Communication Systems Part 3

Communication Systems Preparation Part 3

It is desired that transmission line and load should match for a range of frequencies. The best method is

To use a double stub. When matching over a range of frequencies is desired, double stub is necessary.


Which of the following has the highest input impedance?

CC connection has very high input impedance and low output impedance


In a fascimile reproduction time to scan one line is 2 ms. If it has 4% blanking, the visible trace time is

1.92 ms. (2 ms) (1 - 0.04) = 1.92 ms


Consider the following statements

  • The amplitude of an FM wave is constant
  • FM is more immune to noise than AM
  • FM broadcasts operate in upper VHF and UHF frequency ranges
  • FM transmitting and receiving equipments are simpler as compared to AM transmitting and receiving equipments
Which of the above are correct?

B. FM equipments are complex as compared to AM equipments.


Signal to noise ratio of microphone is defined as the ratio of output when the sound pressure is __________ to the output in the absence of any sound signal.

0.1 Pa. 0.1 Pa (= 0.5 x 10-4 W/m2) is taken as standard sound pressure for defining S/N ratio of microphones.


A generator is feeding power to a transmission line of characteristic impedance Z0. The line is terminated in impedance ZL. Standing waves will be set up if

Both the case, i.e., ZL > Z0 and ZL greater than Z0 give rise to standing waves.


In sound recording the degree of pre-emphasis is about 6 dB/ octave.

False. It erases the matter already existing on the tape.


Space wave may be a direct wave or wave reflected from earth.

False. Strength of space wave depends on distance as it suffers attenuation.


Radio broadcasts are generally

Frequency modulation It gives noise free reception and is used for radio broadcasts.


If the frequency of a wave 20 Hz, the time period is

0.05 secs


Which of the following is taken as reference antenna for directive gain?

Isotropic. Isotropic antenna is one which radiates equally in all directions. It is a standard reference antenna.


Push pull amplifier is

Push pull is a power amplifier.


When the channel is noisy, producing a conditional probability of error p = 0.5; the channel capacity and entropy function would be, respectively,

0 and 1


In CCIR-B system, the time between start of one H syn. pulse and next is

The frequency of H pulses is 15625 Hz.


Counterpoise is used in coils having

Counterpoise is a horizontally buried wire used to provide low grounding resistance in high resistivity soils.


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