FM RADIO RECEIVER
The FM Band transmission has started very recently in India but its superior technique and quality has attracted the listeners. Unlike AM, the FM is a seperate band and its frequency ranges from 88MHz to 108MHz. The FM Band can not be received by the conventional AM receivers. Each and every AM receiver does not incorporate FM facility. The present project is a very low cost project and it can be fitted to any radio receiver/audio system to receive FM transmission. The circuit of this project is very simple and can be easily assembled.
TECHNICAL DESCRIPTION AND WORKING
This project has been developed and tested O.K. in our TV Engineers Technical Lab. The components and PCB used in the projects published in our books are available for sale at resonable price.
Now-a-days there is a necessity of FM projects in the electronic market and it is our duty to make it available to the people. This project is a very low cost project and based on IC 5591 manufactured by Philips Company. Through this project different FM stations can be tuned but in India, presently there is one FM Channel. As such the project is designed for one channel to avoid possible damage of the coil in tuning again and again. The FM Transmission is stereo phonic. As such you can connect it to any stereo deck and enjoy the stereo sound. Now a days two-in-one and radios with FM Band are available in the market. But without replacing your old radio set you can connect this project to your old radio/two-in-one and enjoy the FM transmission. It is quite economical too. Unlike AM receivers, the FM receiver is assembled through different stages which are as follows.
- FM Amplifier
- Descriminator [Detector]
- Audio Pre-Amplifier
All the above functions are performed by the IC5591 which is employed in the circuit. The audio signal available from the preamplifier is fed to audio output amplifier for further amplification. The RF of FM band transmission is fed to pin no. 2 of the IC TA5591 through the aerial, which also works for FM amplifier, oscillator and mixer stage. A ceramic filter of 10.7MHz is connected to the local oscillator pin no. 4, 5 and 6 of IC. A 9 volt DC supply is fed to pin no. 8 of the IC. Pin no. 10 of the IC is discriminator pin. The audio signal is available from pin no. 11 of the IC. Pin no. 18, 19 and 20 of the IC are IF amplifier pins while pin no. 22 and 24 are local oscillator pin. Two trimmers are connected to the circuit. The range of the frequency can be varied by rotating the trimmers. A gang condenser equivalent to the value of the trimmer can also be used in place of trimmer if available. This project can operate in the range of 3V to 12 Volt DC supply. However the trimmers are to be adjusted to get best reception.
PRECAUTIONS WHILE ASSEMBLING THE PROJECT:-
*Please use cermice filter of an exact value and take care while tuning of coils.
*For better responce use long teleshopic aeriel and coil of best quality.
*Check polarity of electrolytic capacitor while mounting on PCB otherwise reverse connection may damage it.
*First of all check all the components as per circuit.
*Check short circuit , while soldering.
*Please use resistance of the exact value as given in the circuit.
IC 5591 = 1
CERAMIC FILTER 10MHz = 2
56E = 1
470 PF = 1
22 PF = 4
.022 = 3
4.7MFD/63V = 2
ONE POLE TWO WAY SWITCH = 1