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Re: [wsjtgroup] Re: [DigitalOnSix] Do you think a sound card interface can make a difference?

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  • Andrew T. Flowers, K0SM
    Bob, and group, Be skeptical of any magic box that appears to takes noise away. Both noise and signal arrive at the antenna in one stream and you can t
    Message 1 of 13 , Nov 7, 2005
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      Bob, and group,

      Be skeptical of any magic box that appears to takes noise away. Both
      noise and signal arrive at the antenna in one stream and you can't
      separate them. If he really did an empirical test something is
      seriously wrong--you might ask what his test setup was and how he
      measured the SNR and what confounds he controlled for.

      It's a little hard to speculate not knowing anything about how this was
      measured (or even what, exactly, was being measured), but here is my
      hunch:

      It almost sounds like he used a big "Y-cable" to hook all the interfaces
      in parrallel (!) to the same radio. If all of these interfaces have a
      different input impedence then we are going to see different amounts of
      power (volume) reaching each sound card...I wouldn't be surprised if the
      AF amp in the rig started limiting too. Did he measure and control for
      this? I believe that most of these soundcards have a resistive network
      that controls how much audio passes--changing one will likely change the
      input power to all of the other interfaces. Of course, there are all
      kinds of other problems that can result from not having the inputs
      isolated from each other, but I'm not even going to go there.

      I've also found some other "reasoning" having to do with the RigExpert
      being outside the "noisy" environment of the computer. If you just
      record dead silence you can indeed hear these birdies. You will
      probably have to crank your volume up all the way to hear them, though.
      Indeed, the noise floor of most sound-card systems is limited in this
      way, at least at 16-bit resolution and higher. However, the level of
      these birdies is typically on the order of *50dB* below what the input
      signal from the radio should be. Unless you have the audio gain set
      *way* too low, this should not be an issue. That's why WSJT gives you
      the green line.

      That's my two cents.

      Andy K0SM/2

      Bob Poortinga wrote:

      >Howard S. White KY6LA writes (in another group):
      >
      >
      >
      >>As a result of my extensive bench testing of virtually every sound
      >>card interface device I could get my hands on such as the MFJ 1279,
      >>the Microham Keyer and the RigBlaster in parallel with the
      >>RigExpert, each on a separate but identical computer but attached to
      >>the same Radios (IC-756 Pro3, IC-2720, IC-706 MKIIG were tested), I
      >>have observed that the RigExpert will decode signals in signal to
      >>noise situations about 10 db better than ANY of the devices based on
      >>the internal PC Sound Cards.. Which means that it will still give
      >>you 100% copy when the internal Sound Card Devices no longer copy
      >>anything.
      >>
      >>
      >
      >So has anyone used a RigExpert (with built-in soundcard) with WSJT?
      >Does it really exhibit a 10db increased S/N on decodes? If so, this
      >could make a huge difference especially in JT65.
      >
      >
      >




      --
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    • Russ K2TXB
      Hi Bob & Randy. Well the page Randy cited is completely different than what I found: I found http://www.mixw.net/RigExpert/. It simply says USB Transceiver
      Message 2 of 13 , Nov 7, 2005
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        Hi Bob & Randy. Well the page Randy cited is completely different than what
        I found: I found http://www.mixw.net/RigExpert/.

        It simply says "USB Transceiver Interface". That was the first result from
        a Google search on RigExpert.

        Now I looked at the rigexpert.com page and can see that it is more than a
        simple interface, they say it has it's own sound card and does not use the
        one in the computer. How can that work for WSJT? WSJT needs to communicate
        with the sound card. Does RigExpert provide an interface via the USB
        connection that looks like a normal sound card, so that WSJT can interface?
        I cannot see on the web page where it says anything about that. It looks to
        me like it is only set up to work with CW and FSK - but not FSK as done by
        WSJT.

        Other that that, it looks like a nice product, but OH the price!

        As for low noise provided by their sound card, maybe, but if WSJT cannot
        interface to it then that benefit will be lost. Also, I suspect that many
        high end sound cards will be just as quiet. There may also be a benefit by
        having the USB interface, so that matching and ground loop problems between
        the computer and the radio are reduced - but you still have to interface the
        radio to the RigExpert... And low noise in those connections is pretty easy
        to accomplish anyway. One only has to pay attention to impedance matching
        and preventing ground loops.

        And finally, it still does not appear that RigExpert can decode anything. I
        think it is still the computer program that does the decoding. However it
        appears, Bob, that what you mean is that signals through the rig expert can
        be decoded when they are 10 db weaker than via other interfaces you have
        tested. That sounds very good, but the question becomes; how did you test
        this, and is your alternate interface set up in the best way to match
        impedances and eliminate ground loops?

        I have no way to verify it, but I think my simple home made interface will
        work as well. I can decode JT65 signals that are as weak as -30 db, and I
        do not recall anyone ever saying they have done better. I doubt I have over
        20 dollars invested.

        73, Russ K2TXB


        > -----Original Message-----
        > From: wsjtgroup@yahoogroups.com
        > [mailto:wsjtgroup@yahoogroups.com] On Behalf Of Bob Poortinga
        > Sent: Monday, November 07, 2005 2:58 PM
        > To: wsjtgroup@yahoogroups.com
        > Subject: Re: [wsjtgroup] Do you think a sound card interface
        > can make a difference?
        >
        > "Russ K2TXB" <k2txb@...> writes:
        >
        > > Bob, what do you mean "RigExpert will decode signals"? Is
        > RigExpert a
        > > program or an interface box? I thought it was a box...
        >
        > RigExpert is not a program but it is more than an interface
        > box. It contains both an interface AND an external sound
        > card. It is this external sound card that provides a 10db
        > S/N improvement over internal sound cards. There are several
        > models of the RigExpert and the RigExpert Tiny does not
        > include the sound card (it is an interface only).
        >
        > 73 de
        > --
        > Bob Poortinga K9SQL
        > Bloomington, Indiana US
        >
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      • Joe - WD0M
        If you re interested in an interface at a much lower price (and without an external sound card), you may want to check out the MicroHam Keyer - much like the
        Message 3 of 13 , Nov 7, 2005
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          If you're interested in an interface at a much
          lower price (and without an external sound card),
          you may want to check out the MicroHam Keyer -
          much like the Rig Expert, and works well. The
          company provides exceptional customer support,
          and provides free firmware/software updates regularly.

          Yes, it's the computer program that does the
          decoding, not "the box". Purportedly, the
          external sound card "helps" by providing a less
          noisy signal to work with. I've been using the
          MicroHam Keyer for WSJT and it does an excellent
          job, along with all the other digital modes. It
          also features the WinKey CW chip, and lets you
          use only USB connections - no serial port issues.

          http://microham.com/

          No financial interest, just a satisfied customer.

          73,
          Joe WDØM
        • Bob Poortinga
          ... Yes. ... Yes, they are pricey. How much would you pay for an antenna that gave you 10 db better S/N? ... The person who tested it (an EE with real test
          Message 4 of 13 , Nov 7, 2005
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            "Russ K2TXB" <k2txb@...> writes:

            > Does RigExpert provide an interface via the USB connection that looks
            > like a normal sound card, so that WSJT can interface?

            Yes.

            > Other that that, it looks like a nice product, but OH the price!

            Yes, they are pricey. How much would you pay for an antenna that gave you
            10 db better S/N?

            > Also, I suspect that many high end sound cards will be just as quiet.
            > And finally, it still does not appear that RigExpert can decode anything.
            > However it appears, Bob, that what you mean is that signals through the rig
            > expert can be decoded when they are 10 db weaker than via other interfaces
            > you have tested.

            The person who tested it (an EE with real test equipment, not me) stated that
            the RigExpert sound card codec (ADC) provides 10 db better S/N. That means
            that under 'no signal' conditions, the noise floor of the sound card is 10 db
            lower than the other tested cards.

            I'd be very interested in any comments from Joe, K1JT, on these figures.

            --
            Bob Poortinga K9SQL
            Bloomington, Indiana US
          • Joe Taylor
            Bob -- ... When something sounds too good to be true, it usually is. Specifications of sound cards that refer to the S/N of the card are completely
            Message 5 of 13 , Nov 7, 2005
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              Bob --

              > RigExpert is not a program but it is more than an interface box. It
              > contains both an interface AND an external sound card. It is this
              > external sound card that provides a 10db S/N improvement over internal
              > sound cards.

              When something sounds too good to be true, it usually is.

              Specifications of sound cards that refer to the "S/N" of the card are
              completely irrelevant to use of the card with WSJT -- or indeed just
              about any other ham radio software. The reason is that the
              signal-to-noise ratio that matters for MS or EME (with WSJT), or for HF
              use of PSK31, is determined far upstream of the device interfacing your
              radio to your computer.

              A sound card would have to be EXTREMELY poor -- so poor that it would be
              unacceptable for "normal" computer uses such as recording/playing music,
              etc. -- before its S/N rating would significantly degrade the decoding
              ability of WSJT and similar programs.

              The noise that the WSJT decoders must cope with is a combination of
              cosmic noise, atmospheric noise, and receiver noise; sound card noise is
              many tens of dBs weaker, and entirely negligible.

              As it happens, there is one way in which poor sound cards can adversely
              affect WSJT signals. It's not S/N, but rather inaccuracies in sampling
              rate. WSJT uses a sample rate of 11025 Hz for both input and output.
              All sound cards claim to support this rate, but some do it by
              interpolating rather poorly from another sampling rate.

              The Rig Expert may be a convenient way to do your radio-computer
              interfacing, but it will NOT gain you 10 dB (or even 1 dB) in detecting
              weak meteor pings or EME signals.

              -- 73, Joe, K1JT
            • Bob Poortinga
              ... Doesn t sampling jitter also introduce noise? Wouldn t a highly-stable sampling clock produce a lower noise floor resulting in better decodes? ...
              Message 6 of 13 , Nov 8, 2005
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                Joe Taylor K1JT <joe@...> writes:

                > As it happens, there is one way in which poor sound cards can adversely
                > affect WSJT signals. It's not S/N, but rather inaccuracies in sampling
                > rate.

                Doesn't sampling jitter also introduce noise? Wouldn't a highly-stable
                sampling clock produce a lower noise floor resulting in better decodes?

                > The Rig Expert may be a convenient way to do your radio-computer
                > interfacing, but it will NOT gain you 10 dB (or even 1 dB) in detecting
                > weak meteor pings or EME signals.

                Thanks, Joe, I was simply looking for a definitive answer in response to
                the claims of others.

                73 de
                --
                Bob Poortinga K9SQL
                Bloomington, Indiana US
              • Joe Taylor
                ... Yes, but for any plausible amount of jitter that noise will cause negligible degradation of the WSJT audio signals sent from your radio to the sound card
                Message 7 of 13 , Nov 8, 2005
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                  Bob Poortinga wrote:
                  > Joe Taylor K1JT <joe@...> writes:
                  >
                  >>As it happens, there is one way in which poor sound cards can adversely
                  >>affect WSJT signals. It's not S/N, but rather inaccuracies in sampling
                  >>rate.
                  >
                  > Doesn't sampling jitter also introduce noise? Wouldn't a highly-stable
                  > sampling clock produce a lower noise floor resulting in better decodes?

                  Yes, but for any plausible amount of jitter that noise will cause
                  negligible degradation of the WSJT audio signals sent from your radio to
                  the sound card input.

                  The "inaccuracies in sampling rate" that I mentioned are not jitter, but
                  rather a sampling rate that is constant but offset from the nominal
                  value by a significant amount. WSJT always requests a sampling rate of
                  11025 samples per second. The actual sample rate can be somewhat
                  different. Some recent sound cards are "off" by as much as 75 Hz,
                  sampling at about 11100 Hz instead of 11025. If uncorrected, this means
                  that the WSJT tone spacing will be off by about 0.7% in both time and
                  frequency, causing a loss of sensitivity up to about 2 dB.

                  The next WSJT version to be released will have the ability to correct
                  for errors in sound card sample rates.

                  >>The Rig Expert may be a convenient way to do your radio-computer
                  >>interfacing, but it will NOT gain you 10 dB (or even 1 dB) in detecting
                  >>weak meteor pings or EME signals.
                  >
                  >
                  > Thanks, Joe, I was simply looking for a definitive answer in response to
                  > the claims of others.
                  >
                  > 73 de Bob, K9SQL

                  Happy to help!

                  -- 73, Joe, K1JT
                • Paul Whatton
                  Hi Joe Do you have any examples so we know which sound cards to avoid? For example at the moment I m using a cheap OEM PCI soundcard. I also have an external
                  Message 8 of 13 , Nov 8, 2005
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                    Hi Joe

                    Do you have any examples so we know which sound cards to avoid? For
                    example at the moment I'm using a cheap OEM PCI soundcard. I also have
                    an external Soundblaster USB card so I wonder if there would be a real
                    advantage in using that instead?

                    Paul G4DCV

                    PS the facility to click on and decode pings & bursts in real time in
                    5.8.6 is wonderful!

                    Bob Poortinga wrote:
                    > Joe Taylor K1JT <joe@...> writes:
                    >
                    > > As it happens, there is one way in which poor sound cards can adversely
                    > > affect WSJT signals. It's not S/N, but rather inaccuracies in sampling
                    > > rate.
                    >
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