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.

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

BOHR’S ATOM

NUCLEUS THE CENTRAL PART OF THE ATOM

CONTAINS :

PROTONS ( + ve CHARGE )

NEUTRONS ( NEUTRAL )

• 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

ORBITS

CONSTITUENT

SYMBOL CHARGE MASS

ELECTRONS E- -1 9.1 X 10-28 G

PROTONS P+ +1 1836 X ELECTRON MASS

NEUTRONS N 0APPROXIMATELY THAT

OF P+

ATOM

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

REGIONλ

(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

VISIBLE7000 - 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

SPECTRUM OF ELECTROMAGNETIC RADIATION

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

RADIO WAVES

Table of ITU Radio Bands

Symbols

Frequency

Range

Wavelength Range

Typical sources

1 ELF3 to 30

Hz

10,000 to 100,000

kmdeeply-submerged submarine communication

2 SLF30 to

300 Hz1000 to

10,000 kmsubmarine communication, ac power grids

3 ULF300 to 3

kHz100 to

1000 kmearth quakes, earth mode communication

4 VLF3 to 30

kHz10 to 100

kmnear-surface submarine communication,

5 LF30 to

300 kHz1 to 10 km AM broadcasting, aircraft beacons

6 MF300 to 3000 kHz

100 to 1000 m

AM broadcasting,

7 HF3 to 30

MHz10 to 100

mSkywave long range radio communication

8 VHF30 to

300 MHz1 to 10 m FM radio broadcast, television broadcast, DVB-T, MRI

9 UHF300 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

10SHF

3 to 30 GHz

1 to 10 cm DBS satellite television broadcasting, WLAN (Wi-Fi), WiMAX, radars

11EHF

30 to 300 GHz

1 to 10 mm

directed-energy weapon (Active Denial System), Security screening (Millimeter wave scanner), intersatellite links, WiMAX, high

resolution radar

VLF

 Very Low Frequency

 3 kHz

 30 kHz

VF  Voice Frequency 300 Hz

 3 kHz

ELF

 Extremely low Frequency

 30 Hz

 300 Hz

ULF

 Ultra Low Frequency

 3 Hz 30 Hz

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

OSCILLATOR WAVES

MASTER OSCILLATOR

CRYSTAL OSCILLATOR

BEAT FREQUENCY OSCILLATOR

LOCAL FREQUENCY OSCILLATOR

TYPES OF 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 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

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 WAVESSPEED OF LIGHT IS 299,792,458 m/secWHICH 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 VACCUMSPEED 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 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 COMPLEX SIMPLE

2. RECEIVER SIMPLE COMPLEX

3. STATIC EXCESSIVE ALMOST NIL

4. BAND WIDTH SMALL LARGE

5. POWER FOR TX 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 DSB-AM SIGNALS

ADVANTAGES

(a ) LESSER FREQUENCY SPACE REQUIRED RESULTING IN LESSER CONGESTION

(b ) LESSER POWER REQUIRED. GREATER RANGES

SINGLE SIDE BANDS

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

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

ELECTROMAGNETIC WAVES

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 OBJECTS COMMENSURATE WITH WAVELENGTHS.

UNINFLUENCED. RADIO WAVES TRAVEL IN STRAIGHT LINES.

TYPES OF RADIO WAVES

GROUND WAVES SKY WAVES

SURFACE WAVES SPACE WAVES

DIRECT WAVES

GROUND REFLECTED WAVES

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

SURFACE WAVES

DIFFRACTION

DIFFRACTION

FREQUENCY

SURFACE WAVES

ATTENUATION

ATTENUATION

FREQUENCY

FACTORS

1. SURFACE

2. FREQUENCY

SURFACE WAVES

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

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

U/V RAYS

GAS MOLECULES

POSITIVE IONS : TOO HEAVY TO INFLUENCE

LEVEL OF IONISATION : EXTENT OF REFRACTION

ELECTRONS

IONOSPHERE

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 & X-RADIATION, 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 PENETRATION-GREATER ATTENUATION

RANGES AVAILABLE

TRANSMISSION POWER

DEPTH OF PENETRATION

ANGLE OF INCIDENCE -- MAX RANGE BY WAVE LEAVING TANGENTIAL TO EARTH

α2

α1

CRITICAL ANGLE

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

α2

α1

CRITICAL ANGLE

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 MEANS A HIGHER RANGE WOULD BE OBTAINED.

HF COMMUNICATION

CRITICAL FREQUENCY fC FOR PREVAILING

ATMOSPHERIC CONDITIONS

MUF = fC X sec θi

LUHF

RANGES AT NIGHT ARE GREATER THAN DAY TIME

IONIZATION LAYER HT

DEPTH OF PENETRATION

NIGHT TRANSMISSION

NIGHT TRANSMISSION

RECOMBINATION

REFLECTING HT MOVES UP

RANGE INCREASES, GREATER SKIP DISTANCE

Frequency Range

Wavelength Range

Typical sources

3 to 30 Hz10,000 to 100,000

kmdeeply-submerged submarine communication

30 to 300 Hz 1000 to 10,000 km submarine communication, ac power grids

300 to 3 kHz 100 to 1000 km earth quakes, earth mode communication

3 to 30 kHz 10 to 100 km near-surface submarine communication,

30 to 300 kHz 1 to 10 km AM broadcasting, aircraft beacons

300 to 3000 kHz

100 to 1000 m AM broadcasting,

3 to 30 MHz 10 to 100 m Skywave long range radio communication

30 to 300 MHz 1 to 10 m FM radio broadcast, television broadcast, DVB-T, MRI

300 to 3000 MHz

10 to 100 cmmicrowave oven, television broadcast, GPS, mobile phone communication (GSM, UMTS, 3G, HSDPA), cordless phones

(DECT), WLAN (Wi-Fi), Bluetooth

3 to 30 GHz 1 to 10 cm DBS satellite television broadcasting, WLAN (Wi-Fi), WiMAX, radars

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

VLF

 Very Low Frequency

 3 kHz

 30 kHz

VF  Voice Frequency 300 Hz

 3 kHz

ELF

 Extremely low Frequency

 30 Hz

 300 Hz

ULF

 Ultra Low Frequency

 3 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

OSCILLATOR PRODUCES RF

RF AMPLIFIER AMPILFIES RF

MICROPHONE CONVERTS AW TO AF

AF AMPLIFIER AMPLIFIES AF

MODULATOR MODULATES RF

WITH AF

POWER AMPLIFIER AMPLIFIES RF+AF

ANTANNAE RADIATES RF+AF

RECEIVER BLOCK DIAGRAM

DEMODULATOR SUPRESSES RF

AND PRODUCES AF

AMPLIFIER AMPLIFIES RF+AF

ANTANNAE RECEIVES RF+AF

AF AMPLIFIER AMPLIFIES AF

SPEAKER CONVERTS AF

INTO AW

SUPERHETORDYNE RECEIVER BLOCK DIAGRAM

MIXER MIXES RF+AF AND LF AND

PRODUCES IF 500 K Hz

ANTANNAE RECEIVES RF+AF

8500 K Hz

AF AMPLIFIER AMPLIFIES AF

SPEAKER CONVERTS AF INTO

AW

AMPLIFIER AMPLIFIES RF+AF

LFO PRODUCES LF 8000 K Hz

LF AMPLIFIERS AMPLIFIES LF

DETECTOR CONVERTS IF INTO AF

BFO AVC SQUELCH

Tuned frequency reciever

Qualities of reciever

superhetrodyne

QUESTIONS ?