Calculating Power

Hello Skydel!

I am trying to calculate the satellite power from log data and cannot seem to connect the dots with the math. The transmitter (satellite) power should be around 14dBW (for GPS L1CA) but I seem to get different answers that are too low. I have the signal strength model turned on and 13 dB of Tx antenna gain. For this example, -4.8 is the relative power level and 182.4 dB was calculated for free space loss. So…

P_received (dBm) = P_transmitted (dB) + gains (dB) - losses (dB)
P_transmitted (dBm) = P_received (dBm) - gains (dB) [Antenna gains] + losses (dB) [Free space loss]
P_transmitted (dBm) = -130 dBm - 13 dB + 179.6
P_transmitted (dBm) = 36.6 dBm or 6.6 dBW

6.6 dBW is pretty far from 14 dBW. I know there are some unaccounted for losses, but I don’t think they would be around 7 dBW.

Can you help me better understand this math and where I might be going wrong? Maybe there are some underlying principles that I’m missing?