Modulation

Discussion in 'The Projects Forum' started by vinayalim, Dec 2, 2008.

  1. vinayalim

    Thread Starter New Member

    Dec 2, 2008
    1
    0
    Dear Forum members,

    I am working as the application Engineer. I am working on modulation circuits. The circuit is built using the best CAD tools. but the output is not coming. Can any one send me the Collector modulation circuit for the AM.

    I have send the circuit in the PDFrmat. Please have a look. Suggwst if any correction is required.

    I want to know more about the Fooster Seelay Circuit for the FM detection.

    regards
    Vinay S
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    I am not familiar with "collector modulation".

    Here is a link to a good article on the Foster-Seeley discriminator.
     
  3. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    287
    Vinay:

    What you have in the schematic is definitely NOT collector modulation...your carrier and modulation signal are shown going to the base.

    Collector modulation requires that your modulated transistor operate in Class C. If the transistor is operated in the linear mode, your two input signals will simply add...you want them to MULTIPLY.

    The way do do this is to modulate the supply voltage of a Class C amplifier. There are two ways to do this....well, actually several, but two SIMPLE ways. One is with a series "pass" transistor between Vcc and the modulated transistor's collector. In this case the series transistor ("modulator") DOES need to be in class A. This method is pretty inefficient and can't give you 100% modulation. A more conventional method is to modulate the collector through a transformer...which can be driven with either a class a or class b modulator.

    Eric
     
  4. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    I'll send some schematics soon.
     
  5. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,039
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