43 km line of sight with USB WiFi stick (2005)

Re:43 km line of sight with USB WiFi stick (2005) by jupp0r on Thursday March 03, 2022 @01:06PM (#30544431)

Yes, radio waves are attenuated in the atmosphere. This is highly frequency dependent - for practical applications the lower the frequency, the less radio waves are attenuated. In comparison with attenuation from obstacles in non-line-of-sight situations, the atmospheric component is not significant.

For really long range propagation on earth, reflections on atmospheric layers are the dominant factor (as there is no line of sights due to the curvature of the planetary surface).

See https://www.sciencedirect.com/topics/engineering/atmospheric... for some nice graphs.

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Re:43 km line of sight with USB WiFi stick (2005) by BizarroLand on Friday March 04, 2022 @02:38PM (#30559359)

Does that mean that there is an electromagnetic frequency that, no matter how much power we can feasibly put into it, it simply will not transmit through earth's atmosphere due to its' instantaneous attenuation outside of a vacuum?

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Re:43 km line of sight with USB WiFi stick (2005) by jupp0r on Saturday March 05, 2022 @11:08AM (#30568662)

Yes, in the terahertz band range for example you have very high attenuation of more than 1000 db/km. It's a spectrum (no pun intended), so depending on where you draw the line on "through earth's atmosphere" in terms of how far you want to transmit, you'll have some frequency where this becomes infeasible or you'll need more directed antennas and/or more transmit power.

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