2B-3V POCKET TRANSISTOR
This is a very low cost project and you can assemble it to listen news, songs, music etc. You can keep it in your pocket also since the size is very small. You can keep it in your pocket also since the size is very small.
TECHNICAL DESCRIPTION & WORKING
This project has been developed and successfully tested at TV Engineers Technical Lab.
Now a days, possession of radio sets is just taken for granted but you feel proud of listening to a radio, which is self assembled one. Here we are giving a circuit of medium wave radio [MW] which receives program broadcast with in the range of 200 meters to 550 meters. This project employs only five transistors along with other components which can be fitted in a small plastic cabinet.
The radio signal received through antenna coil and gang is fed to the base of TR3 BF194B. The oscillator frequency is available through .01 MFD at the emitter of the TR3 BF194B. The intermediate frequency is available at the collector of TR3 BF194B which is given to yellow IF through the oscillator coil.
IF AMPLIFIER, DETECTOR, AGC:
The IF frequency is amplified by the IF amplifer. The IF stage consists of two transistors TR2 BF195C and TR3 BF195D. The amplified IF signal is fed to 3rd IF [white] through the Collector of TR3 [BF195D] again fed to detector diode OA79 through 3rd IF.The detector stage separates the audio frequency from the modulated radio frequency. This detected audio signal is very weak and to enhance its strength , the signal is fed to pre amplifier stage.
The audio section amplifies the audio frequency and feeds the speaker.The speaker delivers us the sound/ programs broadcasted by the radio stations. The audio section consists of driver transistor TR4 [BC148B] and two output transistors TR5 AC128 and TR6 AC128.
PRECAUTIONS WHILE ASSEMBLING THE PROJECT:-
- Check all the components as per the circuit.
- Test all the components [cold test] by multimeter.
- Mount the IFT checking the colour [yellow, Green white & its pin connections].
- Check collector , base and emitter of transistors before soldering.
- Adjust antenna coil with the ferrite rod to obtain maximum gain.
LIST OF COMPONENTS:-
RESISTANCE [ALL 1/4 WATT]
.1 MF 1
.01 MF 2
.02 MF 3
.04 MF 1
10 MF/10V 1
AC 128 2
BC 148 1
VOLOUME CONTROL 10K LOG WITH SWITCH 1
2X GANG 1
OSCILLATOR COIL 1
ANTENNA COIL 1
DRIVER TRANSFORMER 3V 1
IFT 1 SET
SPEAKER 2.5″ 1