500mW FM transmitter

  
The TX500 is a simple to build 500mW FM Transmitter. It consists of three blocks; modulator / oscillator, two stage 500mW VHF amplifier and LED based power meter. The TX500 allows to transmit audio signals to FM band at frequencies from 88 MHz to 108 MHz. Due to the very low power consumption of less than 100mA the circuit may be perfectly powered by using 9-12V battery or power supply if you prefer. The circuit has been divided into separate stages so that it is be better for everyone to understand how every part works independently.
500mW FM transmitter - schematic

The carrier frequency of an oscillator is determined by the capacity of C4, C5 in conjunction with the inductance of the coil L1. 3.5 turns are needed and 27pF for C5 to tune to a lower part of FM band (88-100MHz). To be able to tune to a higher part (100



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