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FM/AM Detectors

Discussion in 'Electronic Basics' started by Jason, Oct 13, 2003.

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  1. Jason

    Jason Guest

    Can anyone explain to me, or post a link on, what an AM/FM detector is and
    specifically what is its purpose? My searches have revealed some schematics
    of detectors but little towards their actual purpose.

    I have a project at school I have chosen to do which is building a simple AM
    radio. The problem is our communications book is extremely unhelpful. I
    believe its only mention of detectors is in a "circuit diagram" which is
    actually nothing more than a square with the words "FM detector" or
    something similar written inside of it.

    Other students have bought radio kits for their projects and the instructor
    accepts those. I on other hand want to design my own and learn the
    principles and theory behind reciever design.

    Thanks in advance.
  2. Go to a library, and look for books on Amateur Radio - in the US, you
    should find the ARRL Radio Amateur's Handbook - that book should cover
    the material you need.
  3. Jason

    Jason Guest

    Alright, thanks.

    I just recieved an older communications book from my brother and it states
    that detection and demodulation are the same thing. That clears things up,
    as I knew what demodulation was. ;)
  4. Steve

    Steve Guest

    it extracts the original signal from a modulated carrier. Try getting
    a better book, sounds like that one isn't worth the paper it's printed

    your favorite radio station modulates music onto a carrier wave for
    transmission. Your radio receives this carrier and demodulates it to
    extract the music. A very simple radio receiver can be made from a
    diode detector and a few bits and peices.

    Plenty on the web about this, there's also amateur radio newsgroups
    that will help you a lot.

    a detector is also known as a demodulator.

  5. In a very simplified nutshell.

    1 If you send a signal to a length of wire, it radiates a bigger signal
    the higher in frequency it is. Audio frequencies don't radiate much at

    2 AM and FM are methods used in order to increase the frequency of the
    signal to achieve bigger radiation as described in 1.

    3 The higher transmission frequency is generated (coded) from the signal
    frequency by a "modulator".

    4 The received signal frequency is generated (decoded) back from the
    transmitted higher frequency by a "detector". A detector is also called
    a "demodulator".

    Thus, 3 and 4 define what a "modulator" and a "detector" are. That is,
    they are devices that convert information at one frequency to
    information at another frequency.

    Kevin Aylward
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
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