239. Frequency and phase modulations differ in which of the following?
A. their actual waveform
B. Compatibility towards each other
C. Different definitions of the modulation indices
D. All of the above

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240. The threshold effect in demodulators is
A. exhibited by all demodulators when the input signal to noise ratio is low
B. the rapid fall on output signal to soise ratio when the input signal to noise ratio falls below a particular value
C. the property exhibited by all AM suppressed carrier coherent demodulators
D. the property exhibited by correlation receivers

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241. An FM signal with modulation index mf is passed through a frequency tripler. The modulation index of the output signal will be
A. mf
B. 3 mf
C. 9 mf
D. 27 mf

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242. A 1000 kHz carrier is simultaneously modulated with 300 Hz and 2 kHz audio sine waves. The frequency which will not be present in the output is
A. 998 kHz
B. 999.7 kHz
C. 1000.3 kHz
D. 700 kHz

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243. A carrier is simultaneously modulated by two sine waves with modulation indicates of 0.3 and 0.4 If the modulated power is 10 kW, the total modulated power will be
A. 12.5 kW
B. 10 kW
C. 10.125 kW
D. 10.5 kW

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244. A RF carrier of 12 kV at 1 MHz is amplitude modulated by a 1 kHz signal of 6 kV peak. The modulation pattern is observed on a CRO calibrated suitably. The voltage indicated will be
A. 1.8 kV
B. 1.001 kV
C. 18 V
D. 36 kV

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245.  An FM radio receiver is tuned to a 90.6 MHz broadcast station. It will receive an image frequency of
A. 110 MHz
B.1121VIHz
C. 114 MHz
D. 120 MHz

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