Scheme wireless microphones, shown in the figure, begins to work at a voltage of 0.8 V, the current consumption is 0.5 mA with a reception distance of about 50 m.
The master oscillator is made on the VT1 transistor, a Positive feedback is determined by the capacitor C7. An output circuit C4, L1 is adjusted to a frequency of about 94 MHz selection of capacitor C4 and the shifting or splitting of turns of the coil L1. Mode DC generator is set by resistor R2.
Coil L1 is made frameless with a winding diameter of 6 mm and has 8 turns, are wound in a number of wire PEL-0,35. Microphone - type FEM-3.
The HAM radio 2/98, p. 25