Showing posts with label stereo. Show all posts
Showing posts with label stereo. Show all posts
Tuesday, April 30, 2013
FM Stereo Transmitter
Youll find that this is a very easy project to build. It will transmit good quality sound in the FM band ( 88 - 108 mhz ). One inportant item is that the IC chip operates on 3 volts DC. The chip will get destroyed if it is operated on any voltage higher than 3.5 volts. The antenna can be a standard telescopic antenna or a 2 foot length of wire. The input is in the millivolt range and you may need to add additional pots for the inputs. I was able to use this circuit for a walkman and a portable CD player in my car. I used the headphone jack on both and varied the signal with the volume control.
Circuit Diagram
Circuit Diagram
To adjust the circuit tune your FM radio to a quite spot then adjust the trimmer capacitor C8 until you hear the signal that you are transmiting. When you have a strong signal adjust the resistor R4 until the stereo signal indicator lights. If the input is to high of a signal you may over drive the IC chip. Use two 15 turn pots on the input signals to bring the level down. You can balance the signal by using headphones. The inductor L1 is 3 turns of .5 mm wire on a 5 mm ferrite core.
Sourced: extremecircuits
Thursday, March 28, 2013
Single Chip Stereo FM Transmitter Circuit
ROHM (www.rohm.com) is originally a resistor producer company, but finally expand their business and produce monolithic IC, and this one used in our circuit is the example. The internal structure of this FM transmitter integrated circuit consist of stereo modulator that creates a stereo composite signal, an FM modulator that modulate a carrier frequency with the composite signal, and an RF amplifier that provide enough power to be transmitted through antenna. This is the figure of the circuit;
The core of this stereo FM transmitter is BA1404 integrated circuit chip. from ROHM. This FM transmitter is ideal for wireless microphone, or for audio interface and distribution for home or car appliance. For example, you can now play your portable mp3/mp4 player on your old car radio sound system that doesn’t have line-input plug. This stereo FM transmitter chip is designed for 75-108 FM band, and you can adjust the operation by trimming the LC network connected to pin 10 of this IC chip. To ease the adjustment, you can use a 22-33p variable capacitor for the 15p capacitor connected to pin 10. Finally, this stereo FM transmitter works with only 1.5-3V power supply, ideal for battery operation. More than 3.5V supply voltage could burn this FM transmitter circuit. [Circuit diagram source: ROHM Application Notes]
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