All India Radio (AIR)

FM Station Dharamshala.

Presented by:

Anuradha

Jv-i/11/4336

B.Tech(ec)-M.Tech(ec)

Radio is the transmission of

signals by Modulation of

electromagnetic waves with

frequencies below those of visible light

Radio is based on wireless

communication or satellite

communication.

In this era of technology due to the need of the

wireless communication, a National service was

planned and developed by the Prasar Bharti

broadcasting corporation of India

• For 75 years, all India radio is one of the largest radio networks in the world. AIR,

reaches the remotest corners of the country.

• All India Radio (abbreviated as AIR), officially known as Akashvani is the radio

broadcaster of India and a division of Prasar Bharati . the headquarters is at the

Akashvani Bhavan, New Delhi.

• Today air has a network of 213 broadcasting centres covering 90% of the area & almost

reaching the entire population of one billion.

• The external services division of all India radio broadcasts in 27 languages to countries

outside of India.

• AIR DHARAMSHALA :

COMMISSIONED ON

23RD FEBRUARY, 1994.

• FM BROADCASTING

STATION.

• FREQUENCY : 103.4MHZ.

IMPORTANT DATA ABOUT AIR

(DHARAMSHALA)

• Transmitter :2x5 kW FM VHF transmitter ( HVB 165/A)

coverage area : 60-80km (in air)

• Height of tower : 100m.

FM transmitting antenna height : 82m

• dipoles used for transmission : six

Distance between each dipole: 2.6m

• Along with the transmission of program from Dharamshala

studio, it also relays some of the program from FM rainbow

(Delhi), Vividh Bharti (AIR Mumbai), AIR Delhi and AIR

Shimla.

Transmission-A radio wave carries

information; signals are converted

into electrical signals. A carrier

wave is then produced from the

modulation .The wave is then

amplified and sent to the antenna

that then converts signal into an

E.M. Wave.

Reception- An

antenna on

receiving the

signal send it to

the receiver this

converts the

electrical signal,

sends it to the

amplifier either a

speaker

/headphones jack,

this is then

converted into a

sound wave.

RADIO BROADCASTING –

Radio broadcasting is the one way wireless transmission over radio waves intended

to reach wide audience .

TYPES OF RADIO BROADCASTING –

AM ( Amplitude Modulation )

FM ( Frequency Modulation )

How radio electromagnetic waves changes to radio waves

AM

(AMPLITUDE

MODULATION)

AM broadcasting is the

process of radio broadcasting

using amplitude modulation

.AM was the first method of

impressing sound on a radio

signal and is still widely used

today.

FM

(FREQUENCY

MODULATION)

FM broadcasting is a

broadcasting technology

pioneered by Edwin Howard

Armstrong which uses

frequency modulation to

provide high- fidelity sound

over broadcast radio.

AM service on low frequency bands is subjected to in

phonic disturbance.FM service has the capacity to carry auxiliary signal without causing any

disturbance to normal broadcast.

FM service having capacity of providing stereo services.

VHF/FM service is fewer suspects able to interference and manmade noise.

Less energy is needed in providing FM service from medium wave service.

Sufficient frequencies are not available in other broadcasting band.

VHF/FM band provides uniform coverage during day and night.

VHF/FM service provides high quality broadcasting

AM is much looser than FMmeaning that less data can besent at one time as it isn’tcompressed .the reason for thedifference in sound quality asa lower bitrate must be sentacross the wave

RADIO

STATION

A radio station is a

broadcasting centre, the

objective being to produce

and disseminate

informative, educational

and entertaining

programmes. A full-

fledged radio station

consists of three centres:

The studio

centre

The control

room

The

transmitting

centre

Thus broadcasting chain involves these two chains:

Studio to control roomControl to transmitter room

(transmission)

BROADCASTING CHAIN - it consists of studios, receiving centre and

transmitter. Studio-It consists of several studios,

designed to meet the special

requirements of broadcasting and a

control room. A microphone is provided

in each studio. The microphone picks

up voice signals and converts these into

electrical signals.

Control room -these electrical

signals are amplified and passed on

to control room and it selects the

studio according to the queue sheet

(time schedule) of various

broadcasts and controls the level of

program.

Transmitter -

these are than

feed to the

transmitter which

radiates the

modulated R.F.

Signal.

Studios are used for production of program and

transmission. The main requirement of a studio is that

the studio should be sound proof. A broadcast studio is

an acoustically treated room. It is necessary that the

place where a programme for broadcast purposes is

being produced should be free of extraneous noise. This

is possible only if the area of the room is insulated from

the outside sound .The studio walls and cuttings are

therefore converted with sound absorbing material such

as glass-wool, perforated hard board (PHB).

Announc

er

Consol

Receivin

g Centre

Equipme

nts

Studio

centre

PRE-AMPLIFIER

60db

PAD

-10db

FADE

R

-10

db

AUDIO DISTRIBUTI

-ONAMPLIFIER

+10db

MIXER

FADE

R

-10

db

AUDIO DISTRIBUTI-

ONAMPLIFIER

+10db

MIXER

LINEAMP-14db

MIKE -10db

-70db -20 -10 -20 -10db db db db +4 db

Equipment

0dbm

(1mW)

FADER

-10db

ADA

+10db

MASTERFADER

-10db

ADA

+10dbLIMITER

TRANS

-MITTER

+4

db-6db +4db

-6db +4db -6db

The block diagram shows that it

consist of limiter, exciter, power

amplifier, power coupler or divider,

harmonic filters and a monitoring and

combining rack which is connected to

the transmission antenna.

A large

variety of

electronic

equipment is

provided at

studio

centre:

Micro

phone

Micro

phones are

the

electro-

acoustic

devices

convert

sound

waves into

electrical

signals

High quality

microphones

are used for

broadcasting

Several

types of

microphon

es are used

for

broadcasti

ng,

dynamic

microphon

e

ribbon

microp

hone

condenser

microphon

e.

3 of them

importan

t types

being:

Amplifiers are

electronic

devices, which

amplify the

signals. The

electrical

signals

obtained from

a microphone

(or other low

level source

such as pick

up or playback

head) are very

weak. The

power of these

signals has to

be increased

(amplified)

before these

can be utilized.

Four

types of

amplifie

rs are

commo

nly used

in

studios:

Preamplifier-

The first

amplifier in

the broadcast

chain. The

output from a

microphone

are a pickup

which is at a

very low level.

The pre-

amplifier has

a gain of

about 60db. A

special

feature of

these

amplifiers is

that their

contributed

Program

Amplifier-

These provide

second stage

noise of

amplification.

The O/P

obtained from

the feeder

box (or

mixing

console) is

fed to the

input of these

amplifiers.

The gain of

this amplifier

is around

40db.

Monitoring

Amplifier -The

O/P available

from program

amplifier is not

enough to drive

loud speakers.

Monitoring

amplifiers are

provided to

boost the signals

further. A

separate

monitoring

amplifier is used

for a group of

loudspeakers

which are located

in studios,

control room,

duty room and

other selected

places for

continuous

monitoring of

Line equalized

Amplifier-the

programs are

fed from the

studio to the

transmitter;

there is

considerable

loss during

this

processing. So,

to equalize the

losses, line

equalisers are

used. Equalizer

line amplifiers

have the

provision for

adjusting the

gain and

frequency

These are variable alternators having constant input and output impedance. The faders are

provided in their fader box in the transmission booth. These are used for fading in and out

the program and combining the program. No. Of faders in the fader box corresponds to the

no. Of sound sources in the booth. The level of the program being fed to the transmitter has

to be controlled. Faders are provided for this purpose.

Two systems of recording used in these days are:

Magnetic discs: In the magnetic system recording is done on the tape, which has a paramagnetic coating

on a plastic base. This is known as tape recording and is extensively used in broadcasting.

Tape Recorders: Utilize magnetic recording. Provide high quality recordings and have a main advantage

that the tape can be used repeatedly for recording by removing the previous recordings when not required.

• Portable tape-recorder (P.T.R)

• Ultra portable tape-recorder (U.P.T.R)

• Gramophone turn tables

FREQUENCY MODULATION: - the type of modulation in which instantaneous frequency

of the carrier is varied acc. to the amplitude of the modulating signal is called frequency

modulation. frequency modulation is widely used in vhf communication systems.

FM TRANSMITTER- This transmitting system consists of two 5kw FM transmitter A and B

operating in parallel in acute standby mode. The output powers of the two transmitters are

combined in a combining unit. Both the transmitters are housed in a single tack.

Block Diagram:-

RF block systematic of a 2x5kw FM transmitter is shown and O/P of 5kw, which are combined in a combining

unit to get an O/P of 10kw. Since a total of 8 power amplifiers unit have to be driven in this transmitter, RF

amplifier stage is 20W normal O/P is used after each exciter. Also 1 x 4 i/p coupler and 4 x 1 O/P coupler has

been used in each transmitter.

Introduction of antenna:-

Antenna is usually a metallic device (as a rod or wire) used for radiating

and receiving the radio waves. The radio frequency power developed at

the final stage of transmitter is delivered through cables / feeders, without

themselves consuming any power; the path of EM waves picks up the

radio waves and delivers useful signals at the input of the receiver.

Tower: -

The tower of good height is required for mounting fm antenna since the

coverage of the transmitter is proportional to the height of tower. For a

100 m. Height, it is about 60km.

• Wide band usage from 88-108 MHz range.

• Omni directional horizontal pattern of field strength.

• Circular polarization for better reception.

• High gain for both vertical & horizontal signals.

• Sturdy design for maintenance free service.

• FM antenna at 82m. Height.

• TV antenna at 65 m. Height.

• Climbing ladder with cage up of 82 m. Height & free fall prevention system above this.

• Cable tray for mounting the rf feeder, mast light, power supply at each platform.

• The tower has been designed on the basis of latest wind speed specification issued by BSNL.

• A universal medium. Can be enjoyed at home, at work, and while driving. Most people listen to the

radio at one time or another during the day.

• This is the only means which can provide multi access two way communication.

• The cost of transmitting information through satellite is independent of distance involved

• Satellite can be used for two way communication or broadcast purpose with the covered area.

• Satellites are capable of handling very high bandwidth.

• It is possible to provide large coverage using satellite.

• Free creative help is usually available.

• Only an audio medium.

• Not as fast as using a phone or internet; could take a little bit.

• Radio is a background medium. Most listeners are doing something else while

listening, which means your ad has to work hard to be listened to and

understood.

• The line could get fuzzy, or not clear.