This may be a very dumb question, but I was wondering, does amplitude function as a measurement for "strength" for a radio signal (by strength I mean the ability of one wave to dominate another on a receiver)? I know that hertz defines the frequency, which I understand as the part of the spectrum a given signal occupies (which is, if I'm not totally off base, simply a measurement of where in the possible range of wavelengths, that particular wave's wavelength falls). I know that amplitude is a measurement of the magnitude of change in a wave. So frequency is the distance between peaks, and amplitude is the distance of peak-to-trough. I also know that amplitude is a measurement of strength for sound waves. When I looked it up, amplitude on sound waves are measured in decibels. So far so good. The more amplitude, the louder it is. I can understand that easily from a lay-perspective. But apparently the unit of measurement for amplitude isn't the same for all waves. I looked on Wikipedia and it says that displacement is the unit of measurement for waves moving through a medium or down a string, which seems to me is measuring a different quality. First, last time I checked sound moved through air, so why is it measured with a different unit than other waves traveling through a medium? I could see how displacement could be an effective measurement of wave strength (the more stuff it moves the stronger it is) but will that correlate to how far the wave will move through the medium? For instance, a sound can be very loud, can travel very far, and not displace a large amount of air. I'm thinking particularly of high frequency sounds, which can travel far, and be very loud, without producing any air compression (a function of air displacement) detectable by the human body. I'm sure the same could be said for any wave moving through a medium. Clearly there is more than one possible measurement of "strength" for a wave. I think it's very likely I'm confusing myself, but the various definitions of amplitude aren't helping. :) Why are multiple units of measurement needed to define the same quality of various waves? Now back to radio waves. I basically understood none of what Wikipedia said on radio wave amplitude. Does it still function as a unit of measurement to define strength? If so, how does it work? If two radio signals were being broadcast at the same frequency, say, the one that car radios use, but one is twice the amplitude, how would my car radio translate that? If amplitude isn't an effective measurement of strength, what serves this function for radio waves? I know that when I'm in my car often I can hear two signals on the same frequency but one is dominate and almost completely drowns the other out. I also know that my little iPod FM broadcaster can drown out some stations but not others, so obviously there is a function of radio wave strength independent of frequency, but what is it and how does it work? Is there more than one way to measure strength on radio waves (like there seems to be for waves in a medium)?