A point-to-point communication mode is seen in

• satellite cable communication

• television transmission

• fax transmission

• FM radio transmission

If the heights of transmitting and the receiving antennas are each equal to h, the maximum line-of-sight distance between them is (R is the radius of the earth)

• $\sqrt{2 \mathrm{Rh}}$

• $\sqrt{4 \mathrm{Rh}}$

• $\sqrt{6 \mathrm{Rh}}$

• $\sqrt{8 \mathrm{RH}}$

A repeater is a combination of

• receiver and modulator

• receiver and transducer

• receiver and transmitter

• receiver and amplifier

Find the mismatch

• Sky wave communication : Frequency upto 30 MHz

• Line of sight communication : Frequency greater than 40 MHz

• Mobile telephony : Frequency range 800 – 950 kHz

• Facsimile : Static document 

A television tower of height 140 m can broadcast its signal upto a maximum area of (Radius of earth = 6.4 x 10⁶ m)

• 1.56 × 10⁶ km²

• 5.6 × 10³ km²

• 5.6 × 10¹⁰ km²

• 1.56 × 10⁹ km²

The waves that are bent down by the ionosphere are

• ground waves

• surface waves

• sky waves

• space waves

A ground receiver in line-of-sight communication cannot receive direct waves due to

• its low frequency

• curvature of earth

• its high intensity

• smaller antenna

In an amplitude modulation with modulation index 0.5, the ratio of the amplitude of the carrier wave to that of the side band in the modulated wave is

• 4 : 1

• 1 : 1

• 1 : 2

• 2 : 1

29.

The distance of coverage of a transmitting antenna is 12.8 km. Then, the height of the antenna is (Given that radius of earth = 6400 km)

• 6.4 m

• 12.8 m

• 3.2 m

• 16 m

If E_c = 20 sin 10⁵ πt and E_m = 10 sin 400 πt are carrier and modulating signals, the modulation index is

• 56 %

• 30 %

• 50 %

• 48 %