The difference between double side band long carrier (DSB LC) and double side band short carrier (DSB SC) is the is how the amplitude modulation (AM) is referenced in the carrier wave.
fc>2fm
The AM power content of the carrier is maximum when the modulation index is zero. At this point, there is no modulation applied to the carrier signal, meaning the entire power is concentrated in the carrier frequency itself. As the modulation index increases, the power is distributed between the carrier and the sidebands, resulting in a decrease in the carrier's power content. Thus, maximum carrier power occurs at zero modulation.
A: A carrier carry information by modulation either Amplitude or Frequency modulation. Therefore AM and FM RADIO M stand for modulation
Modulation Index is the ratio of the maximum deviation frequency to the frequency of modulation. In other words it is the ratio of the spread in frequency spectrum to the frequency that was used to modulate the carrier. For FM, modulation index is given by the formula mf= df/f where, mf=modulation index for FM df=difference in carrier frequency f=frequency of the signal
The most fundamental difference, I would say, is that Amplitude Modulation (AM) is a kind of Analog Modulation Technique (the modulation is applied continuously in response to the analog information signal) where Amplitude Shift Keying is a type of Digital Modulation Technique ( an analog carrier signal is modulated by a discrete signal, digital modulation methods can be considered as digital-to-analog conversion, and the corresponding demodulation or detection as analog-to-digital conversion. The changes in the carrier signal are chosen from a finite number of M alternative symbols).
AM imply amplitude modulation of a carrier signal
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
In case of coherent demodulation carrier used for demodulation purpose is in phase and frequency synchronism with carrier used for modulation purpose. For non-coherent demodulation it is not in synchronism.
In modulation u r sending two signals but their frequencies are sum or difference of carrier frequency and signal frequency.In addition u send two signals at two different frequencies so more interference.
In amplitude modulation, modulation depth refers to the ratio of the unmodulated carrier amplitude to the amplitude deviation for which the modulated carrier wave reaches its minimum value. If this minimum value is zero, the modulation depth is 100%.For amplitude modulation,modulation depth = (a-b)/(a+b),wherea is the unmodulated carrier amplitude, andb is the minimum amplitude deviation.The modulation depth ratio is also referred to as the modulation index.
low level amplitude modulation occurs when the carrier signal is first modulated and then amplified,whereas in high level modulation,the carrier signal is first amplified and then is modulated.