Have a look at this. You can test a NEO GPS module using a laptop and serial UART module e.g CH340 with Windows USB driver and Windows terminal app set for 9600 baud. Or you can just put 5V on the VCC pin and connect nothing else but its antenna. If the NEO board red time lock led isn’t flashing there’s no locked satellite signal found and mine repeatedly transmits blocks of junk data. It doesn’t even stop and allow me to send some control codes back either. As I’m just learning sketches, I don’t know what they make of this startup junk data phase, before NEO gets satellite lock? I would expect internal firmware to block everything until a valid lock is received, unless my cheap Chinese modules have inferior firmware?