Question

The maximum shift in frequency is 3kHz and the minimum and maximum deviation in frequency of the actual signal are 149.97MHz and 150.03MHz. What is the carrier frequency?

(a) 150MHz

(b) 153MHz

(c) 140MHz

(d) 100Mhz

The question was asked in an international level competition.

The query is from Frequency, Phase Modulation, Modulation Index and Sidebands in division Amplitude & Frequency Modulation of Avionics

Answer 1

Right answer is (a) 150MHz

For explanation: Maximum deviation in frequency = carrier frequency + maximum shift in frequency

         Minimum deviation in frequency = carrier frequency – maximum shift in frequency

         Carrier frequency = Maximum deviation in frequency – maximum shift in frequency

         Carrier frequency = 150.03MHZ – 0.03MHz = 150MHz.