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?
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?
