What's the commercial GPS rx S/N general spec.?

Dear sirs,
I would like to calculate GPS receiver link budget, so I need to know how about the GPS receiver information for link budget.
Does anyone can tell me, or point out the key.
Thanks!
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GPS(USA) L1 frequency
GPS receiver on the ground
GPS receiver antenna noise temperature: Unknow?(NEED HELP)

Hi,
Refer Kaplan understanding GPS ....
Also look at the ICD and signal spcification freely available on the web.
The Antenna noise temperature is debatable issue. For all practical calculations use an NF of 4dB + implementation losses.
Hope this helps,
Madhukar