Modulation is the process of converting Data (Morse Code, Audio or Digital Data) into a radio signal that can be sent via an Antenna, this is the primary job of the Radio Transmitter.
CW (Continuous Wave)
CW (Morse Code) is sent by turning on and off the “Carrier Wave”, which is essentially a wave that matches the frequency of the radio. When detected by the receiver, it replaces the wave’s signal with an audio tone, to allow operators to hear it.
Amplitude Modulation (AM)
Amplitude Modulation is used to send an audio signal by changing the amplitude of a signal. The “carrier wave” is cropped to match the audio wave, and is then transmitted.
When transmitted, AM Signals consist of an unmodulated carrier in the center. On each side of the carrier is the modulated signal (like above). Because of the wide number of frequencies produced by AM transmitters, they require more power. As a result, differen versions of AM modes were invented. Double Sideband (DSB) is the same as AM radio, but the carrier is removed. Single Side Band (SSB) is where both the carrier and one of the sidebands are removed, resulting in a single sideband. SSB signals consist of either an Upper Side Band (USB) or a Lower Side Band (LSB). Depending on what band you are on, a different form is used.
Frequency Modulation sends a signal by changing the frequency of the signal.
In order to send Digital data, data is translated into audio or a wave form and is then sent using SSB, AM or FM. There are hundreds of different ways data can be encoded: everything from sending text, self-error correcting, TV, FAX, E-Mail and even the internet.