2. TRANSMITTER RECEIVER An AC CURRENT is fed into the transmitter Makes ELECTRONS in the METAL TRANSMITTER AERIAL OSCILLATE Which produce RADIO WAVES Which make ELECTRONS in the METAL RECEIVER AERIAL OSCILLATE And a matching AC CURRENT comes out of the receiver
4. RADIO WAVES are used for….. Studying the Universe Carrying information Control signals Navigation and radar
5. The Radio Spectrum LW MW SW LF MF HF VHF UHF SHF 300 kHz 300 MHz 3 MHz 30 MHz 3 GHz 1 km 1m 100m 10m 10 cm RADIO STATIONS & Navigation beacons TV, remote controlled toys, garage doors etc Mobiles, m’wave ovens, wireless, satellites Radar
6. LONG WAVE radio signals can ‘bend around’ the curve of the Earth’s surface and so have a LONG RANGE.
7. ionosphere reflections from the ground MEDIUM WAVE radio waves are reflected by a layer of charged particles (ions) in the upper atmosphere called the IONOSPHERE. Reflections from the ground can give a very long range, but the ionosphere has several layers whose height and density change making reception very variable
8. SHORT WAVE (microwave) radio waves pass through the ionosphere to space and so can be used for satellite relays, which can pass a signal around the world
9. ANALOGUE AND DIGITAL Radio and TV signals were carried by ANALOGUE radio wave signals. These are now being replaced by DIGITAL radio wave signals. An ANALOGUE signal can have any value Eg 0.02, 0.47, 0.53, 0.85, 0.79, 0.33, -0.14, -0.38 A DIGITAL signal can only be ON or OFF (0 or 1) Eg 0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 0, 0, 0, 1, 1 1 0
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11. Why are digital signals not affected by interference? Whenever a signal travels (through a wire or as waves through the air), two things happen: it gets WEAKER and it picks up NOISE GETS WEAKER PICKS UP NOISE ANALOGUE DIGITAL
12. DIGITAL signals use an amplifier called a REGENERATOR which just decides whether the signal is a ‘0’ or a ‘1’ and then recreates it. If we use an amplifier to make an analogue signal stronger, the noise is amplified as well. (Turning up the volume on a crackly station doesn’t help!) AMPLIFIER (original) REGENERATOR
14. Communications: satellites As microwaves pass through the ionosphere, they can be used to send TV, Internet and mobile ‘phone signals up to a satellite which then relays them around the world
15. Mobile phones are portable microwave transmitters and receivers combined in one handset . All phone companies are part of the world wide GSM* network *Global System for Mobile communications
16. A mobile communicates with base stations by microwave signals. Base stations can be powerful transmitters that cover large areas of countryside or weaker transmitters for small areas of towns
17. The GSM network can pass information around the world in a fraction of a second Base Station Exchange Internet Landline network Satellite Relay Exchange Satellite Relay Microwave Cable Base Station Base Station
18. A mobile is constantly sending out short microwave signals to find the nearest base station to get the best signal. The phone companies (and the police) can locate where the phone was at any time from records of how these signal change.
19. Cooking: Microwaves with just the right frequency (2,450MHz) can make water molecules strongly vibrate . This heats up objects containing water as energy is transferred from the microwaves to the water molecules microwaves
20. In a microwave oven, objects containing water heat up all the way through. Objects in normal (infra red) ovens heat up from the outside first. Temperatures of test tubes of cold water in a microwave and in a normal oven after 1 minute Water HOT Glass tube cold Glass tube hot Water still cold
21. Are Mobile Phones a Health Risk? Although the microwave transmitters in phones are much less powerful than in microwave ovens, phones DO transfer energy to the tissue in the head when the phone is being used. The question is does this cause damage?
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23. Researchers in Sweden have found that just two minutes' exposure to energy waves from a handset can disable a defence mechanism in the body designed to prevent harmful proteins and toxins in the blood from entering the brain. Once the proteins enter brain tissue there is a higher risk of brain and nerve diseases such as Alzheimer's, Parkinson's and multiple sclerosis developing. Other effects reported include: Skin and brain cancer Cancer of the middle ear Damage to DNA in cells Damage to the immune system Other ‘nervous system’ effects Tests on lab animals and on tissue samples
24. This research was carried out on 16 people who had complained of symptoms from using mobile phones. It was found 13 suffered symptoms including nausea, headaches and dizziness which researchers believe are a clear indication of radiation. IDEA chairman Dr Philip Michael said: "This is causing disabilities in a large section of the population. "We are working on funding for a far larger study which will use blind testing to prove beyond doubt that mobile phones are responsible, but we believe the evidence is now overwhelming. “ The brain is an electrical instrument, and the frequency of radiation produced is very close to that used in the brain, so it's no big surprise to find a phone is interfering with that frequency, causing headaches, nausea and the other problems." Tests on people
25. Federation of the Electronics Industry: "We firmly believe that there is no link between use of mobile phones and any adverse human health effect . "This is based on many years of research. The mobile phone industry is a global industry and research into the safety of phones is done on a global scale - probably $60m has been spent on this particular issue”. “ The Government set the guidelines that the industry follows, and all mobile phones sold in the UK are designed, built and tested to these standards which take account of all the scientific research into this issue” The Phone Companies say :
26. A government-funded committee headed by scientist Sir William Stewart concluded that while there was no direct evidence of a health risk from using mobiles, more research was needed to prove their safety. The chairman said: "I don't think we can put our hands on our hearts and say mobile phones are safe. If there are risks, and we think there may be risks, then the people who are going to be most affected are children." He advised people to limit the time they spend on their mobile, and to try to stay away from mobile phone masts. The Government says:
27. HOW CAN YOU REDUCE YOUR MICROWAVE DOSE? HIGH SIGNAL STRENGTH LOW You will get a bigger dose if: The transmitter is CLOSE to your head You use the device for LONGER Microwave oven Mobile mast (20m away) Mobile phone Cordless phone Bluetooth headsets
