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Digital voice

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  • Peter
    Thanks to a youtube video I have discovered that I can hear digital voice on HF here in the UK. With something like WinDRM and my 394 could I decode it easily
    Message 1 of 5 , May 12 3:50 AM
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      Thanks to a youtube video I have discovered that I can hear digital
      voice on HF here in the UK. With something like WinDRM and my 394 could
      I decode it easily enough?

      peter
    • Richard Lowery
      Peter, How does that work? It must be some kind of device and software? I would like to do the same. Rick Peter wrote: Thanks to a
      Message 2 of 5 , May 12 7:00 AM
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        Peter,
        How does that work?
        It must be some kind of device and software?
        I would like to do the same.
        Rick

        Peter <radio@...> wrote:
        Thanks to a youtube video I have discovered that I can hear digital
        voice on HF here in the UK. With something like WinDRM and my 394 could
        I decode it easily enough?

        peter






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      • Tom Holden
        The answer is a qualified yes . You will need to add a downconverter from the 455kHz second IF to a 3rd IF in the audio frequency range, typically 12kHz. The
        Message 3 of 5 , May 12 8:03 AM
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          The answer is a qualified "yes". You will need to add a downconverter from the 455kHz second IF to a 3rd IF in the audio frequency range, typically 12kHz. The 3rd IF output feeds the audio input of a fast-enough computer running WinDRM or the free Dream software. The software does the decoding of the DRM stream to audio and text.

          You will find considerable description of DX-394 conversions by searching the Master Index of Mods, the Message Archive and the Links for "DRM".

          Best results are obtained with the DX-394B as it has a more stable 2nd Local Oscillator. The earlier versions can be modified for similar stability with the insertion of a buffer amp after the 2nd LO.

          It's been a few years since I was dabbling with DRM on the DX-394. I found it a very fascinating but unreliable mode for SW. I think there is better success with local and ground wave coverage than with distant sky wave. My shack and antennas are currently in disarray so I'm not au courant with DRM.

          Tom VE3MEO


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        • Peter
          I see, somthing to think about for me! many thanks Peter ... From: Tom Holden To: RADIOSHACKDX394@yahoogroups.com Sent: Monday, May 12, 2008 4:03 PM Subject:
          Message 4 of 5 , May 12 11:45 AM
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            I see, somthing to think about for me!


            many thanks


            Peter
            ----- Original Message -----
            From: Tom Holden
            To: RADIOSHACKDX394@yahoogroups.com
            Sent: Monday, May 12, 2008 4:03 PM
            Subject: Re: [RADIOSHACKDX394] Digital voice


            The answer is a qualified "yes". You will need to add a downconverter from the 455kHz second IF to a 3rd IF in the audio frequency range, typically 12kHz. The 3rd IF output feeds the audio input of a fast-enough computer running WinDRM or the free Dream software. The software does the decoding of the DRM stream to audio and text.

            You will find considerable description of DX-394 conversions by searching the Master Index of Mods, the Message Archive and the Links for "DRM".

            Best results are obtained with the DX-394B as it has a more stable 2nd Local Oscillator. The earlier versions can be modified for similar stability with the insertion of a buffer amp after the 2nd LO.

            It's been a few years since I was dabbling with DRM on the DX-394. I found it a very fascinating but unreliable mode for SW. I think there is better success with local and ground wave coverage than with distant sky wave. My shack and antennas are currently in disarray so I'm not au courant with DRM.

            Tom VE3MEO

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          • Tom Holden
            Consider it as an opportunity, Peter! I did succeed in decoding DRM with my DX-394A before adding the buffer. The buffer elevated the DRM signal-noise ratio
            Message 5 of 5 , May 12 12:46 PM
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              Consider it as an opportunity, Peter! I did succeed in decoding DRM with my DX-394A before adding the buffer. The buffer elevated the DRM "signal-noise ratio" and, I think, the decoding success rate as a result. It's not essential to add the buffer.

              There may even be a way of getting a decodable DRM stream at audio frequency with a minimalist mod. This involves overriding the selection of the narrow filter in the SSB mode so that the AM filter stays in circuit - the "Switchable IF Filter" mod or a variant of it will provide the control. Then, connect the Tape Out from the receiver to the computer sound card. Set the DX-394 to USB mode and tune to the DRM frequency minus 6 kHz. This will output through the tape jack whatever portion of the DRM 10kHz wide spectrum makes it through the 1st and 2nd IF filters, with the nominal centre of the channel at 6kHz. Dream will lock its reference to 6kHz if there is enough of the DRM spectrum left and may succeed in decoding. It's worth a try and has worked with other receivers that have a wide IF bandwidth mode.

              73, Tom VE3MEO
              ----- Original Message -----
              From: Peter
              To: RADIOSHACKDX394@yahoogroups.com
              Sent: Monday, May 12, 2008 2:45 PM
              Subject: Re: [RADIOSHACKDX394] Digital voice


              I see, somthing to think about for me!

              many thanks

              Peter

              .


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