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Very Good, Low Cost Audio to USB Interfaces For Digital Modes

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  • Jim Brown
    In the last few days I ve been evaluating a couple of low cost audio to USB interfaces for use primarily with digital modes -- RTTY, PSK, JT65, FSK441. My
    Message 1 of 3 , Mar 8 6:11 PM
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      In the last few days I've been evaluating a couple of low cost audio to
      USB interfaces for use primarily with digital modes -- RTTY, PSK, JT65,
      FSK441. My primary objective is to improve decode performance at low
      signal levels. I studied the catalogs and chose two low cost units that
      looked like they would do the job and would not have RF problems.

      Here's a link to a little Numark adapter that I bought for $33. t's as
      cute and easy as it looks. Power from the computer, a couple of RCA to
      1/8-in cables for gozinata and gozouta.

      http://www.bhphotovideo.com/c/product/639303-REG/Numark_STEREO|IO_Stereo_iO_USB.html


      The other one I bought is this Tascam unit. A bit larger, more
      mechanically robust, mostly metal enclosure, more flexible with respect
      to levels. The 1/4-in jacks for guitar and mic have more gain, so will
      work with lower signal levels. $70

      http://www.bhphotovideo.com/c/product/648495-REG/Tascam_US_100_US_100_USB_2_0_Computer.html


      To evaluate them I hooked them to different Thinkpads running JT65-HF
      and fed both of them from the line of a K3, then compared their decode
      performance, and also compared them with the Thinkpads' internal sound
      card. The two new adapters performed equally well, and often produced
      almost twice as many JT65 decodes on a given pass as the the internal
      cards. Next I transmitted through them and looked at their spectrum on a
      P3 hooked up to a second K3. Distortion products are minimal on both
      units. The characteristics that make them good on JT65 will also make
      them good for other digital modes like RTTY and PSK.

      I also pulled them apart and studied their construction. Both use
      proper construction that avoids the "Pin One Problems" that cause RFI
      issues. Now that I'm sure that they work well, I'm rewiring my station
      to use them in place of the sound cards built into my Thinkpads for SO2R
      contesting and everyday digital operation on both HF and VHF.

      Both of these units are a real bargain from well known audio vendors.
      Their interface to the K3 (and other rigs) is really simple. They don't
      do any control functions, so you still need a serial or USB to serial
      for that. I use VOX to key the K3. I haven't tried them with other
      rigs. The lower cost Numark unit has much less gain than the Tascam.
      It's just enough for the K3, and may not be enough to drive the line
      inputs of some other rigs, but it's plenty for driving a mic input. The
      Tascam unit is flexible enough to work with anything. Both units come
      with a USB cable. You'll have to supply (buy or build) the two cables
      for input and output to/from your radio.

      Both units are available from other vendors, but B&H had the best prices
      I found, and shipping by UPS Ground was free.

      73, Jim K9YC
    • Bill Vodall
      ... Steve/WA8LMF writes up some good pages and following his advice I ve purchased on iMic and will probably get another when I have the opportunity.
      Message 2 of 3 , Mar 15 2:29 PM
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        > Here's a link to a little Numark adapter that I bought for $33.  t's as
        > cute and easy as it looks.  Power from the computer, a couple of RCA to
        > 1/8-in cables for gozinata and gozouta.
        >
        > http://www.bhphotovideo.com/c/product/639303-REG/Numark_STEREO|IO_Stereo_iO_USB.html

        Steve/WA8LMF writes up some good pages and following his advice I've
        purchased on iMic and will probably get another when I have the
        opportunity.

        http://wa8lmf.net/ham/imic.htm

        73
        Bill - WA7NWP
      • Jeff Moore
        Neither the manuf. or Newegg currently have the iMic in stock. It does look like a nice option for soundcard modes. I currently use a SignaLink USB which I
        Message 3 of 3 , Mar 15 4:35 PM
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          Neither the manuf. or Newegg currently have the iMic in stock.  It does look like a nice option for soundcard modes.  I currently use a SignaLink USB which I like a lot!
           
          Jeff Moore  --  KE7ACY
           
          ----- Original Message ----- From: Bill Vodall
          Steve/WA8LMF writes up some good pages and following his advice I've
          purchased on iMic and will probably get another when I have the
          opportunity.

          http://wa8lmf.net/ham/imic.htm

          73
          Bill - WA7NWP
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