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Re: [softrock40] Re: LF-Interface with Lite v8.3 - About BC Image Rejection

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  • Dave - WB6DHW
    ... Hidehiko: Even the C grade of the Si570 will go to 200+ MHz. The 74AC74 will toggle well over 100 MHz. It must be something else in the circuit or how
    Message 1 of 11 , Nov 30, 2008
      qrper723 wrote:
      > Hi all,
      >
      > Thanks for suggestions for me and others.
      > Finally I made a 400kHz Cut-Off LPF for front-end of LF-IF kit.
      > I put some new photos on "Photo Albums > ja9mat".
      >
      > <Result>
      >
      > 40kHz,60kHz -- domestic time standard signal from 800km far
      > from my home can be heard!
      > 250kHz and 370kHz NDB 300km far a way can be heard here!
      >
      > But I feel the Dead Area(NOT OSCILLATE?) of the frequency
      > range above the 1300kHz beacuse of the upper limit of the
      > Si570 or 74AC74. 1300kHz x 64 = 83.2MHz.
      >
      > Can anyone use this LF IF kit for Middle Wave Broadcast Listening
      > above the 1300kHz (until about 1700kHz)?
      >
      > Any suggestion welcome.
      >
      > Thanks again!
      > 73,ja9mat Hidehiko.
      >
      Hidehiko:
      Even the "C" grade of the Si570 will go to 200+ MHz. The 74AC74 will
      toggle well over 100 MHz. It must be something else in the circuit or
      how the 74AC74 is hooked up. Are you running the 74AC74 on 3.3V or 5V.
      It will toggle faster at 5V. You didn't by chance get a 74HC74?

      Dave - WB6DHW
      <http://wb6dhw.com>
    • qrper723
      Hi Dave, Yes,I apply 5V to 74AC74. I measure the waveform from Si570 and the output level decrease from about 80MHz (3V-pp). Other problem does not seen yet.
      Message 2 of 11 , Nov 30, 2008
        Hi Dave,

        Yes,I apply 5V to 74AC74.
        I measure the waveform from Si570 and the output level decrease
        from about 80MHz (3V-pp).
        Other problem does not seen yet.

        Thanks,73.

        ja9mat Hidehiko.

        > how the 74AC74 is hooked up. Are you running the 74AC74 on 3.3V or
        5V.
        > It will toggle faster at 5V. You didn't by chance get a 74HC74?
        >
        > Dave - WB6DHW
        > <http://wb6dhw.com>
        >
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