P5e - Satellite Communication Flashcards
Fill in the blanks.
For low orbit satellites, the signals are usually ______ frequency, and for geostationary satlellites, the signals have usually ________ frequencies.
- low.
- higher.
Why is it difficult to directly communicate using radio waves or microwaves with the other side of the Earth? How is this overcome?
- the Earth curves, whilst the waves can only travel in straight lines.
- therefore, signals are transmitted to satellites, which are retransmitted back to Earth.
Why is the size of a satellite dish many times larger than the wavelength of the waves?
- to ensure that there is little diffraction, so the beam is very narrow.
- it is therefore important to align the receiving and transmitting dishes.
Fill in the blanks.
Long wavelength waves, such as ____________, are reflected by the _________. Waves with a shorter wavelength, such as ____________, pass straight through, and are therefore transmitted to Earth by _____________.
- radio waves.
- ionsphere.
- microwaves.
- satellites.
Fill in the blanks.
If the frequency is below ______, the waves are __________ by the ionsphere. If the frequency is between ___________________, the waves can ___________ the atmopshere. If the frequency is above _______, the waves are ________________ by dust and rain etc.
- 30MHz.
- reflected.
- 30MHz and 30GHz.
- pass through.
- 30GHz.
- absorbed and scattered.
When does diffraction occurs? When does maximum diffraction occur?
- diffraction occurs when waves pass through a gap or an object.
- maximum diffraction occurs when the gap and the wavelength are similar size.
How is matching the wavelength to the height of an obstacle helpful when trasmitting radiowaves?
By matching the wavelength to the height of an obstacle, the wave diffracts. This means that the waves can reach the other side of the obstacle, and can be received.
