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.
ATOM CONSIST OF :
A) NUCLEUS
B) ORBITS
AN
BOHR’S 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
N
0
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
λ
(ANGS)
λ
(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
Sym
bols
Frequency
Range
Wavelength
Range
Typical sources
1
ELF
3 to 30 Hz
10,000 to
100,000 km
deeply-submerged submarine communication
2
SLF
30 to 300
Hz
1000 to
10,000 km
submarine communication, ac power grids
3
ULF
300 to 3
kHz
100 to 1000
km
earth quakes, earth mode communication
4
VLF
3 to 30
kHz
10 to 100 km
near-surface submarine communication,
5
LF
30 to 300
kHz
1 to 10 km
AM broadcasting, aircraft beacons
6
MF
300 to
3000 kHz
100 to 1000
m
AM broadcasting,
7
HF
3 to 30
MHz
10 to 100 m
Skywave long range radio communication
8
VHF
30 to 300
MHz
1 to 10 m
FM radio broadcast, television broadcast, DVB-T, MRI
9
UHF
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
SHF
3 to 30
GHz
1 to 10 cm
DBS satellite television broadcasting, WLAN (Wi-Fi), WiMAX, radars
11
EHF
30 to 300
GHz
1 to 10 mm
directed-energy weapon (Active Denial System), Security screening (Millimeter wav
scanner), intersatellite links, WiMAX, high resolution radar
VL
F
Very Low Frequency
VF
Voice Frequency
EL Extremely low
F Frequency
UL
F
Ultra Low Frequency
3 kHz
300
Hz
30
Hz
3 Hz
30
kHz
3 kHz
300
Hz
30
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
WAVE LENGTH
(l)=
( l ) METERS
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
WAVELENGTH
3 - 30 K Hz
30 - 300 K Hz
100 - 10 km
10,000 - 1000 m
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
300 - 3000 M Hz
100 - 10 cm
SHF
3000 - 30000 M Hz
10 - 01 cm
EHF
30000 - 300000 MHz
1 - 0.1 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 108 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 TYPE OF MODULATION ARE
(a) KEYING
(b) AMPLITUDE MODULATION
(c) FREQUENCY MODULATION
(d) PULSE 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
CARRIER
WAVE
CONSTANT
OF
THE
IS
KEPT
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 THESE SIDE BANDS.
AM CW
COMPRISES OF
CW FREQ
CW FREQ + AUDIO FREQ
CW FREQ - AUDIO FREQ
AM CW SIDEBANDS
SPECTRAL REPRESENTATIONS OF DSBAM 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,
WARMING UP THE SURFACE LAYER
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
GROUND
REFLECTED WAVES
RADIO SPECTRUM
ABREVIATION
VLF
LF
FREQUENCY
WAVELENGTH
3 - 30 K Hz
30 - 300 K Hz
100 - 10 km
10,000 - 1000 m
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
300 - 3000 M Hz
100 - 10 cm
SHF
3000 - 30000 M Hz
10 - 01 cm
EHF
30000 - 300000 MHz
1 - 0.1 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
SEVERE
VHF
ABOVE
LEAST
70 - 100 nm
NIL
LOS ONLY
ALONG SURFACE
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
α2
α1
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
α2 IS THE CRITICAL ANGLE
CRITICAL ANGLE
α2
α1
FOR THE SAME FREQUENCY AN INCREASE IN INCIDENCE
BEYOND α2 WOULD ENSURE AN UNINTERRUPTED
RETURN ALTHOUGH POWER MAY HAVE TO BE INCREASED
IF THE FREQUENCY WERE INCREASED AT α2 , 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
A
HIGHER
RANGE
WOULD
BE
HF COMMUNICATION
CRITICAL FREQUENCY fC FOR PREVAILING
ATMOSPHERIC CONDITIONS
MUF = fC X sec θi
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,
300 kHz
1 to 10 km
AM broadcasting, aircraft beacons
3000 kHz
100 to 1000 m
AM broadcasting,
30 MHz
10 to 100 m
Skywave long range radio communication
300 MHz
1 to 10 m
FM radio broadcast, television broadcast, DVB-T, MRI
3000 MHz
10 to 100 cm
30 GHz
1 to 10 cm
microwave oven, television broadcast, GPS, mobile phone communication (GSM, UMTS, 3G, H
WLAN (Wi-Fi), Bluetooth
DBS satellite television broadcasting, WLAN (Wi-Fi), WiMAX, rad
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
F
Very Low Frequency
VF
Voice Frequency
EL Extremely low
F Frequency
UL
F
Ultra Low Frequency
3 kHz
300
Hz
30
Hz
3 Hz
30
kHz
3 kHz
300
Hz
30
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 SQUELCH
LFO PRODUCES
LF 8000 K Hz
LF AMPLIFIERS
AMPLIFIES LF
AF AMPLIFIER
AMPLIFIES AF
Tuned frequency reciever
Qualities of reciever
superhetrodyne
QUESTIONS ?