Satellites have max 20 watts transmit!

@geoffkait 

That’s because of the very high gain receivers at the other end. You have to account for free space loss.

Wrongo Geoffy.  Terrestrial GNSS receivers detect the unique pseudo random code that modulates the L1 carrier to ensure they are tracking the same satellite(s) consistently. Others use DSP to lower the noise floor. Hel-loo! High gain signal amplification will (rpt will) amplify noise as well as the signal, a self-defeating means to an end. Get on the knowledge train Geoffy 🚂 🚂 🚂 Toot! Toot!

TBF, antennas are often described as "high gain" so I’m not sure Geoff was speaking purely about active amplification.

With up to 70m wide dishes, I’m sure those antennas are of extremely high gain, not to mention the digital signal processing and at least some electronic gain that occurs down the pipeline.


https://en.wikipedia.org/wiki/NASA_Deep_Space_Network#Antennas



Best,
E

Bingo! Arecibo antenna in Puerto Rico is another good example, with diameter of 305m. And the very large log period HF antennas on certain US buildings. The satellite link budget equations I worked with were so long it took a whole page to write them out.