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RF question

 
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johnyaya



Joined: 30 May 2001
Posts: 149
Helped: 17
Location: YoyoDyne
Post16 Oct 2001 22:54   
Is there a rule-of-thumb regarding an RF transmission through the air (line-of-site, no obstructions) relating signal loss (-db) to distance (km) as a function of wavelength?
Does this number change for FM, AM, ASK, etc.?

Thanks much.
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bastos4321



Joined: 01 Jan 1970
Posts: 334
Helped: 24
Post17 Oct 2001 10:10   
Attenuation in free space

Ao=-20*log10(c/(4*pi*F*d))

F - Frequency
d - distance
c - speed of ligth

It does not depend on the type of modulation.

Regards bastos
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