2 ms·
It would be interesting to learn more about these systems in the context of today's systems (say, a cell-phone receiving GPS signals), in terms of power receive
by bluenose69 5y ago
It would be interesting to learn more about these systems in the context of today's systems (say, a cell-phone receiving GPS signals), in terms of power received, bandwidth, signal:noise ratio, and so forth.
This kind of comparison can be really enlightening, especially to younger folks. (I'm not one of those folks ... I find it simply amazing how the tiny antenna in my cellphone can receive GPS signals at enough power to be useful for decoding position.)
- kens 5y agoYou may know that GPS is built around pseudo-random sequences. By correlating the known sequence with what you receive, you can extract the signal from a lot of noise. By determining the time offset in the correlation you get the distance from the satellite. The interesting thing is that Apollo used a very similar system for determining the distance of the spacecraft. They sent a pseudorandom signal from the ground and the spacecraft returned it. By correlating the sent and received signals, they determined the distance of the spacecraft.