STRUCTURE OF AN ATOM

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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

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BOHRS ATOM
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NUCLEUS

• THE CENTRAL PART OF THE ATOM CONTAINS
• PROTONS ( ve CHARGE )
• NEUTRONS ( NEUTRAL )

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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

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ATOM
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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
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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
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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.

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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

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SPECTRUM OF ELECTROMAGNETIC RADIATION
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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
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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
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TYPES OF OSCILLATOR
MASTER OSCILLATOR CRYSTAL OSCILLATOR BEAT
FREQUENCY OSCILLATOR LOCAL FREQUENCY OSCILLATOR
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PHOTO OF OSCILLATOR
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ELECTRICAL AND MAGNETIC FIELD
SPEED OF LIGHT ELECTRICAL FIELD
MAGNETIC FIELD
THEREFORE MAGNETIC COMPONENT IS VERY SMALL
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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

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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.

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RELATIONSHIP BETWEEN FREQUENCY WAVELENGTH
FREQUENCY ( f ) Hz SPEED OF LIGHT ( c )
METERS/SEC WAVE LENGTH ( l ) METERS WAVE
LENGTH ( l ) SPEED OF LIGHT ( c )
METERS/SEC FREQUENCY ( f ) Hz
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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
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RADIO SPECTRUM ABREVIATION
FREQUENCY WAVELENGTH
VLF 3 - 30 K Hz
100 - 10 km LF
30 - 300 K Hz
10,000 - 1000 m
MF 300 - 3000 K Hz
1000 - 100 m
HF 3 - 30 M Hz
100 - 10 m
VHF 30 - 300 M Hz
10 - 01 m
UHF 300 - 3000 M Hz
100 - 10 cm
SHF 3000 - 30000 M Hz
10 - 01 cm
EHF 30000 - 300000
MHz 1 - 0.1 cm
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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

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PHASE
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PHASE DIFFERENCE
EXAMPLES
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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

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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.

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POLAR DIAGRAM

• 
  
  

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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

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• POLARISATION

POLARISATION
ANTENNAS ARE DESIGNED TO PICK UP ELECTRICAL
COMPONENT ONLY
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• 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

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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.

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TYPES OF MODULATION

• AMPLITUDE MODULATION
• FREQUENCY MODULATION
• PULSE MODULATION

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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

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AMPLITUDE MODULATION
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AMPLITUDE MODULATION (AM)
   
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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

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TEMPORAL REPRESENTATIONS OF DSB-AM SIGNALS  
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IMPORTANCE OF MOD. DEPTH

• 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
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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

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FM
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ADVANTAGES OF FM

• 1. NOISELESS RECEPTION
• 2. HIGH EFFICIENCY
• 3. HI-FI RECEPTION.

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DISADVANTAGES OF FM

• 1. COMPLICATED RECEIVERS
• 2. OPERATES ON VHF, HENCE
  
  RANGE IS LESS.

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• COMPARISON OF AM AND FM
• 
  
• AM FM
• 1. TRANSMITTER
  COMPLEX SIMPLE
• 2. RECEIVER
  SIMPLE COMPLEX
• 3. STATIC
  EXCESSIVE ALMOST
  NIL
• 4. BAND WIDTH
  SMALL LARGE
• 5. POWER FOR TX LARGE
  SMALL

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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.
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AM CW COMPRISES OF CW FREQ CW
FREQ AUDIO FREQ CW FREQ - AUDIO FREQ
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AM CW SIDEBANDS
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SPECTRAL REPRESENTATIONS OF DSB-AM SIGNALS  
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SINGLE SIDE BANDS
ADVANTAGES (a ) LESSER FREQUENCY SPACE REQUIRED
RESULTING IN LESSER CONGESTION (b ) LESSER POWER
REQUIRED. GREATER RANGES
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FM CW LARGER BAND WIDTH DUE MULTIPLE SIDE
BANDS. THIS IS WHY FM CW CAN OPERATE MAINLY IN
VHF BAND.
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FM CW
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PULSE MODULATION

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

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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
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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
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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
OBJECTS COMMENSURATE WITH WAVELENGTHS. UNINFLUENCE
D. RADIO WAVES TRAVEL IN STRAIGHT LINES.
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TYPES OF RADIO WAVES GROUND WAVES SKY
WAVES SURFACE WAVES SPACE WAVES
DIRECT WAVES
GROUND REFLECTED
WAVES
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RADIO SPECTRUM ABREVIATION
FREQUENCY WAVELENGTH
VLF 3 - 30 K Hz
100 - 10 km LF
30 - 300 K Hz
10,000 - 1000 m
MF 300 - 3000 K Hz
1000 - 100 m
HF 3 - 30 M Hz
100 - 10 m
VHF 30 - 300 M Hz
10 - 01 m
UHF 300 - 3000 M Hz
100 - 10 cm
SHF 3000 - 30000 M Hz
10 - 01 cm
EHF 30000 - 300000
MHz 1 - 0.1 cm
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SURFACE WAVES DIFFRACTION
DIFFRACTION
FREQUENCY
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SURFACE WAVES ATTENUATION

• FACTORS
• SURFACE
• FREQUENCY

ATTENUATION
FREQUENCY
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SURFACE WAVES
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SUMMARY OF GROUND RANGES FROM RADIO WAVES
ATTENUATION DIFFRACTION RANGE VLF
LEAST MAXIMUM 3000 - 4000
nm LF LESS REDUCING
1500 nm MF INCREASING REDUCING 300
- 500 nm LAND 1000 nm OVER SEA HF
SEVERE LEAST 70
- 100 nm

VHF NIL
LOS ONLY ABOVE ALONG SURFACE
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DISADVANTAGES OF LOW FREQUENCIES LOW EFFICIENCY
AERIALS SEVERE STATIC HIGH INSTALLATION COST
AND POWER REQT
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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
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DUCT PROPAGATION / SUPERREFRACTION
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IONOSPHERE
U/V RAYS
ELECTRONS
GAS MOLECULES
POSITIVE IONS TOO HEAVY TO INFLUENCE LEVEL OF
IONISATION EXTENT OF REFRACTION
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PROPAGATION SKY WAVES
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
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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 X-RADIATION, VHF SIGNALS MAY RETURN
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11 YEAR SUNSPOT CYCLE
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ATTENUATION IN ATMOSPHERE DENSITY OF LAYERS
GREATER DENSITY -- GREATER ATTENUATION FREQ
IN USE LOWER FREQ -- GREATER ATTENUATION
PENETRATION DEPTH HIGHER THE FREQ -- GREATER THE
PENETRATION-GREATER ATTENUATION
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RANGES AVAILABLE TRANSMISSION POWER DEPTH OF
PENETRATION ANGLE OF INCIDENCE -- MAX RANGE BY
WAVE LEAVING TANGENTIAL TO EARTH
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CRITICAL ANGLE
a2
a1
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
a2 IS THE CRITICAL ANGLE
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CRITICAL ANGLE
a2
a1
FOR THE SAME FREQUENCY AN INCREASE IN INCIDENCE
BEYOND a2 WOULD ENSURE AN UNINTERRUPTED RETURN
ALTHOUGH POWER MAY HAVE TO BE INCREASED IF THE
FREQUENCY WERE INCREASED AT a2 , THE CRITICAL
ANGLE WOULD INCREASE AS THE WAVES WOULD TEND TO
ESCAPE (DUE TO HIGHER ELECTRON DENSITY AND LOWER
INCIDENCE REQUIREMENT) THIS ALSO MEANS A HIGHER
RANGE WOULD BE OBTAINED.
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HF COMMUNICATION CRITICAL FREQUENCY fC FOR
PREVAILING ATMOSPHERIC CONDITIONS MUF fC X sec
?i LUHF
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NIGHT TRANSMISSION
RANGES AT NIGHT ARE GREATER THAN DAY TIME
IONIZATION LAYER HT



DEPTH OF PENETRATION
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NIGHT TRANSMISSION
RECOMBINATION REFLECTING HT MOVES UP
RANGE INCREASES, GREATER SKIP DISTANCE
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NIGHT TRANSMISSION
LOWERING OF FREQUENCY ADJUSTS SKIP
DISTANCE LOWER FREQUENCIES REFLECT FROM LOWER
HTS REQUIRE SMALLER CRITICAL ANGLE
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• 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

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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.
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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.
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• 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
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• 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

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microphone
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speaker
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TRANSMITTER BLOCK DIAGRAM
ANTANNAE RADIATES RFAF
OSCILLATOR PRODUCES RF
RF AMPLIFIER AMPILFIES RF
MODULATOR MODULATES RF WITH AF
POWER AMPLIFIER AMPLIFIES RFAF
MICROPHONE CONVERTS AW TO AF
AF AMPLIFIER AMPLIFIES AF
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RECEIVER BLOCK DIAGRAM
ANTANNAE RECEIVES RFAF
SPEAKER CONVERTS AF INTO AW
DEMODULATOR SUPRESSES RF AND PRODUCES AF
AMPLIFIER AMPLIFIES RFAF
AF AMPLIFIER AMPLIFIES AF
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SUPERHETORDYNE RECEIVER BLOCK DIAGRAM
ANTANNAE RECEIVES RFAF 8500 K Hz
AMPLIFIER AMPLIFIES RFAF
SPEAKER CONVERTS AF INTO AW
DETECTOR CONVERTS IF INTO AF
MIXER MIXES RFAF AND LF AND PRODUCES IF 500 K Hz
AF AMPLIFIER AMPLIFIES AF
BFO AVC SQUELCH
LF AMPLIFIERS AMPLIFIES LF
LFO PRODUCES LF 8000 K Hz
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Tuned frequency reciever
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Qualities of reciever
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superhetrodyne
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