[SOLVED] replacement of a modulator in FM encoder

[fareen]

hey
**broken link removed**
this is the circuit o FM encoder, i have simulated this circuit on proteus, got the required results.
but doing on hardware cause problem. the modulator is not producing the required output. the FFT of the signal before the bandpass filter shows lots of harmonics as it should be , but the final output also shows these harmonics outside the range of bandpass filter. bandpass filter has frequency range of 23KHz to 53Khz.
any idea abt the replacement of the modulator?

 

[chuckey]

Thats whats meant to happen. You are modulating a square wave so you expect modulation products at Fc, 3 X Fc, 5 X Fc, etc. thats why the filter is there, to select the right ones ( FC, 38 KHZ +- sidebands).
Frank

 

[fareen]

yes Frank, you are right