TS EAMCET Communication Systems — practice questions
68 free MCQs with worked solutions. Tap any question for the answer + explanation, or practice them all in the app.
Practice TS EAMCET Communication Systems in the app →Why do audio signals need a carrier wave for radio transmission?A demodulator is a circuit that performs which process?Which device combines a modulator and a demodulator for two-way communication?Which technique lets many channels share a single cable, as in cable television?In amplitude modulation, what is varied according to the message signal?In frequency modulation, the instantaneous amplitude of the message changes which carrier property?In phase modulation, the message amplitude varies which carrier property?Amplitude Shift Keying represents digital data by varying which carrier property?Which keying scheme changes the carrier frequency to encode information?Binary PSK and QPSK are forms of which digital modulation family?QAM sends several bits per symbol by varying which properties together?OFDM splits data across many closely spaced what?Which technique spreads signal energy across a wide band to resist interception?A modem sends digital bits over a telephone line by representing them as what?Digital modulation methods can be viewed as which kind of conversion?Who made the first AM transmission on 23 December 1900 at Cobb Island?Which device, invented in 1906 by Lee de Forest, solved the amplification problem of early AM radio?Who formulated the first mathematical description of amplitude modulation in 1915?In standard AM, at least what fraction of the transmitted power sits in the carrier?What information does the carrier signal in standard AM carry?What is a disadvantage of all amplitude modulation techniques at the receiver?If the AM modulation index m exceeds 1, what occurs?How many frequency components does a single-tone AM wave contain?In AM radio, which feature of the transmitted wave is determined by the message signal?Which AM variant is widely used in amateur radio and voice communication?In a traditional telephone local loop, the battery direct current acts as a carrier of what frequency?In on-off keying, how are ones and zeros represented?AM was the earliest modulation method used for what purpose?In angle modulation, which quantity in the carrier equation stays constant?What benefit does wideband FM offer despite using more bandwidth?Skywave propagation depends on radio waves returning to Earth from which region?Which kind of propagation uses ionospheric reflection to reach beyond the horizon?Skywave signals above about 10 MHz typically propagate most efficiently when?Mediumwave and shortwave frequencies below about 10 MHz travel best by skywave at what time?VHF signals above about 30 MHz usually do what at the ionosphere?Roughly what altitude range does the ionosphere cover?What ionizes neutral air in the ionosphere?A signal bouncing several times between Earth and the ionosphere shows what type of propagation?Near-vertical-incidence skywaves mainly serve what kind of communication?Why is the skip distance of skywaves larger at night?Marconi's 1901 transatlantic signal went from Cornwall, England to which place?Skywave propagation is usually degraded during which event?Skywave propagation differs from which type, where waves travel in a straight line?Which of these is a transmission-line based communication channel?Which channel model has several senders using a shared medium to reach one destination?In which channel do intermediate repeater nodes help a sender reach its destination?In an interference channel, what do the two senders do?An established phone call is an example of which channel service?A repeater transmits at 146.94 MHz and listens 0.6 MHz lower. On what frequency does a ham transmit to it?What property of fibre cladding keeps light in the core?Total internal reflection needs light to hit the boundary at what angle?Kao and Hockham proposed in 1965 that fibre attenuation could fall below what value?Compared with copper cables, attenuation in modern optical fibre is what?Fibres with a core wider than 10 micrometres, analysed by geometrical optics, are called what?In graded-index fibre, how does the core refractive index vary from axis to cladding?The range of entry angles over which light can travel down a fibre is called what?An optical fibre is described as a cylindrical dielectric what?About how fast does light travel in a vacuum, in kilometres per second?Which scientists first demonstrated guiding of light by refraction in Paris in the early 1840s?A receiving antenna is usually what fraction of the wavelength it receives?The device that performs both modulation and demodulation in two-way communication is a:In frequency modulation, which carrier property follows the instantaneous message amplitude?Which scheme represents digital data by using a finite set of carrier amplitudes?Quadrature amplitude modulation is equivalent to a combination of which two schemes?Which of these is a pulse modulation method that sends an analog signal as a digital code?Which is an analog-over-analog pulse modulation method?The lower frequency band occupied by the message signal before modulation is called the:Which modulation form is used on the AM radio broadcasting band?