The RF oscillator using the
inverter N2 and 10.7Mhz ceramic filter is driving the
parallel combination of N4 to N6 through N3.Since these
inverters are in parallel the output impedance will
be low so that it can directly drive an aerial of 1/4th
wavelength. Since the output of N4-N6 is square wave
there will be a lot of harmonics in it. The 9th harmonics
of 10.7Mhz (96.3Mhz) will hence be at the center of
the FM band .
N1 is working as an audio amplifier.
The audio signals from the microphone are amplified
and fed to the varycap diode. The signal varies the
capacitance of the varycap and hence varies the oscillator
frequency which produce Frequency Modulation. |
