Kwarciany frequency modulated transmitter with high efficiency on 418,8 MHz
The master oscillator of the transmitter is performed on the transistor VT1. Its frequency stabilized by a quartz resonator ZQ1 frequency 69,8 MHz, which is excited on the first mechanical harmonic. Coil L1 is used to set the depth of modulation of the master oscillator.
On the VT2 transistor is made frequency doubler, the output circuit L3C5 which is configured to 139,6 MHz.
Cascade performed on the transistor. VT3 is the amplifier working mode, the output circuit L4C8 which stands sixth harmonic oscillator. Fine tuning to the frequency 418,8 MHz by varying the capacitance of trimmer capacitor C8.
The coil L1 is wound around the wire PEL - 0.1 mm on the frame with a diameter of 1.5 mm and contains 50 turns. All other coil - frameless wound on mandrels with a diameter of 1.5 mm wire sew - 0.25 mm. L2 contains 14 turns, L3 - 8, L4 - 4 turns. To increase the efficiency of the output stage, the coil L4 can be performed silver plated wire of the same diameter.