What does the term "modulation" refer to in radio communications?

The term "modulation" in radio communications refers to the variation of a carrier signal to transmit information. In this context, modulation involves altering a particular characteristic of the carrier wave—such as its amplitude, frequency, or phase—in order to encode the information being sent. This is essential for effective communication, as it allows the signal to be transmitted over varying distances and through different mediums while masking the information being sent from potential interference or eavesdropping.

For instance, amplitude modulation (AM) and frequency modulation (FM) are two common techniques where the amplitude or frequency of the carrier signal is varied, respectively, to encode the desired information. This modulated signal can then be transmitted efficiently and can be demodulated by the receiving equipment to retrieve the original message. Understanding modulation is foundational for anyone operating within the field of radio communications, especially for tasks involving signal transmission and reception.