Comment by trumpdong
7 hours ago
FWIW this is how almost every communication system works. They're all weaker than background noise (e.g. sunlight) but you extract them by correlating with some kind of carrier signal (often but not always a sine wave)
Err what?
No, conventional radio broadcasts can be received with a low noise amplifier and a tuned filter.
The received GPS signal, at ground level, is lower than the thermal noise floor. And the 1.023MHz code is modulated on the RF carrier anyway.
> and a tuned filter
So correlating it with a sine wavelet?
No? Old AM radio required only rectification. You can receive it with accidental diodes.
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