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Big signal at 0 Hz even with SR40 is off

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  • Jerry Flanders
    Using PowerSDR with my newly constructed 80/40 SR40 v6.1, I see a big carrier sig in the center of the range (equiv to 7056 KHz tuned freq). I assumed this
    Message 1 of 21 , Sep 30 8:26 AM
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      Using PowerSDR with my newly constructed 80/40 SR40 v6.1, I see a big
      "carrier" sig in the center of the range (equiv to 7056 KHz tuned
      freq). I assumed this was just some kind of leakage from the LO which
      I didn't understand, but now I have discovered it stays on even when
      the SR40 is powered down (even unplugged from sound card). It also
      does not appear when I use a laptop (mono mic input) instead of the
      desktop computer (line in, stereo).

      It is big, -44dB vs nearby "grass" of -130 (SR40 off).

      It is obviously something at DC being generated in my sound card
      (cheapie Motherboard Realtek AC'97).

      Anybody know a way to null this out or reduce it short of replacing
      the sound card?

      Jerry W4UK
    • Mike
      The big signal is 60 Hz pickup. The solution is isolation transformer (s), in the audio lines and/or at the antenna connection. Running on battery can help to,
      Message 2 of 21 , Sep 30 9:40 AM
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        The big signal is 60 Hz pickup. The solution is isolation transformer
        (s), in the audio lines and/or at the antenna connection. Running on
        battery can help to, or a non-grounded power cube. These will help to
        reduce the mountain at the center but may not eliminate it entirely.

        73 - Mike WA8BXN
      • Jerry Flanders
        I have it even when I unplug the SR from the sound card - no apparent change in vol. Jerry W4UK
        Message 3 of 21 , Sep 30 10:05 AM
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          I have it even when I unplug the SR from the sound card - no apparent
          change in vol.

          Jerry W4UK

          At 16:40 9/30/2006, you wrote:

          >The big signal is 60 Hz pickup. The solution is isolation transformer
          >(s), in the audio lines and/or at the antenna connection. Running on
          >battery can help to, or a non-grounded power cube. These will help to
          >reduce the mountain at the center but may not eliminate it entirely.
          >
          >73 - Mike WA8BXN
        • Cecil KD5NWA
          The person that responded to you is correct, you will pickup 60Hz hum and harmonics even if the unit is turned off. The magnetic fields from wiring in your
          Message 4 of 21 , Sep 30 10:40 AM
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            The person that responded to you is correct, you will pickup 60Hz hum
            and harmonics even if the unit is turned off. The magnetic fields
            from wiring in your house are always there, the power to the unit and
            the audio shield also causes a ground loop creating a signal to the
            sound card, running on batteries or a isolated power supply will help.

            At 12:05 PM 9/30/2006, you wrote:
            >I have it even when I unplug the SR from the sound card - no apparent
            >change in vol.
            >
            >Jerry W4UK
            >
            >At 16:40 9/30/2006, you wrote:
            >
            > >The big signal is 60 Hz pickup. The solution is isolation transformer
            > >(s), in the audio lines and/or at the antenna connection. Running on
            > >battery can help to, or a non-grounded power cube. These will help to
            > >reduce the mountain at the center but may not eliminate it entirely.
            > >
            > >73 - Mike WA8BXN
            >
            >
            >
            >
            >Yahoo! Groups Links
            >
            >
            >
            >
            >
            >
            >


            Cecil Bayona
            KD5NWA
            www.qrpradio.com

            'Never argue with an idiot. They drag you down to their level then
            beat you with experience.'
          • Mike
            Is it still there if you short the input to the sound card? Are the jacks for input directly on the sound card, or are they on the front panel with wires
            Message 5 of 21 , Sep 30 10:46 AM
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              Is it still there if you short the input to the sound card? Are the
              jacks for input directly on the sound card, or are they on the front
              panel with wires between the card and jacks. Possibly a bad connection
              somewhere if that is the case, or maybe rerouting the wire a bit may
              help. It is 60 Hz pickup somewhere.

              73 - Mike WA8BXN
            • Cecil KD5NWA
              Also everyone s computer is different, the people who designed the original PC s had no concept of low signal work, and made the power supply connect to the
              Message 6 of 21 , Sep 30 11:26 AM
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                Also everyone's computer is different, the people who designed the
                original PC's had no concept of low signal work, and made the power
                supply connect to the earth ground at multiple points inside the PC,
                creating a whole bunch of ground loops internal to the PC.

                Some people will report almost no noise in the center while others
                with the same sound card will report huge spikes, I have personally
                notice that myself when I did a test on several sound cards and found
                them to consistently misbehave with some computers.


                At 12:40 PM 9/30/2006, you wrote:
                >The person that responded to you is correct, you will pickup 60Hz hum
                >and harmonics even if the unit is turned off. The magnetic fields
                >from wiring in your house are always there, the power to the unit and
                >the audio shield also causes a ground loop creating a signal to the
                >sound card, running on batteries or a isolated power supply will help.
                >
                >At 12:05 PM 9/30/2006, you wrote:
                > >I have it even when I unplug the SR from the sound card - no apparent
                > >change in vol.
                > >
                > >Jerry W4UK
                > >
                > >At 16:40 9/30/2006, you wrote:
                > >
                > > >The big signal is 60 Hz pickup. The solution is isolation transformer
                > > >(s), in the audio lines and/or at the antenna connection. Running on
                > > >battery can help to, or a non-grounded power cube. These will help to
                > > >reduce the mountain at the center but may not eliminate it entirely.
                > > >
                > > >73 - Mike WA8BXN
                > >
                > >
                > >
                > >
                > >Yahoo! Groups Links
                > >
                > >
                > >
                > >
                > >
                > >
                > >
                >
                >
                >Cecil Bayona
                >KD5NWA
                >www.qrpradio.com
                >
                >'Never argue with an idiot. They drag you down to their level then
                >beat you with experience.'
                >
                >
                >
                >
                >Yahoo! Groups Links
                >
                >
                >
                >
                >
                >
                >


                Cecil Bayona
                KD5NWA
                www.qrpradio.com

                'Never argue with an idiot. They drag you down to their level then
                beat you with experience.'
              • Jerry Flanders
                This happens with NO CONNECTION to the sound card - no SR40, no mike, not even speakers - No connection of any kind to the sound card inputs. Hence, no ground
                Message 7 of 21 , Sep 30 11:51 AM
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                  This happens with NO CONNECTION to the sound card - no SR40, no mike,
                  not even speakers - No connection of any kind to the sound card
                  inputs. Hence, no ground loop. Nada.

                  Do you (or anybody) have any continuous signal at your PowerSDR
                  (SR40) center freq? Anything at all above the grass? Level? Does it
                  stay when you unplug all?

                  Jerry W4UK

                  At 17:40 9/30/2006, you wrote:

                  >The person that responded to you is correct, you will pickup 60Hz hum
                  >and harmonics even if the unit is turned off. The magnetic fields
                  >from wiring in your house are always there, the power to the unit and
                  >the audio shield also causes a ground loop creating a signal to the
                  >sound card, running on batteries or a isolated power supply will help.
                  >
                  >At 12:05 PM 9/30/2006, you wrote:
                  > >I have it even when I unplug the SR from the sound card - no apparent
                  > >change in vol.
                  > >
                  > >Jerry W4UK
                  > >
                  > >At 16:40 9/30/2006, you wrote:
                  > >
                  > > >The big signal is 60 Hz pickup. The solution is isolation transformer
                  > > >(s), in the audio lines and/or at the antenna connection. Running on
                  > > >battery can help to, or a non-grounded power cube. These will help to
                  > > >reduce the mountain at the center but may not eliminate it entirely.
                  > > >
                  > > >73 - Mike WA8BXN
                  > >
                  > >
                  > >
                  > >
                  > >Yahoo! Groups Links
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >
                  >
                  >Cecil Bayona
                  >KD5NWA
                  >www.qrpradio.com
                  >
                  >'Never argue with an idiot. They drag you down to their level then
                  >beat you with experience.'
                  >
                  >
                • py2wm
                  This is an artifact from the sound card which was not intended to digitize below 10~20 Hz. It s a kind of noise from the ADC (analog to digital converter).
                  Message 8 of 21 , Sep 30 12:19 PM
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                    This is an artifact from the sound card which was not intended to
                    digitize below 10~20 Hz. It's a kind of "noise" from the ADC (analog
                    to digital converter).

                    It is not 60 Hz line hum, which can be easily seen on zoomed
                    spectrograph display at 60, 120 , 180 Hz and also at negative
                    frequencies. Rather, the SDR software treats as single signal, you
                    can hear it as a carrier as you tune across it.

                    73,

                    João De Marco, PY2WM




                    --- In softrock40@yahoogroups.com, Jerry Flanders <jeflanders@...>
                    wrote:
                    >
                    > Using PowerSDR with my newly constructed 80/40 SR40 v6.1, I see a
                    big
                    > "carrier" sig in the center of the range (equiv to 7056 KHz tuned
                    > freq). I assumed this was just some kind of leakage from the LO
                    which
                    > I didn't understand, but now I have discovered it stays on even
                    when
                    > the SR40 is powered down (even unplugged from sound card). It also
                    > does not appear when I use a laptop (mono mic input) instead of
                    the
                    > desktop computer (line in, stereo).
                    >
                    > It is big, -44dB vs nearby "grass" of -130 (SR40 off).
                    >
                    > It is obviously something at DC being generated in my sound card
                    > (cheapie Motherboard Realtek AC'97).
                    >
                    > Anybody know a way to null this out or reduce it short of
                    replacing
                    > the sound card?
                    >
                    > Jerry W4UK
                    >
                  • Jerry Flanders
                    Thanks for the help, guys. I see that if I load PowerSDR on different computers around here, I get differing levels of that center freq peak on different
                    Message 9 of 21 , Sep 30 1:02 PM
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                      Thanks for the help, guys. I see that if I load PowerSDR on different
                      computers around here, I get differing levels of that center freq
                      peak on different computers. One is so good the peak is only 10-15 Db
                      above the "grass".

                      Must be 60 Hz, as many said, or else some small DC leakage into the
                      input ckt on the one I was using.

                      Thanks again.

                      Jerry W4UK


                      At 17:40 9/30/2006, you wrote:

                      >The person that responded to you is correct, you will pickup 60Hz hum
                      >and harmonics even if the unit is turned off. The magnetic fields
                      >from wiring in your house are always there, the power to the unit and
                      >the audio shield also causes a ground loop creating a signal to the
                      >sound card, running on batteries or a isolated power supply will help.
                      >
                      >At 12:05 PM 9/30/2006, you wrote:
                      > >I have it even when I unplug the SR from the sound card - no apparent
                      > >change in vol.
                      > >
                      > >Jerry W4UK
                      > >
                      > >At 16:40 9/30/2006, you wrote:
                      > >
                      > > >The big signal is 60 Hz pickup. The solution is isolation transformer
                      > > >(s), in the audio lines and/or at the antenna connection. Running on
                      > > >battery can help to, or a non-grounded power cube. These will help to
                      > > >reduce the mountain at the center but may not eliminate it entirely.
                      > > >
                      > > >73 - Mike WA8BXN
                      > >
                      > >
                      > >
                      > >
                      > >Yahoo! Groups Links
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      >
                      >Cecil Bayona
                      >KD5NWA
                      >www.qrpradio.com
                      >
                      >'Never argue with an idiot. They drag you down to their level then
                      >beat you with experience.'
                      >
                      >
                    • Jerry Flanders
                      Thanks for the help, guys. I see that if I load PowerSDR on different computers around here, I get differing levels of that center freq peak on different
                      Message 10 of 21 , Sep 30 3:10 PM
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                        Thanks for the help, guys. I see that if I load PowerSDR on different
                        computers around here, I get differing levels of that center freq
                        peak on different computers. One is so good the peak is only 10-15 Db
                        above the "grass".

                        Must be 60 Hz, as many said, or else some small DC leakage into the
                        input ckt on the one I was using.

                        Thanks again.

                        Jerry W4UK


                        At 17:40 9/30/2006, you wrote:

                        >The person that responded to you is correct, you will pickup 60Hz hum
                        >and harmonics even if the unit is turned off. The magnetic fields
                        >from wiring in your house are always there, the power to the unit and
                        >the audio shield also causes a ground loop creating a signal to the
                        >sound card, running on batteries or a isolated power supply will help.
                        >
                        >At 12:05 PM 9/30/2006, you wrote:
                        > >I have it even when I unplug the SR from the sound card - no apparent
                        > >change in vol.
                        > >
                        > >Jerry W4UK
                        > >
                        > >At 16:40 9/30/2006, you wrote:
                        > >
                        > > >The big signal is 60 Hz pickup. The solution is isolation transformer
                        > > >(s), in the audio lines and/or at the antenna connection. Running on
                        > > >battery can help to, or a non-grounded power cube. These will help to
                        > > >reduce the mountain at the center but may not eliminate it entirely.
                        > > >
                        > > >73 - Mike WA8BXN
                        > >
                        > >
                        > >
                        > >
                        > >Yahoo! Groups Links
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        >
                        >Cecil Bayona
                        >KD5NWA
                        >www.qrpradio.com
                        >
                        >'Never argue with an idiot. They drag you down to their level then
                        >beat you with experience.'
                        >
                        >
                      • Jerry Flanders
                        Thanks for the help, guys. I see that if I load PowerSDR on different computers around here, I get differing levels of that center freq peak on different
                        Message 11 of 21 , Sep 30 3:53 PM
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                          Thanks for the help, guys. I see that if I load PowerSDR on different
                          computers around here, I get differing levels of that center freq
                          peak on different computers. One is so good the peak is only 10-15 Db
                          above the "grass".

                          Must be 60 Hz, as many said, or else some small DC leakage into the
                          input ckt on the one I was using.

                          Thanks again.

                          Jerry W4UK


                          At 17:40 9/30/2006, you wrote:

                          >The person that responded to you is correct, you will pickup 60Hz hum
                          >and harmonics even if the unit is turned off. The magnetic fields
                          >from wiring in your house are always there, the power to the unit and
                          >the audio shield also causes a ground loop creating a signal to the
                          >sound card, running on batteries or a isolated power supply will help.
                          >
                          >At 12:05 PM 9/30/2006, you wrote:
                          > >I have it even when I unplug the SR from the sound card - no apparent
                          > >change in vol.
                          > >
                          > >Jerry W4UK
                          > >
                          > >At 16:40 9/30/2006, you wrote:
                          > >
                          > > >The big signal is 60 Hz pickup. The solution is isolation transformer
                          > > >(s), in the audio lines and/or at the antenna connection. Running on
                          > > >battery can help to, or a non-grounded power cube. These will help to
                          > > >reduce the mountain at the center but may not eliminate it entirely.
                          > > >
                          > > >73 - Mike WA8BXN
                          > >
                          > >
                          > >
                          > >
                          > >Yahoo! Groups Links
                          > >
                          > >
                          > >
                          > >
                          > >
                          > >
                          > >
                          >
                          >Cecil Bayona
                          >KD5NWA
                          >www.qrpradio.com
                          >
                          >'Never argue with an idiot. They drag you down to their level then
                          >beat you with experience.'
                          >
                          >
                        • Cecil Bayona
                          ... You are a lucky person if that is all you get. I have one out of 5 PC s that behaves that way but the rest do not behave that way. It has a clean vertical
                          Message 12 of 21 , Sep 30 9:34 PM
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                            py2wm wrote:
                            > This is an artifact from the sound card which was not intended to
                            > digitize below 10~20 Hz. It's a kind of "noise" from the ADC (analog
                            > to digital converter).
                            >
                            > It is not 60 Hz line hum, which can be easily seen on zoomed
                            > spectrograph display at 60, 120 , 180 Hz and also at negative
                            > frequencies. Rather, the SDR software treats as single signal, you
                            > can hear it as a carrier as you tune across it.
                            >
                            > 73,
                            >
                            > João De Marco, PY2WM
                            >
                            >
                            >
                            >
                            > --- In softrock40@yahoogroups.com, Jerry Flanders <jeflanders@...>
                            > wrote:
                            >> Using PowerSDR with my newly constructed 80/40 SR40 v6.1, I see a
                            > big
                            >> "carrier" sig in the center of the range (equiv to 7056 KHz tuned
                            >> freq). I assumed this was just some kind of leakage from the LO
                            > which
                            >> I didn't understand, but now I have discovered it stays on even
                            > when
                            >> the SR40 is powered down (even unplugged from sound card). It also
                            >> does not appear when I use a laptop (mono mic input) instead of
                            > the
                            >> desktop computer (line in, stereo).
                            >>
                            >> It is big, -44dB vs nearby "grass" of -130 (SR40 off).
                            >>
                            >> It is obviously something at DC being generated in my sound card
                            >> (cheapie Motherboard Realtek AC'97).
                            >>
                            >> Anybody know a way to null this out or reduce it short of
                            > replacing
                            >> the sound card?
                            >>
                            >> Jerry W4UK
                            >>
                            >
                            >
                            You are a lucky person if that is all you get. I have one out of 5 PC's
                            that behaves that way but the rest do not behave that way. It has a
                            clean vertical spike and 200Hz away your down to the noise floor. The
                            Softrock also picks up the signal from it's own LO which adds to the
                            center spike, but only at the LO frequency, the other noise extending to
                            several KHz is all the other stuff.

                            The center spike is several KHz in width for most people , and has a
                            buzzing sound when you listen to it, it does not have a clean tone like
                            that one PC does. The thing was that no matter which of the cards I
                            tried on that one PC I would not get the wide noise, but put the same
                            cards in other PC's and the central noise are was several KHz wide.
                            Unfortunate for me that one pc with a clean central spike was not a very
                            fast PC compared to the others.

                            It's unfortunate because you could easily pick up weak signals a couple
                            of 100Hz away where in the other PC's you need to be several KHz away.
                            --

                            Cecil
                            KD5NWA
                            www.qrpradio.com www.hpsdr.com

                            "Sacred Cows make the best Hamburger!" Don Seglio Batuna
                          • Mark J. Dulcey
                            ... Many modern computers use a spread-spectrum main clock. (Your one PC with the nice clean noise spike was probably too old to use the technique.) In other
                            Message 13 of 21 , Sep 30 10:29 PM
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                              Cecil Bayona wrote:
                              >
                              > You are a lucky person if that is all you get. I have one out of 5 PC's
                              > that behaves that way but the rest do not behave that way. It has a
                              > clean vertical spike and 200Hz away your down to the noise floor. The
                              > Softrock also picks up the signal from it's own LO which adds to the
                              > center spike, but only at the LO frequency, the other noise extending to
                              > several KHz is all the other stuff.
                              >
                              > The center spike is several KHz in width for most people , and has a
                              > buzzing sound when you listen to it, it does not have a clean tone like
                              > that one PC does. The thing was that no matter which of the cards I
                              > tried on that one PC I would not get the wide noise, but put the same
                              > cards in other PC's and the central noise are was several KHz wide.
                              > Unfortunate for me that one pc with a clean central spike was not a very
                              > fast PC compared to the others.
                              >
                              > It's unfortunate because you could easily pick up weak signals a couple
                              > of 100Hz away where in the other PC's you need to be several KHz away.

                              Many modern computers use a spread-spectrum main clock. (Your one PC
                              with the nice clean noise spike was probably too old to use the
                              technique.) In other words, the main clock, instead of being a nice
                              stable 33 megahertz or whatever, randomly wobbles a bit around that
                              frequency.

                              In a typical PC, the motherboard generates one clock frequency, and most
                              of the clocks used in the computer are derived from it. For example, a
                              computer might use a 33.3MHz basic clock. This would be used directly as
                              the clock for the PCI bus. It would be multiplied by 4 to provide a
                              133MHz clock for ATA133. A X6 multiplier might serve for the memory
                              interface to DDR400 memory, which uses a master clock frequency of
                              200MHz. That same 200MHz clock would also be given to the CPU, which
                              would in turn use a X10 PLL multiplier to get it to the 2GHz speed used
                              inside the processor.

                              From the PC manufacturer's point of view, this has some real
                              advantages. The FCC standards on RF emissions set a maximum signal level
                              that PCs can emit; they measure the PEAK emission level that comes from
                              a computer, not the total amount of RF that comes out. With a non-spread
                              clock, there are large noise peaks at the fundamental clock frequencies
                              used inside the PC. These days, that means the PCI bus clock of 33 MHz,
                              the memory front speed bus clock which can range anywhere from 66 to 500
                              MHz, the ATA speed of 33, 66, 100, or 133 MHz, the SATA speed of 150 or
                              300 MHz, and so forth. The actual CPU clock is generated by a PLL inside
                              the CPU chip, and is a large multiple of one of the other clocks;
                              because that clock is confined inside the CPU, not much of the external
                              noise is related to it.

                              If instead you use a spread clock, the noise peaks get broadened. There
                              is less energy at the center point, and it is therefore easier to comply
                              with the FCC limits. The total amount of RF leaking out of the computer,
                              however, is not lessened at all, and the broadband nature of the noise
                              may make it HARDER for the ham to deal with it, not easier. For example,
                              phase-technique noise reduction boxes like the MFJ 1026 are far less
                              effective.

                              On some computers, especially ones that come from small system builders
                              or which are personally built by the users, there is a BIOS setup option
                              for whether to use a spread-spectrum clock. On the big brand-name
                              systems, you're probably stuck with whatever choice the manufacturer made.

                              Even without any intentional move toward a spread-spectrum clock, a
                              modern PC isn't likely to have nice clean noise peaks. There are all
                              those PLLs, after all, and mobody has bothered to engineer them for
                              minimum phase noise.
                            • Marco IK1ODO
                              ... Also, soundcards have significant noise at low frequencies. It s called 1/f noise since it increases decreasing the frequency. To give a figure, the
                              Message 14 of 21 , Oct 1, 2006
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                                At 21.19 30/09/2006, you wrote:

                                >This is an artifact from the sound card which was not intended to
                                >digitize below 10~20 Hz. It's a kind of "noise" from the ADC (analog
                                >to digital converter).
                                >
                                >It is not 60 Hz line hum, which can be easily seen on zoomed
                                >spectrograph display at 60, 120 , 180 Hz and also at negative
                                >frequencies. Rather, the SDR software treats as single signal, you
                                >can hear it as a carrier as you tune across it.
                                >
                                >73,
                                >
                                >João De Marco, PY2WM

                                Also, soundcards have significant noise at low
                                frequencies. It's called 1/f noise since it increases decreasing the frequency.
                                To give a figure, the Audiophile 192 has a 30dB
                                noise increment going down from 1000Hz to 20Hz.
                                This is intrinsic, and independent from PC noise
                                and hum (that are present too in a typical setup, of course).

                                There would be also a peak at 0Hz due to DC
                                imbalance of the ADC inputs, but the ADCs used in
                                24bit souncards have an internal high pass filter
                                cutting under 1 or 2Hz, suppressing that.

                                73 - Marco IK1ODO
                              • n3hkn
                                I switched off the spread pectrum BIOS option in my home made PC and the width of the noise spike is now vey narrow. Looks like almost a single frequency
                                Message 15 of 21 , Oct 1, 2006
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                                  I switched off the spread pectrum BIOS option in my "home made" PC
                                  and the width of the noise spike is now vey narrow. Looks like almost
                                  a single frequency carrier.

                                  Dick N3HKN



                                  --- In softrock40@yahoogroups.com, Marco IK1ODO <ik1odo@...> wrote:
                                  >
                                  > At 21.19 30/09/2006, you wrote:
                                  >
                                  > >This is an artifact from the sound card which was not intended to
                                  > >digitize below 10~20 Hz. It's a kind of "noise" from the ADC
                                  (analog
                                  > >to digital converter).
                                  > >
                                  > >It is not 60 Hz line hum, which can be easily seen on zoomed
                                  > >spectrograph display at 60, 120 , 180 Hz and also at negative
                                  > >frequencies. Rather, the SDR software treats as single signal, you
                                  > >can hear it as a carrier as you tune across it.
                                  > >
                                  > >73,
                                  > >
                                  > >João De Marco, PY2WM
                                  >
                                  > Also, soundcards have significant noise at low
                                  > frequencies. It's called 1/f noise since it increases decreasing
                                  the frequency.
                                  > To give a figure, the Audiophile 192 has a 30dB
                                  > noise increment going down from 1000Hz to 20Hz.
                                  > This is intrinsic, and independent from PC noise
                                  > and hum (that are present too in a typical setup, of course).
                                  >
                                  > There would be also a peak at 0Hz due to DC
                                  > imbalance of the ADC inputs, but the ADCs used in
                                  > 24bit souncards have an internal high pass filter
                                  > cutting under 1 or 2Hz, suppressing that.
                                  >
                                  > 73 - Marco IK1ODO
                                  >
                                • Sam Morgan
                                  ... just curious, how new is your motherboard? I guess if u told me what cpu it s running that might also help. I m thinking everything I have it to old, I
                                  Message 16 of 21 , Oct 1, 2006
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                                    n3hkn wrote:
                                    > I switched off the spread pectrum BIOS option in my "home made" PC
                                    > and the width of the noise spike is now vey narrow. Looks like almost
                                    > a single frequency carrier.
                                    >
                                    just curious, how new is your motherboard? I guess if u told me what cpu it's
                                    running that might also help. I'm thinking everything I have it to old, I don't
                                    remember seeing anything like that in the settings on any of them.

                                    --
                                    GB & 73's
                                    KA5OAI
                                    Sam Morgan
                                  • Alberto I2PHD
                                    Marco IK1ODO wrote: There would be also a peak at 0Hz due to DC imbalance of the ADC inputs, but the ADCs used in 24bit souncards have an internal high pass
                                    Message 17 of 21 , Oct 1, 2006
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                                      Marco IK1ODO wrote:
                                      There would be also a peak at 0Hz due to DC 
                                      imbalance of the ADC inputs, but the ADCs used in 
                                      24bit souncards have an internal high pass filter 
                                      cutting under 1 or 2Hz, suppressing that.
                                        
                                      Marco is quite right, as demonstrated by these two screen captures. The first is the digitizing process carried on by Adobe Audition, using the onboard AC'97 chipset, with the card input left open. As you can easily see, there is a substantial DC offset produced by the ADC.



                                      The same chipset produced this strong zero frequency peak, entirely caused by the DC offset :


                                      73  Alberto  I2PHD

                                    • John
                                      I am playing with mine also. Maybe those of us with Cheap sound cards fine this, I do. Two things: If just a single frec it is most likely the math finding a
                                      Message 18 of 21 , Oct 1, 2006
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                                        I am playing with mine also.

                                        Maybe those of us with “Cheap” sound cards fine this, I do.

                                         

                                        Two things:

                                          If just a single frec it is most likely the math finding a 0 hrz tone.

                                          If two peaks close together it may be 60 hz pickup in the audio cord.&nbs

                                        (Message over 64 KB, truncated)

                                      • Cecil Bayona
                                        ... The picture of the single stand alone spike is what one of PC s has, the other four have the typical spike with noise going out quite a ways slowly and
                                        Message 19 of 21 , Oct 1, 2006
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                                          Alberto I2PHD wrote:
                                          > Marco IK1ODO wrote:
                                          >> There would be also a peak at 0Hz due to DC
                                          >> imbalance of the ADC inputs, but the ADCs used in
                                          >> 24bit souncards have an internal high pass filter
                                          >> cutting under 1 or 2Hz, suppressing that.
                                          >>
                                          > Marco is quite right, as demonstrated by these two screen captures. The
                                          > first is the digitizing process carried on by Adobe Audition, using the
                                          > onboard AC'97 chipset, with the card input left open. As you can easily
                                          > see, there is a substantial DC offset produced by the ADC.
                                          >
                                          >
                                          >
                                          > The same chipset produced this strong zero frequency peak, entirely
                                          > caused by the DC offset :
                                          >
                                          >
                                          > 73 Alberto I2PHD
                                          >
                                          >
                                          The picture of the single stand alone spike is what one of PC's has, the
                                          other four have the typical spike with noise going out quite a ways
                                          slowly and meeting the noise floor about 2-3 KHz away.

                                          On most PC's that is a rare item most people don't have that kind of
                                          response.

                                          --

                                          Cecil
                                          KD5NWA
                                          www.qrpradio.com www.hpsdr.com

                                          "Sacred Cows make the best Hamburger!" Don Seglio Batuna
                                        • n3hkn
                                          Spread Spectrum... CPU=AMD 2600 ECS is motherboadr mfg. KT-600 Dick N3HKN It is about 2 years old--- In softrock40@yahoogroups.com, Sam Morgan ... PC ...
                                          Message 20 of 21 , Oct 2, 2006
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                                            Spread Spectrum...

                                            CPU=AMD 2600
                                            ECS is motherboadr mfg. KT-600

                                            Dick N3HKN


                                            It is about 2 years old--- In softrock40@yahoogroups.com, Sam Morgan
                                            <ka5oai@...> wrote:
                                            >
                                            > n3hkn wrote:
                                            > > I switched off the spread pectrum BIOS option in my "home made"
                                            PC
                                            > > and the width of the noise spike is now vey narrow. Looks like
                                            almost
                                            > > a single frequency carrier.
                                            > >
                                            > just curious, how new is your motherboard? I guess if u told me
                                            what cpu it's
                                            > running that might also help. I'm thinking everything I have it to
                                            old, I don't
                                            > remember seeing anything like that in the settings on any of them.
                                            >
                                            > --
                                            > GB & 73's
                                            > KA5OAI
                                            > Sam Morgan
                                            >
                                          • Sparkes, John
                                            Yep, same here. Big peak at 0 with no inputs to D44. Totally goes away when 9V battery powered SR40V6 on-line. John JX________________________________From:
                                            Message 21 of 21 , Oct 2, 2006
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                                              Yep, same here. Big peak at 0 with no inputs to D44. Totally goes away when 9V battery powered SR40V6 on-line.
                                               
                                              John JX


                                              From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On Behalf Of Mike
                                              Sent: Sunday, 1 October 2006 00:41
                                              To: softrock40@yahoogroups.com
                                              Subject: [softrock40] Re: Big signal at 0 Hz even with SR40 is off

                                              The big signal is 60 Hz pickup. The solution is isolation transformer
                                              (s), in the audio lines and/or at the antenna connection. Running on
                                              battery can help to, or a non-grounded power cube. These will help to
                                              reduce the mountain at the center but may not eliminate it entirely.

                                              73 - Mike WA8BXN

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