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DIGITAL VS ANALOGUE
LEARNING TARGET
I CAN... DESCRIBE THE DIFFERENCE
BETWEEN ANALOGUE AND DIGITAL
SIGNALS TO EXPLAIN THE
ADVANTAGES AND DISADVANTAGES
OF USING EACH SIGNAL.
WHAT TYPE(S) OF
ELECTROMAGNETIC WAVES ARE
USED FOR COMMUNICATION?
• THE RADIO AND MICROWAVE SPECTRUM IS
DIVIDED INTO FREQUENCY BANDS.
• THE HIGHER THE FREQUENCY OF THE
WAVE:
• THE MORE INFORMATION THEY CARRY.
• THE SHORTER THEIR RANGE
• THE LESS THEY SPREAD OUT (DIFFRACT)
Waveband
Frequency range
Use
Microwave
+3000 MHz
Satellite TV, phones
UHF
(ultra-high frequency)
300-3000 MHz
Terrestrial TV, Mobile
phones
VHF
(very high frequency)
30-300 MHz
Local Radio, emergency
services
MF
(medium frequency)
300 kHz – 3 MHz
National Radio
(analogue)
LF
(low frequency)
Less than 300 MHz
International Radio
(analogue)
Radio waves are not absorbed strongly by walls, which is
why radio (and television) signals can be received indoors.
Tall objects, like buildings and hills, can prevent radio
waves travelling directly from a transmitter, but this is
not always a problem.
In some areas, the
reflection of waves
off other buildings or
hills can actually lead
to improved radio
reception.
Low frequency (up to 3 MHz) radio
waves travel along the Earth’s
surface and can travel hundreds of
miles. These ground waves are used
for local and national radio.
Higher frequency radio waves (3–30
MHz) are reflected off the ionosphere
high in the atmosphere. These sky
waves are used for international and
amateur radio.
The ionosphere is stronger in the
summer than winter so you can listen to
radio stations from a greater distance.
Microwaves are very high frequency
radio waves (over 30 MHz).
Unlike other radio waves, they
are not reflected by the
ionosphere but pass straight
through and into space.
This means that they can be
picked up by satellites and
transmitted over very large
distances right round the Earth.
In your own words answer these on your
guided notes:
1. Describe the difference between using radio waves
and microwaves for communication.
2. Explain how the ionosphere is used for
communication. Draw a diagram to support your
explanation.
Think about other methods of sending a signal between
two locations.
Optical fibers are increasingly being
used for communications instead of
traditional copper wires.
Optical fibers have a number advantages
over copper wires:
 They are cheaper.
 They are thinner and lighter.
 Signals can travel further.
 Not affected by electromagnetic signals so no interference.
 Several digital signals can be carried by one fiber.
 Signals do not weaken as much while they travel.
 More secure – they are almost impossible to bug.
An Analogue Wave:
Amplitude varies
continuously
Frequency varies
continuously
It can have any value within
a range.
Where used:
Dimmer switches,
thermometers, speedometers
and old-fashioned watches.
These are coded pulses.
Only made up of two values –
1 ‘on, or 2 ‘off’.
Where used:
On/off switches, digital clocks
and meters.
current
An Digital Wave:
time
In your own words answer these
on your guided notes:
1. Describe the difference between an
analogue and digital signal.
2. Describe the advantages of using a
digital signal over an analogue
signal.