OCR Gateway P1g

Frage	Antworten
P1g - Wireless Signals	Electromagnetic radiation can be used for wireless communications. For example: - radio waves are used to transmit television and radio programmes - microwaves are used to transmit mobile phone calls.
Interference	Radio stations whose transmitters are near each other need to broadcast on different frequencies to avoid interference between the signals.
DAB Vs FM	DAB - Digital Audio Broadcasting - is a digital system for transmitting radio programmes. FM, Frequency Modulation, is an analogue system for transmitting radio programmes. Both have advantages and disadvantages. For example: DAB makes more radio stations available and suffers from less interference from other broadcasts. On the other hand, DAB may have a poorer audio quality than FM, and not all areas of the UK are currently covered by DAB broadcasts.
Refraction	Radio waves are refracted by different layers in the Earth’s atmosphere. This leads to a reduction in the signal, making it difficult for them to be received over long distances. Unlike radio waves, microwaves are not refracted, so they are used for satellite communications.
Diffraction	Radio waves are diffracted when they meet an obstruction. Microwaves do not diffract and therefore the transmitter and receiver needs to be in line of sight.

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