The oscillator shown in the figure can generate signals between 3 and 15 MHz approximately, depending only on the frequency of the chosen crystal. In this case, the frequency given as an example was 7 MHz, which corresponds to that used by amateur radio transmissions in the 40 meters. The resonant circuit in the transistor collector allows you to select the output so that harmonics are only used by the external circuit. Capacitors must be ceramic and power must be provided by source stability. In the capacitive divider of the oscillator where we find the capacitors of 25 pF and 100 pF, these components, for greater stability should be silver mica. 2N2222A equivalent transistors such as BF494 and BF254 can be used without problems.
