[rcxdude]

A strong signal 'that's obviously there' is only obviously there after you've already filtered it to some extent. If you were to look at the raw broadband RF environment on a scope you very much would not see the vast majority of signals there. And when you're demodulating you do often need to tune the phase and frequency of the carrier you're demodulating with, as well. GNSS signals are just generally quite low bandwidth and so that process takes a while.

Not to say that such codes aren't a neat trick, but it's useful to consider that these are in many ways the same thing.

[ralferoo]

By "obviously there", I meant take some old analogue receiver and twiddle the tuning knob. The vast majority of radio transmissions are many orders of magnitude louder than the noise floor. They are very obviously there.

Tune your SDR radio down to 1.023MHz, you'll see nothing there at all. The signal is about 20dB below the noise floor. The only way you can pick out anything at all is by correlating it against the PRNG with the correct offset in the sequence.

The GP post (to be fair, I should have replied to the post 2 higher up) was arguing that all signals are weaker than the noise floor and demodulating using a carrier was exactly the same thing. It is in one way, but also not in another - in that you need to keep trying different offsets in the PRNG sequence until you find a correlation. That's why I think "correlation" is a sensible term for Gold Codes, but "demodulation" is better for signals modulated by a sine wave carrier.

[trumpdong]

What you're describing is correlating the received signal with complex sine wavelets of various frequencies.