The Radio World and GPS – An Introduction
So what does the above has to do with Radio signals and GPS? Radio signals are short electromagnetic waves that are used to carry data about just anything from one place to another. Once the data is received by your unit, it is interpreted to display something or play some sound to you. In a manner similar to the way human hearing works, the GPS receivers collect radio waves using an antenna that are sent or conducted to a separate processing chip for interpretation.
Basically, when we refer to "wireless," we are speaking of radio signals. WiFi, WLAN, Bluetooth, and almost every other wireless device depends on radio signals to receive and send data.
For wired ones, you do not need radio signals. The copper wire (in twisted pair) or the center lead (in coaxial cable) serve as good conductors that offer less resistance to the data being carried. Except for very short distances, the way transmission modes work are the same.
For very short distances, like from your computer to your printer, the data need not be changed into an analog (waveform) format. But for longer ranges, the data is transformed into analog format, superimposed on the radio signals, and are released.This is how AM and FM radio work.
For these broadcasts, any device capable of receiving and interpreting the data can strip out the data from the radio signal and convert it back to digital format for further processing.
The same process is employed in GPS also. The GNSS satellites convert data into analog signals before superimposing them on radio signals. Converting into analog form implies a signal that shows +y for ones and -y for zeros. The end of transmission (EoT) is indicated by x=y=0. These radio signals cross the vacuum and different atmospheric layers to reach your GPS unit. Once your GPS antenna receives the radio waves, it sends it to the GPS receiver which filters the additional noise gathered during the travel of radio signals and then, you get the final output on your GPS display.
The only disadvantage of radio signals is that they lose strength over long distances and that they cannot penetrate solid substances. This is why you experience incorrect GPS observations or no signals. Still, radio world and GPS technology has advanced to handle weak signal GPS to offer you a lower probability of errors.