The carrier is typically at a much higher frequency than the baseband signal. Thereafter, in a radio communication environment, we perform the task of radio signal modulation to transfer the amplitude and frequency variant baseband signal to a radio frequency electrical waveform called the Carrier. We will from hereon refer to this information signal as the Baseband signal. The electrical output from a microphone can thereafter be processed and amplified as desired to produce a strong electrical signal that continuously varies in frequency and amplitude in accordance with the original sound of the voice. For instance, the human voice that propagates for short distances through the air by virtue of the variation of air pressure has to be converted to an equivalent electric voltage variation. In this article, let us try to recap some of the fundamentals of radio signal modulation and its hows and whys…Ī simple illustration to depict a typical radio signal modulation method to produce AM RF signal from a transmitter.Somehow the information that we need to send across has to be first converted to its electrical equivalent. Most of us take modulation for granted and rarely give it a second thought. All of them are forms of radio signal modulation. With the dawn of the digital age, we are all exposed to PSK (as used in PSK31), FSK (as used in RTTY), and ASK (as used in CW often as OOK). For instance, we are conversant with the terms Amplitude modulation (AM), Frequency modulation (FM), single-sideband modulation (SSB), etc. We are all perhaps familiar with some of the fundamental aspects of the process of radio signal modulation. We as radio amateurs have had the radio as a medium for almost a century in various forms and experimented with various aspects. The applications of radio communication are endless. Other than these, messages are transmitted from one place to another for commercial use, military, maritime-mobile, aviation, space communication, telemetry, etc. Then again, we have television broadcast transmissions that allow us to see motion pictures along with the synchronized sound. For instance, we are all familiar with medium-wave and shortwave AM radio broadcast, or the FM radio that not only sounds better than typical AM broadcast radio but is also capable of stereophonic transmission. There are several ways of achieving the objective. For serving the purpose as a practical communication medium, the radio wave has to undergo a process of radio signal modulation.