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

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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 1 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 2 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 3 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 4 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 5 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 6 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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