because of wadda
If we discount on/off switching af a carrier (c.w.), for instance as used for the transmission of Morse, then it must be m.c.w. in which an a.m. carrier is keyed on and off.
Analog modulationIn analog modulation, the modulation is applied continuously in response to the analog information signal.Common analog modulation techniques are:Amplitude modulation (AM) (here the amplitude of the modulated signal is varied) Double-sideband modulation (DSB) Double-sideband modulation with unsuppressed carrier (DSB-WC) (used on the AM radio broadcasting band)Double-sideband suppressed-carrier transmission (DSB-SC)Double-sideband reduced carrier transmission (DSB-RC)Single-sideband modulation (SSB, or SSB-AM), SSB with carrier (SSB-WC)SSB suppressed carrier modulation (SSB-SC)Vestigial sideband modulation (VSB, or VSB-AM)Quadrature amplitude modulation (QAM)Angle modulation Frequency modulation (FM) (here the frequency of the modulated signal is varied)Phase modulation (PM) (here the phase shift of the modulated signal is varied)
Amplitude modulation (AM) is a method used in telecommunications to vary the strength (amplitude) of a carrier signal in proportion to the waveform being sent. This modulation technique allows the transmission of audio or data signals through changes in the amplitude of the carrier signal. AM is commonly used in broadcast radio to carry audio signals.
To encode binary data onto a carrier in the electromagnetic spectrum, modulation techniques are employed. These techniques, such as amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM), alter specific properties of the carrier wave to represent binary values. For instance, in amplitude modulation, the amplitude of the carrier wave is varied to correspond to binary 1s and 0s. This allows the transmission of digital information over various communication channels.
In television system for video transmission AM is used and for audio transmission FM is used....
If the modulation index is greater than 1 (more than 100% modulation) the modulated carrier signal is periodically reduced to zero. This does not effect the transmitter but at the receiver these "dead carrier" intervals result in dropouts in the audio stream from the loudspeaker producing a distorted output that is difficult to understand.
The maximum modulation index for a carrier signal without resulting in over-modulation typically depends on the modulation scheme being used. For standard amplitude modulation (AM), the maximum modulation index is generally 1, meaning the peak envelope power of the modulated signal should not exceed the carrier power. In frequency modulation (FM), the modulation index can be higher, but it should still be kept within limits defined by the system to avoid distortion. Ultimately, the precise value can vary based on specific application requirements and the desired quality of the transmitted signal.
amplitude modulation is used
Tone modulation through of modulating a carrier frequency using the charactoristics of a sound, its the method used for telephone
FM stands for frequency modulation. The definition is: when the frequency of the carrier wave is changed in accordance with the intensity of the signal, it is called frequency modulation. In frequency modulation, only the frequency of the carrier wave is changed in accordance with the signal. However, the amplitude of the carrier wave remains unchanged.
One disadvantage of the standard amplitude modulation system is that 67% of the power is used for the carrier, but the carrier transmits no information, so it can be considered as wasted power.The 34% remaining power is split between two mirror opposite sidebands so, in effect, you really only have 17% of your power used to carry the signal.
Amplitude Modulation (AM) and Frequency Modulation (FM) are commonly used for sound signals. AM varies the amplitude of the carrier wave to encode the audio information, making it simple and effective for broadcasting over long distances. FM, on the other hand, varies the frequency of the carrier wave, providing better sound quality and resistance to noise, which is why it is often preferred for music and high-fidelity audio transmission. Both methods allow for efficient transmission of audio signals over radio waves.