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11535Re: [wsjtgroup] Ongoing Audio Questions

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  • Joe Subich, W4TV
    Aug 29, 2013
    • 0 Attachment
      > The SignaLink USB, at least with Windows 7 does not have a "line"
      > input - only "microphone".

      "microphone" vs. "Line" is only a matter of the USB CODEC used -
      one would assume the hardware designer chose the appropriate
      input voltage level (and internal gain settings in the CODEC)
      for the device being used.

      > The first thing I noticed was that to bring the audio level from the
      > SignaLink (step 7) up to 20 or 25 dB I had to turn it all the way up.
      > May very well be due to the fact that I turned the Windows input from
      > 100% down to 65%.

      Then increase the Windows input. In theory increasing the input on
      the sound card driver would make it easier to overdrive the CODEC but
      perhaps your device is gain limited (or the transceiver is output
      limited).

      > Does the position of the cursor in the waterfall have any bearing on
      > what is decoded?

      Read K1JT's documentation - page 25:

      > For operator convenience the decoder goes through its full procedure
      > twice: first over a narrow range around the selected Rx frequency,
      > and then in the full displayed frequency range (or in JT9+JT65 mode,
      > the displayed range above the blue JT65 nnnn JT9 marker).

      When "dual mode" decode is enabled, the process becomes - 1) decode at
      the cursor, 2) decode broadly the mode selected for transmit (above or
      below the JT65/JT9 dividing line as appropriate), 3) decode broadly
      the "other" mode.

      > If the immediate area under the cursor is decoded more vigorously,
      > maybe that is part of my problem?

      I don't know why you should have any more problem decoding the area
      of the cursor than the broad decode but it might be that your sound
      card is noisy or unstable. That brand does not have a good reputation
      for being exactly "clean" or have a particularly flat audio response:
      http://www.frenning.dk/OZ1PIF_HOMEPAGE/SignaLinkUSB-mods.html
      http://www.youtube.com/watch?v=at9z0kDTs_w
      http://www.youtube.com/watch?v=kgqxq5_o7sI
      http://freedv.org/tiki-index.php?page=Tigertronics

      73,

      ... Joe, W4TV


      On 8/29/2013 7:32 PM, Dave 'Doc' Corio wrote:
      > Joe, I really appreciate the detailed response! Setting up the
      > system per your email, and one big thought occurred to me. The SignaLink
      > USB, at least with Windows 7 does not have a "line" input - only
      > "microphone". If I recall, mic is much higher input than line, so
      > therefore I MAY very well have been over-driving the decoder, simply by
      > having the Windows input gain set at max.
      >
      > The first thing I noticed was that to bring the audio level from
      > the SignaLink (step 7) up to 20 or 25 dB I had to turn it all the way
      > up. May very well be due to the fact that I turned the Windows input
      > from 100% down to 65%.
      >
      > Going to try this for a bit & see if I notice any improvement in my
      > decode problems. Let me ask one more question, either of you or anyone
      > in the group who may know:
      >
      > Does the position of the cursor in the waterfall have any bearing
      > on what is decoded? In other words, is the area where the
      > transmit/receive indicators are located decoded any different than the
      > rest of the waterfall? My ongoing problem has been losing decodes of the
      > station I'm trying to work, while everyone else within the bandwidth
      > decodes just fine. If the immediate area under the cursor is decoded
      > more vigorously, maybe that is part of my problem?
      >
      > In the meantime, trying these new settings!!
      >
      > Thanks Again!!
      > 73
      > Doc
      > KB3MOW
      >
      > On 8/29/2013 4:53 PM, Joe Subich, W4TV wrote:
      >>
      >>
      >> Here is the way I set-up receive audio - regardless of the sound card
      >> or transceiver:
      >>
      >> 1) start with the rig off
      >> 2) turn the *hardware* input level of your sound card to zero or
      >> disconnect the audio input to the sound card.
      >> 3) Set the Windows 7/Windows 8 "Sounds" Control Panel | Recording
      >> Devices | <sound card> | Line | Levels to between 50 and 80
      >> 4) Set Wide graph to Zero = 0, Gain = 0, Slope = 0.0 and select
      >> "Current"
      >> 5) Adjust the audio slider in the WSJT-X main window until the
      >> main window audio level is 0 dB. This sets the WSJT-X input
      >> gain to unity and matches the WSJT-X noise floor to the no
      >> signal noise floor of your sound card.
      >> 6) connect audio from your transceiver to the sound card if you
      >> disconnected it in step 2
      >> 5) turn on the transceiver, select a dummy load or disconnect
      >> the antenna input and adjust the *hardware* input level (level
      >> from the radio if the rig has an adjustable output or the "RX
      >> level" on your interface) until the WSJT-X Main audio level is
      >> between 20 and 25 dB.
      >> 6) connect your antenna - at this point you may want to adjust
      >> "Slope" (only) in the "Wide graph" just enough to flatten the
      >> high end.
      >>
      >> As conditions change (noisy vs. quiet band), you may want to
      >> touch up the transceiver output level or the interface input
      >> level slightly to keep the WSJT-X main audio level below 40 dB
      >> between xx:48 and xx:60. If signals are very strong you may
      >> need to turn off the receiver preamp, turn on an attenuator or
      >> back off the RF gain to prevent overloading the sound card.
      >>
      >> Note: If your transceiver does not have an adjustable output level
      >> and your interface does not have an adjustable input level, it may
      >> be necessary to substitute Windows' attenuator (Sound control
      >> panel | Recording Devices | <sound card being used> | Line | Level)
      >> for the adjustment in step 5.
      >>
      >> The goal of this process is to match the noise floor of the sound
      >> card to the zero signal level of WSJT-X (or *any other* digital
      >> package) and set the transceiver's zero signal level roughly 20
      >> dB above the sound card noise floor while not introducing any more
      >> gain than necessary so the sound card's analog to digital converter
      >> will not clip at maximum signal levels.
      >>
      >> 73,
      >>
      >> ... Joe, W4TV
      >>
      >
      >
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