P5e: Satellite Communication

Using microwave and satellite technology, you can call anyone from anywhere on the planet, or receive a TV signal via a satellite dish. This technology has moved at a rapid pace. But how does the signal from our mobile phones get to the person receiving the call and how do TV and radio broadcasts reach the viewer and listener? This item looks at why we use microwaves to transmit information and the physics behind the communications industry. 

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What wavelength do radio waves have?
Very long wavelengths.
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What can radio waves do around large objects? Give two examples of large objects.
'Spread' around large objects, e.g. buildings and hills
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Talk about radio waves in the earth's atmosphere.
They are reflected by the ionosphere (part of the Earth's atmosphere)
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Talk about microwaves in the earth's atmosphere.
They pass through the Earth's atmosphere.
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What wavelength do microwaves have?
Short wavelengths.
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What type of frequency is used to communicate low orbit satellites?
Relative lower frequency
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What type of frequency is used to communicate geostationary satellites?
Relative higher frequency.
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What frequencies are used for low orbit satellites and geostationary satellites?
Different satellites.
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How can information be transmitted using microwaves to orbiting artificial satellites and then retransmitted back to Earth or to other satellites?
Information from Earth is transmitted to geostationary satellites using microwaves carrying digital signals. These signals are then retransmitted as microwaves. This may be to another satellite, or back down to Earth.
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Why are digital signals used to communicate with satellites?
because they are affected by less noise than analogue signals - and they don't attenuate (lose energy) as quickly.
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Complete the sentence: Satellite television dishes are examples of the sort of _________ receivers needed.
Satellite television dishes are examples of the sort of parabolic receivers needed.
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Why do satellite transmitters and receiving dishes need to be very carefully aligned?
The wavelength of microwaves emitted by satellites is usually between 1&10cm.The dishes that emit them from satellites usually have a diameter much larger than this.This produces very little diffraction,giving a narrow beam that doesn't spread out
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How do electromagnetic waves with frequencies below 30MHz behave in the atmosphere?
They are reflected by the ionosphere.
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How do electromagnetic waves with frequencies about between 30MHz and 30MGz behave in the atmosphere?
Rain, dust and other atmospheric effects reduce the strength of the signal due to absorption and scattering.
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How do electromagnetic waves with frequencies above 30MGz behave in the atmosphere?
Can pass through the Earth's atmosphere.
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What does the amount of diffraction depend on?(2)
The size of the gap and the wavelength of the wave.
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What are the conditions for maximum diffraction?
Maximum diffraction happens when the gap is the same size as the wavelength, producing semi-circular waves.
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Why do long radio waves have a very long range?
Because they have very large wavelengths - so it will diffract lots.
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Other cards in this set

Card 2

Front

What can radio waves do around large objects? Give two examples of large objects.

Back

'Spread' around large objects, e.g. buildings and hills

Card 3

Front

Talk about radio waves in the earth's atmosphere.

Back

Preview of the front of card 3

Card 4

Front

Talk about microwaves in the earth's atmosphere.

Back

Preview of the front of card 4

Card 5

Front

What wavelength do microwaves have?

Back

Preview of the front of card 5
View more cards

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