The sound signal of a standard NTSC television signal is frequency modulated.
AM - Amplitude Modulation FM - Frequency Modulation
Aplitude ModulationAn AM transmitter is a Amplitude Modulated transmitter where the amplitude of the Radio Frequency signal is modulated, usually used in the lower frequency bands where the frequency is to low for Frequency Modulation (FM), it was the first type of modulation used in radio communication FM was developed in the late 1950's and is not sensitive to static interference as AM AnswerAM is Amplitude Modulation that is the RF signals amplitude is modulated with the audio signal. this modulation is done because the audio signal being of low frequency cannot be transmitted to longer distance so the audio signal is amplitude modulated with RF signal and then transmitted into the air
Normal frequency range for amplitude modulation is 550kHz to 1610kHz
Amplitude Modulation (AM) is used for the picture portion of a television transmission while Frequency Modulation (FM) is used for the audio portion.
In a analog transmitter the RF carrier have to be modulated with the analog signal either by AM or FM where in digital transmitter the carrier is simply switched on and off a off = a zero and on = a one
Frequency modulation have some advantages over amplitude modulation, FM is not sensitive to the amplitude noise, and have high efficient use of transmitted power
am is amplitude modulation, fm, frequency modulation
because noise usually changes the amplitude not frequency.
Amplitude of the (high frequency) Carrier signal is varied with respect to low frequency of message signal is called amplitude modulation. Frequency of the carrier signal is varied with respect to low frequency of message signal is called frequency modulation.
In Frequency Modulation (FM), if the modulation frequency is doubled, the modulation index does not necessarily double; it depends on the amplitude of the modulating signal. In Amplitude Modulation (AM), the modulation index is defined as the ratio of the peak amplitude of the modulating signal to the carrier amplitude, so it remains unchanged with varying modulation frequency. For Phase Modulation (PM), similar to FM, the modulation index is influenced by the amplitude of the modulating signal and does not inherently double with the modulation frequency. Thus, modulation frequency and modulation index are not directly linked in this way for FM, PM, or AM.
Amplitude Modulation (AM) Frequency Modulation (FM)
In frequency modulation (FM) the amplitude does not remain constant. Instead, the amplitude varies according to the modulation index and the frequency of the modulating signal. This is in contrast to amplitude modulation (AM), where the amplitude of the carrier signal is modulated while the frequency remains constant.