When you make a call using your mobile the
phone sends a digital signal at a frequency in the region of 900 MHz, this is in the microwave
region of the electromagnetic spectrum. A local transmitting/receiving station receives this
call via a selected frequency and reroutes via other stations, if needed, to the receiving
phone.
The country is divided into cells with each cell containing one "relay" station.
In regions where the phone traffic is high more cells are needed in a given area. In cities one
station covers around 2 km whereas in the country this may extend to over 25 km. You will
probably have seen some of these relay stations springing up all over the place if you travel
around the country. The size of the cell (hence the name cellular phones) also depends on
the frequency of that particular band. Higher frequencies do not travel so far without
distortion and so the cells are smaller. The frequency bands used by mobile phones in Britain
are from 880 MHz to 960 MHz, 1710 MHz to 1880 MHz; the upload and download bands being different within each of the two main bandwidths.
A
mobile phone is really just a low powered radio and mini computer which is why you need so many of the relay
stations and cells to cover the country.
Mobile phones can be really useful but always think about other people when using your mobile! Talk quietly and always switch it off when you are somewhere where an incoming call might upset people near you. I have been at a concert where the music was spoiled by someone's phone going off. Many people use mobile phones to send text messages instead of talking – texting is much less of a nuisance than using your voice.
There has been a lot of public concern about the dangers of microwave radiation to your brain when using a mobile phone but at present there has not been any firm conclusions. However I do know people who use text messages rather than holding the phone up close to their heads when making a call. The wavelengths of microwaves used to transmit information using a mobile phone is normally just under 30 cm compared with the 12 cm used in microwave ovens. The shorter wavelength means a higher energy and so more damaging to human tissue.