Hello,

Here some information which may "light" you.

The Mars Global Surveyor UHF relay delivers 1.30W at 437.1 MHz (Pt = 1.30W = 31.1dBm) in an isotrop antenna (Gt = 0dBm). The distance is d=5.4x10^9 meters from earth.
The Stanford parabolic antenna diameter used for reception is D=46 meters.


The reception parabolic antenna gain is given by :
Gr = 10.log (n.(PI.D / lambda)^2)
with n=0.4 (output of antenna)
Gr = 47.9dBm


The transmission path loss can be approached by the formula :
PathLoss(dBm) = 10.log (4.PI.d/lambda)^2 = -220dBm

The received power is :
Pr = Pt - PathLoss + Gt + Gr - Lt - Lr
Lt and Lr are transmission pathlosses between antenna and receiver or transmitter and are considered to 0 for simpliest computation.

Pr = 31.1 - 220 + 47.9 = -141dBm

This power can be detected by good receivers and preamplifiers.

The following link gives you a summury of values taking into account other parameters for more accurate values.
http://mars.jpl.nasa.gov/mgs/sci/m...ables.html

You will see the received power is -150dBm. The simply computation above is not too bad !


Regards
Stephane, F1TJJ