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Radio waves
tend to travel in straight lines. This can be a bit of a
nuisance if the person you want to send a radio message to is
on the other side of a hill but fortunately mother nature in
her infinite wisdom foresaw this and gave us the ionosphere,
which is a belt of charged particles up in the atmosphere
which reflects radio waves downwards, provided that the
wavelength is not too high. As a result a wave from a
transmitter can hit the ionosphere and bounce down to a spot a
very very very long way away! Furthermore upon hitting the
ground it is possible for this wave to be reflected right back
up, hit the ionosphere and bounce back down again, thus
skipping all the way around the world; the only drawback being
that every time it bounces it loses a lot more of its power.
So okay it works, it is possible to transmit radio waves right
around the globe but since they are getting weaker and weaker
is there a better way? Yes, there certainly is! Turn your
radio signal in a concentrated beam up to a satellite which is
always in exactly the same position relative to the earth
(geo-stationery) and put in it a device called a transponder
which will receive the radio signal, amplify it and then fire
it straight back down to earth again. Not only have you lost
no signal strength in the bounce but you will also be unable
to amplify it; not only have you the ability to send a signal
back down to earth a long distance from where it first
originated but you can also send it in a concentrated beam to
another receiving station on earth which can do exactly the
same thing; receive the signal, amplify it and then send it off
to another satellite! It is therefore possible to send a radio
message right the way round the globe without losing any
power!
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The first satellite in space was the Russian Sputnik which
frightened a whole generation of Americans because no one had
a clue up until then that the Russians were so far ahead of
the USA in the necessary technology! Engineers and technicians
went into overdrive and a rather primitive, and pretty well
useless, satellite using a tape recorder to store and then
rebroadcast voice messages was sent up by the Americans but
the first really successful telecommunications satellite was
Telstar which was launched in 1962 and sponsored by various
companies including the British GPO, the French equivalent and
Bell Telephone laboratories in the United States. Satcom had
been well and truly born.
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