Recent questions and answers in Communication systems

Two waves A and B frequencies $2\;MHz$ and $3MHz$ respectively are beamed in the same direction for communication via sky wave .Which one of there is likely to travel longer distance in the ionosphere before suffering total internal reflection ?

answered May 2, 2017 by dekadhanmni

2 answers

An AM transmitter records an antenna current of $10.5\;A$ . The antenna current drops to $10\;A$ when only carrier is transmitted. What is the percentage modulation ?

answered Oct 3, 2016 by meena.p

1 answer

When a broad cast AM transmitter is $50\%$ modulated its antenna current is $12\;A$ . What would be the carrier current ?

answered Oct 3, 2016 by meena.p

1 answer

If $V_r$ is velocity of red light and $V_b$ is the velocity of blue light in vacuum, then

answered Oct 3, 2016 by meena.p

1 answer

The TV transmission tower in Delhi has a height of $340\;m$ . The distance up to which the broad cost can received , (taking the radius of earth to be $6.4 \times 10^{6}m)$ is

answered Oct 3, 2016 by meena.p

1 answer

Refractive index of ionosphere is

answered Oct 3, 2016 by meena.p

1 answer

The electro magnetic waves of frequency $2\; MHz$ to $30\;MHz$ are used

answered Oct 3, 2016 by meena.p

1 answer

Which of the following frequencies will be suitable for beyond the horizon communication ?

answered Oct 3, 2016 by meena.p

1 answer

A radio station has two channels . One is AM at $1020\;KHz$ and the other FM at $89.5\;MHZ$ For good result you will use

answered Oct 3, 2016 by meena.p

1 answer

LANDSAT series of satellite move in near polar orbits at an attitude of

answered Oct 3, 2016 by meena.p

1 answer

The sky wave with a frequency of $50\;MHz$ is incident on D- region at an angle of $30^{\circ}$ then angle of refraction is

answered Oct 3, 2016 by meena.p

1 answer

When radio waves passes through ionosphere , phase difference between space current and captive displacement current is .

answered Oct 3, 2016 by meena.p

1 answer

Modem is a device which perform

answered Oct 3, 2016 by meena.p

1 answer

Calculate the phase velocity of electro magnetic wave having electron density and frequency for D layer , $N = 400\; electron /cc, \nu = 300\;kHz$

answered Oct 3, 2016 by meena.p

1 answer

The maximum range of ground or surface wave propagation depends on

answered Oct 3, 2016 by meena.p

1 answer

Calculate the length of half wave dipole antenna at $300\;MHz$

answered Oct 3, 2016 by meena.p

1 answer

A 400 watt carrier is modulated to a depth of $75\%$ . calculate the total power in the modulated wave .

answered Oct 3, 2016 by meena.p

1 answer

A broad cast AM transmitter radiates $50 \;kw$ of carrier power . What will be the radiated power at $85 \%$ modulation ?

answered Oct 3, 2016 by meena.p

1 answer

A T.V tower has a height of 100 m , How much population is covered by the T.V broad cast if the average population density around the town is $5000 \;km^{-2}$ ?

answered Oct 3, 2016 by meena.p

1 answer

Out of the following which is not an essential element of a communication system ?

answered Sep 30, 2016 by meena.p

1 answer

A repeater is a combination of

answered Sep 30, 2016 by meena.p

1 answer

If $\lambda$ is wave length of radio signals to be transmitted , then the length of Hertz antenna is

answered Sep 30, 2016 by meena.p

1 answer

Line of sight propagation is

answered Sep 30, 2016 by meena.p

1 answer

The correct radiation between plasma frequency $\nu$ of a radio wave length and electron density N of the ionosphere

answered Sep 30, 2016 by meena.p

1 answer

Sky wave propagation is also called

answered Sep 30, 2016 by meena.p

1 answer

What is the value of frequency at which an e.m wave must be propagated for the D- region to have a refractive index of $0.49$ Electron density for D- layer is $10^9m^{-3}$

answered Sep 30, 2016 by meena.p

1 answer

A T.V transmission town antenna is at a height of 20 m . How much service area can it cover if the receiving antenna at a height of 25 m

answered Sep 30, 2016 by meena.p

1 answer

A T.V transmission town antenna is at a height of 20 m . How much service area can it cover if the receiving antenna at ground level

answered Sep 30, 2016 by meena.p

1 answer

Compute the LC product of a tuned amplifier circuit which requires a carrier wave of $1\;MHz$ for amplitude modulation

answered Sep 30, 2016 by meena.p

1 answer

The maximum amplitude of an A.M wave is found to be $3\;v$ What is modulation index?

answered Sep 30, 2016 by meena.p

1 answer

Would sky waves be suitable for transmission of TV signal of $60\; MHZ$ frequency ?

answered Sep 30, 2016 by meena.p

1 answer

Which of the following :- Would produce digital signals

answered Sep 30, 2016 by meena.p

1 answer

Which of the following :- Would produce analog signals

answered Sep 30, 2016 by meena.p

1 answer

A TV transmission tower has a height of $240 \;m$ signal broad cast from this will be received by LOS Communication at a distance of (assume the radius of earth to be $6.4 \times 10^6 \;m)$

answered Sep 30, 2016 by meena.p

1 answer

An audio signal of $15\;KHz$ , frequency can not be transmitted over long distances without modulation because

answered Sep 30, 2016 by meena.p

1 answer

Identify the mathematical expression for amplitude modulated wave

answered Sep 30, 2016 by meena.p

1 answer

A basic communication system consists of A)transmitter B) Information Source C) User of information D) Channel E) receiver Choose the correct sequence in which these are arranged in a basic communication system

answered Sep 29, 2016 by meena.p

1 answer

A made voice after modulation - transmission sounds like that of a female to the receiver . The problem is due to

answered Sep 29, 2016 by meena.p

1 answer

A message signal of frequency $w_m$ is super posed on a carrier wave of frequency $w_c$ to get an amplitude modulated wave (Am). The frequency of the AM wave will be

answered Sep 29, 2016 by meena.p

1 answer

A speech signal of $3\;kHz$ is used to modulate a carrier signal of frequency $1\;MHz$ , using amplitude modulation . The frequencies of the side band will be

answered Sep 29, 2016 by meena.p

1 answer

A 1 Kw signal is transmitted using as communication channel which provides attention at the rate of $-2 dB$ per km. If the communication channel has a total length of 5 km , the power of the signal received is [ gain in $dB = 10 log \bigg( \Large\frac{P_0}{P_c}\bigg) ]$

answered Sep 29, 2016 by meena.p

1 answer

A $100\;m$ antenna is mounted on a $500\;m$ tall building . The complex can become transmission tower for waves with $\lambda$

answered Sep 29, 2016 by meena.p

1 answer

Three waves A,B and C of frequencies $1600\;kHz, 5 MHz$ and $60\;MHz$ respectively are to be transmitted from one place to another . Which of the following is the most appropriate mode of communication ?

answered Sep 29, 2016 by meena.p

1 answer

For an amplitude modulated wave , the maximum amplitude is found to be 10 v while the minimum amplitude is found to be $2v$ .What would be the value of $\mu$ if the minimum amplitude is zero volt ?

answered Sep 29, 2016 by meena.p

1 answer

For an amplitude modulated wave , the maximum amplitude is found to be 10 v while the minimum amplitude is found to be $2v$ . Determine the modulation index $\mu$ .

answered Sep 29, 2016 by meena.p

1 answer

A modulatiy signal is a square wave as shown in the figure . The carrier wave is given . $c(t) = 2 \sin (8 \pi t) volt.$ Find modulation index.

answered Sep 29, 2016 by meena.p

1 answer

A carrier wave of Peak voltage $12\;v$ is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of $75\%$

answered Sep 28, 2016 by meena.p

1 answer

Is it necessary for a transmitting antenna to be at the same height on that of the receiving antenna for the line of sight communication ? A T.v transmitting antenna is $81 m$ tall.How much service area it can cover if the receiving antenna is at the ground level ?

answered Sep 28, 2016 by meena.p

1 answer

Digital signals (i) do not provide a continuous set of values (ii) represent values as discrete steps (iii) can utilize only binary system and (iv) can utilize decimal as well as binary system . which of the following options is true ?

answered Sep 28, 2016 by meena.p

1 answer

Frequencies in the UHF range normally propagate by means of

asked Sep 28, 2016 by meena.p

1 answer

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