246.  The minimum value of m1 for an FM system required to produce a noticeable improvement in S/N ratio over comparable AM system with m =1 is
A.1
B.2
C.3
D.4

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247.  An FM signal with a deviation 8 is passed through a mixer and has its frequency reduced fivefold. The deviation in the output of the mixer is
A.58
B. intermediate
C.8
D.8

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248.  Two carriers 40 MHz and 80 MHz respectively are frequency modulated by a signal of frequency 4 kHz, such that the band-widths of the FM signal in the two cases are the same. The peak value deviation in the two cases are in the ratio of
A. 1 :4
B. 1: 2
C. 1 :1
D. 2:1

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249.  A superheterodyne receiver has an IF of 465 kHz. If it is tuned to a station broadcasting at 500 kHz and its oscillator is operating at 965 kHz, then the 1430 kHz frequency would be the
A. adjacent channel frequency
B. image frequency
C. gyrofrequency
D. maximum usable frequency

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250.  As the modulation index of an FM signal with sinusoidal modulation is increased from zero to three, the power in the carrier component will
A. increase continuously
B. decrease continuously
C. first increase, attain a maximum and then decrease
D. first decrease, become zero and then increase

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251.  The ratio amplitude modulation with identical total transmitted power (mf is modulated index of FM) is9 ,
A. ?2
B.3 2 ?2 mi
C.
D.

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252. A radio station works at 800 kHz and uses AM. If this is a public broadcast system, it should transmit using
A. parabolic reflector to transmit all round
B. turnstile antenna for therequired band
C. half-wave long horizontal wire
D. a vertical antenna less than quarter for practical reasons

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