003 (Those are aquired for LNA
                        Message 11 of 17 , Jan 26, 2009
                        • 0 Attachment
                          Thanks Phil, I got a copy.

                          From that, I found you use BGA616 for filter loss recovery.

                          I have a bunch of BGA5689 and BGA2003 (Those are aquired for LNA
                          application for 2.4GHz, but never been used for) . Do you think
                          those can be used as well? If not I can get BGA614 from local vender.

                          So far, I do not see any microstrip from your schematic, is that
                          correct observation?

                          Finally, the PC side DSP description is not there. I hope to have a
                          glimpse of internal information about what's going on the DSP.


                          --- In spectrumanalyzer@yahoogroups.com, "Phil Harman" <phil@...>
                          wrote:
                          >
                          > I'll add the latest schematics to the Wiki since lots of folks
                          seem to be interested and Yahoo appears to strip attachments.
                          >
                          > Phil...
                          >
                          >
                          > ----- Original Message -----
                          > From: changwonson
                          > To: spectrumanalyzer@yahoogroups.com
                          > Sent: Monday, January 26, 2009 10:31 AM
                          > Subject: [spectrumanalyzer] Re: Coaxial Cavity Filter
                          >
                          >
                          > Attachment is not there.
                          > Would you check that again?
                          >
                          > --- In spectrumanalyzer@yahoogroups.com, "Phil Harman" <phil@>
                          > wrote:
                          > >
                          > > Hi,
                          > >
                          > > Please find attached a copy of the current Cyclops schematics.
                          > >
                          > > Regards
                          > >
                          > > Phil....
                          > >
                          > >
                          > >
                          > > ----- Original Message -----
                          > > From: Derward Myrick
                          > > To: spectrumanalyzer@yahoogroups.com
                          > > Cc: wdmyrick@
                          > > Sent: Monday, January 26, 2009 12:08 AM
                          > > Subject: Re: [spectrumanalyzer] Re: Coaxial Cavity Filter
                          > >
                          > >
                          > >
                          > >
                          > > ----- Original Message -----
                          > > From: Phil Harman
                          > > To: spectrumanalyzer@yahoogroups.com
                          > > Sent: Sunday, January 25, 2009 3:56 AM
                          > > Subject: Re: [spectrumanalyzer] Re: Coaxial Cavity Filter
                          > > Hi,
                          > >
                          > > I do have a working prototype and can send you schematics if
                          > you like. It's still
                          > > very much experimental but I expect to go to prototype PCBs
                          > very shortly.
                          > >
                          > > Phil....
                          > >
                          > >
                          > > Phil,
                          > >
                          > > I would like to receive the schematics if you don't mind.
                          > >
                          > > Thanks
                          > >
                          > > Derward Myrick KD5WWI
                          > >
                          > >
                          > > .
                          > >
                          > >
                          > >
                          > >
                          > >
                          > >
                          > > ----------------------------------------------------------
                          > -----------
                          > >
                          > >
                          > >
                          > > No virus found in this incoming message.
                          > > Checked by AVG - http://www.avg.com
                          > > Version: 8.0.176 / Virus Database: 270.10.13/1914 - Release
                          > Date: 1/24/2009 8:40 PM
                          > >
                          >
                          >
                          >
                          >
                          >
                          >
                          > -------------------------------------------------------------------
                          -----------
                          >
                          >
                          >
                          > No virus found in this incoming message.
                          > Checked by AVG - http://www.avg.com
                          > Version: 8.0.176 / Virus Database: 270.10.13/1915 - Release
                          Date: 1/25/2009 6:13 PM
                          >
                        • Dan Andersson
                          ... As soon as you start to add gain to recover losses, you start to eat up your SA s prestanda and once lost - never regained. //Dan, M0DFI
                          Message 12 of 17 , Jan 26, 2009
                          • 0 Attachment
                            On Monday 26 January 2009 14:20:26 changwonson wrote:
                            > Thanks Phil, I got a copy.
                            >
                            > From that, I found you use BGA616 for filter loss recovery.
                            >
                            > I have a bunch of BGA5689 and BGA2003 (Those are aquired for LNA
                            > application for 2.4GHz, but never been used for) . Do you think
                            > those can be used as well? If not I can get BGA614 from local vender.
                            >
                            > So far, I do not see any microstrip from your schematic, is that
                            > correct observation?
                            >
                            > Finally, the PC side DSP description is not there. I hope to have a
                            > glimpse of internal information about that's going on the DSP.
                            >
                            >

                            As soon as you start to add gain to recover losses, you start to eat up your
                            SA's prestanda and once lost - never regained.

                            //Dan, M0DFI
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