Stereo FM Transmitter Using BA1404

This circuit , whose only active component is an integrated circuit , to listen to your radio walkman headband or the signal from a computer, a stereo TV or hi-fi . It has excellent signal to noise ratio , very good channel separation is easy to adjust and the range is more than adequate for home use. Another possible use is in the car to enter the vehicle's stereo signal a Discman or MP3 player even when the team does not have line inputs , simply tune the transmitter on a free position and ready .

Stereo FM Transmitter Circuit Diagram

FM Transmitter Circuit Diagram

As you can see the circuit is very simple. The incoming stereo audio signal is conditioned and leveled by a handful of resistors and capacitors and then enter the integrated circuit . Other components are responsible for the generation of a pilot signal, the signal combination to achieve the MPX and the output buffer to the antenna.

The circuit operates at 3V . If powered with any voltage than directed will destroy the IC. The antenna may be a wire rod or 60cm long telescopic FM antenna . The signal input operates in the millivolt range and can attach knobs to adjust the audio level.

First tunes into a radio ( preferably digital and good quality ) dial a position where there is no broadcasting station . Then Turn On the transmitter and turning the trimmer 47pF , tune the transmitter so that the audio signal at the inputs is heard in the receiver. When you get the strongest signal possible to adjust the 50K preset until the stereo station indicator lights on your receiver . If the input signal is too strong ( it shows when the receiver is distorted ) will be convenient to put knobs on the transmitter input to lower the sensitivity.

The coil in parallel with the trimmer 47pF is formed by three turns of wire on a 0.5mm 5mm ferrite core .

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