Frequency Modulation reaches several meters to kilo meter with low power transmitter circuit. Here two transistor based FM circuit diagram given for hobby use. The condenser mic converts voice signal into audio signal and transistor Q2 amplifies the audio (message) signal. The Q1 transistor is produces Carrier frequency. Amplified audio(message) from Q2 transistor is directly applied to the Q1 transistor base terminal. Hence frequency of carrier signal varies according to the audio (message) signal. By the way we get FM wave from the collector terminal of Q1 transistor. By using lengthy monopole antenna we can transmit FM wave up to several kilometres.
(always tune the FM Carrier frequency in the transmitter to a license free band)
|3.||Gang capacitor (variable capacitor) 4 to 40pF||1|
|4.||Capacitor 1 &uF (disc type)||2|