The oscillator indicated can produce signals from 50 kHz (approximately) to 7 MHz, depending only on coils L1 and L2 and capacitor C. The circuit power is of the order of 500 mW with 12 V power. The circuit works with voltages of 6 to 12 V and transistors equivalent to the one suggested, such as TIP31, can be used. For a frequency of 1 MHz, the coil will be formed by 80 turns of wire 28 with a central socket on a ferrite rod 1 cm in diameter and 10 to 20 cm in length. L2 is formed by 20 turns of the same wire over L1. In this case, C will have 470 pF. For 7 MHz, wrap 30 turns of wire 28 in the same ferrite rod, use for L2 10 turns and a C of 100 pF. C can be variable for frequency adjustment. All capacitors must all be ceramic.
