The following posts explains how to build a simple to build FM stereo transmitter circuit using IC BA1404.
About the IC BA1404
An exceptional stereo audio FM wireless transmitter circuit is presented below.
The circuit relies upon the IC BA1404 from ROHM Semiconductors.
BA1404 is a monolithic FM stereo modulator which includes integrated stereo modulator, FM modulator, RF amplifier circuitry.
The FM modulator could be controlled from 76 to 108MHz and power source for the circuit could be nearly anything between one.25 to three volts.
In the circuit R7, C16, C14 and R6, C15, C13 makes the pre-emphasis system for the right and left stations respectively.
This is achieved for complementing the frequency response of the FM transmitter with the FM receiver.
Inductor L1 and capacitor C5 is employed to fix the oscillator frequency. Group C9,C10, R4,R5 enhances the station splitting up.
38kHz crystal X1 is linked between pins 5 and 6 of the IC. Composite stereo reception is formed by the stereo modulator circuit employing the 38kHz quartz regulated frequency.
Construct the circuit on a high quality PCB.
Operating the circuit from a battery pack minimizes disturbances.
Work with an 80 cm copper cable as antenna.
For L1 try to make three turns of 0.5mm dia enamelled copper wire on a 5mm dia ferrite core.