# Electronics and Communication Engineering - Communication Systems

46.

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

 A. Half wave dipole B. Elementary doublet C. Isotropic D. Infinitesimal dipole

Explanation:

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

47.

Push pull amplifier is

 A. voltage amplifier B. current amplifier C. power amplifier D. none of the above

Explanation:

Push pull is a power amplifier.

48.

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

 A. 1 and 1 B. 1 and 0.5 C. 0.5 and 1 D. 0 and 1

Explanation:

.

49.

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

 A. 64 μs B. 6.4 μs C. 640 μs D. 0.64 μs

Explanation:

The frequency of H pulses is 15625 Hz.

Hence .

50.

Counterpoise is used in coils having

 A. high resistivity B. low resistivity C. medium resistivity D. both (b) and (c)