The circuit of the figure operates in an overtone of the crystal frequency, that is, in the fundamental frequency or in harmonics that correspond to odd multiples of the fundamental frequency such as 3f, 5f, 7f, 3, etc. Note that the LC circuit in the drain of the field effect transistor must be tuned to the frequency at which we want the oscillations. The field effect transistor can be of any type that oscillates in the desired frequency range. This circuit operates at frequencies of a few hundred megahertz.
