P5e - Satellite communications

Transmitting and receiving• Microwaves are used.• Why is a different

frequency used to send info back to Earth?

Revision - Frequency• Frequency is…

• It is measured in…

The ionosphere• The ionosphere is…

• Radio waves are _________ by it

• Microwaves have a ________ frequency and pass through

Atmospheric effects

DiffractionDiffraction

If it were not for diffraction, there would be many areas where radio waves would not reach.

Waves can still be detected even when they cannot travel in a straight line, from where they are being produced, to where they are to be received. This is because waves can be diffracted.

DiffractionDiffractionThe size of the gap affects the amount that the waves are diffracted.

A large gap producessmall diffraction.

A small gap produceslarge diffraction.

DiffractionDiffractionThe size of the gap affects the amount that the waves are diffracted.

A large gap produces

small diffraction. A small gap produces

large diffraction.

Radio waves diffract easily and so they are very suitable for broadcasting.

Long wave radio waves have a very long transmission range because they diffract around hills and over the horizon.

Diffraction of waves

Don’t despair if you live behind a big hill!

Short wave

Long wave

Diffraction of waves at the dishShort wave Long wave

Amplitude modulation (AM)

Frequency modulation (FM)