229 + Interview Questions in COMMUNICATION-SYSTEM IN GENERAL AWARENESS Page 1 InterviewSolution

1.	The need for doing modulation isA. to increase the intensity of auido signalB. to decrease the intensity of audio signalC. to transmit audio signal to large distancesD. to increase the frequency of the audio signal
Answer» Correct Answer - C

Discussion

2.	The most commonly employed analog modulation technique in satellite communication is theA. amplitude modulationB. frequency modulationC. phase modulationD. amplitude modulation
Answer» Correct Answer - B

Discussion

3.	The process of recovering the audio signal from the modulated wave is known asA. amplificationB. rectificationC. modulationD. demodulation
Answer» Correct Answer - D

Discussion

4.	A modulating signal is a square wave as shown in the following figure . While the carries wave is given by `e=4 sin (8 pi t)` volt . What is the modulation index ?A. 0.15B. 0.25C. 0.35D. 10.5
Answer» Correct Answer - B The amplitude of the modulating signal =1V The amplitude of carries wave =4V Thus , `A_(m)=1V and A_(c)=4V ` `:. mu=(A_(m))/(A_(c))=(1)/(4)=0.25`

Discussion

5.	Which of the following is used to produce radio waves of constant amplitude?A. filterB. rectifierC. FETD. oscillator
Answer» Correct Answer - D

Discussion

6.	Which of the following frequencies will be suitable for beyond the horizon communication using sky waves ?A. 10 kHzB. 10 MHzC. 1 GHzD. 1000 GHz
Answer» 10 kHz frequencies cannot be radiated due to large antenna size , 1 GHz and 1000 GHz will be generated . So option (b) is correct .

Discussion

7.	Among the follwing frequencies one will be suitable for beyond-the horizon communication using sky waves isA. `10 kHz`B. `10 MHz`C. `1 GHz`D. `1000 GHz`
Answer» Correct Answer - B

Discussion

8.	In frequency modulationA. Frequency of `CW` remains constant but amplitude changes in accoradance with modulating wave frequencyB. Frequency of `CW` changes in accordance with the modulating wave frequency but the amplitude also changes.C. Frequency of `CW` changes in accordance with the modulating wave frequency but the amplitude remains constant.D. Frequency of `CW` changes in accordance with the amplitude of modulating wave amplitude
Answer» Correct Answer - C

Discussion

9.	The number of telephonic messages which are carried by a fibre at an instant with much less intensity loss areA. 2400B. 2200C. 2000D. 1800
Answer» Correct Answer - C 2000 number of telephonic messages can be carried by a optical fibre at an instant .

Discussion

10.	Which of the following frequencies will be suitable for beyond the horizon communication using sky waves?A. 10 kHzB. 10 MHzC. 1 GHzD. 1000 GHz
Answer» Correct Answer - B Beyond horizon, a signal can reach via ionospheric reflection or sky wave mode. Frequency range suitable is 3 MHz to 30 MHz.

Discussion

11.	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 communicarion system.A. ABCDEB. BADECC. BDACED. BEADC
Answer» Correct Answer - B

Discussion

12.	The difference between phase and frequency modulationA. practically they are same but theoretically they differB. lies in the power audio response of phase modulationC. lies in the poorer audio response of frequency modulationD. lies in the definitions of modulation and their modulation index
Answer» Correct Answer - A

Discussion

13.	In a detector, output circuit consists of `R = 10kOmega and C = 100 p F.` Calculate the frequency of carrier signal it can detect.A. ` gt gt 1 MHz `B. ` 0.1 kHz `C. `gt gt 1 GHz `D. `10^(3) Hz `
Answer» Correct Answer - A Time constant of the circuit `tau=RC=10^(4) xx 10^(-10)=10^(-6) s ` For demodulation , `(1)/(f_(c)) lt lt RC ` ` or f_(c) gt gt (1)/(RC) or f_(c) gt gt (1)/(10^(-6))=10^(6)Hz `

Discussion

14.	The mobile telephones operate typically in the range ofA. ` 1-100 MHz `B. 100-200 MHzC. 1000-2000 MHzD. 800-950 MHz
Answer» Correct Answer - D The mobile telephone operate typically in the range of 800-950 MHz.

Discussion

15.	Which type of communication is employed in Mobile Phones ?
Answer» Space wave mode of propagation is employed in mobile phones .

Discussion

16.	Intelset satellite works as a -A. transmitterB. repeaterC. absorberD. none of these
Answer» Correct Answer - B Repeaters add on energy to received signals and retransmit them.

Discussion

17.	`I-V` characterstic of four devices are shown in Fig. `15.1` Identify devices that can be used for modulation:A. `i` and `iii`B. only `iii`C. `ii` and some regions of `iv`D. All the devices can be used
Answer» Correct Answer - C A square law modulator is the device which can produce modulated waves by the apllication of message signal and the carrier wave. Square law modulator is used for modulation purpose. Charactersitics shown by (`i`) and (`iii`) correspond to linear devices. And by (`ii`) and same part of (`iv`) corresponds to square law device which shows non-linear relations. Hence (`ii`) and (`iv`) can be used for modulation.

Discussion

18.	A basic communication system consist of (`a`) transmitter (`b`) information source (`c`) channel (`d`) receiver Choose the correct sequence in which these are arranged in a basic communication system:A. `ABCDE`B. `BADEC`C. `BDACE`D. `BEADC`
Answer» Correct Answer - B From the block diagram of basic communication system, the sequence can be arranged.

Discussion

19.	The frequency which is not part of `AM` broadcastA. `100 kHz`B. `700 kHz`C. `600 kHz`D. `1500 kHz`
Answer» Correct Answer - A

Discussion

20.	Cellular Mobile works in the frequency range ofA. `840` to `935 MHz`B. `3.7` to `4.2 GHz`C. `420` to `890 MHz`D. `30` to `300 GHz`
Answer» Correct Answer - A

Discussion

21.	A male voice after modulation-transmission sounds like that of a female to the receiver. The problem is due toA. poor selection of modulation index (selected `0ltmlt1`)B. poor bandwidth selection of amplifiers.C. poor selection of carrier frequencyD. loss of energy in transmission
Answer» Correct Answer - B The frequency of modulated signal received becomes more due to more improper selection or band width and band width `=2f_(m)` But frequency of male voice is less than that of a female.

Discussion

22.	Frequency range used in down linking in satellite communication isA. `0.896` to `0.901 GHz`B. `0.420` to `0.890 GHz`C. `5.925` to `6.425 GHz`D. `3.7` to `4.2 GHz`
Answer» Correct Answer - D

Discussion

23.	A male voice after modulation-transmission sounds like that of a female to the receiver. The problem is due toA. poor selection of modulation indexB. poor bandwidht selection of amplifiersC. poor selection of carrier frequencyD. loss of energy in transmission
Answer» Correct Answer - B Due to poor bandwidth selection , nature of voice is affected.

Discussion

24.	A male voice after modulation-transmission sounds like that of a female to the receiver. The problem is due toA. poor selection of modulation index (selected `0ltmlt1`)B. poor bandwidth selection of amplifiersC. poor selection of carrier frequencyD. loss of energy in transmission.
Answer» Correct Answer - B Here, in this question, the frequency of modulated signal received becomes more, which is possible with the poor bandwidth selection of amplifiers. This happens because bandwidth in amplitude modulation is equal to twice the frequency of modulating signal. But, the frequency of male voice is less than that of a female.

Discussion

25.	In the satellite communication, the uplinking frequency range isA. `0.896` to `0.901 GHz`B. `0.420` to `0.890 GHz`C. `5.925` to `6.425 GHz`D. `3.7` to `4.2 GHz`
Answer» Correct Answer - C

Discussion

26.	In a communication system, noise is most likely to affect the signalA. at the transmitterB. In the channel or in the transmission lineC. In the information sourceD. At the receiver
Answer» Correct Answer - B

Discussion

27.	The frequency of a FM transmitter without signal input is calledA. Lower side band frequencyB. Upper side band frequencyC. Resting frequencyD. None of these
Answer» Correct Answer - C

Discussion

28.	The frequency of a `FM` transmitter without signal input is calledA. Lower side band frequencyB. Upper side band frequencyC. Resting frequencyD. None of these
Answer» Correct Answer - C

Discussion

29.	A carrier is simultaneously modulated by two sine waves with modulation indices of `0.4` and `0.3`. The resultant modulated index will beA. 1B. 0.7C. 0.5D. 0.35
Answer» Correct Answer - c

Discussion

30.	Name the device fitted in the satellite which receives signals from Earth station and transmits them in different directions after amplification.
Answer» Correct Answer - Transponder.

Discussion

31.	While tuning in a certain broad cast station with a receiver, we are actuallyA. Varying the local oscillator frequencyB. Varying the frequency of the radio signal to be picked upC. Tuning the antennaD. None of these
Answer» Correct Answer - A

Discussion

32.	1000 kHz carrier wave is amplitude modulated by the signal frequency 200-4000Hz . The channel width of this case isA. 8kHzB. 4kHzC. 7.6kHzD. 3.8 kHz
Answer» Correct Answer - A Band width `= 2 xx f_(m)=8 kHz `

Discussion

33.	Two waves A and B of frequencies 2MHz and 3 MHz, respectively are beamed in the same direction for communication via sky wave. Which one of these is likely to travel longer distance in the ionosphere before suffering total internal reflection?A. AB. BC. Both (a) and (b)D. None of these
Answer» Correct Answer - B Refractive index increases with frequency . `:.` For higher frequency waves , refraction is less or bending is less. So , total internal reflection is achieved by 3MHz wave in larger distance .

Discussion

34.	Two waves A and B of frequencies 2MHz and 3 MHz, respectively are beamed in the same direction for communication via sky wave. Which one of these is likely to travel longer distance in the ionosphere before suffering total internal reflection?
Answer» As the frequency of wave B is more than wave A, it means the refractive index of wave B is more than refractive index of wave A (as refractive index increases with frequency increases). For higher frequency wave (i.e., higher refractive index) the angle of refraction is less i.e., bending is less. So, wave B travel longer distance in the ionosphere before suffering total internal reflection.

Discussion

35.	Would sky waves be suitable for transmission of TV signals of 60 MHz frequency?
Answer» A signal to be transmitted through sky waves must have a frequency range of 1710 kHz to 40 MHz. But, here the frequency of TV signals are 60 MHz which is beyond the required range. So, sky waves will not be suitable for transmission of TV signals of 60 MHz frequency.

Discussion

36.	The maximum and minimum amplitude of AM wave is found to be 15 V and 3 V , respectively . The amplitudes of carrier wave and modulating wave will beA. 9 and 6 VB. 6 and 9 VC. 18 and 9 VD. 24 and 16 V
Answer» Correct Answer - A Given , `A_("max")=A_(c)+ A_(m)=15V ` .........(i) ` A _("min")=A_(c)-A_(m)=3V `.......... (ii) From Eq. (i) ` A_(c) =15-A_(m)`. Now , put it in Eq. (ii) ,we get ` 15-A_(m)-A_(m)=3 ` `implies 2A_(m)=12 ` `implies A_(m)=6V ` From Eqs . (i) `:. A_(c)=15-6=9V `

Discussion

37.	An `AM` wave is given by `V=1500[1+0.5sin12560t]sin(5.26xx10^(5)t)`. The modulating frequency isA. `2.0 kHz`B. `1.0 kHz`C. `12.5 kHz`D. `50 kHz`
Answer» Correct Answer - A `C_(m)(t)=A_(c)(1+musin omega_(m)t)sin omega_(c)t` `f_(m)=(omega_(m))/(2pi)=(12560)/(2pi)=2khz`

Discussion

38.	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 appropriate mode of communication?A. A is transmitted via space wave while B and C are transmitted via sky waveB. A is transmitted via ground wave, B via sky wave and C via space waveC. B and C are transmitted via ground wave while A is transmitted via sky waveD. B is transmitted via ground wave while A and C are transmitted via space wave
Answer» Correct Answer - B Mode of communication frequency range Ground wave propagation - 530 kHz to 1710 kHz Sky wave propagation - 17 kHz to 40 MHz Space wave propagation - 54MHz to 42GHz

Discussion

39.	A `100m` long antenna is mounted on a `500m` tall building. The complex can become a transmission tower of waves with `lambda`A. `~ 400 m`B. `~ 25 m`C. `~ 150 m`D. `~ 2400 m`
Answer» Correct Answer - A Given, length of the building (l) is given by l = 500m we know that, wavelength of the wave which can be transmitted by `lambda~4l = 4 xx 100 = 400m`

Discussion

40.	In space communcation , the information can be passed from on place to another at a distance of 100 km inA. 1 sB. 0.5 sC. 0.003 sD. None of these
Answer» Correct Answer - D In space communication , the information can be passed from one place to another with the speed of light ` (c=3 xx 0^(8) ms^(-1))` . Hence , time taken for a distance of ` 100 kkm =(100 xx 10^(3))/( 3 xx 10^(8))=3.3 xx 10^(-4)s `

Discussion

41.	The frequency of a wave propagating in D-region having refractive index of 0.5 isA. ` 420 kcs^(-1) `B. ` 300 kcs^(-1) `C. `329.5 kcs ^(-1)`D. `350 kcs^(-1)`
Answer» Correct Answer - C Electron density of D-region is ` 10^(-3)` ` mu=1-(81.45 N)/( v^(2))` Given refractive index ,` mu =0.5 ` ` implies 0.5 sqrt(1-(81.45xx 10^(9))/(v^(2)))` ` implies v=329.5 kcs^(-1)`

Discussion

42.	A TV transmission tower has a height of 240 m. Signals broadcast from this tower will be received by LOS communication at a distance of (assume the radius of earth to be `6.4 xx 10 ^(6) m`)A. 100 kmB. 24 kmC. 55 kmD. 50 km
Answer» Correct Answer - B::C::D In LOS communication maximum distance upto which a signals can be received from tower is `d=sqrt(2rh)` `=sqrt(2xx6.4xx 10^6xx240) ` `55xx 10^3 m` `= 55 km`.

Discussion

43.	A T V transmission tower antenna is at a height of 20 m. How much service area can it cover if the receiving antenna is (i) at ground level, (ii) at a height of 25 m? Calculate the percentage increase in area covered in case (ii) relative to case (i).
Answer» Correct Answer - B::C::D (i) When receiver is at ground level, then service area covered. =`pid^2=pi(sqrt(2Rh))^(2)` =`2piRh` =`2xx pixx6.4xx 10^6xx20` =`804 km^2` (ii) When receiver is at height of 25 m,area covered. =`pid_1^2 + pid_2^2` =`pi(sqrt(2Rh_(T)))^(2)+ pi(sqrt(2Rh_(R)))^(2)` =`2piR(h_T +h_R)` =`2xx pixx6.4xx10^6xx45(m^2)` `~~ 3608 km^(2)` (iii) Percentage increase in area covered. =`(A_2-A_1)/(A_1)xx 100` =`(3608-804)/(804)xx100` =`349 %`.

Discussion

44.	Why is it necessary to use satellites for long distance TV transmission?
Answer» Television signals are not properly reflected by thed ionosphere. So, reflection is affected by satellites.

Discussion

45.	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 bands will beA. 1.003 MHz and 2. 997 MHzB. 3001 kHz and 2997 kHzC. 1003 kHz and 1000 kHzD. 1 MHz and 0.997 MHz
Answer» Correct Answer - A Sideband frequencies are : Lower sideband `(LSB) = omega_c - omega_m` `= 1xx10^6 Hz - 3xx10^3 Hz` `(1000- 3)xx 10^3 Hz` `2997 kHz` `and = 2.997 MHz` Upper sideband `(USB) = omega _c + omega_m` `1xx 10^6 Hz + 3xx 10^3 Hz` `1003 kHz` `= 1.003 MHz`.

Discussion

46.	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 bands will beA. 1.003 MHz and 0.997 MHzB. 3001 kHz and 2997 kHzC. 1003 kHz and 1000 kHzD. 1 MHz and 0.997 MHz
Answer» Correct Answer - A Given, frequency of carrier signal is `omega_(c )` = 1 MHz and frequency of speech signal = 3 kHz `= 3 xx 10^(-3)` MHz 0.003 MHz Now, we know that, Frequencies of side bands `= (omega_(c ) pm omega_(m))` `=(1 pm 0.003)` = 1.003 MHz and 0.997 MHz

Discussion

47.	If `V_(c)` is amplitude of carrier wave in `AM` transmitter where modulation factor is `m` then amplitude of side bands can beA. `(V_(c))/(2m)`B. `(m)/(2)V_(c)`C. `mV_(c)`D. `(V_(c))/(2)`
Answer» Correct Answer - B Amplitude of `LSB=USB=mu(A_(c))/(2)`

Discussion

48.	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 bands will beA. `1.003 MHz` and `0.997 MHz`B. `3001 kHz` and `2997 kHz`C. `1003 kHz` and `1000 kHz`D. `1 MHz` and `0.997 MHz`
Answer» Correct Answer - A the frequencies of side bands are `LSB=f_(c)-f_(m)` (Lower side Band) `USB=f_(c)+f_(m)` (Upper side Band)

Discussion

49.	For a carrier frequency of 100 kHz and a modulating frequency of 5kHz what is the width of AM transmission-A. 5 k HzB. 10 kHzC. 20 kHzD. 200 kHz
Answer» Correct Answer - B `Delta omega=2 omega_(n)=2xx5=10 kHz`

Discussion

50.	Fraction of total power carried by side bands is given by-A. `(P_(s))/(P_(T))=m^(2)`B. `(P_(s))/(P_(T))=1/(m^(2))`C. `(P_(s))/(P_(T))=(2+m^(2))/(m^(2))`D. `(P_(s))/(P_(T))=(m^(2))/(2+m^(2))`
Answer» Correct Answer - D `("side band power")/("total power") =(P_(s))/(P_(T))=(m^(2))/(2+m^(2))`

Discussion

Explore topic-wise InterviewSolutions in .

The need for doing modulation isA. to increase the intensity of auido signalB. to decrease the intensity of audio signalC. to transmit audio signal to large distancesD. to increase the frequency of the audio signal

The most commonly employed analog modulation technique in satellite communication is theA. amplitude modulationB. frequency modulationC. phase modulationD. amplitude modulation

The process of recovering the audio signal from the modulated wave is known asA. amplificationB. rectificationC. modulationD. demodulation

A modulating signal is a square wave as shown in the following figure . While the carries wave is given by `e=4 sin (8 pi t)` volt . What is the modulation index ?A. 0.15B. 0.25C. 0.35D. 10.5

Which of the following is used to produce radio waves of constant amplitude?A. filterB. rectifierC. FETD. oscillator

Which of the following frequencies will be suitable for beyond the horizon communication using sky waves ?A. 10 kHzB. 10 MHzC. 1 GHzD. 1000 GHz

Among the follwing frequencies one will be suitable for beyond-the horizon communication using sky waves isA. `10 kHz`B. `10 MHz`C. `1 GHz`D. `1000 GHz`

The number of telephonic messages which are carried by a fibre at an instant with much less intensity loss areA. 2400B. 2200C. 2000D. 1800

Which of the following frequencies will be suitable for beyond the horizon communication using sky waves?A. 10 kHzB. 10 MHzC. 1 GHzD. 1000 GHz

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 communicarion system.A. ABCDEB. BADECC. BDACED. BEADC

The difference between phase and frequency modulationA. practically they are same but theoretically they differB. lies in the power audio response of phase modulationC. lies in the poorer audio response of frequency modulationD. lies in the definitions of modulation and their modulation index

In a detector, output circuit consists of `R = 10kOmega and C = 100 p F.` Calculate the frequency of carrier signal it can detect.A. ` gt gt 1 MHz `B. ` 0.1 kHz `C. `gt gt 1 GHz `D. `10^(3) Hz `

The mobile telephones operate typically in the range ofA. ` 1-100 MHz `B. 100-200 MHzC. 1000-2000 MHzD. 800-950 MHz

Which type of communication is employed in Mobile Phones ?

Intelset satellite works as a -A. transmitterB. repeaterC. absorberD. none of these

`I-V` characterstic of four devices are shown in Fig. `15.1` Identify devices that can be used for modulation:A. `i` and `iii`B. only `iii`C. `ii` and some regions of `iv`D. All the devices can be used

A basic communication system consist of (`a`) transmitter (`b`) information source (`c`) channel (`d`) receiver Choose the correct sequence in which these are arranged in a basic communication system:A. `ABCDE`B. `BADEC`C. `BDACE`D. `BEADC`

The frequency which is not part of `AM` broadcastA. `100 kHz`B. `700 kHz`C. `600 kHz`D. `1500 kHz`

Cellular Mobile works in the frequency range ofA. `840` to `935 MHz`B. `3.7` to `4.2 GHz`C. `420` to `890 MHz`D. `30` to `300 GHz`

A male voice after modulation-transmission sounds like that of a female to the receiver. The problem is due toA. poor selection of modulation index (selected `0ltmlt1`)B. poor bandwidth selection of amplifiers.C. poor selection of carrier frequencyD. loss of energy in transmission

Frequency range used in down linking in satellite communication isA. `0.896` to `0.901 GHz`B. `0.420` to `0.890 GHz`C. `5.925` to `6.425 GHz`D. `3.7` to `4.2 GHz`

A male voice after modulation-transmission sounds like that of a female to the receiver. The problem is due toA. poor selection of modulation indexB. poor bandwidht selection of amplifiersC. poor selection of carrier frequencyD. loss of energy in transmission

A male voice after modulation-transmission sounds like that of a female to the receiver. The problem is due toA. poor selection of modulation index (selected `0ltmlt1`)B. poor bandwidth selection of amplifiersC. poor selection of carrier frequencyD. loss of energy in transmission.

In the satellite communication, the uplinking frequency range isA. `0.896` to `0.901 GHz`B. `0.420` to `0.890 GHz`C. `5.925` to `6.425 GHz`D. `3.7` to `4.2 GHz`

In a communication system, noise is most likely to affect the signalA. at the transmitterB. In the channel or in the transmission lineC. In the information sourceD. At the receiver

The frequency of a FM transmitter without signal input is calledA. Lower side band frequencyB. Upper side band frequencyC. Resting frequencyD. None of these

The frequency of a `FM` transmitter without signal input is calledA. Lower side band frequencyB. Upper side band frequencyC. Resting frequencyD. None of these

A carrier is simultaneously modulated by two sine waves with modulation indices of `0.4` and `0.3`. The resultant modulated index will beA. 1B. 0.7C. 0.5D. 0.35

Name the device fitted in the satellite which receives signals from Earth station and transmits them in different directions after amplification.

While tuning in a certain broad cast station with a receiver, we are actuallyA. Varying the local oscillator frequencyB. Varying the frequency of the radio signal to be picked upC. Tuning the antennaD. None of these

1000 kHz carrier wave is amplitude modulated by the signal frequency 200-4000Hz . The channel width of this case isA. 8kHzB. 4kHzC. 7.6kHzD. 3.8 kHz

Two waves A and B of frequencies 2MHz and 3 MHz, respectively are beamed in the same direction for communication via sky wave. Which one of these is likely to travel longer distance in the ionosphere before suffering total internal reflection?A. AB. BC. Both (a) and (b)D. None of these

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

Would sky waves be suitable for transmission of TV signals of 60 MHz frequency?

The maximum and minimum amplitude of AM wave is found to be 15 V and 3 V , respectively . The amplitudes of carrier wave and modulating wave will beA. 9 and 6 VB. 6 and 9 VC. 18 and 9 VD. 24 and 16 V

An `AM` wave is given by `V=1500[1+0.5sin12560t]sin(5.26xx10^(5)t)`. The modulating frequency isA. `2.0 kHz`B. `1.0 kHz`C. `12.5 kHz`D. `50 kHz`

A `100m` long antenna is mounted on a `500m` tall building. The complex can become a transmission tower of waves with `lambda`A. `~ 400 m`B. `~ 25 m`C. `~ 150 m`D. `~ 2400 m`

In space communcation , the information can be passed from on place to another at a distance of 100 km inA. 1 sB. 0.5 sC. 0.003 sD. None of these

The frequency of a wave propagating in D-region having refractive index of 0.5 isA. ` 420 kcs^(-1) `B. ` 300 kcs^(-1) `C. `329.5 kcs ^(-1)`D. `350 kcs^(-1)`

A TV transmission tower has a height of 240 m. Signals broadcast from this tower will be received by LOS communication at a distance of (assume the radius of earth to be `6.4 xx 10 ^(6) m`)A. 100 kmB. 24 kmC. 55 kmD. 50 km

A T V transmission tower antenna is at a height of 20 m. How much service area can it cover if the receiving antenna is (i) at ground level, (ii) at a height of 25 m? Calculate the percentage increase in area covered in case (ii) relative to case (i).

Why is it necessary to use satellites for long distance TV transmission?

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 bands will beA. 1.003 MHz and 2. 997 MHzB. 3001 kHz and 2997 kHzC. 1003 kHz and 1000 kHzD. 1 MHz and 0.997 MHz

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 bands will beA. 1.003 MHz and 0.997 MHzB. 3001 kHz and 2997 kHzC. 1003 kHz and 1000 kHzD. 1 MHz and 0.997 MHz

If `V_(c)` is amplitude of carrier wave in `AM` transmitter where modulation factor is `m` then amplitude of side bands can beA. `(V_(c))/(2m)`B. `(m)/(2)V_(c)`C. `mV_(c)`D. `(V_(c))/(2)`

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 bands will beA. `1.003 MHz` and `0.997 MHz`B. `3001 kHz` and `2997 kHz`C. `1003 kHz` and `1000 kHz`D. `1 MHz` and `0.997 MHz`

For a carrier frequency of 100 kHz and a modulating frequency of 5kHz what is the width of AM transmission-A. 5 k HzB. 10 kHzC. 20 kHzD. 200 kHz

Fraction of total power carried by side bands is given by-A. `(P_(s))/(P_(T))=m^(2)`B. `(P_(s))/(P_(T))=1/(m^(2))`C. `(P_(s))/(P_(T))=(2+m^(2))/(m^(2))`D. `(P_(s))/(P_(T))=(m^(2))/(2+m^(2))`