Electromagnetic waves and attenuation

[dervast]

Hi i am trying to understand how long a electromagnetic wave can travel... What is the attenuation that the electromagnetic wave face in the atmosphere... This question arised when i have read that marconni at the beginning of 20th century has sent electromagnetic waves from england to canadA! How long the electromagnetic wave can travel in a free space model?

 

[jtbell]

This is really in the domain of classical electrodynamics, not quantum physics, by the way.

Propagation of radio and television signals is a very practical subject and has been extensively studied. Try a Google search on "radio signal propagation" and "television signal propagation" and you'll get many useful links.

I've gotten interested in this subject myself recently, because I'm one of those old-fashioned people who gets TV "over the air" from terrestrial broadcasters, rather from cable or satellite, and I've recently switched from analog TV to digital TV. I'm in a "deep fringe" area where most TV transmitters are over 50 miles (80 km) away. I want to improve my digital TV reception, so I'm starting to study signal propagation, antenna design, etc.

 

[dervast]

Thx a lot but i think if i search in google about signal atenuation i will get a headache with all these info ... Can u please suggest me sth else?

 

[jtbell]

Well, I'm just starting to look so I haven't found anything comprehensive yet. I did find this just now, though: a BBC TV broadcast from London in 1938 that was carried to New York by freak atmospheric conditions and filmed off a TV screen by engineers at RCA laboratories!

http://www.apts.org.uk/recording.htm

 

[Meir Achuz]

Short wave radio waves bounce off the ionosphere, which greatly increases their range. This is more effective at night, which is noticeable even for long radio waves.