Op-Amp question

Discussion in 'The Projects Forum' started by pbreaction, Oct 20, 2009.

  1. pbreaction

    Thread Starter New Member

    Oct 20, 2009
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    I am trying to make a 1mHz sine oscillator for a AM Transmiter and i was going to use a wien-bridge oscillator but i am having trouble trying to figure out what op-amp to use and what exactly i am looking for in spec sheets to achieve 1mHz.



    Thanks, Mark
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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  3. SgtWookie

    Expert

    Jul 17, 2007
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    You DO know that 1MHz is right in the middle of the commercial AM broadcast band, right?

    And you also know that the FCC has absolutely no sense of humor when people transmit RF in frequencies that they are not authorized for, right?
     
  4. wr8y

    Active Member

    Sep 16, 2008
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    Oh, I would not say that.... they got 4,000 laughs over a business who was doing just that:

    http://www.arrl.org/news/stories/2009/10/06/11124/?nc=1
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Yeah, well - they're awfully quick to slap fines and jail time on those who are transmitting illegally; and they often don't hand out warnings - AFAIK.

    LC oscillators are mighty broadband when compared to crystal oscillators. If you want to stay legal, and keep a narrow transmit frequency, better look into the FCC regs on what frequencies it IS legal to transmit on without a license, and what kind of transmissions you can make on said frequencies.

    Better yet to join a local ARRL chapter and get hands-on guidance from some of the "old pros" there.
    http://www.arrl.org
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    As far as I know it is still legal as long as it is under 10mw, and the antenna is less than 10' long. Most small 9V transmitters have no problem meeting these requirements, but don't try to optimize the power either.

    I built my share when I was learning oscillators on my own. Of course, I'd build it, test it, then recover the parts. Most 300 in 1 project kits have something similar. What is the application for this?

    Have the rules changed?
     
  7. zimbarak

    Active Member

    Feb 8, 2009
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    you can use the LM 741 or the LM 324 (4 amp) both can work perfecly for wien oscillator !
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    But not at 1 MHz.
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    Hehe, you'd be lucky to get 50Khz out of a 741.

    Op amps have their uses, but AM radios have been built using transistors since transistors were invented. Op amps aren't truely RF devices, though some video amps come close.
     
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