AM modulator with MC1496 project problem

Discussion in 'The Projects Forum' started by tzitzikas, May 9, 2010.

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  1. tzitzikas

    Thread Starter Active Member

    Jun 3, 2007
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    Hello, i have done this project. It is an experimental oscillator - modulator for mw frequencies. The schematics are here:
    oscillator:
    http://tzitzikas.webs.com/oscillator-1.JPG
    modulator:
    http://tzitzikas.webs.com/modulator-1.jpg

    The problem is that the designer told me to use an 1kohm variable series resistance between oscillator and modulator (after

    c9=22n capacitor of oscillator) to adjust the carrier level. I saw that the 1kohm variable series resistance is not enought

    because with 1kohm series resistance the audio was't very good. I think that the carrier level was high. So i change this

    resistance with another 4.7kohm. Now i am using about 2kohm of this series resistance. The modulation is very good But i

    think that the audio signal in the radio is not at the center of the frequency but a little above.
    (The operation frequency is 1000khz but i listen the audio with quality and strong voice at 1003khz.)
    which is the problem? how i can fix it, to listen the audio very well at center frequency and not at sideband?
     
  2. bertus

    Administrator

    Apr 5, 2008
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