Modulation Types RNAV
Amplitude modulation alters the "size" of the wave, so you will see the wave getting bigger or smaller (vertically) but without the wave being compressed or extended (horizontally).
AMAM —Amplitude Modulated) graph" />
Frequency modulation does not alter the "size" of the wave but the frequency — this results in either a compression or an extension (horizontally) of the wave, very much like a slinky.
FMFM —Frequency Modulated) graph" />
Phase modulation is a complex type of modulation where (as far as radio navigation is concerned) the phase of the carrier wave is reversed. This is used in GPSGPS —Global Positioning System (USA).
Keyed modulation simply turns the signal on or off — think of morse code.
Note that with all of these it is the carrier wave that is changed — that is the "vessel" for carrying the information. (The information is the modulating signal, which we do not want to change.)