Communication Systems Part 2

In radar systems PRF stands for

PRF in radar systems means pulse repetition frequency.

Which of the following cannot be the Fourier series expansion of a periodic signal?

x(t) = cos t + 0.5 not satisfies the Dirichlet condition. The integration of constant term is ∞

Which of the following is the indirect way of FM generation?

Armstrong modulator generates FM through phase modulation.

A telephone exchange has 9000 subscribers. If the number of calls originating at peak time is 10, 000 in one hour, the calling rate is

10/9. Calling rate is the number of calls per subscriber.

If C is capacity of noisy channel, (bits/s), δf is bandwidth Hz and S/N is signal to noise ratio, then

bandwidth multiply by sum of 1 and signal to noise ratio

As the frequency increases, the absorption of ground wave by earth's surface

Increases. Because of this reason ground waves can be used for frequencies upto about 1600 kHz only.

The velocity of sound waves in air

varies directly as square root of absolute temperature. V is directly proportionl to square root of T

The range of a cordless telephone is about

The range depends on quality of instrument and is about 100 m.

An earth mat for a communication tower consists of

a large number of radials extending from base of tower at a depth of about 30 cm. The number of radials is large and depth is about 30 cm.

Degaussing in a picture tube means

Removing residual magnetism in mask, shield etc. Since gauss is a unit of magnetic flux, degaussing means removal of magnetism

The rate at which information can be carried through a communication channel depends on

Rate of information depends on bandwidth.

Some types of traps used in video IF amplifier of colour TV are

shunt, series and absorption traps

Direct and reflected sound waves may interfere with each other.

False. PAS use moving coil microphones

A carrier is simultaneously modulated by two sine waves having modulation indices of 0.4 and 0.3. The total modulation index will be

0.5. m1 = 0.4, m2 = 0.3 AND SQUARE ROOT OF THEIR SUM ALONG WITH SQUARING INDIVIDUALLY.

In standing wave pattern on a transmission line

voltage nodes and current antinodes as well as current nodes and voltage antinodes coincide. When standing wave is set up voltage maxima and current minima and voltage minima and current maxima coincide.

If the bandwidth is increased by 2, the γFM γAM (where γ is the ratio of SNR of output to SNR at input, FM is frequency modulation and AM is amplitude modulation) is increased by a factor of

4.Doubling of frequency increase SNR in frequency modulation by 4. It has no effect in AM.

A carrier wave carries information.

False. Carrier does not have any information.

Frequency shift keying is used mostly in

Frequency shift keying (FSK) is a system of frequency modulation used in telegraphy.