Convention used Left mouse click option available not recommended in this lesson

Advanced Studies Unit 18a BTecAdvanced Studies Unit 18a BTec

Convention usedConvention used

Left mouse click optionLeft mouse click optionavailablavailablee

not not recommendedrecommended

in this lessonin this lesson


Advanced RadioAdvanced Radio


1.1. communicatingcommunicating

44//

Communication may be defined as Communication may be defined as the the “exchange of information”“exchange of information”

CommunicatinCommunicatingg

introductiointroductionn

55//

Speech is one method of communication .

you need a voice to “transmit” a message (in the form of

sound energy)

and ears to “receive” the reply

CommunicatingCommunicating

transmitter = voice and

receiver = ears

66//

• Speed of travel is quite slow in air: Speed of travel is quite slow in air: 340 m/s at 20ºC 340 m/s at 20ºC or 760 or 760 mph (the speed of propagation of sound).mph (the speed of propagation of sound). * *

• Sound will not travel through a vacuumSound will not travel through a vacuum • it needs a substance or “it needs a substance or “mediummedium” (normally air) to transmit the ” (normally air) to transmit the

energy.energy. • ……although the medium can also be although the medium can also be liquidliquid (eg water or (eg water or

mercury?) or a mercury?) or a solidsolid (eg bar of steel or a quartz crystal) (eg bar of steel or a quartz crystal)

CommunicatinCommunicatingg

Up until the Invention of the Guttenberg Up until the Invention of the Guttenberg Printing Press in 1436 we used sound in Printing Press in 1436 we used sound in

the form of speech to communicate widely.the form of speech to communicate widely.

…but sound has its drawbacks

* speed 350 m/s or 780 mph at 30ºC

so the hotter the day …the faster the speed of sound

88//a longitudinal wave

direction of wave propagation

tickets

Note:1. the ‘action’ or energy goes in the same direction as

the propagation …ie lies in the same planelies in the same plane

2. none of the people (the ‘medium’) moved closer to the destination after the shove had finished

3. …but the shove/wave doesdoes move or propagate towards the destination

4. the shove/wave isn’t an object …it has no weight or mass. It’s an experience, a phenomenon

Hey!Nobody’s getting

served any quicker!

99//a longitudinal wave

direction of wave propagation

tickets

The plane of action or energy

Woah!Did the

Earth just move for

you?

Not from where I’m standing!

Sound is …Sound is …

1010//Sound limitationsSound limitations

• sound does not travel very far in air , even if you sound does not travel very far in air , even if you have a loud voice. It becomes ‘attenuated’ or have a loud voice. It becomes ‘attenuated’ or weakened by theweakened by the spongy airspongy air

• ……but sound can travel for but sound can travel for thousandsthousands of kilometers of kilometers through the sea and through the earth’s solid through the sea and through the earth’s solid surface …and at 1000s of MPHsurface …and at 1000s of MPH

• echoes, wind and other unwanted noises hamper echoes, wind and other unwanted noises hamper receptionreception

1111//

Let’s look at Let’s look at howhow sound sound travels through various travels through various

mediamedia

1212//

sound wave

longitudinal

Air compressionAir decompression

Ambient Air Pressure =

1Bar

1

Propagation or velocity of sound in Propagation or velocity of sound in air

Graphical representation of localised air

pressure

(760 mph)

340 metres per sec

input

Speed of propagation …in air at 20ºC

……ie at normal ie at normal UK temperaturesUK temperatures

AmbientAmbient

pressurepressure

Propagation or velocity of sound in Propagation or velocity of sound in air

……but at higher temperatures, the but at higher temperatures, the speed of sound increasesspeed of sound increases

nb …that’s why early in 1950’s, the ‘sub-sonic’ RAF world speed records were conducted in the hot

desert

…to delay reaching the so called ‘sound barrier’

1414//

Nothing to compress ?

vacuuvacuumm

Air Pressure = 0 Bar

0

Propagation; sound in Propagation; sound in vacuum

input

NO SOUND HEARD!

NO SOUND HEARD!

1515//

vacuuvacuumm

Air Pressure = 0 Bar

0

Propagation; sound in Propagation; sound in vacuum

input

That is why,( if you have ever noticed it), that audio, alarms and That is why,( if you have ever noticed it), that audio, alarms and announcements in an aeroplane on the ground are ‘too loud’ for announcements in an aeroplane on the ground are ‘too loud’ for comfort.comfort.

Why is that do you think?

If the aeroplane lost cabin pressure at altitude how will an If the aeroplane lost cabin pressure at altitude how will an alarm audio sound to the passengers and crew who are not alarm audio sound to the passengers and crew who are not on intercom?? on intercom??

All announcements, alarms or bells will be VERY All announcements, alarms or bells will be VERY much quieter.much quieter.

1616//

Liquids cannot compress …so transmits

the sound very efficientlyvery efficiently and very very fast!fast! …and over great distancesgreat distances

Propagation; sound in liquid (Propagation; sound in liquid (water?)?)

Liquid (eg water or mercury?)

14831483 metres per sec

(3,3003,300 mph)…in

water

1717//

uncompressible …so transmits sound even faster and more efficiently

using soundsound through quartz crystals is extensively used in electronics such as TV and Radar processing circuits

Propagation; sound in Propagation; sound in solids (steel?) (steel?)

Solid (Rock? or Quartz Crystal? Steel?


(10,00010,000+ mph!!)…in solid steelsolid steel

Strange but true!

…or quartz crystalquartz crystal…or The EarthThe Earth

1818//

Propagation; soundPropagation; sound

Air 760mph

Water 3300mph

Steel 10,000mph

Speed of Sound in …Speed of Sound in …

RecapRecap

…and for not very far

…and for maybe 1000miles +

Vacuum 0 mph

…it doesn’t


340340 m/sec

14831483 metres/sec

Check of understandingCheck of understanding 1919//

2020//

QQ. So, how do these astronauts communicate

by voice, outside the International Space Station

… without using a radio?

Sound Sound cannot travel cannot travel through a through a vacuum!!vacuum!!

2121//

A. By touching space-helmets!

…and, surprisingly, they do this quite often to

co-ordinate their work

computer won’t computer won’t open the pod open the pod

doors, Sergei !doors, Sergei !

Oh! oh!Oh! oh!not so not so

simplessimples

radio communicationradio communication

CommunicatingCommunicating2222//

2323//

Let’s now look at how Radio Waves travelLet’s now look at how Radio Waves travel

Radio WavesRadio Waves

2424//Radio WavesRadio Waves

• Radio – uses a different energy Radio – uses a different energy

• A radio communications system consists of a transmitter (Tx), A radio communications system consists of a transmitter (Tx), to send the message to send the message

• ……and a receiver (Rx) to receive the reply and a receiver (Rx) to receive the reply

2525//Radio WavesRadio Waves

soso……

shorthand for a radio transmitter isshorthand for a radio transmitter is

TxTx …remember this abbreviation! …remember this abbreviation!

……and for a receiver it isand for a receiver it is

RxRx …again, remember this abbreviation too! …again, remember this abbreviation too!

2626//RadioRadio

• The link between the Tx and Rx this time is not sound energy, The link between the Tx and Rx this time is not sound energy, but electro-magnetic (em) energy, (radio waves)but electro-magnetic (em) energy, (radio waves)

• light and radio waves can travel very well through air, but more light and radio waves can travel very well through air, but more perfectlyperfectly through a vacuum – and they travel at the same through a vacuum – and they travel at the same extremely high speedextremely high speed

• ……the speed of lightthe speed of light

• ……no matter what the speed of the transmitter or receiver isno matter what the speed of the transmitter or receiver is

2727//RadioRadio

……exactly the speed of exactly the speed of light!!light!!

3 x 103 x 1088 metres per metres per secondsecond (sometimes written as m/s or ms-1)

Or, if you prefer to put that Or, if you prefer to put that speed in context, it isspeed in context, it is

186, 000 miles per second!!186, 000 miles per second!!

remember

this

speed !!

!

300,000,000 ms-1

or

0r 669,600,00 mph!

2828//

Electro-magnetic radiation travels in waves in a similar Electro-magnetic radiation travels in waves in a similar

fashion to ripples on a pond.fashion to ripples on a pond.

The waves travel in all directions from their source The waves travel in all directions from their source

rather like the pattern produced when a stone is rather like the pattern produced when a stone is

dropped indropped in

A typical wave can be imagined like this…A typical wave can be imagined like this…

Electro-magnetic energyElectro-magnetic energy

2929//electromagnetic energyelectromagnetic energy

it would seem that there is no theoretical it would seem that there is no theoretical limit to the frequency of em waves, limit to the frequency of em waves, neither lower nor upper.neither lower nor upper.

the expression “the expression “electro-magnetic spectrumelectro-magnetic spectrum” ” has been coined to embrace all radiations of this has been coined to embrace all radiations of this type, which include heat and light. type, which include heat and light.

… …but we will only concern ourselves with but we will only concern ourselves with the Radio & Radar regionthe Radio & Radar region

HighFreqs

LowFreqs

plus infra red & visible light,

damaging Ultra

Violet, dangerous X-

rays and lethal Gamma rays

Radio wave Frequencies

Long wavelengthShort wavelength

HighFreqs

LowFreqs

plus infra red & visible light,

damaging Ultra

Violet, dangerous X-

rays and lethal Gamma rays

Radio wave Frequencies

Long wavelengthShort wavelength

3232//From transmitter to From transmitter to receiverreceiver

A radio Tx converts information into em radiation.

information could be voice, TV pictures or digital codes

em radiation from the Transmitter (Tx) will then travel from the aerial or antenna

A radio Rx picks up this signal via a suitable aerial and converts the em radiation back into information.

simples

3333//TransmittersTransmitters

You know…

TxsTxs come in all shapes and sizes?

think about it!think about it!

PLB

…aircrew Personal

Locator Beacon

the car alarm remote is another

such devices will have a very small power output of about ½ Watt

( not enough to light a single Xmas tree light)

to a couple hundreds of Wattscouple hundreds of Watts for a ‘freesat’ satellight.

your mobile

phone?

WiFi home hub?

AnyAny WiFi device

Man-made satellights?

3434//TransmittersTransmitters

You know…

TxsTxs come in all shapes and sizes?think about it!think about it!

but a BBC television or a Medium Frequency (MF) radio transmitter will, on the other hand, have a power rating of up to

500,000500,000Watts

ie ½ Megawatt½ MegawattThese very high-powered equipments are needed to make transmissions reach to all parts of the country and combat terrestrial interference and losses within the Earth’s atmosphere.

your television

remote control is

one

the car alarm remote is another

such devices will have a very small power output of about ½ Watt to a couple hundreds of Watts for a satellite.

your mobile

phone?

WiFi home hub?

AnyAny WiFi device

Man-made satellights?

ReceiversReceivers

Rx also come in all shapes and sizesRx also come in all shapes and sizes

think about it!think about it!

Obviously …

Obviously …

your personal

your personal

radioradio

……and your TV

and your TVGPS satnavGPS satnav

Car Car

immobiliser immobiliser

huge radio telescopes

huge radio telescopes

eg eg JJodrell Bankodrell Bank

RWRsRWRs……RRadar adar WWarning arning RReceivers eceivers on aircrafton aircraft

3636//What is What is eelectro-lectro-mmagnetagnetiic c energy? energy?

When an alternating electric current flows in a wire, both electricelectric and magneticmagnetic fieldsfields are produced surrounding the outside of the wire.

The frequencyfrequency of the alternating current will determine the frequencyfrequency of the of the eemm waves waves produced, and its power rating and frequency chosen will govern how that radiation behaves in the Earth’s atmosphere .

There is no theoretical limit to the frequency of eemm waves and, as we’ve seen, the expression ““electromagnetic spectrumelectromagnetic spectrum”” has been coined to embrace all radiations of this type, which include heat and light.

Electricity can be ‘static’, like the energyElectricity can be ‘static’, like the energy

that can make your hair stand on end. that can make your hair stand on end.

Magnetism can also be ‘static’, as it is in a refrigerator magnet.

3737//

electric fieldelectric field ‘E’‘E’

BB

magnetic fieldmagnetic field

’’B’B’

What is What is eelectro-lectro-mmagnetagnetiic c energy? energy?

3838//

A changing A changing magneticmagnetic field will induce a changing field will induce a changing electric electric field and field and vicevice--versaversa——the two are linkedthe two are linked..

These changing fields form These changing fields form electroelectromagneticmagnetic waves. waves.

What is What is eelectro-lectro-mmagnetagnetiic c energy? energy?

3939//What is electromagnetic What is electromagnetic energy? energy?

Wire conductor

---

+

-Direct current

DCDC

+ -

BBBBBB

BB

• If we apply a dc voltage from a battery or generator to a wire conductor …we generate a magnetic field around the wire and it is usual to show the ‘magnetic field’ as a letter BB and it flows along the direction of the red arrows.

strongstrong

weakweak

Magnetic Magnetic fieldfield


Wire conductor

---

++

--Direct current

DCDC

++ --

BBBBBB

BB

• This isn’t a radio wave …it’s just a constant magnetic field. You would need a magnetic compass to detect it. It quickly becomes very weak the further from the conductor. It’s constant or ‘static’ …the magnetic field is going nowhere… and will only last as long as there is a current flowing in the conductor.

Let’s now look at applying anLet’s now look at applying an

aalternating lternating ccurrent (ac)urrent (ac)

to the wireto the wire

What is electromagnetic What is electromagnetic energy? energy?

4141//

4242//

• Now this alternating current introduces a new complexity which Now this alternating current introduces a new complexity which results in an electromagnetic wave being transmittedresults in an electromagnetic wave being transmitted


Wire conductor

~

+

-+

-

Alternating current

+- +-

4343//

As before, the current produces a magnetic field B as shown


Wire conductor

~

Alternating current

Let’s just slow things

down

BB

BB

BB

Wave

fro

nt

Wave

fro

nt

4444//

but its changing strength and direction in sympathy with the conductor’s electric current.


Wire conductor

~

Alternating current

BB

BB

BB

……butbut

4646//

• You can’t change a magnetising force without

generating an electric field ..ee


Wire conductor

~

eehh

ee

eehh

hh

…… but …but!but …but!


Wire conductor

~

eeBB

ee

eeBB

BB

…again at right angles to the

electric field that caused it

• You can’t change an electricelectric fieldfield without

generating anotheranother magnetic B fieldB field

chickenchicken andand egg egg andand chickenchicken andand egg, egg, andand chickenchicken andand egg, egg, andand chickenchicken andand egg etcegg etc

BB

ee

--BB

--ee

magnetic magnetic fieldfield

Wire conductor

~

AnsAns:: Well … Well … forever!forever!

Provided the wave remains Provided the wave remains ‘‘in space’in space’ and it isn’t and it isn’t weakened by air or weakened by air or

absorbed by other physical absorbed by other physical objects. objects.

electric fieldelectric field

How long does this How long does this action continue action continue ……when the radio when the radio

frequency ac power frequency ac power source is removed?source is removed?

……but! but! But! But! But!!But!!

Although this process is ever lastingAlthough this process is ever lasting

it pushes itself forever it pushes itself forever outwardsoutwards

And forms a perpetual, ever radiating And forms a perpetual, ever radiating radio waveradio wave


Wire conductor

~

eeBB

ee

eeBB

BB

…and the speed at which it radiates is…

~RFRF

The speed of light!

3 x 103 x 1088 m/s m/s


Wire conductor

~

Alternating current

ee

BB

ee

ee

BB

BB

ee

BB Magnetic Field Magnetic Field ‘B’‘B’

electric field

electric field e voltse volts

ee

BB Magnetic field Magnetic field ‘B’‘B’

electric field


Both fields are Both fields are 90º to each 90º to each

otherother

At exactly 3 x 10At exactly 3 x 1088 ms ms-1-1

And they propel the electro-And they propel the electro-magnetic radio wave at 90º magnetic radio wave at 90º

to both to both ee and and BB fields fields

no fasterno faster

no slower no slower

3 x 10

3 x 1088

ms

ms -1-1

ee

hh Magnetic fieldMagnetic field

‘‘B’B’

electric field


Both fields are Both fields are 90º to each 90º to each

otherother

……at the original frequencyat the original frequencyand the and the ee & & BB fields remain fields remain

3 x 10

3 x 1088

ms

ms -1-1

Long after they have left the solar system , Long after they have left the solar system , the milky way and the local group of galaxies the milky way and the local group of galaxies

on their way to infinity!on their way to infinity!

5656//electromagnetic energyelectromagnetic energy

• The frequency of the radio frequency, alternating The frequency of the radio frequency, alternating current will determine the frequency of the em current will determine the frequency of the em waves produced waves produced

NASA’s NASA’s Pioneer 10Pioneer 10 and and 11 11 spacecraft were launched in spacecraft were launched in 1972/731972/73

40 years old 40 years old technology technology

It has a radio to keep in touch It has a radio to keep in touch with earth with earth

The power supply for the whole space The power supply for the whole space craft is 2 nuclear generators on the end craft is 2 nuclear generators on the end of the arms shown. Originally giving a of the arms shown. Originally giving a barely 140 Watts, when it sped past barely 140 Watts, when it sped past Saturn the power decayed to 100W.Saturn the power decayed to 100W.

The radio which has been sending a signal back The radio which has been sending a signal back to earth has a power of a mere to earth has a power of a mere 40W 40W barely barely enough for a domestic light bulb.enough for a domestic light bulb.


3metres3metres

(it’s not (it’s not big)big)


That radio was turned off by That radio was turned off by command from NASA in 2003command from NASA in 2003

These spacecraft were, however,These spacecraft were, however,

8 billion miles8 billion miles away. away.

……and transmitting 40W at a frequency of 2 GHz and transmitting 40W at a frequency of 2 GHz

(your microwave operates at 3 GHz and blasts out (your microwave operates at 3 GHz and blasts out 800w)800w)

It took It took 12 hours12 hours for the radio signal wave front to for the radio signal wave front to reach the spacecraft and reach the spacecraft and anotheranother 12 hr12 hr for the for the return signal to reach Earth.return signal to reach Earth.


3metres3metres

(it’s not (it’s not big)big)


That radio was turned off by That radio was turned off by command from NASA in 2003command from NASA in 2003

These spacecraft are, however,These spacecraft are, however,

8 billion miles8 billion miles away. away.

it appears that it appears that radio wavesradio waves are very robust and can are very robust and can go a go a long long long long way for very little powerway for very little power

It was 80 times the distance the Earth is from It was 80 times the distance the Earth is from the Sunthe Sun

Low

Freqs

kHz MHz GHz

long long range range radioradio

BBC BBC World World SvcSvc

Radio Radio HamsHams

ATC radiosATC radios

R/C modelsR/C models

Mobile Mobile PhonesPhones

RadarsRadars

TelevisionTelevision

Sat TVSat TV

Radio HamsRadio Hams

Digital & WiFiDigital & WiFi

TelemetryTelemetry

Microwave Microwave OvensOvens

RadarRadar

Missile Missile GuidanceGuidance

Data LinksData Links

The Electromagnetic Spectrum

Radio & Radar RegionRadio & Radar RegionHigh

Freqs

Low

Freqs

kHz MHz GHz

long long range range radioradio

BBC BBC World World SvcSvc

Radio Radio HamsHams

ATC radiosATC radios

R/C modelsR/C models

Mobile Mobile PhonesPhones

RadarsRadars

TelevisionTelevision

Sat TVSat TV

Radio HamsRadio Hams

Digital & WiFiDigital & WiFi

TelemetryTelemetry

Microwave Microwave OvensOvens

RadarRadar

Missile Missile GuidanceGuidance

Data LinksData Links

Radio & Radar RegionRadio & Radar RegionHigh

Freqs

MFMF & & HFHF VHF VHF

& & UHFUHF

EHFEHF & &

SHFSHF

ieie

EExtra xtra HHi i FFreqreq &&

SSuper uper HHi i FFreqreq

6161//

definitionsdefinitions

We need to cover a few definitions to We need to cover a few definitions to progress our understanding of Radio progress our understanding of Radio furtherfurther

6262//

• FrequencyFrequency (ff) – the number of complete vibrations or fluctuations each second (ie cycles per sec).

• AmplitudeAmplitude (aa) – the height of the wave-crest on the field strength or power axis.

• Wavelength (Wavelength () – the distance between any two ) – the distance between any two identical points in a wave (ie peak to peak ~the identical points in a wave (ie peak to peak ~the length of one whole wave). Greek letter length of one whole wave). Greek letter pronounced pronounced LambdaLambda

• VelocityVelocity () – the speed with which the waves moves has the relationship:

6363//

Greek letter actually

pronounced

“NuNu”

…but don’t worry, most people just

remember it as “VV””

=ff

definitionsdefinitions

Measured in Measured in Hertz HzHertz Hz

A number of A number of Units availableUnits available

Measured in Measured in metres, cm or metres, cm or

mmmm

……in Metres per in Metres per second …second …

alwaysalways

3 x 103 x 108 m/s8 m/s


• AmplitudeAmplitude (aa) – the height of the wave-crest on the field strength axis.

• WavelengthWavelength () – the distance between any two identical points in a wave (ie peak to peak ~the length of one whole wave).

• Velocity Velocity () – the speed with which the waves moves has the relationship:

6464//electromagnetic energyelectromagnetic energydefinitionsdefinitions

This Greek This Greek letter is letter is

pronounced pronounced “Lambda” “Lambda” being a being a

Greek L for Greek L for ““length”length”

The most useful form The most useful form of this expression is to of this expression is to

calculate wavelength calculate wavelength for aerial selectionfor aerial selection

……so, rearranging for so, rearranging for =f


• AmplitudeAmplitude (aa) – the height of the wave-crest on the field strength axis.

• WavelengthWavelength () – the distance between any two identical points in a wave (ie peak to peak ~the length of one whole wave).

• Velocity Velocity () – the speed with which the waves moves has the relationship:

6565//electromagnetic energyelectromagnetic energydefinitionsdefinitions

=f

6666//

Advantages of emAdvantages of em

Using em energy to carry our communications Using em energy to carry our communications information has many advantages compared information has many advantages compared with sound energywith sound energy

Speed of travel is Speed of travel is unimaginablyunimaginably fast fast

… …the speed of light the speed of light ((alwaysalways 3 x 10 3 x 1088 m/s),

……but let’s get that into the context of but let’s get that into the context of computerscomputers

6767//


Using Using emem energy to carry our energy to carry our communications information has many communications information has many advantages compared with sound energyadvantages compared with sound energy

Speed of travel is Speed of travel is unimaginablyunimaginably fast fast

… …the speed of light the speed of light ((alwaysalways 3 x 10 3 x 1088 m/s),

……but let’s get that into the context of but let’s get that into the context of computerscomputers

Speed of travel is Speed of travel is unimaginablyunimaginably fast fast……the speed of light (always the speed of light (always 3 x 103 x 1088 m/s) m/s)

Intel

Pentium

3 GHz speed A typical PC Central

Processor Unit

(CPU)

So, how far can our radio wave travel in the So, how far can our radio wave travel in the time for 1 cycle of this ‘chip’?time for 1 cycle of this ‘chip’?

Answer: 1 wavelength of 3 GHzAnswer: 1 wavelength of 3 GHz … …

Which is Which is VV = = 3 x 103 x 1088

ff 3 x 103 x 1099 = 10cm or = 10cm or 4”4”

6868//


Intel

Pentium

3 GHz speed A typical PC Central

Processor Unit

(CPU)

A Radio em wave cannot get further away than A Radio em wave cannot get further away than 10cm or 4” before, the next cycle begins10cm or 4” before, the next cycle begins

= 10cm or = 10cm or 4”4”

This is a severe limiting factor for This is a severe limiting factor for PC CPU speeds PC CPU speeds

We need faster radio We need faster radio waves or smaller waves or smaller

CPUsCPUs

We cant have We cant have different ‘newness’ different ‘newness’ of data from one of data from one

side of a chip to the side of a chip to the other!other!

All of a sudden, the All of a sudden, the speed of lightspeed of light doesn’t seem quite so quick!doesn’t seem quite so quick!

6969//

7070//Electromagnetic wavesElectromagnetic waves

• Em waves will travel through a vacuum and so can be Em waves will travel through a vacuum and so can be used for communication in space.used for communication in space.

• Em waves travel a very, very long way for a given transmitter power …providing no material or ‘medium’ is ‘in the way’

7171//

Aerial LengthAerial Lengthaerials used for transmission or reception operate aerials used for transmission or reception operate

best with certain wavelengths.best with certain wavelengths.

the length of the aerial dictates the frequency it will receive most readily.

aerial lengthsaerial lengths ofof /22 andand /44 are particularly efficient…are particularly efficient… ie ie halfhalf and and quarterquarter of wavelengthof wavelength

As we know the As we know the velocityvelocity of the waves, we can now of the waves, we can now calculatecalculate the best the best aerial lengthaerial length for a for a particular particular frequencyfrequency by finding the by finding the wavelengthwavelength of the wave. of the wave.

7272//

• eg For f = 200 kHz,

= f

& =300,000,000 m/sec*

* = ‘ C ’ speed of light=300,000,000

200,000

= 1500 metres

Aerial LengthAerial Length

As we know

Wavelength

We need to rearrange

300000,000200,000

….nearly there!

7373//


= 1500 metres

So, given that the wavelength for our

200kHz200kHz radio is …

The best aerial length would be /2

or /4

Which would be… 750m 375mor

7474//


• So what aerial lengths would best suit a frequency of 100 MHz?

= f = 300,000,000100,000,000

3 metres=

…best Ae length? λ/2 λ/41.5 m 0.75

mor

7575//


3 metres=

…best Ae length? λ/2 λ/41.5 m 0.75

mor

λ

Notice – the Notice – the higherhigher the frequency, the frequency, the the shortershorter the aerial required. the aerial required.

What does this tell us about the What does this tell us about the operating frequency of a car-mounted operating frequency of a car-mounted radio aerial compared to a hand held radio aerial compared to a hand held

mobile phone? mobile phone?

for 100 MHz?

OK, they were a few fundamentals to be OK, they were a few fundamentals to be going on with…going on with…

Let’s look back in time to see how ‘radios’ Let’s look back in time to see how ‘radios’ got started.got started.

7676//

7777//

in 1901 the Italian born inventor, entrepreneur and businessman … Gulielmo Marconi claimed his system was the ‘first to transmit and ‘first to transmit and receive long range radio signals from Cornwallreceive long range radio signals from Cornwall toto Newfoundland’Newfoundland’ (not yet part of Canada at that time).

Marconi

this has since been disputed for a number of robust scientific reasons but, as a publicity stunt, it worked. What is not disputed What is not disputed is the fact that his system was the most effective in The World at is the fact that his system was the most effective in The World at that time.that time.

7878//

previously, in 1899 in the USA, the Marconi instruments were tested and they found his wireless system “… the principle component of “… the principle component of which was discovered some twenty years ago, and this was the only which was discovered some twenty years ago, and this was the only electrical device contained in the apparatus electrical device contained in the apparatus that is at all newthat is at all new""

also, Nikola TeslaNikola Tesla, a rival in transatlantic transmission, stated after being told of Marconi's 1901 transmission that : "Marconi is a good Marconi is a good fellow. Let him continue. He is using 17 of my patents.fellow. Let him continue. He is using 17 of my patents.““

it didn’t matter. The Funds poured init didn’t matter. The Funds poured in

Marconi

Tesla

7979//

Marconi, stung by criticisms and incredulity, prepared a better organized and documented test.in February 19021902, the SS Philadelphia sailed west from Great Britain with Marconi and his receiver aboard, carefully recording signals sent daily from the Cornwall station. The test results produced audio reception up to 3,378 kilometres (2,099 mi) nearly the same distance as the Newfoundland test…but unlike that test, it was at night!it was at night! During the daytimedaytime, signals had onlyonly been received up to about 1,125 kilometres (699 mi). …this is in accordance with present day theory and experience.

night ranges are always greater than by day … …so what about his first 1901 test?so what about his first 1901 test?

8080//

the Marconi radio waves , originally called Lorenzian waves, were sent in groups of short and long signals by switching the transmitter off and on. ie Morse CodeMorse Code. His 1901 transmission consisted of 1 letter ‘S’ Morse code being endlessly repeated. Possibly why the 1901 results may have been imagined whereas 1902 results were conclusive. No matter, he was a world-beater.

although effective, this system did depend on the operators interpreting the Morse Code sequence– not something everybody could do.

8787//Amplitude Amplitude

modulationmodulation

What was needed was a means to use speech to modulate the CW rather like a tap can modulate the flow of water

The superhetsuperheterodyne principle offers a way to achieve this

The ‘superhet’‘superhet’ principle involves the effect that one ‘sine wave’ has over another adjacent ‘sine wave’ … which is of a different frequency

Notice that no mention has been made of electronics…!!!

This is because it is quite simply a mathematicalmathematical process …



This is because it is quite simply a mathematicalmathematical process …

It applies to things that rotate or vibrate or just change over a period of time …in a sinusoidal fashion

that is … Simple Harmonic Motion …or SHM which includes pendulums

two car enginestwo car engines running at slightly different speeds

egeg

two waves in the seatwo waves in the sea meeting and interacting

Or the interaction of Or the interaction of two ac electrical signalstwo ac electrical signals

of different frequencies of different frequencies

superheterodynsuperheterodynee



this principle which demonstrate that if you ‘mixmix’ or ‘modulatemodulate’ any sort of sinewave force (that’s the dyne bit) with another sinewave (of a same similar …that’s the hetero bit), the result is a

complex wave which has sumsum and differencedifference frequencies embedded within it.




sumsum && differencedifference

frequenciesfrequencies




the upper sinewave has a lower frequency

f1 than the next down sinewave of

frequency f2

f1

f2

&

Adding two sinewaves

the resultant wave form shows another virtual sine

wave of frequency f2 - f1

Join up the peaks and troughs and …

composite



f1

f2

+


the resultant wave is the

differencedifference frequencyfrequency

ff2 2 - f- f11



f1

f2

+


sum

……this is the virtual waveform of thethis is the virtual waveform of the difference difference frequencyfrequency

So if ff11 = 250250 kHz kHz (ie 250,000 Hz250,000 Hz) & ff22 = 252252 kHzkHz Then …Then …

F F (difference)(difference) == F F dd ==252 kHz252 kHz -- 250 kHz250 kHz == 2 kHz2 kHz

Fd d

differ

ence

frequ

ency

F F dd== 2 kHz2 kHz



f1

f2

+

Adding two sinewaves –the SUM SUM freqfreq

sum

the resultant wave form shows another

virtual sine wave of frequency ff11 ++ ff22== ffSUMSUM

So if ff11 = 250250

kHzkHz & f f22 = 252252

kHzkHzThen …Then …

Then …Then …Then …Then …

ffSUMSUM == 502502 kHz kHz

Fsumsum frequency



……this applies to interaction of this applies to interaction of allall sinusoidal sinusoidal waveswaves

they could be soundwaves

oror wave-motion at sea

oror engines at slightly different speeds to each other

…which creates an unpleasant ‘‘beat beat frequency’frequency’ of vibration ..which can be catastrophic!

Sum & Difference Sum & Difference FrequenciesFrequencies

This effect has This effect has even resulted in even resulted in

old, badly old, badly designed propeller designed propeller airliners shaking airliners shaking themselves into themselves into

fatigue failure and fatigue failure and even destruction! even destruction!



……this applies to interaction of this applies to interaction of allall sinusoidal sinusoidal waveswaves

they could be soundwaves

oror wave-motion at sea

oror engines at slightly different speeds to each other

…which creates an unpleasant ‘‘beat beat frequency’frequency’ of vibration ..which can be catastrophic!

Sum & Difference Sum & Difference FrequenciesFrequencies

This effect has This effect has even led to even led to

propeller airliners propeller airliners shaking shaking

themselves into themselves into fatigue failure and fatigue failure and even destruction! even destruction!

This is caused This is caused by the by the

difference in difference in frequency frequency

between the between the twotwo

Amplitude Amplitude modulationmodulation

……it is entirely a physical example of a simple, it is entirely a physical example of a simple, mathematical, mathematical, trigonometricaltrigonometrical relationship. relationship.

… … which we will not go in to! which we will not go in to!

This ‘beating together’ phenomenon This ‘beating together’ phenomenon also applies to electrical currents & also applies to electrical currents & radio wavesradio waves

but just take on board; but just take on board; 2 frequencies 2 frequencies beating together do produce beating together do produce

SumSum and and Difference Difference frequenciesfrequencies

9797//


modulationmodulation Sum & Sum &

Difference Difference FrequenciesFrequencies

AAmplitude mplitude MModulation with regards to odulation with regards to

Radio WavesRadio Waves


modulationmodulation Sum & Sum &

Difference Difference FrequenciesFrequencies

let’s look at this in a graphical way

frequencyfrequency is along the bottom of the graph

…and signal strength or amplitudeamplitude is along the vertical

frequency

am

plit

ude

This view is

called the frequency

frequency domain

domainSo So frequency

frequency

rules! OK?

rules! OK?

We’re now going to look, using the using the

frequency domainfrequency domain, at a hypothetical radio transmitter receiver on a

random frequency, say , 2182kHz or 2182000Hz if you wish

2182kH

z

transmittertransmitter

101101//Amplitude Amplitude modulationmodulation the frequency domainthe frequency domain

Radio Radio FrequencyFrequency

2182 kHzFF00

Sig

nal st

rength

Sig

nal st

rength

Watt

sW

att

s

We now transmit (Tx) on We now transmit (Tx) on an RF of, say, an RF of, say, 21822182 kHz kHz

You You wouldn’t wouldn’t actually actually

hear hear anything anything

on on frequency frequency …yet!…yet!

It’s far, far It’s far, far

too high for too high for

you to ‘hear’ you to ‘hear’

if it was if it was

soundsound

Electromagnetic spectrum

Amplitude Amplitude modulationmodulation CWCW

102102//Amplitude Amplitude modulationmodulation Let’s look at this effect another way Let’s look at this effect another way ……


2182 kHzFF00

Sig

nal st

rength

Sig

nal st

rength

We now stop We now stop transmitting transmitting

That is how That is how Morse Code Morse Code

could be sentcould be sent

……and very and very efficiently too!efficiently too!

on

off



… … but you’ll need a but you’ll need a

specialist receiver specialist receiver

with a with a Beat Beat Frequency OscillatorFrequency Oscillator to be able to hear any to be able to hear any Morse CodeMorse Code

103103//

Let’s look at this effect another way Let’s look at this effect another way ……


2182 kHzFF00

Sig

nal st

rength

Sig

nal st

rength

This is interrupted This is interrupted CContinuousontinuous WWaveave ((i-i-CWCW)) but very often but very often

referred to as just…referred to as just…

CWCW transmissiontransmission



104104//


2182 kHzFF00

Sig

nal st

rength

Sig

nal st

rength CWCW transmissiontransmission


ReceptionReception2182kH

z

Nothing heard on

frequency!

Ordinary AM radioOrdinary AM radio

Amplitude Amplitude modulationmodulation CW CW MorseMorse

Now let’s look how a radio with aNow let’s look how a radio with a BBeateat FFrequencyrequency

OOscillatorscillator

BFOBFOwould receive that same transmission.would receive that same transmission.

106106//


2182 kHzFF00

Sig

nal st

rength

Sig

nal st

rength CWCW


ReceptionReception2182

kHz

Dah Dah Dit

AM radio with a Beat Freq

OscBFO


……but but how?how?


107107//

……basically, in all basically, in all

radios, most of the radios, most of the

processing and processing and

amplification is done amplification is done

at a fixed, at a fixed,

iintermediate ntermediate

ffrequency requency (i.f.)(i.f.)..For our example radio For our example radio

we will assume that, no we will assume that, no

matter what the receiver matter what the receiver

is tuned to, the received is tuned to, the received

signal is converted down signal is converted down

to an to an i.fi.f based at, say, based at, say,

30kHz30kHz


108108//

The Beat Frequency OscillatorThe Beat Frequency Oscillator

((BFOBFO))

generates a very small generates a very small

continuous, steady continuous, steady

sinewave signalsinewave signal into the into the i.f.i.f. circuits circuits

……but at abut at a slightlyslightly different frequencydifferent frequency to the intermediateto the intermediate frequency (frequency (i.f.i.f.) of ) of the radio receiver. the radio receiver. In this case signal In this case signal now scaled to

now scaled to 3030kHzkHz

30 kHz

i.f.

BFOBFOi.f.

Received signal Received signal reduced to 30kHz

reduced to 30kHz


31 kHz

109109//

What do we know happens What do we know happens when you ‘mix’ 2 sinewave when you ‘mix’ 2 sinewave

frequencies together ?frequencies together ?

Ans: We generate Sum and, more importantly here,

DifferencDifference frequencies!

Clue: they ‘Clue: they ‘BeatBeat’ together just like two ’ together just like two car engines at slightly differing speedscar engines at slightly differing speeds


110110//

……but what the difference is but what the difference is depends on where the listener depends on where the listener

moves the BFO moves the BFO (Beat Freq Osc)(Beat Freq Osc) knob knob toto

BFO freq differenceBFO freq difference0

1.0

1.5

2.0

30 kHz

31 31 kHz

11

Dah Dit Dah Dit Dit

as 1kHz pulsed tonesas 1kHz pulsed tones

i.f.


111111//

0

1.0

1.5

2.0

……but what the difference is but what the difference is depends on where the listener depends on where the listener

moves the BFO moves the BFO (Beat Freq Osc)(Beat Freq Osc) knob knob toto

BFO freq differenceBFO freq difference

30 kHz

31.5 31.5 kHz

1.1.55

Dah Dit Dah Dit Dit

You hear it as You hear it as higherhigher 1½ kHz pulsed1½ kHz pulsed tonestones

i.f.


112112//

113113//


30 kHz

Sig

nal st

rength

Sig

nal st

rength CWCW ReceptionReception218

2 kHz

Dah Dit Dah Dit Dit

AM radio with a Beat Freq

OscBFO

i.f.

????

the pitch of the tone / the pitch of the tone / Morse you hear is Morse you hear is dependant upon your BFO dependant upon your BFO setting setting

……it’s entirely the it’s entirely the listeners choicelisteners choice



Who would use such a Who would use such a

primitive and archaic mode primitive and archaic mode

of communication?of communication?

……well, it’s no longer a primary, well, it’s no longer a primary, secondary or even tertiary mode for

secondary or even tertiary mode for NATO military communications NATO military communications where Morse skills have all but where Morse skills have all but disappeareddisappeared

……but there is a massive World-

but there is a massive World-

wide network of amateur radio

wide network of amateur radio

enthusiasts known as enthusiasts known as Radio Radio

Hams Hams who use this mode to who use this mode to

‘keep in touch’.‘keep in touch’.

……and this mode will ‘get and this mode will ‘get through’ when none of the through’ when none of the

other modes canother modes can

114114//

115115//Amplitude Amplitude modulationmodulation


300 kHz

FF00

Sig

nal st

rength

Sig

nal st

rength

Now, what happens if we Now, what happens if we modulatemodulate the Carrier Wave the Carrier Wave with an amplified single with an amplified single tone of say tone of say 1.51.5 kHz? kHz?

This generates This generates AAmplitude mplitude

MModulation of the odulation of the ccarrier arrier

giving giving sumsum and and

differencedifference frequenciesfrequencies

Notice: power is Notice: power is shared between the shared between the

sumsum, , differencedifference

and and carriercarrier frequenciesfrequencies

When there is no When there is no 1.5 kHz tone 1.5 kHz tone

modulation all modulation all of the power is of the power is transmitted at transmitted at

the the CCarrier freq arrier freq

When the tone is When the tone is present, the present, the Carrier Wave is Carrier Wave is being modulated being modulated ie diminished/ ie diminished/ attenuated to attenuated to provide power for provide power for the Sum and the Sum and Difference Difference frequencies.frequencies.

301.5301.5 kHz298.5298.5 kHz

-1.5 -1.5 kHzkHz

+1.5 +1.5 kHzkHz



345 kHz

FF00

Sig

nal st

rength

Sig

nal st

rength

-1 -1 kHzkHz

+1 +1 kHzkHz

AmplitudeAmplitude Modulated Modulated

Carrier WaveCarrier Wave Only a simple Rx Only a simple Rx requiredrequired

Tone

on

Ordinary AM radioOrdinary AM radio

(MCW)(MCW)

345 kHz

Dah Dit Dah Dit Dit

The pitch/tone of The pitch/tone of the Morse is set the Morse is set

by the by the transmittertransmitter



345 kHz

FF00

Sig

nal st

rength

Sig

nal st

rength

-1 -1 kHzkHz

+1 +1 kHzkHz

……mainly used for mainly used for Aircraft ‘Aircraft ‘NavaidNavaid’ ’ Beacons Morse Beacons Morse

Code Code Identification Identification

signalssignals

Tone

on

Tone

OffOff



345 kHz

FF00

Sig

nal st

rength

Sig

nal st

rength

-1 -1 kHzkHz

+1 +1 kHzkHz

Amplitude Amplitude Modulated Modulated Carrier WaveCarrier Wave Only a simple Rx Only a simple Rx

requiredrequired

Tone

on



345 kHz

FF00

Sig

nal st

rength

Sig

nal st

rength

-1 -1 kHzkHz

+1 +1 kHzkHz

Modulated Carrier Modulated Carrier WaveWave

Only a simple Rx Only a simple Rx requiredrequired

……but does but does not carry as not carry as far as CW far as CW

morsemorse

Power is divided

between upper, lower and carrier

120120//

but instead of using a single but instead of using a single tonetone to to

‘modulate’‘modulate’ the carrier wave … the carrier wave …

……what if we used voice or music what if we used voice or music to to AAmplitudemplitude MMoodulatedulate the Carrier the Carrier WaveWave over a over a bandband of frequencies ? of frequencies ?


121121//

Carr

ier

Wave

Blah!

Di Dum ………………...

Di!Li Laaaaahh

Transmitte

r


122122//Amplitude Amplitude modulationmodulation Let’s look at that in the Let’s look at that in the

““Frequency Domain” againFrequency Domain” again


1442 kHzFF00

……Centred on Tx Freq of Centred on Tx Freq of Say, 1442kHzSay, 1442kHz

When the speaker talks When the speaker talks …he …he Amplitude Amplitude ModulatesModulates the strength the strength of the carrier wave …of the carrier wave …

not at not at oneone single single frequency but a broad frequency but a broad

bandband of frequenciesof frequencies

Which needs to Which needs to convey most of the convey most of the

tonestones in his voice in his voice

‘Sum’Sum’

freqsfreqs

‘‘DifferenceDifference’’

freqsfreqs

Radio Luxembur

g Freq



1442 kHz

FF00

‘Sum’Sum’

freqsfreqs


freqsfreqs

Carr

ier

Carr

ier

Wave

Wave

upperupper sidebandsideband

lower lower sidebandsideband


1442 kHz

FF00

‘Sum’Sum’

freqsfreqs


freqsfreqs

Carr

ier

Carr

ier

Wave

Wave



To recreate the original To recreate the original voice, in a simple voice, in a simple superhetsuperhet receiver … receiver …requires the reception of requires the reception of BOTHBOTH side bands to be side bands to be intelligible.intelligible.


1442 kHz

FF00

‘Sum’Sum’

freqsfreqs


freqsfreqs

Carr

ier

Carr

ier

Wave

Wave



The transmitted power is The transmitted power is shared between both shared between both sidebands sidebands andand the carrier. the carrier.

Tx power is Tx power is being wastedbeing wasted

each sideband is each sideband is the mirror image of the mirror image of

the otherthe other


1442 kHz

FF00

‘Sum’Sum’

freqsfreqs


freqsfreqs

Carr

ier

Carr

ier

Wave

Wave



AMAM is OK for V/UHF Air is OK for V/UHF Air Traffic comms as it is Traffic comms as it is cheap, reliable and the cheap, reliable and the equipment common and equipment common and light.light.

Quality or ‘fidelity’ is Quality or ‘fidelity’ is limited with AM due to the limited with AM due to the RF band-width available RF band-width available between channelsbetween channels

Hi Fidelity requirements for modern Hi Fidelity requirements for modern radio entertainment has been radio entertainment has been addressed with the advent of addressed with the advent of

FFrequency requency MModulation and then odulation and then more recently, more recently, DigitalDigital Radios Radios

allowing, far higher quality in terms allowing, far higher quality in terms of interference and audio freq rangeof interference and audio freq range


Cranwell Tower, ASCOT213 on

Uniform 268 decimal 625268 decimal 625 request join downwind for

Runway 26 Left hand for visual approach to land.

267.000VHF

UHFGuard V

Guard U

Tone

ASCOT213 nothing heard, changing to

Victor

select

268.000268.600268.625

simple Double Side-Band simple Double Side-Band

AMAM

upper

lower

AM

268.625127127//

Cranwell Tower, ASCOT213 now

on Victor, 125 decimal 05125 decimal 05 request join downwind for


VHFUHF

Guard V

Guard U

Tone

select

268.625268.050168.050135.050125.050


simple Double Side-Band simple Double Side-Band

AMAM

268.625125.05128128//

Cranwell Tower, ASCOT213 now

on Victor, 125 decimal 05125 decimal 05 request join downwind for


VHF

UHF

Guard V

Guard U

Tone

select

268.625268.050168.050135.050125.050


Mode now simplyMode now simply

Modulated Carrier Wave Modulated Carrier Wave

MCWMCW

I think I may have microphone

amplifier failure …I will try to

transmit the radio failure code using

1kHz ‘tone’ dashes and my transmit switch

125.05

+1 kHz

-1 kHz

MHz

121.5

243.0

129129//


1442 kHz

FF00

‘Sum’Sum’

freqsfreqs


freqsfreqs

Carr

ier

Carr

ier

Wave

Wave



BUTBUT those techniques still don’t give a those techniques still don’t give a transmitter greater range…needed for transmitter greater range…needed for HF commsHF comms

What if we put all transmitted power in to What if we put all transmitted power in to oneone or the or the

other other side bandside band and suppressed the carrier? and suppressed the carrier?


6742 kHz

FF00

upperupper sideband sideband

onlyonly

What if we put all transmitted power in to What if we put all transmitted power in to oneone or the or the

other other side bandside band and suppressed the carrier? and suppressed the carrier?

nb…the trouble is that nb…the trouble is that receiving SSB on an receiving SSB on an ordinary domestic ordinary domestic medium wave AM medium wave AM

radio; the audio would radio; the audio would

be utterly be utterly garbledgarbled and not decipherable in and not decipherable in

any way! any way!

“Gbble hmblfmbgb Pmmblwrbbl”

Ordinary AM radio RxOrdinary AM radio Rx6742


6742 kHzFF00


A A SSingle ingle SSide ide BBand and

(SSB) (SSB) receiverreceiver overcomes this by overcomes this by

re-synthesising re-synthesising the missing the missing sideband and sideband and carrier wave …carrier wave …in the receiverin the receiver

nb…the trouble is that nb…the trouble is that receiving this on an receiving this on an ordinary domestic ordinary domestic medium wave AM medium wave AM

radio; the audio would radio; the audio would

be utterly be utterly garbledgarbled and not decipherable in and not decipherable in

any way! any way!

Single Side Single Side BandBand

6742


6742 kHzFF00


A A SSingle ingle SSide ide BBand and

(SSB) (SSB) receiverreceiver overcomes this by overcomes this by

re-synthesising re-synthesising the missing the missing sideband …in sideband …in the receiverthe receiver


Single Single side-band side-band RxRx CW DSB

SSB UU

SSB LL

mode

6742


6742 kHz‘Sum’Sum’

freqsfreqs


freqsfreqs

CCarr

ier

arr

ier

Wave

Wave



Missing sideband re-synthesised Missing sideband re-synthesised on on receptionreception by Single Sideband by Single Sideband

Receiver (SSB) RxReceiver (SSB) Rx

Has range Advantage over DSB mode

Doubles channels available.

fidelityfidelity too poor too poor

for for entertainment entertainment radioradio

Mainly used atMainly used at HFHF

and and MFMF frequencies frequencies for Global Coveragefor Global Coverage

not not

transmittetransmitte

dd

……but no but no point point

atV/UHF atV/UHF freqsfreqs



6742 kHz



Civil & Military long Civil & Military long range voice comms range voice comms tends to use Upper tends to use Upper Side BandSide Band

(in the HF freq (in the HF freq bandband))

Used extensively Used extensively Military and Military and Merchant NavyMerchant Navy

Used by Used by ArmiesArmies for for beyond line of sight beyond line of sight communicationscommunications

Military Tactical Data Military Tactical Data Link tends to use Link tends to use Lower Side BandLower Side Band

(in the HF freq band)(in the HF freq band)



6742 kHz






Used by Armies Used by Armies for beyond line for beyond line of sight of sight communicationscommunications



Shanwick this is Rafair2134 on 88918891 upperupper, position 5630 North, Ten West at 1510, estimating Iceland boundary at… over!

8000880088908891

upper

lower

kHzkHz








Used by Armies Used by Armies for beyond line for beyond line of sight of sight communicationscommunications



Shanwick this is Rafair2134 on 88918891 upperupper, position 5630 North, Ten West at 1510, estimating Iceland boundary at… over!

0000

upper

lower

6000670067106715

Link Manager from Tactical Director; ‘Alligator’ Data Link frequency now 6715 lower.6715 lower.

kHzkHz

not not transmittetransmitte

dd


The legitimate nick-name for NATO

Link 11aLink 11a is

If you actually listen to the audio that the If you actually listen to the audio that the link data makes it’s an awful croaking link data makes it’s an awful croaking

scraping sound…scraping sound…

……just like an Alligator’s mating calljust like an Alligator’s mating call

……and that is exactly how it and that is exactly how it got it’s namegot it’s name

… … AlligatorAlligator

138138//

139139//

Largely surpassed in quality and effectiveness by SatSatellite ellite ComCommunicationsmunications but SATCOM on-airon-air time is expensive

…SSBSSB remains an extensively used prime communications method in the HF band

SSB onon-airair time is …free!

but not necessarily the commercial services you might request

Amplitude Amplitude modulationmodulation Single Side Single Side

BandBand

SSBSSB

It is used for:

Procedural control of military & Procedural control of military & commercial aircraft on long commercial aircraft on long range trans-oceanic flightsrange trans-oceanic flights

Military long range Flight Military long range Flight Following servicesFollowing services and VOLMET VOLMET aviation weather servicesaviation weather services

eg Shanwick , Iceland, New York

etc

eg RAF ‘TASCOM’ and ‘RAF VOLMET’

USAF ‘MAINSAIL’

Long Range, Link 11a Alligator Long Range, Link 11a Alligator Data LinkData Link

NATO air and naval units

etc etc etcetc etc etc

140140//

SSBSSB

It is not used for:

Entertainment Radio Channels Entertainment Radio Channels

Because …

you need an expensive, you need an expensive, specialist SSB radio specialist SSB radio receiver which can receiver which can

synthesise the missing synthesise the missing side-bandside-band

audio quality or ’fidelity’ is audio quality or ’fidelity’ is limitedlimited

141141//

Let’s now review the

AMAM

radio modes and their uses

142142//

• CWCW Carrier WaveCarrier Wave (Morse only – no voice). (Morse only – no voice). Needs a receiver BFO. Pitch of Needs a receiver BFO. Pitch of

received tones set by the listener using BFO. Generally in HF band. received tones set by the listener using BFO. Generally in HF band.

Ideal for very long range comms. Used by, mainly “Hams” now, but Ideal for very long range comms. Used by, mainly “Hams” now, but

still some Military & Commercial operational messages. Can ‘still some Military & Commercial operational messages. Can ‘get get

throughthrough’’

• MCWMCW Modulated Carrier WaveModulated Carrier Wave (Morse and data - no voice) (Morse and data - no voice) …s…simple basic radio imple basic radio

receiver required. Ideal for NAVAID ident letter codes and ‘distress receiver required. Ideal for NAVAID ident letter codes and ‘distress

tones’ in MF, HF, VHF and UHF. Not as range efficient as CW tones’ in MF, HF, VHF and UHF. Not as range efficient as CW

• DSBDSB Double Side BandDouble Side Band (Voice, line-of-sight tactical Digital Data-Link (Voice, line-of-sight tactical Digital Data-Link (in UHF band)(in UHF band) and and

NAVAID beacon data)NAVAID beacon data) -operational or entertainment, ranging from MF -operational or entertainment, ranging from MF

(Medium Wave) broadcasters through to VHF commercial stations to (Medium Wave) broadcasters through to VHF commercial stations to

Air Traffic and Citizen Band radios. Limited quality/fidelity due to Air Traffic and Citizen Band radios. Limited quality/fidelity due to

channel spacing.channel spacing.

• SSBSSB Single Side BandSingle Side Band (long range voice and ‘beyond the horizon’ tactical Digital Data-(long range voice and ‘beyond the horizon’ tactical Digital Data-

Link in, mainly, HF band.)Link in, mainly, HF band.) Used by commercial Oceanic Control agencies, Used by commercial Oceanic Control agencies,

commercial and very long range military Ship to Shore connections, commercial and very long range military Ship to Shore connections,

RAF, USAF and commercial Flight Watch services. RAF, USAF and commercial Flight Watch services.

• CWCW Carrier WaveCarrier Wave (Morse only – no voice). (Morse only – no voice). Needs a receiver BFO. Pitch of Needs a receiver BFO. Pitch of

received tones set by the listener using BFO. Generally in HF band. received tones set by the listener using BFO. Generally in HF band.

Ideal for very long range comms. Used by, mainly, “Hams”, now but Ideal for very long range comms. Used by, mainly, “Hams”, now but

still some Military & Commercial operational messages.still some Military & Commercial operational messages.

• MCWMCW Modulated Carrier WaveModulated Carrier Wave (Morse and data - no voice) (Morse and data - no voice) …s…simple basic imple basic

radio receiver required. Ideal for NAVAID ident letter codes and radio receiver required. Ideal for NAVAID ident letter codes and

‘distress tones’ in MF, HF, VHF and UHF. Not as range efficient as ‘distress tones’ in MF, HF, VHF and UHF. Not as range efficient as

CW CW

• DSBDSB Double Side BandDouble Side Band (Voice, line-of-sight tactical Digital Data-Link (Voice, line-of-sight tactical Digital Data-Link (in UHF band)(in UHF band)

and NAVAID beacon data)and NAVAID beacon data) -operational or entertainment, ranging from MF -operational or entertainment, ranging from MF

(Medium Wave) broadcasters through VHF commercial stations and (Medium Wave) broadcasters through VHF commercial stations and

Taxis to Air Traffic and Citizen Band radios. If analogue, then limited Taxis to Air Traffic and Citizen Band radios. If analogue, then limited

quality/fidelity due to channel spacing.quality/fidelity due to channel spacing.

• SSBSSB Single Side BandSingle Side Band (long range voice and ‘beyond the horizon’ tactical Digital (long range voice and ‘beyond the horizon’ tactical Digital

Data-Link in, mainly, HF band.)Data-Link in, mainly, HF band.) Used by commercial Oceanic Control Used by commercial Oceanic Control

agencies, commercial and very long range military Ship to Shore agencies, commercial and very long range military Ship to Shore

connections, RAF, USAF and commercial Flight Watch services. connections, RAF, USAF and commercial Flight Watch services.

All of these All of these

are…are…

AAmplitude mplitude

MModulatedodulated

modesmodes

Now let us look at

Now let us look at

the the FFrequency requency

MModulated mode

odulated mode

145145//

146146//


88.90 MHz

FF00

Sig

nal st

rength

Sig

nal st

rength

This single 1This single 111//22 kHztone kHztone AAmplitude mplitude MModulation of odulation of

the the ccarrier generates arrier generates

sumsum and and differencedifference frequenciesfrequencies

-1.5 -1.5 kHzkHz

+1.5 +1.5 kHzkHz


BBC radio2

VHF

Under

Under

constr

uction

constr

uction

It is now accepted that there are around 100 to It is now accepted that there are around 100 to 200 thunderstorms per day across the globe…200 thunderstorms per day across the globe…

…recent satellite data indicates that there are around 3million flashes per day

……producing 30 flashes per second around the globeproducing 30 flashes per second around the globe

…each producing a spike of em radio radiation

…these flashes are cloud to ground, or cloud to cloud or even weaker ones which shoot 400 miles in to space and have names

such as sprites, elves and ‘blue jets’.

…but 10% of all flashes are the renegade ‘positive flashes’ which produces

10 times the power

It’s all natural It’s all natural

interferenceinterference

147147//

Sparks from machinery such as Sparks from machinery such as electric motors, vehicles etcelectric motors, vehicles etc

Then there is man-made Then there is man-made interference interference

148148//

149149//


88.00 MHz

FF00

Sig

nal st

rength

Sig

nal st

rength

This interference shows This interference shows up on the frequency up on the frequency domain view domain view

-1.5 -1.5 kHzkHz

+1.5 +1.5 kHzkHz

……as fleeting and as fleeting and ever changing ever changing spikes spread spikes spread across the em across the em spectrumspectrum

Single tone Single tone

MCWMCW


This interference ruins This interference ruins the fidelity of the the fidelity of the

received signal and received signal and appears as crackles and appears as crackles and

bangs to the listenerbangs to the listener

How can we get How can we get around this around this

interference?interference?

150150//

With radio Frequency Modulation With radio Frequency Modulation (FM); audio or information is (FM); audio or information is

conveyed over a carrier wave by conveyed over a carrier wave by varying its instantaneous varying its instantaneous

frequencyfrequency. This contrasts with . This contrasts with amplitude modulation, in which amplitude modulation, in which the the amplitudeamplitude of the carrier is of the carrier is

varied while its frequency varied while its frequency remains constant. remains constant.

Frequency ModulationFrequency Modulation151151//

With radio Frequency Modulation With radio Frequency Modulation (FM); audio or information is (FM); audio or information is

conveyed over a carrier wave by conveyed over a carrier wave by varying its instantaneous varying its instantaneous

frequencyfrequency. This contrasts with . This contrasts with amplitude modulation, in which amplitude modulation, in which the the amplitudeamplitude of the carrier is of the carrier is

varied while its frequency varied while its frequency remains constant. remains constant.

Frequency ModulationFrequency Modulation152152//

Frequency ModulationFrequency Modulation

Time-Line view

time

Example is a simple Example is a simple single tone…but single tone…but could be voice or could be voice or

musicmusic

AAmplitude mplitude MModulation of the odulation of the carriercarrierFFrequency requency MModulation of the odulation of the carriercarrier

instantaneous instantaneous AmplitudeAmplitude is key is key to extracting the to extracting the information from information from

the signalthe signal

instantaneous instantaneous FrequencyFrequency is key is key to extracting the to extracting the information from information from


Amplitude is Amplitude is (nearly) irrelevant (nearly) irrelevant with FMwith FM

So interference So interference spikes are not spikes are not

processedprocessed

FM FM is is suitable for HiFi suitable for HiFi transmissionstransmissions

153153//

Frequency ModulationFrequency Modulation

Time-Line view

time

Example is a simple Example is a simple single tone…but single tone…but could be voice or could be voice or

musicmusic

AAmplitude mplitude MModulation of the odulation of the carriercarrierFFrequency requency MModulation of the odulation of the carriercarrier

instantaneous instantaneous Amplitude is key Amplitude is key to extracting the to extracting the information from information from


instantaneous instantaneous Frequency is key Frequency is key to extracting the to extracting the information from information from


Amplitude is Amplitude is (nearly) irrelevant (nearly) irrelevant with FMwith FM

So interference So interference spikes are not spikes are not

processedprocessed

FM FM is is suitable for HiFi suitable for HiFi transmissionstransmissions

154154//

Amplitude ModulationAmplitude Modulation

The process of The process of extracting the extracting the

information /sound information /sound signal from a signal from a AMAM signal is called …signal is called …

back in time

…after tuner

DetectionDetection

AMAM Received signalReceived signal

detector

155155//

Amplitude ModulationAmplitude Modulation

The process of The process of extracting the extracting the

information /sound information /sound signal from a signal from a FMFM signal is called …signal is called …

back in time

…after tuner

DiscriminatioDiscriminationn

FMFM Received signalReceived signal

discriminator

156156//

157157//recarecappCWCW

MCWMCW

AMAM

SSBSSB

FMFM

DigitaDigitall

Continuous Continuous WaveWave

Modulated Modulated CWCW

Amplitude Amplitude ModulationModulation

Single Side bandSingle Side band

Frequency Frequency ModulationModulation

Morse only.Morse only. efficientefficientNeed specialist Need specialist Rx with a BFO. Rx with a BFO.

No VoiceNo VoiceMorse dentification of Morse dentification of Radio BeaconsRadio Beacons

Inferior range to Inferior range to CW but simple CW but simple RxRx

****

Radio ‘hams’ around the world still Radio ‘hams’ around the world still enthusiastically use this modeenthusiastically use this mode

……the futurethe future

Radio 5 Live at 330 Radio 5 Live at 330 kHz?kHz?OrOr Cranwell Tower 125.05 MHz or MF NAVAIDSCranwell Tower 125.05 MHz or MF NAVAIDS

RAF Flight Watch 6742-upper RAF Flight Watch 6742-upper or Shanwick or Iceland or New or Shanwick or Iceland or New York OCAs on 8879-upperYork OCAs on 8879-upper

Data Links, entertainment TV & radio and new Data Links, entertainment TV & radio and new inter-ship marine comms including Distress inter-ship marine comms including Distress CommsComms

entertainmententertainment radio, marine channels & radio, marine channels & NAVAIDSNAVAIDS

158158//

‘‘EM’ radio energy can be made to EM’ radio energy can be made to carry speech if we carry speech if we combinecombine or or mix mix

the low-frequency (the low-frequency (AAudioudio FFrequencyrequency)currents produced by )currents produced by

speaking into a microphone, with the speaking into a microphone, with the high-frequency currents (high-frequency currents (CWCW) that ) that

produce radio waves. This produce radio waves. This combination process is called combination process is called amplitude modulation (amplitude modulation (AMAM). ).


159159//

It is an electronic circuit called an It is an electronic circuit called an

oscillatoroscillator which produces the which produces the

continuous high-frequency (continuous high-frequency (RRadio adio

FFrequency) current which has a fixed requency) current which has a fixed frequency chosen from the frequency chosen from the EM spectrumEM spectrum. . This fixed-frequency alternating current This fixed-frequency alternating current

produces the em “produces the em “ccarrier arrier wwaveave”.”.


160160//

The audio-frequency (AF) current and the radio-frequency (RF) current are mixed in the transmitter so that the carrier wave is

MODULATED by the AF current, in such a way as to duplicate the pattern of sound waves fed into

the microphone. A carrier wave can be modulated in one of two ways, either by

amplitude modulation (AM) or by frequency modulation (FM).

161161//

Amplitude Modulation Amplitude Modulation (AM) (AM)

The simplest form of transmission is basically the way Marconi sent his first transatlantic

message. The transmitter is switched alternately “ON” and “OFF” to interrupt the carrier wave. This modulates the amplitude from maximum to zero , and then back to maximum, producing pulses of different

lengths which represent the dots and dashes of the Morse Code

162162//

Whist this system is ideal for Morse, it is not good enough for speech or music, because

sound requires many more variations (or steps) to achieve an accurate reproduction. An improvement is to alter the amplitude, or ‘modulatemodulate’ the RF Radio Frequency of the

carrier wave in step with the much lower AF Audio Frequency.

163163//Fig 1-6: AM transmitter block Fig 1-6: AM transmitter block diagram diagram

• Fig 1-6: AM transmitter block diagram

164164//Parts of the basic Parts of the basic transmittertransmitter

• Master Oscillator. This generates a sinusoidal voltage (the carrier) at the required RF frequency (fo). Oscillators are often crystal-controlled to ensure good frequency stability.

• Buffer Amplifier. This isolates the oscillator from the power amplifying stage, and prevents instability occurring.

• Power Amplifier. This is used to increase the power of the signal to the required level before radiation from the aerial (fm).

• Amplifier. This amplifies the microphone signal to the desired level for output.

165165//

The modulation takes place in the power amplifier stage. If the input frequencies to the

modulator are fo from the oscillator and fm

from the microphone, we find that the output of the power amplifier will consist of 3

frequencies:

166166//Amplitude ModulatedAmplitude Modulatedtransmitter block diagram transmitter block diagram

AM transmitter block diagram

167167//Parts of the basic Parts of the basic transmittertransmitter

• Master Oscillator. This generates a sinusoidal voltage (the carrier) at the required RF frequency (fo). Oscillators are often crystal-controlled to ensure good frequency stability.

• Buffer Amplifier. This isolates the oscillator from the power amplifying stage, and prevents instability occurring.

• Power Amplifier. This is used to increase the power of the signal to the required level before radiation from the aerial (fm)

• Amplifier. This amplifies the microphone signal to the desired level for output.

168168//

• The modulation takes place in the power amplifier stage. If the input frequencies to the modulator are fo from the oscillator and fm from the microphone, we find that the output of the power amplifier will consist of 3 frequencies:

• The carrier (fo).

• The carrier minus the audio frequency band (ie speech) (fo

– fm).

• The carrier plus the tone frequency band (fo + fm).

169169//

For example, if the audio frequency ranged from 30 to 300 Hz* and the carrier was 1 MHz, then the frequencies in the output would look like:

* This is small range would only give pretty poor quality or fidelity eg like the quality a telephone!

170170//

Transmitting only one sideband …by by suppressingsuppressing the Carrier the Carrier Wave Wave and the other duplicate sidebandand the other duplicate sideband mea means all of the ns all of the output power can be applied to the remaining sidebandoutput power can be applied to the remaining sideband – far, far more efficient; giving a much greater range for the same Tx power available and potentially releasing 50+% of available frequency space.

SSB SSB

It is only used in the long wave

frequency band of 2 to 30Mhz.

172172//

SSB operation, however demands a more sophisticated and expensive transmitter.

More importantly, the receiver is expensive because the missing sideband has to be, somehow generated, to make the resultant audio intelligible;

ie it is not possible to understand SSB voice traffic on a simple AM receiver. It sounds completely garbled!

SSB equipment, therefore, is not used for entertainment or domestic radio broadcasts.

SSB SSB

173173//

One great drawback of the simpler double sideband AM system is the need for such a large bandwidth to accommodate all radio stations including both sidebands,

Another drawback is that for High Fidelity quality ~ HiFi ,approximately 20KHz is needed for each sideband. A massive chunk of the available frequencies for broadcasting for just one station.

in a limited Radio Frequency spread (30 KHz to 3 MHz in Medium Frequency MF and High Frequency HF bands).

this means, in reality, that the MF-AM system could not handle Hi Fi and only have 148 stations at any one time.

174174//

Try tuning through an AM band radio and see how close the stations are together!

175175//

Obviously, when many transmitters are crammed into a small band and overlap each other there is a big problem with signals from other transmissions breaking into the one you are using – this is known as “mutual interference”.

… and we are only discussing MonoMono systems. For stereo transmissions the problem would be doubled. As a result there are nono StereoStereo AM transmissions in the MF and HF broadcast frequencies.

176176//

Another great drawback is that random electrical ‘noise’, (some natural generated some man-made generated ), is received and amplified the same as any information or music sent from a transmitter. The result is distortion, ‘crackling’ and ‘fading’ which affects the quality of reception (ie fidelity)fidelity)

There are 40,000 thunderstorms per day

177177//

To overcome AMAM limitations of mutual interferencemutual interference (crowding) and

lack of HiFilack of HiFi, the use of short-range ffrequency requency mmodulatedodulated systems has become necessary.

178178//Frequency Modulation (FM)Frequency Modulation (FM)

With frequency modulation, the carrier wave has a constant amplitude and a much higher frequency than AM signals.

Modulation is achieved by shifting the carrier frequency, f0 ,up

and down slightly in step with the audio frequency.

Although this shift is small it gives better results because it is less prone to atmospheric or man-made noise.

179179//Try listening to an AM signal as you pass by an electric pylon

or enter a tunnel. The AM signal is distorted or lost, but an FM signal will be largely unaffected by the same conditions. FM is used in the range 88-108 MHz for high quality broadcasting; this frequency range is known as the Very High Frequency

(VHF) range. The emergency services, such as Coastguard and Lifeboats, used FM radios using VHF freqs above Civil Air Traffic (AM) …around 150MHz

Emergency and maritime agencies, plus boat and ship owners have now been Emergency and maritime agencies, plus boat and ship owners have now been banished from FM VHF and must use a much more sophisticated and secure banished from FM VHF and must use a much more sophisticated and secure system ; system ; GMDSSGMDSS, a digital system using Digital Selective Calling , a digital system using Digital Selective Calling (DSC)(DSC), , whereby every ‘participant’ or vessel has a unique ‘digital address number’ or whereby every ‘participant’ or vessel has a unique ‘digital address number’ or Maritime Mobile Address Identity (MMAI) which allows one-to-one conversations Maritime Mobile Address Identity (MMAI) which allows one-to-one conversations in a busy radio environment. Yet to be implemented in RAF SAR helicopters who in a busy radio environment. Yet to be implemented in RAF SAR helicopters who retain the old FM VHF radios so voice co-ordination with emergency services is retain the old FM VHF radios so voice co-ordination with emergency services is therefore problematical. A huge number of people with boats will be using this therefore problematical. A huge number of people with boats will be using this now. It’s probably the most commonly used radio system by civilians on a day to now. It’s probably the most commonly used radio system by civilians on a day to day basis. We will not, currently, look any further at GMDSS or DSCday basis. We will not, currently, look any further at GMDSS or DSC

GGlobal lobal MMaritimearitime DDistress istress SSafety afety SSystem ystem it’s big!it’s big!

180180//Phase TestPhase TestWhat is the speed of light?

3 x 1033

m/sec

3 000 metres per

sec

300 000 000 000 metres per sec

3 x 101111

m/sec


3 x 101010

m/sec

300 000 000 metres per sec

3 x 1088

m/sec

Click Buttons to enter your answer

181181//Phase TestPhase Test

300 x 1010

m/sec

3 000 metres per sec


3 x 101111

m/sec


3 x 101010

m/sec

Click to proceed

What is the speed of light?

300 000 000 metres per

sec

3 x 1088

m/sec


(v = f x λ) (v = f + λ) (v = f- λ)

(f = v - λ)

D

frequency frequency =

velocity -

wavelength (f = v - λ)

A

velocityvelocity =

frequency x wavelength

(v = f x λ)B

velocityvelocity = frequency+waveleng

th (v = f + λ)

Cvelocityvelocity =

frequency – wavelength

(v = f- λ)

Click Buttons to enter your answer

What is the relationship What is the relationship

between between frequencyfrequency ( (ff), ),

wavelengthwavelength ( (λλ) and ) and velocityvelocity

of light (of light (vv) is given in the ) is given in the formula:formula:

A B C D


Click Buttons to continue

184184//Phase Phase TestTest

Assessment Questions3. If the velocity of radio waves are 300

x 106, what would be the value of λ for a frequency of 3 x 106?a. 1000mb. 10mc. 100md. 1m4. What does the abbreviation SSB stand for:a. Single Side Band.b. Single

Silicone Band.c.Ship to Shore Broadcast.d. Solo Side Band.

185185//

• If the velocity of radio waves is 3 x 108 8 m/sec,

what would be the value of for a frequency of

3 x 1066 Hz ?

Phase TestPhase Test

3 MHz = f

186186//

• If the velocity of radio waves is 3 x 108 8 m/secm/sec,


3 x 1066 Hz ?


f 3 x 1088

3 x 1066

221

1 x 101 x 1022 100100mm

187187//

• If the velocity of radio waves is 3 x 108 8 m/secm/sec,


3 x 1066 Hz ?


f 3 x 1088

3 x 1066

221

1 x 101 x 1022 100100mm

f = 3 MHz

3 x 1088 m/secm/sec

=

= = 100m100m


f 3 x 1088

3 x 1066

221

f = 3 MHz

3 x 1088 m/secm/sec

=

= = 100m100m

Ideal antenna length?

//44

//22

Dipole type

Whip type

50m50m

2525mm


f 3 x 1088

3 x 1066

221

f = 3 MHz

3 x 1088 m/secm/sec

=

= = 100m100m

Ideal antenna length?

//44

//22

Dipole type

But remember …a radio wave is a transversetransverse wave so these aerials would need to be turned through 90º to work!

Whip type

50m50m

2525mm

Electric ‘E’ waveElectric ‘E’ wave

verticallyvertically polarised polarised


Assessment QuestionsWhat is the speed of light?

a.300 x 108 ms-1b.300 x 106 ms-1c.300 x 109 ms-1d.300 x 101 ms-12.

The relationship between frequency (f), wavelength (λ) and velocity of light (v) is given in the formula:a.velocity = frequency x wavelength (v = f x λ)b.velocity = frequency + wavelength (v = f x λ)c.velocity = frequency - wavelength (v = f x λ)d.frequency = velocity - wavelength (v = f x λ)3.

If the velocity of radio waves are 300 x 106, what would be the value of λ for a frequency of 3 x 106?a.1000mb. 10mc. 100md. 1m4. What does the abbreviation SSB stand for:a. Single Side Band.b. Single Silicone Band.c.Ship to Shore Broadcast.d. Solo Side Band.


What does What does SSBSSB stand for? stand for?

Single Silicon Single Silicon

Band ?Band ?

Single Side

Single Side Band ?Band ?

Ship to Shore Buffer ?

Ship to Shore Buffer ?

Solo Side Band?Solo Side Band?

Click on Click on youryour answeranswer


Correct !Correct !

193193//ReviewReview

CWCW

Marconi’s first Marconi’s first

transmissionstransmissions

EfficientEfficient

Only good for Only good for

MorseMorse

but you can’t but you can’t hear hear anything on anything on frequency frequency unless …unless ……your Rx can

your Rx can generate a single generate a single tone when it

tone when it receives CWreceives CW

interrupted - ie OnOn - - OffOff

Ordinary radios do Ordinary radios do notnot normally normally have this have this

tonetone facilityfacility


CWCW

interrupted - ie OnOn - - OffOff


196196//endend

ENDEND



3 x 1033

m/sec


30000 000000 000000 000000 metres per

sec

3 x 101111

m/sec


3 x 101010

m/sec


sec

3 x 1088

m/sec

Click to return



3 x 1033

m/sec



3 x 101111

m/sec

300 000000 000000 000000 metres per sec

3 x 101010

m/sec


sec

3 x 1088

m/sec

Click to return


3 x 1033

m/sec



3 x 101111

m/sec


3 x 101010

m/sec

Click to return

30000 000000 000 000 metres per sec

3 x 1088

m/sec




3 x 1033

m/sec

3 000000

metres per sec


300 x 1099

m/sec


300 x 1088

m/sec


sec

300 x 1066

m/sec

Click to return


Relationship between , f and

(v = f x λ)

= f

Click to return



= f ++

Click to return



= f --

Click to return



f = --

Click to return


No !No !

Return …

Documents

Convention used Left mouse click option available not recommended in this lesson