This circuit, shown in the figure, can operate from 4 to 100 MHz, based on a 2N2222 transistor or equivalent. The recommended supply voltage for this circuit is 12V and as the power of the generated signal is low, for small transmitters, at least two amplification steps must be used before modulation. The capacitor between the emitter and the circuit ground must have its value obtained experimentally in the range of 22 to 100 pF, according to the characteristics of the crystal and the RF shock used. This shock must have values between 100 uH and 1 mH depending on the frequency of the circuit.
