Frequency Reducer/ Division

Discussion in 'The Projects Forum' started by kahafeez, Jan 1, 2009.

  1. kahafeez

    Thread Starter Active Member

    Dec 2, 2008
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    hi all, happy new year....


    i need to convert a 14MHz wave to a wave which has a freq between 200 to 450KHz..... keeping the data intact...... how can i do this????


    plz suggest the easiest way.....
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    You need to include real baud rate, as well as modulation scheme before we can even begin.
     
  3. kahafeez

    Thread Starter Active Member

    Dec 2, 2008
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    the modulation scheme is BFSK and the baud rate is 4.8kbps

    the signal has 14MHz for 0 and 14.3MHz for 1
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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  5. kahafeez

    Thread Starter Active Member

    Dec 2, 2008
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    i had this concept as the last option..... cz one the mixer ic 1495 or 1496 is a bit costly bt that isnt really a problem....

    i'll have to design a local oscillator and then gang tune them all..... this i guess would be a mess :(

    apart from that i've always been wondering how does the local oscillator detects the incoming freq as it always has to produce incmg freq + 10.7MHz in FM


    can someone plz share a schematic of the local oscillator or the whole heterodyne system ?
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Did you have a look at the philips NE602 ?
    This is a mixer with oscillator.

    Greetings,
    Bertus
     
  7. kahafeez

    Thread Starter Active Member

    Dec 2, 2008
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    i just got an idea..... see the attached image.....

    will this work??? well, it should.....

    can anyone plz tell any part number for an RF amplifier????
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    282
    Some looking turned up this circuit - http://www.edn.com/archives/1994/081894/graphs/17di4fg1.htm.

    It's regenerative, so care must be taken in construction to get a stable receiver, but it works up in the 14 MHz range.

    The 300 KHz separation between the ones and zeroes might be interesting to resolve. A low-Q receiver is the thing. Most superhet IF bandwidths are much less. Designing an IF for 300 KHz would be interesting, but time consuming.
     
  9. bertus

    Administrator

    Apr 5, 2008
    15,648
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    Hello,

    You say your data is 14.0 Mhz for 0 and 14.3 Mhz for 1.
    If you mix 14.3 with these frequecies you will end up with 300 khz and 0.
    When you mix with 13.8 Mhz , you will get 200 khz and 500 khz.

    Greetings,
    Bertus

    PS how did you choose the frequencies?
    They are in the 20 meter radioamateur band. This run from 14.000 to 14.350 Mhz
    The IARU will not be happy when you actually transmit on these frequencies.
    The local authorities have to look after the respecting of the band plans.
     
    Last edited: Jan 2, 2009
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