GPS signals are extremely weak - less than the ambient noise level. It is indeed a wondrous feat that your GPS chip can pick up the signal at all, let alone guide you round the skies. My guess therefore is the GPS electronics would be very low noise generators, otherwise the GPS wouldn't be able to work. I understand there are different frequencies involved and that the GPS has to generate frequencies to beat, but noise is noise and you imagine a GPS must be the quietest thing that isn't a mouse.