BASIC RADIO THEORY

STRUCTURE OF AN ATOM
THERE ARE 108 ELEMENTS IN NATURE
ATOMS ARE THE SMALLEST PARTICLE OF AN
ELEMENT THAT SHOWS ITS PROPERTIES.
ATOMS

ARE BUILDING BRICKS OF ALL

MATTER AND MATTER IS ELECTRICAL IN

NATURE. AN ATOM CONSIST OF :
A)

NUCLEUS

B)

ORBITS

BOHRS ATOM

NUCLEUS
THE CENTRAL PART OF THE ATOM
CONTAINS :

PROTONS

( + ve CHARGE )

NEUTRONS

( NEUTRAL )

ORBITS
OUTER PART OF THE ATOM
CONTAINS ELECTRONS WHICH HAVE
A - ve CHARGE.
MASS OF ELECTRON IS NEGLIGIBLE.
CHARGE IS EQUAL AND OPPOSITE TO
THAT OF A PROTON.
ATOMIC NO = NO OF PROTONS
= NO OF ELECTRONS

ATOM
CONSTITUEN
T

SYMBOL

CHARGE

MASS

ELECTRONS

E-

-1

9.1 X 10-28 G

PROTONS

P+

+1

1836 X ELECTRON MASS

NEUTRONS

APPROXIMATELY THAT
OF P+

VALENCE SHELL & FREE ELECTRONS

THE OUTER SHELL IS CALLED VALANCE SHELL.
ELECTORNS IN OUTER SHELL ARE CALLED FREE
ELECTRONS.
THESE ELECTRONS IN OUTER SHELL CAN BE
EASILY DISLODGED.
THE NUMBER OF ELECTRONS WHICH CAN BE
ACCOMODATED IN ANY ORBIT IS 2 N SQUARE,
WHERE N IS NUMBER OF ORBIT.
SO IN THIRD ORBIT WE CAN ACCOMMODATE
2 * 3 * 3 = 18 ELECTRONS

VALENCE SHELL & FREE ELECTRONS

IF THE OUTER SHELL THAT IS VALANCE SHELL
CONTAINS MORE THAN FOUR ELECTRONS WE
CALL IT CONDUCTOR. EXAMPLE
IF THE OUTER SHELL THAT IS VALANCE SHELL
CONTAINS LESS THAN FOUR ELECTRONS WE
CALL IT INSULATOR. EXAMPLE
IF THE OUTER SHELL THAT IS VALANCE SHELL
CONTAINS MORE THAN FOUR ELECTRONS WE
CALL IT SEMI CONDUCTOR. EXAMPLE

ELECTROMOTIVE FORCE
FOR A CHARGE TO FLOW THROUGH, A
CONDUCTOR REQUIRES A FORCE.
THIS FORCE IS PROVIDED BY THE
POTENTIAL DIFFERENCE APPLIED
ACROSS THE TERMINALS.

ALTERNATING CURRENT
THE CURRENT THAT PERIODICALLY
CHANGES
DIRECTION
&
CONTINUOUSLY CHANGES MAGNITUDE
IT CAN BE PRODUCED BY :
a) STATIONARY COIL AND MOVING
MAGNETIC FIELD
b) STATIONARY MAGNETIC FIELD AND
MOVING COIL

THE
ELECTROMAGNETIC
SPECTRUM

THE ELECTROMAGNETIC
SPECTRUM

THE VISIBLE SPECTRUM

SPECTRUM OF ELECTROMAGNETIC RADIATION

REGION

(ANGS)

(cm)

C
(HZ)

ENERGY
(EV)

RADIO

> 109

> 10

< 3 X 109

< 10-5

MICRO

109 - 106

10 - 0.01

3 X 109 - 3 X 1012

10-5 - 0.01

INFRARED

106 - 7000

0.01 - 7 X 10-5

3 X 1012 - 4.3 X 1014

0.01 - 2

7000 - 4000

7 X 10-5
4 X 10-5

4.3 X 1014
7.5 X 1014

2-3

UV

4000 - 10

4 X 10-5 - 10-7

7.5 X 1014 - 3 X 1017

3 - 103

X-RAYS

10 - 0.1

10-7 - 10-9

3 X 1017 - 3 X 1019

103 - 105

GAMMA

< 0.1

< 10-9

> 3 X 1019

> 105

VISIBLE

RADIO WAVES
RADIO WAVE IS AN ELECTRO-MAGNETIC WAVE
WHICH

HAS

ELECTRICAL

AND

MAGNETIC

COMPONENT PERPENDICULAR TO EACH OTHER.

IN FREE SPACE ALL RADIO WAVES & EM WAVES
TRAVEL

IN A STRAIGHT LINE AT THE SPEED OF

LIGHT.
ITS FREQUENCY IS FROM 3 K Hz TO 300 G Hz

Table of ITU Radio Bands

Sy
mb
ols

Frequen
cy
Range
3 to 30
Hz

ELF

SLF

30 to
300 Hz

Wavelengt
h Range
10,000 to
100,000
km
1000 to
10,000 km

ULF

300 to 3
kHz

100 to
1000 km

earth quakes, earth mode communication

VLF

3 to 30
kHz

10 to 100
km

near-surface submarine communication,

LF

1 to 10 km

AM broadcasting, aircraft beacons

MF

100 to
1000 m

AM broadcasting,

HF

10 to 100
m

Skywave long range radio communication

VH
F

30 to
300 MHz

1 to 10 m

FM radio broadcast, television broadcast, DVB-T, MRI

UH
F

300 to
3000
MHz

10 to 100
cm

microwave oven, television broadcast, GPS, mobile phone

communication (GSM, UMTS, 3G, HSDPA), cordless phones (DECT
WLAN (Wi-Fi), Bluetooth

10

SH
F

3 to 30
GHz

1 to 10 cm

DBS satellite television broadcasting, WLAN (Wi-Fi), WiMAX, rada

11

EH
F

30 to
300 GHz

1 to 10
mm

directed-energy weapon (Active Denial System), Security screenin

(Millimeter wave scanner), intersatellite links, WiMAX, high
resolution radar

30 to
300 kHz
300 to
3000
kHz
3 to 30
MHz

Typical sources
deeply-submerged submarine communication
submarine communication, ac power grids

VL Very Low
F Frequency
VF Voice Frequency
EL
F
UL
F

Extremely low
Frequency
Ultra Low
Frequency

3
kHz
300
Hz
30
Hz

30
kHz
3
kHz
300
Hz
30
3 Hz
Hz

OSCILLATOR WAVES

THE OSCILLATOR IS AN ELECTRONIC

DEVICE FOR CREATING VOLTAGES
THAT CAN BE MADE TO SURGE BACK
AND
FORTH
AT
WHATEVER
FREQUENCY IS DESIRED
WHEN RF ENERGY IS APPLIED TO A
CONDUCTOR
(ANTENNA),
THE
ANTENNA
RESONATES
(VIBRATES).
THE ANTENNA PROVIDES A MEANS OF
RADIATING THE ELECTROMAGNETIC
(EM) WAVES INTO THE AIR

TYPES OF OSCILLATOR
MASTER OSCILLATOR
CRYSTAL OSCILLATOR
BEAT FREQUENCY OSCILLATOR
LOCAL FREQUENCY OSCILLATOR

PHOTO OF OSCILLATOR

ELECTRICAL AND MAGNETIC FIELD

SPEED OF LIGHT = ELECTRICAL

FIELD
MAGNETIC FIELD

THEREFORE MAGNETIC
COMPONENT IS VERY SMALL

TERMS AND DEFINITIONS

1. CYCLE ONE COMPLETE SERIES OF VALUES OR ONE COMPLETE

PROCESS, RETURNING TO VALUES OF ORIGIN.
2. FREQUENCY (f ) No OF CYCLES/SEC. UNITS ARE HERTZ.
1 Hz = 1 C/S, 1 K Hz = 10 C/S
1 M Hz = 10 C/S, 1 G Hz = 10 C/S

TERMS & DEFINITIONS

CYCLE :

ONE COMPLETE SERIES OF

VALUES OR ONE COMPLETE PROCESS IS
ONE CYCLE.

WAVELENGTH : THE PHYSICAL

DISTANCE TRAVELLED BY THE WAVE IN

ONE CYCLE.

AMPLITUDE : THE MAXIMUM

DISPLACEMENT OF THE WAVE ABOUT ITS

MEAN POSITION.

FREQUENCY : THE NO OF CYCLES

OCCURRING IN ONE SECOND.

RELATIONSHIP BETWEEN FREQUENCY WAVELENGTH

FREQUENCY ( f ) Hz =

SPEED OF LIGHT ( c ) METERS/SEC

WAVE LENGTH ( ERS

WAVE LENGTH ( =

SPEED OF LIGHT ( c ) METERS/SEC

FREQUENCY ( f ) Hz

RELATIONSHIP BETWEEN FREQUENCY WAVELENGTH

FOR CALCULATION PURPOSE CONVERT FREQUENCY

INTO METERS AND WAVE LENGTH INTO METERS
UNIT OF FREQUENCY I CYCLE PER SECOND = 1 Hz
1000 Hz = 1 KILO Hz
1000 K Hz = 1 MEGA Hz
1000 M Hz = 1 GIGA Hz

100 CM = 1 METERS

RADIO SPECTRUM
ABREVIATION
VLF

LF

FREQUENCY
3 - 30 K Hz
30 - 300 K Hz

WAVELENGTH
100 - 10 km
10,000 - 1000

MF

300 - 3000 K Hz

1000 - 100 m

HF

3 - 30 M Hz

100 - 10 m

30 - 300 M Hz

10 - 01 m

VHF
UHF
SHF

300 - 3000 M Hz

100 - 10 cm

3000 - 30000 M Hz

10 - 01 cm

PHASE
THE INSTANTANEOUS POSITION OF A
PARTICLE IN A WAVE OR POSITION OF A
PARTICLE AT A GIVEN TIME
TWO WAVES OF THE SAME FREQUENCY
WHEN TRANSMITTED AT THE SAME TIME
ARRIVE AT A POINT IN PHASE
PHASE DIFFERENCE IS THE ANGULAR
DIFFERENCE
BETWEEN
THE
CORRESPONDING
POINTS
ON
THE
WAVEFORMS

PHASE

PHASE DIFFERENCE

EXAMPLES

SPEED OF RADIO WAVES

SPEED OF LIGHT IS 299,792,458 m/sec
WHICH IS APPROX
=
3 X 10 8 m/sec
= 162,000 Nm/sec
= 186,000 Sm/sec
= 300,000 km/sec
EFRACTIVE INDEX IS RATIO OF SPEED OF
LIGHT IN A MEDIA AND SPEED OF LIGHT IN
VACCUM
SPEED OF RADIO WAVE IS MOST IN VACCUM
SPEED OF RADIO WAVE IS MORE OVER
WATER THAN LAND

POLAR DIAGRAM
IT IS THE LINE JOINING POINTS OF
EQUAL INTENSITY AT A GIVEN TIME.
OR
A LINE SO PLOTTED THAT IT GIVES
THE RELATIVE VALUES OF THE
FIELD STRENGTHS OR THE POWER
RADIATED AT VARIOUS POINTS IN
BOTH HORIZONTAL AND VERTICAL
PLANES.

POLAR DIAGRAM

POLARIZATION
ELECTRICAL AND MAGNETIC
FIELDS ARE PRODUCED WHEN E/M
WAVES TRAVEL THROUGH SPACE
THESE FIELDS ARE AT RIGHT
ANGLES TO EACH OTHER
A VERTICAL AERIAL TRANSMITS
THE ELECTRICAL FIELD IN A
VERTICAL PLANE

POLARISATION

POLARISATION
ANTENNAS ARE DESIGNED TO PICK UP
ELECTRICAL COMPONENT ONLY

MODULATION
PROCESS
OF
IMPRESSING
INTELLIGENCE
ON
A
RADIO
CARRIER WAVE (CW) IN ORDER TO
CONVEY INFORMATION
VARIOUS
ARE

TYPE

OF

MODULATION

(a) KEYING
(b) AMPLITUDE MODULATION
(c) FREQUENCY MODULATION

NEED FOR MODULATION

1. PRACTICAL ANTENNA HEIGHT:
LOWER THE FREQUENCY LARGER
THE ANTENNA.
2. OPERATING RANGE :

LOWER THE
FREQUENCY LOWER THE RANGE.

3.

WIRELESS COMMUNICATION :
AUDIO
FREQUENCIES
WHEN
TRANSMITTED
THROUGH
SPACE
GET ATTENUATED.

TYPES OF MODULATION
AMPLITUDE MODULATION
FREQUENCY MODULATION
PULSE MODULATION

AMPLITUDE MODULATION
THE AMPLITUDE OF THE
CARRIER IS CHANGED IN
ACCORDANCE
WITH
THE
INTENSITY OF THE SIGNAL
THE FREQUENCY OF THE
CARRIER
WAVE
IS
KEPT
CONSTANT

AMPLITUDE MODULATION

AMPLITUDE MODULATION
(AM)

MODULATION DEPTH
THE RATIO OF THE AMPLITUDES
OF THE
SIGNAL TO
THE
UNMODULATED CARRIER WAVE
EXPRESSED IN PERCENTAGE
MOD. DEPTH = AMPLITUDE OF SIGNAL *100
AMPLITUDE OF CW

TEMPORAL REPRESENTATIONS OF
DSB-AM SIGNALS

IMPORTANCE OF MOD. DEPTH

1. IF DEPTH LESS THAN 50% - AUDIO
SIGNALS NOT VERY STRONG
2. IF DEPTH MORE THAN 75% - AUDIO
SIGNALS ARE STRONG AND CLEAR
3. IF DEPTH MORE THAN 100% DISTORTION IN RECEPTION &
WASTAGE OF POWER

GREATER THE MODULATION, LESSER

THE RANGE

FREQUENCY MODULATION
THE FREQUENCY OF THE
CARRIER IS CHANGED
IN
ACCORDANCE
WITH THE
INTENSITY
OF THE
AF
SIGNAL
THE AMPLITUDE OF THE
CARRIER
WAVE
IS
KEPT
CONSTANT

FM

ADVANTAGES OF FM
1. NOISELESS RECEPTION
2.

HIGH EFFICIENCY

3. HI-FI RECEPTION.

DISADVANTAGES OF FM
1. COMPLICATED RECEIVERS
2. OPERATES ON VHF, HENCE
RANGE IS LESS.

COMPARISON OF AM AND FM
AM

FM

1. TRANSMITTER
2. RECEIVER
COMPLEX
3. STATIC

COMPLEX
SIMPLE

SIMPLE

EXCESSIVE

4. BAND WIDTH
5. POWER FOR TX

SMALL
LARGE

ALMOST
NIL
LARGE
SMALL

SIDE BANDS
WHENEVER A CONTINUOUS
WAVE IS MODULATED BY A
FREQUENCY
LOWER THAN
ITSELF,
ADDITIONAL
FREQUENCIES
OCCUR
ON
EITHER SIDE OF THE CW
FREQUENCY
THESE
ARE
CALLED SIDE BANDS.
THE
INTELLIGENCE IS CARRIED IN

AM CW
COMPRISES OF
CW FREQ
CW FREQ + AUDIO
FREQ
CW FREQ - AUDIO
FREQ

AM CW SIDEBANDS

SPECTRAL REPRESENTATIONS OF
DSB-AM SIGNALS

SINGLE SIDE BANDS

ADVANTAGES
(a ) LESSER FREQUENCY SPACE
REQUIRED RESULTING IN
LESSER CONGESTION
(b ) LESSER POWER REQUIRED.
GREATER RANGES

FM CW
LARGER BAND WIDTH DUE
MULTIPLE SIDE BANDS. THIS
IS WHY FM CW CAN OPERATE
MAINLY IN VHF BAND.

FM CW

PULSE MODULATION
PHASE MODULATION CONSISTS OF
PULSE AMPLITUDE
PULSE FREQUENCY
PULSE WIDTH
MAINLY USED IN RADARS

ELECTROMAGNETIC WAVES
WHEN WAVES MEET A BOUNDARY, WHERE
THE MEDIUM CHANGES, THEY MAY:
REFLECT - BOUNCE BACK
REFRACT - GO THROUGH THE BOUNDARY,
USUALLY
CHANGING
SPEED
AND
DIRECTION
GET ABSORBED - GIVE UP THEIR ENERGY,

DIFFRACTION
WHEN WAVES MEET A GAP IN A BARRIER, THEY
CARRY ON THROUGH THE GAP. THIS MAY SEEM
OBVIOUS, BUT WHAT HAPPENS ON THE FAR SIDE
OF THE GAP ISN'T SO STRAIGHTFORWARD.
THE WAVES ALWAYS 'LEAK' TO SOME EXTENT
INTO THE SHADOW AREA BEYOND THE GAP. THIS
IS CALLED DIFFRACTION
THE EXTENT OF THE SPREADING DEPENDS ON
HOW THE WIDTH OF THE GAP COMPARES TO THE
WAVELENGTH OF THE WAVES

GENERAL PROPERTIES OF RADIO WAVES

IN A GIVEN MEDIUM, RADIO WAVES TRAVEL AT A
CONSTANT SPEED. (FREE SPACE - 3 X 10 M/S)
WHEN PASSING FROM ONE MEDIUM TO ANOTHER
OF DIFFERENT REFRACTIVE INDEX THE VELOCITY
OF THE WAVES CHANGES.
THEY ARE ALSO
DEFLECTED TOWARDS THE MEDIUM OF HIGHER
REFRACTIVE INDEX
RADIO WAVES ARE REFLECTED BY
COMMENSURATE WITH WAVELENGTHS.
UNINFLUENCED.
RADIO
STRAIGHT LINES.

WAVES

OBJECTS

TRAVEL

IN

TYPES OF RADIO WAVES

GROUND WAVES
SURFACE WAVES

SKY WAVES
SPACE WAVES
DIRECT WAVES

WAVES

GROUND
REFLECTED

RADIO SPECTRUM
ABREVIATION
VLF

LF

FREQUENCY
3 - 30 K Hz
30 - 300 K Hz

WAVELENGTH
100 - 10 km
10,000 - 1000

MF

300 - 3000 K Hz

1000 - 100 m

HF

3 - 30 M Hz

100 - 10 m

30 - 300 M Hz

10 - 01 m

VHF
UHF
SHF

300 - 3000 M Hz

100 - 10 cm

3000 - 30000 M Hz

10 - 01 cm

SURFACE WAVES
DIFFRACTION

DIFFRACTION

FREQUENCY

SURFACE WAVES
ATTENUATION
FACTORS
1. SURFACE

ATTENUATION

2. FREQUENCY

FREQUENCY

SURFACE WAVES

SUMMARY OF GROUND RANGES FROM RADIO

WAVES
ATTENUATION

DIFFRACTION

VLF LEAST

MAXIMUM

LF

LESS

REDUCING

MF

INCREASING

REDUCING

RANGE
3000 - 4000 nm
~ 1500 nm

300 - 500 nm LAND

~1000 nm OVER SEA

HF
VHF

SEVERE

LEAST
NIL

70 - 100 nm
LOS ONLY

DISADVANTAGES OF LOW FREQUENCIES

LOW EFFICIENCY AERIALS
SEVERE STATIC
HIGH INSTALLATION COST AND POWER REQT

SPACE WAVES

REFRACTIVE INDEX ( n ) OF ATMOSPHERE IS A FUNCTION OF

PRESSURE, TEMP & HUMIDITY
AS ALT INCREASES, n REDUCES. AS A RESULT, WAVES
REFRACT TOWARDS EARTH CAUSING RANGE TO INCREASE

D = 1.25

HT

1.25

HR

DUCT PROPAGATION / SUPERREFRACTION

IONOSPHERE
U/V RAYS
ELECTRONS

GAS MOLECULES

POSITIVE IONS : TOO HEAVY TO

INFLUENCE
LEVEL OF IONISATION : EXTENT OF
REFRACTION

THE IONOSPHERE
ELECRICALLY CONDUCTING SPHERE
D LAYER : 50 - 100 KM, AVG 75 KM
E LAYER : 100 - 150 KM, AVG 125 KM
F LAYER : 150 - 350 KM, AVG 225 KM

DENSITY OF IONOSPHERE
D LEAST , F MAXIMUM
DIURNAL ACTIVITY : DAY -- DENSITY INCREASES
REFLECTING HT MOVES DN
SEASONAL ACTIVITY : MAX -- EARTH CLOSEST
TO SUN. CAUSES SPORADIC ACTIVITY,
RESULTING IN SPORADIC-E RECEPTION IN VHF
BAND (~150 MHz )

11 YEAR SUN-SPOT CYCLE : ENHANCED UV & XRADIATION, VHF SIGNALS MAY RETURN

11 YEAR SUNSPOT CYCLE

ATTENUATION IN ATMOSPHERE
DENSITY OF LAYERS :
GREATER DENSITY -- GREATER

ATTENUATION

FREQ IN USE
LOWER FREQ -- GREATER ATTENUATION
PENETRATION DEPTH
HIGHER THE FREQ -- GREATER THE PENETRATIONGREATER ATTENUATION

RANGES AVAILABLE
TRANSMISSION POWER
DEPTH OF PENETRATION
ANGLE OF INCIDENCE -- MAX RANGE BY WAVE
LEAVING TANGENTIAL TO EARTH

CRITICAL ANGLE

2
1

FOR A GIVEN FREQUENCY AS THE ANGLE OF INCIDENCE

IS INCREASED, DEGREE OF REFRACTION INCREASES
SUCH THAT AN ANGLE IS REACHED WHERE TIR TAKES
PLACE

2 IS

THE CRITICAL ANGLE

CRITICAL ANGLE

2
1
FOR THE SAME FREQUENCY AN INCREASE IN INCIDENCE
BEYOND

WOULD

ENSURE

AN

POWER

MAY

RETURN ALTHOUGH
INCREASED

UNINTERRUPTED
HAVE

IF THE FREQUENCY WERE INCREASED AT

TO

BE

2 ,

THE

CRITICAL ANGLE WOULD INCREASE AS THE WAVES

WOULD TEND TO ESCAPE (DUE TO HIGHER ELECTRON
DENSITY AND LOWER INCIDENCE REQUIREMENT)
THIS ALSO
OBTAINED.

MEANS

HIGHER

RANGE

WOULD

BE

HF COMMUNICATION
CRITICAL FREQUENCY fC FOR PREVAILING
ATMOSPHERIC CONDITIONS

MUF = fC X sec i
LUHF

NIGHT TRANSMISSION

RANGES AT NIGHT ARE GREATER THAN DAY

TIME
IONIZATION LAYER HT

DEPTH OF PENETRATION

NIGHT TRANSMISSION
RECOMBINATION
REFLECTING HT MOVES UP

RANGE INCREASES, GREATER SKIP DISTANCE

o 30 Hz

10,000 to 100,000
km

deeply-submerged submarine communication

o 300 Hz

1000 to 10,000 km

submarine communication, ac power grids

to 3 kHz

100 to 1000 km

earth quakes, earth mode communication

30 kHz

10 to 100 km

near-surface submarine communication,

1 to 10 km

AM broadcasting, aircraft beacons

to 3000
kHz

100 to 1000 m

AM broadcasting,

30 MHz

10 to 100 m

Skywave long range radio communication

1 to 10 m

FM radio broadcast, television broadcast, DVB-T, MRI

300 kHz

300 MHz

to 3000
MHz

10 to 100 cm

30 GHz

1 to 10 cm

microwave oven, television broadcast, GPS, mobile phone communication (GSM, UMTS
(DECT), WLAN (Wi-Fi), Bluetooth

DBS satellite television broadcasting, WLAN (Wi-Fi), WiMAX, r

NIGHT TRANSMISSION

LOWERING OF FREQUENCY ADJUSTS SKIP DISTANCE

LOWER FREQUENCIES REFLECT FROM LOWER HTS
REQUIRE SMALLER CRITICAL ANGLE

SKIP DISTANCE AND DEAD SPACE

FOR A GIVEN FREQ, SKIP DIST VARIOUS WITH TIME OF THE DAY
( AND ALSO SEASONS)
DEAD SPACE POSSIBLE ONLY IN HF

VL Very Low
F Frequency
VF Voice Frequency
EL
F
UL
F

Extremely low
Frequency
Ultra Low
Frequency

3
kHz
300
Hz
30
Hz

30
kHz
3
kHz
300
Hz
30
3 Hz
Hz

ANTANNAE
An antenna (or aerial) is a transducer designed to transmit or
receive electromagnetic waves. In other words, antennas convert
electromagnetic waves into electrical currents and vice versa.
They are used with waves in the radio part of the
electromagnetic spectrum, that is, radio waves, and are a
necessary part of all radio equipment.
They are used with waves in the radio part of the
electromagnetic spectrum, that is, radio waves, and are a
BEGINNING OR END all radio equipment.

An antenna (or aerial) is a

transducer designed to transmit or
receive electromagnetic waves. In
other words, antennas convert
electromagnetic waves into electrical
currents and vice versa. They are used
with waves in the radio part of the
electromagnetic spectrum, that is,
radio waves, and are a necessary part
of all radio equipment.

 1.
Atannae gain is ratio between radiation
intensity in a given direction and that produced by an
ideal antannae which transmits in all direction. What is
loop antannae with two arms used in ADF

2.
EIRP stands for effective isotropically
radiated power. it is the amount of power that a
theoretical isotropical antennae would emit to produce
peak power in direction of maximum antannae gain.
EIRP = power at transmitter - cable loss + antannae gain

microphone

speaker

TRANSMITTER BLOCK DIAGRAM

ANTANNAE
RADIATES RF+AF

OSCILLATOR
PRODUCES RF

RF AMPLIFIER
AMPILFIES RF

MODULATOR
MODULATES RF
WITH AF

MICROPHONE
CONVERTS AW
TO AF

AF AMPLIFIER
AMPLIFIES AF

POWER AMPLIFIER
AMPLIFIES RF+AF

RECEIVER BLOCK DIAGRAM

ANTANNAE
RECEIVES RF+AF
SPEAKER
CONVERTS AF
INTO AW
AMPLIFIER
AMPLIFIES RF+AF

DEMODULATOR
SUPRESSES RF
AND PRODUCES
AF

AF AMPLIFIER
AMPLIFIES AF

SUPERHETORDYNE RECEIVER BLOCK DIAGRAM

ANTANNAE
RECEIVES RF+AF
8500 K Hz

AMPLIFIER
AMPLIFIES RF+AF

MIXER MIXES RF+AF

AND LF AND
PRODUCES IF 500 K Hz

SPEAKER
CONVERTS AF INTO
AW

DETECTOR
CONVERTS
IF INTO AF

BFO AVC

LFO PRODUCES LF
8000 K Hz

LF AMPLIFIERS
AMPLIFIES LF

SQUELCH

AF AMPLIFIER
AMPLIFIES AF

Tuned frequency reciever

Qualities of reciever

superhetrodyne

QUESTIONS ?