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Re: [linuxham] Problem with using pseudofsk

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  • Martin
    I spent a lot time with this problem while assisted VE6YP in YPlog development (this project is now dead unfortunately). YPlog uses the same trick (rectifying
    Message 1 of 8 , Feb 1, 2009
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      I spent a lot time with this problem while assisted VE6YP in YPlog
      development (this project is now dead unfortunately). YPlog uses the
      same trick (rectifying of the sound card output) to generate a precisely
      timed high speed CW and as far as I know, it has still the most precise
      CW above ~70 wpm.

      The main problem were the timing constants introduced by the interface.
      A too low value of filtering capacitor caused insufficient filtering,
      the radio tended to follow the sound card output frequency (if set too
      low). A too high value of this capacitor caused poor, smeared CW. Also,
      the response of different radios was different, therefore we used
      selectable envelope shape of the code element (exponential or
      trapezoidal). To save the bandwidth, the solution was to use HIGH AUDIO
      FREQUENCY output from the sound card (> 10 kHz) and quite low value of
      filtering capacitor, say ~ 0.022 uF. fldigi should use for the pseudo
      FSK a frequency in the 10-30 kHz range. Also, the interface schematic
      should me modified, I recommend full wave bridge rectifier with a 0.022
      uF capacitor. The transformer I used was 600 ohms (sound card side) to
      10 kohms (rectifier side).

      73,
      Martin, OK1RR

      w1hkj napsal(a):
      > n2uz wrote:
      >> Hi all,
      >> I am trying to use pseudofsk with my Elecraft K3. The print on the
      >> receiving end is bad.
      >>
      >> I am running fldigi under Ubuntu.
      >> ASFK with rtty is ok.
      >> Switching the polarity of the pseudofsk signal in the K3 does not help.
      >> Switching the rev on the receiving end does not help.
      >>
      >> I made the circuit in the help files to generate the pseudofsk signal
      >> and it works ok when I use it to key the K3 for cw, so that is not
      >> the problem.
      >>
      >> Has anyone used the psuedofsk to run their rig? All indications on my
      >> end point to something wrong in that 1000 hz signal on the right
      >> channel not being correct.
      >>
      >> Jerry, N2UZ
      >>
      > Do you have a dual channel oscilloscope available Jerry? If you do you
      > can look at both the right and left channels. The left should be the
      > AFSK and the right channel the on-off keyed 1000 Hz tone. Check to be
      > sure that the on-off keying corresponds with the frequency shift on the
      > AFSK (left side). Then do the same with your derived TTY control
      > signal. Make sure that you do not have any glitches occurring on that
      > final signal as they might provide false triggering to the K3. Finally,
      > have you used the K3 in FSK mode with any other signal source?
      >
      > Dave
      >
    • n2uz
      Dave, Did you have any success with your kenwood 450 under fsk and did you receive the pdf files of the output that I sent? snip............ ... indications on
      Message 2 of 8 , Feb 7, 2009
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        Dave,

        Did you have any success with your kenwood 450 under fsk and
        did you
        receive the pdf files of the output that I sent?


        snip............
        >> Has anyone used the psuedofsk to run their rig? All
        indications on
        my
        >> end point to something wrong in that 1000 hz signal on the
        right
        >> channel not being correct.
        >>

        Jerry N2UZ
      • w1hkj
        ... Sorry, but I have not had a chance to test that yet. Yes I received the files. Dave
        Message 3 of 8 , Feb 7, 2009
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          n2uz wrote:
          > Dave,
          >
          > Did you have any success with your kenwood 450 under fsk and
          > did you
          > receive the pdf files of the output that I sent?
          >
          >
          > snip............
          > >> Has anyone used the psuedofsk to run their rig? All
          > indications on
          > my
          > >> end point to something wrong in that 1000 hz signal on the
          > right
          > >> channel not being correct.
          > >>
          >
          > Jerry N2UZ
          >
          Sorry, but I have not had a chance to test that yet. Yes I received the
          files.

          Dave
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