In the first of a new series of byte-sized blogs, Rapid product manager (and R.E.M. fan) Janice Ratcliffe (right) shares a fascinating fact or two from the ever mindblowing world of electronics.
This week: Radio frequency
If the earth was flat, as some people still insist, it would
make higher radio frequency communication a lot less complicated.
Waves could be transmitted and received in a straight line,
without the problems created by that pesky curvature of the Earth, which
effectively creates a ‘dead zone’ past a certain point meaning some waves go
drifting off into the atmosphere. This is called ‘the radio horizon’ and that is
why radio antennas have to be located at certain distances to keep signals on
the straight and narrow.
The line of sight to the horizon depends on how high up you
are and the height of what you are looking at. If you are a person 2 metres tall standing
on a beach you can see 5.1 kilometres whereas a radio mast 20 metres high that you can see
dotted around – even the crazy ones that are made to look like trees – will be able to talk
to another of 20 metres with aerials on top. If you were at the top of one you could see the other from about 30 kilometres apart.
Depending on the frequency some waves can be reflected and
refracted, pass through walls, and others can bounce off the atmosphere just to
complicate it. Those of a certain generation will be able to remember pirate radio that
sounded better at night due to the change in the atmospheric layer the radio
signals bounced off.
What frequency to use? It just depends!
Take a look at the Rapid website for a wide range of RF and wireless products.
1 comment :
So, roughly a kilometre of reach for every metre of elevation? That explains my dramatic increase in FM radio strength upon raising the aerial from the garage roof to the eaves of the house. Nearly a millivolt here in Exeter from the North Hessary Tor mast, and even the low powered BBC Radio Cornwall is now audible. Nothing previously.
As for those pirates... well in the buccaneering days MW reception behaviour depended where you lived. In London Carollne 199 was good all day, but got submerged at night when skywave brought in the continentals. Conversely, today's legitimate and low-powered MW Caroline is absent (of course) from Devon in the daytime, but marginally received at night.
Gosh, you don't get all this wireless fun with DAB, or streaming... etc....
Post a Comment