Radio microphone bug
L1 = 9 turns on the mandrel with a diameter of 3 mm.
L2 = 100 turns on the resistor MLT - 0.25, or to increase the efficiency, it is better to take a ferrite core of grade 20 HF with a diameter of 2-3 mm and a length of 5-10 mm (its inductance must be ~ an order of magnitude larger than the inductance L1).
The initial version of the circuit was tested on transistors CT 3130A9. But, since their cut-off frequency is about 150 MHz, for the output stage I chose a very good microwave transistor 2T 657A2 (both CT 3130A9 and 2T 657A2 have SMD enclosures).
In principle, any high-frequency (F1> 150 MHz), the same infamous KT315, is suitable here.
At supply voltages above 5 V, in order to limit the collector current VT2 in series with L2, a resistor of 30 ohms is switched on.
The transmitter output power is approximately 10 mW (2T 657A2, 3 V).
The microphone is taken electret, condenser type FEM-3 or better, of course, the microphone "Pine" M1 - A2. I want to note, "Pine" does not like the supply voltage of more than 3 V.