Multiple Choice Questions

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A signal wave of frequency 12 kHZ is modulated with a carrier wave of frequency 2.51 MHz. The upper and lower side band frequencies are respectively

  • 2512 kHz and 2508 kHz

  • 2522 kHz and 2488 kHz

  • 2502 kHz and 2498 kHz

  • 2522 kHz and 2498 kHz


D.

2522 kHz and 2498 kHz

Upper side band (USB) frequency = fc + fm

  = (2.51) MHz + (12) kHz

  = (2510 + 12) kHz

  = 2522 kHz

Lower side band (LSB) frequency = fc − fm

  = (2.51) MHz − (12) kHz

  = (2510 − 12) kHz

  = 2498 kHz


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Which of the following statement is wrong ?

  • Ground wave propagation can be sustained at frequencies 500 kHz to 1500 kHz.

  • Statellite communication is useful for the frequencies above 30 MHz.

  • Sky wave propagation is useful in the range of 30 to 40 MHz.

  • Sky wave propagation takes place through tropospheric space.