In the figure we have an oscillator with a single transistor that can generate signals in the range of 7 to 100 MHz, with the use of a crystal that oscillates in overtone. The transistor used is 2N2222 or any equivalent that oscillates at the desired frequency. The RF XRF shock must have a high reactance at the operating frequency and typically 200 to 500 uH types can be used. L1 and L2 depend on the oscillation frequency according to the following table:
Frequency Diameter of C4 turns/ Coils / wire
7 - 9 MHz 9 mm w / core 30 / 0.18 mm 220 pF
10 - 15 MHz 9 mm w / core 25 / 0.20 mm 150 pF
16 - 24 MHz 9 mm w / core 15 / 0.20 mm 100 pF
25 - 30 MHz 5 mm w / core 12 / 0.30 mm 68 pF
31 - 50 MHz 5 mm w / core 7 / 0.40 mm 47 pF
51 - 70 MHz 5 mm without core 6 / 0.40 mm 27 pF
71 - 100 MHz 5 mm without core 4 / 0.40 mm 22 pF
The coil L2 is wound on L1 and consists of 32 or 3 turns of the same wire. The ideal operating current for this circuit is around 12 mA.
