FM RADIO RECEIVER
Frequency Modulation
Frequency Modulation (FM) means varying a radio signal's
frequency (instead of amplitude) to transmit useful
information.
Some assistive listening devices, ALDs, and some assistive
listening systems, ALSs, use FM to transmit the signal
representing sound from a transmitter to a receiver.
Many movie theaters now transmit the soundtrack of the
movie in a low powered FM signal throughout the theater. The
theater will loan hard of hearing people a special receiver they
can use to receive that FM signal and therefore to hear better.
You can buy personal FM systems that you can use at home, in
restuarants or in the car to hear someone you are with better
... or even to hear the television at home.
Now, even some hearing aids can receive FM with an
integrated (built-in) or boot receiver.
There is even a special frequency ranges that are assigned for
use by assistive listening systems. FM has advantages and
disadvantages. It can be used outdoors, and it can transmit
through walls -- there is an alternative transmission method, IR,
that uses infrared light to transmit the signal that has different
advantages and disadvantages.
Whether the signal is transmitted via FM or IR, the advantage
of using an ALD to transmit the signal is that it overcomes
distance and can eliminate background noise.
DESCREPTION
IC SONY CXA1916BS is specially designed for fm receiver
circuit.it contain the AM,FMand IF section built with in the
ic.This ic is manufactured by the sony company.IC cxa1619BS is
a 30 pin micro dil ic.
In this circuit we used this ic.Whole circuit works on 6v to 12v
dc power supply.Power supply is given between pin no.27 of ic
and ground.Pin no.24 is audio output pin. Which connected to
audio amplifier ic TBA810 via volume control 10k for further
amplification.Variable resistor 10k is act as a volume
control.Amplified sound is available on pin no.12 of tba810
ic.this output is connected to loud speaker through 470 micro
farad capacitor.L2 is power supply indicator LED.L1 is a tunning
LED.It will light up when your FM station is tuned properly.
Part list
Resistors
R1-4.7
R2-1K
R3,R10-100K
R4-180K
R5-22
R6,R7,R8,R9-220
R11-150
R12-560
P1-10K Potentiometer
CAPACITORS
C1-100KPF
C2-680PF
C3-10KPF
C4,C6-470Micro farad
C5,C7,C13-100Micro farad
C8-220 Micro farad
C9-4.7 Micro farad
C10,C14,C22,C18,C19-22KPF
C11-10 Micro farad
C12-4.7PF
C15-1KPF
C16,C17,C21-22PF
C20-4.7KPF
X1- 3P3 PIN 10.7MHZ Resonator
X2-2 PIN 10.7Mhz Resonator
Gang-FM Gang White
SEMICONDUCTORS
D1-1N4007-Rectifier Diode
U1-TBA810-AMPLIFIER IC
U2-CXA1619BS FM IC
L1,L2-3MM Red/green LED
MISCELLANEOUS
SPK-2.5 Speaker
-Battery Snapper
-Wires
3T-3 Turn coil
4T-4 Turn coil
5T-5 Turn coil
ADVANTAGES
1-Lesser distortion. Frequency modulated wave is less
susceptible to intereferences from buildings, traffic etc which
provides improved signal to noise ratio (about 25dB) w.r.t. to
man made interference.
2- Waves at higher frequencies can carry more data than the
waves at low frequency.
3- Smaller geographical interference between neighboring
stations.
4- Less radiated power.
5- Well defined service areas for given transmitter power.
6-Very Portable
7-Very easy to set up and use
8-Offers great flexibility of movement
9-Used indoors or outdoors
10-Appropriate for mild to profound losses
11-Receiver can be covered or put in the pocket
12-No fluctuation in strength of signal
DISADVANTAGES
1-Since attenuation is directly proportional to frequency, so FM
suffers more attenuation tham AM signal.
2- FM signals propagate as line-of-sight phenomenon, so if
there is a large hill between transmitter and receiver, the
receiver will not receive any signal. AMsignals, on the other
hand, are at low frequencies which are reflected back by
ionospehere and thus, using sky-wave-propagation
phenomenon, can travel farther distances. FM waves penetrate
ionosphere and are not refracted back.
3- Much more Bandwidth (as much as 20 times as much).
4- More complicated receiver and transmitter.
5-Receiver are required for every one
6-Receivers vary in quality and durability
7-Potential for outside interference
8-72-76Mhz BW allotted by fcc
9-Police band,construction walkie talkies,pagers
10-Receiver and transmitter must be on the same channel
11-There must be 1 free channel between systems used in close
proximity
