What is the typical maximum frequency deviation for Wide Band FM (WBFM) used in FM broadcasting?

Explanation:

Wide Band Frequency Modulation (WBFM) is a type of frequency modulation used in FM broadcasting where the frequency of the carrier wave is varied in proportion to the instantaneous amplitude of the modulating signal. WBFM is characterized by a relatively large frequency deviation, which is essential for high-quality audio transmission.

The typical maximum frequency deviation for Wide Band FM used in FM broadcasting is 75 kHz. This deviation is standardized and widely adopted in FM broadcasting systems to ensure high fidelity in audio transmission, making it the correct answer (Option 3).

Technical Details:

• In FM broadcasting, the maximum frequency deviation of 75 kHz is paired with a standard baseband bandwidth of 15 kHz (the range of frequencies in the audio signal).
• The Carson's Rule, which estimates the bandwidth required for FM signals, is given as:
  B = 2 × (Δf + fm)
  Where:
  • B: Total bandwidth
  • Δf: Maximum frequency deviation (75 kHz)
  • fm: Maximum modulating frequency (15 kHz)
  Substituting the values:
  B = 2 × (75 kHz + 15 kHz) = 180 kHz
  Thus, the FM signal occupies a bandwidth of approximately 180 kHz.
• The 75 kHz deviation ensures sufficient dynamic range and minimizes distortion in audio signals.
• FM broadcasting systems are designed to operate within the 88 MHz to 108 MHz frequency band, with each station allocated a bandwidth of 200 kHz. The 75 kHz deviation fits well within this allocation while leaving room for guard bands to prevent interference between adjacent channels.
   

Correct Option Analysis:

The correct option is:

Option 3: 75 kHz

This is the standard maximum frequency deviation used in Wide Band FM for FM broadcasting. It provides an optimal balance between audio quality and efficient use of the frequency spectrum, making it the correct answer