[Ronja] Vacuum tube in Ronja preamplifier

[Tomasz Koprowski]

On Sunday 14 of October 2007 15:25, Gullik Webjorn wrote:

> Spot size = tan(1.9e-3) * 1400 m = 2.66 m
> Receive lens = 0.065^2 * PI = 0.0132 m2
> Rec power = 0.017 W * 0.0132/(2.66)^2 = 31 uW = -45 dBW = -15 dBm
(...)
>
> Do you agree with my calculations, or did I miss something?

What comes to my mind is atmospheric loss due to absorption and scattering
which can go from a few dB/km in good conditions to 150 dB/km in dense fog. 
[1] 

Regards,
Tomek

[1] Gesellschaft fur optische Kommunikationssysteme mbH. "Theoretical 
background of FSO", 2003. 
http://www.cbl.de/downloads/pdf/Whitepaper%20-%20Technology%20of%20FSO.pdf