# Satellite earth station problem

Satellite is at 6/4GHz and bandwidth 72MHz. Bellow is the earth station. I have Pt = 200 Watt , Gt=30dB (gain satellite) ,Gr=42dB, Lm=6.7dB( loss other than free space loss) and distance is d=35870km . Earth station temperature is 20 Celsius.

Pt is transmit power
Gt is gain transmit (satelitte antenna)
Gr is earth antenna gain
L  loss


S/N of threshold is 15dB after amplifier and i need to calculate the gain of the LNA.
I can calculate Pr receive power but then i am not sure what to do. I cant calculate Teff(effective system temperature) as i dont have noise temperature of transmition line or filter. Also i dont know what has earth station temperature has to do with the system. S/N or C/N should be the same as i know but this really confuses me. All formulas calculate system temperature but i havent found how to calculate when it is between.

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Too many undefined variables, acronyms and other assumed context. – Olin Lathrop Sep 16 '12 at 23:10
@OlinLathrop, i tried to fix it. What other is assumed ?These are all the data – Parhs Sep 16 '12 at 23:16
What do you mean by "S/N ratio is 15dB"? Are you saying your system can only tolerate that ratio or is that the SNR that your system is receiving? – Kellenjb Sep 17 '12 at 2:33
S/N of threshold is 15db after the amplifier.. – Parhs Sep 21 '12 at 19:05