ce lab combined exam

When the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant. The modulation system is

• Amplitude modulation

• Phase modulation

• Frequency modulation

• any of the three

Indicate which of the following system is digital.

• Pulse-position modulation

• Pulse-code modulation

• Pulse-width modulation

• Pulse-frequency modulation

_______ determines the number of sideband components in FM.

• Carrier frequency

• Modulation frequency

• Modulation index

• Deviation ratio

Identify a modulation method, or methods in use for a common-emitter configuration

• Base modulation

• Emitter modulation

• Collector modulation

• Both Base and Collector modulation

One of the advantages of the base modulation over collector modulation of a transistor class C amplifier is

• The lower modulating power required

• Higher power output per transistor

• Better efficiency

• Better linearity

An Am signal and a narrow band FM signal with identical carriers, modulating signals and modulation indices of 0.1 are added together. The resultant signal can be closely approximated by

• Broad Band FM

• SSB with carrier

• DSB-SC

• SSB-with out carrier

In a FM system, a carrier of 100MHz is modulated by a sinusoidal signal of 5 KHz. The bandwidth by Carson's approximation is 1 MHz. if y(t)=(modulated waveform)^3 , then by using carson's approximation, the band width of y(t) and the spacing of spectral components are, respectively

• 3 MHz, 5 kHz

• 1 MHz, 15 kHz

• 3 MHz, 15 kHz

• 1 MHz, 5 kHz

AM signal is Demodulated using envelope detector. The carrier frequency is 1 MHz and message frequancy is 2 kHz. a suitable value for the time constant of the envelope detector is

• 
  

  $0.2\mu\sec$

• $1\mu\sec$

• $20\mu\sec$

• $500\mu\sec$

a 100 MHz carrier is frequency modulated by a sinusoidal signal of amplitude 20 V and frequency 100 kHz.The frequency sensitivity of Modulator is 25 kHz/ Volt. Determine the bandwidth

• 1.5 MHz

• 1.2 MHz

• 1.8 MHz

• 1.4 MHz

A carrier signal is frequency modulated by a sinusoidal signal and the frequency deviation is 8 kHz ,The message signal frequency is 2 kHz. Determine the modulation index?

• 2

• 4

• 3

• 8