Final answer:
In square law modulation for both AM and FM, the carrier frequency is crucial in transmitting the audio signal without varying its own amplitude or basic frequency. AM stations use a frequency range of 540 to 1600 kHz with an allowance of ±5 kHz, while FM stations use 88 to 108 MHz with a leeway of 100 kHz. The higher the carrier frequency, the more data that can be transmitted per unit of time.
Step-by-step explanation:
The requirement of a carrier frequency and a message bandwidth in a square law modulator relates to the transmission of information using electromagnetic waves. In amplitude modulation (AM), the carrier wave is modulated in such a way that its amplitude varies according to the audio information being sent, without changing its basic frequency. The message bandwidth needs to be within the range of audible frequencies, typically for AM broadcasting between 540 to 1600 kHz, and each station has a regular carrier frequency with an allowance of ±5 kHz for slight variations.
For frequency modulation (FM), the carrier frequency is also essential but in this case, it is the frequency that is modified by the audio signal. FM broadcasting is assigned to frequencies ranging from 88 MHz to 108 MHz, with each station allowed to use 100 kHz on either side of its carrier frequency to transmit the required information.
The bandwidth is important in determining how much information can be transmitted. The higher the frequency of the carrier wave, the higher the capacity for data transmission, allowing for greater variations of the signal over time. This fact explains why communication methods like laser telephone transmission, which operate at much higher visible frequencies, carry more data per optical fiber compared to traditional electronic wiring. Conversely, communication with submarines using extremely low frequency (ELF) radio must deal with much lower data rate transmission.