Receiver RF Input Power

 Equation:    Pr = ((Pp x G2 x δ  x λ2) / ((4xpi)3 x r4))    = Watt
 
Where:
 Pr   = power receiver input (Watt)
 Pp   = peak RF power (Watt)
 G    = antenna gain (figure)
 δ    = target Radar Cross Section (sq. m)
 λ     = wavelength (m)
 r     = target range (m)
 
 Use the Microsoft Calculator (or any other) and don`t forget to type in the brackets!
   Pp                   G2          δ            λ2                    pi              r4
 Pr =  ((1 000 000 x 10 000 000 x 1 x 0.008326562) / (1984.4 x 2.7984121)) 
 

      = 1.5-14 Watt or - 138 dBW