229 + Interview Questions in COMMUNICATION-SYSTEM IN GENERAL AWARENESS Page 4 InterviewSolution

151.	The short wave Radio broadcasting band isA. `7 MHz` to `22 MHz`B. `88MHz` to `108 MHz`C. `30 KHz` to `300 KHz`D. `3 GHz` to ` 30 GHz`
Answer» Correct Answer - A

Discussion

152.	In Amplitude modulationA. The amplitude of the carrier wave varies in accordance with the amplitude of the modulating signalB. The amplitude of carrier wave remains constant frequency changes in accordance with the modulating signalC. The amplitude of carrier wave varies in accordance with the frequency of the modulating signalD. The amplitude changes in accordance with the wave length of the modulating signal
Answer» Correct Answer - A

Discussion

153.	the FM Radio broad casting band isA. `5 MHz` to `30 MHz `B. `88 MHz` to `108 MHz`C. `30 KHz ` to `300 KHz`D. `3 GHz` to `30 GHz`
Answer» Correct Answer - B

Discussion

154.	The higher frequency TV broad casting bands range isA. `54-72 MHz` and `76` to `88 MHz`B. `174-216 MHz` and `420` to `890 MHz`C. `896` to `901 MHz` and `840` to `935 MHz`D. `5.925` to `6.425 GHz` and `3.7` to `4.2 GHz`
Answer» Correct Answer - B

Discussion

155.	In amplitude modulation, carrier wave frequencies are:A. lower compared to those in frequency modulationB. higher compared to those in frequency modulationC. some as in frequency modulationD. lower sometimes and higher sometimes to those in frequency modulation
Answer» Correct Answer - A In Am, carrier wave frequencies are lower (0.5 -20 MHz ) compared to those in frequency modulation (80 MHz onwards ).

Discussion

156.	In amplitude modulation, carrier wave frequencies are….. Than that compared to those in frequency modulationA. lowerB. higherC. sameD. lower or higher
Answer» Correct Answer - A

Discussion

157.	Amplitude modulation is used for broad casting becauseA. it is more noise immuneB. it requires less transmitting powerC. it has simple circuitD. it has high fidelity(faithful reproduction)
Answer» Correct Answer - C

Discussion

158.	In amplitude modulationA. only amplitude is changed but frequency remains sameB. both amplitude & frequency changes equallyC. both amplitude & frequency changes unequallyD. only frequency changes but amplitude remains constant.
Answer» Correct Answer - A

Discussion

159.	Draw backs of Amplitude modulationA. During transmission extreneous noise creeps in.B. Most of the transmitting power is wasted, as it does not contain useful information.C. The reception is not clear in the case of weak signals due to noiseD. The receiver set is complex
Answer» Correct Answer - B

Discussion

160.	An amplitude modulated wave is modulated to `50%`. What is the saving in power if carrier as well as one of the side band are suppressed?A. `70%`B. `65.4 %`C. `94.4 %`D. `25.5 %`
Answer» Correct Answer - C

Discussion

161.	A radiowave that travels in a straight line from the transmitting antenna to the receiving antenna is know asA. sky waveB. ground waveC. space waveD. ionospheric wave
Answer» Correct Answer - A Sky waves are used for very long distance radia communication at medium and high frequencies . A radiowaves that travels in a straight line from the transmitting antenna to the receiving antenna is known as sky waves .

Discussion

162.	The antenna current of an `AM` transmitter is `8A` when only the carrier is sent but increases to `8.96A` when the carrier is modulated sinusoidally . The percentage modulation isA. `50%`B. `60%`C. `65%`D. `71%`
Answer» Correct Answer - D

Discussion

163.	When the modulating frequency is doubled, the modulation index is halved and the modulating voltage constant the modulation system isA. Amplitude modulationB. Phase modulationC. Frequency modulationD. All of the above
Answer» Correct Answer - C

Discussion

164.	Because of tilting, which waves finally disappear?A. MicrowavesB. Surface wavesC. Sky wavesD. Space waves.
Answer» Correct Answer - B Conceptual

Discussion

165.	When microwave signals follow the curvature of earth, this is known as:A. windowB. the Faraday effectC. ionospheric reflectionD. ducting
Answer» Correct Answer - D

Discussion

166.	Choose correct statements in the followingA. A vibrating tuning fork produce analog signalB. A muscial sound due to vibrating sitar string prodduce analog signalC. Light pulse produce digital signalD. Out put of `NAND` Gate produce digital signal
Answer» Correct Answer - A::B::C::D Analog signals are continous signals bit digiatal signals are in the form of pulses

Discussion

167.	In amplitude modulation, the modulation index mu, is kept less than or equal to 1 because.A. `mgt1`, will result in interference between carrier frequency and message frequency, resulting into distortion.B. `mgt1` will result in overlapping of both side bands resulting into loss of information.C. `mgt1` will result in change in phase between carrier signal and message signal.D. `mgt1` indicates amplitude of message signal greater than amplitude of carrier signal resulting into distortion.
Answer» Correct Answer - B::D Here `mu=(A_(m))/(A_(c))` when `mgt1` overlapping of both side bands takes place and it results loss of information and alos amplitude of message signal will be greater than amplitude or carrier signal which results destortion.

Discussion

168.	The frequency response curve (Fig. `15.2`) for the filter circuit used for production of `AM` waves should beA. (`i`) followed by (`ii`)B. (`ii`) followed by (`i`)C. (`iii`)D. (`iv`)
Answer» Correct Answer - A::B::C To produce an amplitude modulated wave, band width `=omega_(USB)-omega_(LSB)=2omega_(m)`

Discussion

169.	The frequency response curve (figure) for the filter circuit used for production of AM wave should be A. (i) followed by (ii)B. (ii) followed by (i)C. (iii)D. (iv)
Answer» Correct Answer - A::B::C Here, for the production of amplitude modulated wave, bandwidth is given by = frequency of upper side band - frequency of lower side band `=omega_(USB)-omega_(LSB)=(omega_(c)+omega_(m))-(omega_(c)-omega_(m))`

Discussion

170.	Statement-I : Diode lasers are used as optical sources in optical communication. Statement-II : Diode lasers consume less energy.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explanation of the assertion.C. If assertion is true but reason is false.D. If the assertion and reason both are false.
Answer» Correct Answer - B

Discussion

171.	Optical fibers are the best medium of transmission over copper wires, becauseA. The loss of data in optical fibers is very-very highB. optical fiber is cheap and easy to constructC. The optical fibers are made of glass and they are automatically isolated from the currentD. The optical fibers can take few number of telephonic message at a time.
Answer» Correct Answer - C

Discussion

172.	Assertion: The Microwave propagation is better than the sky wave propagation. Reason: Microwaves have frequency `100` to `3001 GHz, which have very good directional properties.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explanation of the assertion.C. If assertion is true but reason is false.D. If the assertion and reason both are false.
Answer» Correct Answer - a

Discussion

173.	The sky wave propagation is suitable for radiowaves of frequencyA. upto 2 MHzB. from 2 MHz to 20 MHzC. from 2 MHz to 30 MHzD. `0.56 xx10^(12) m^(-3)`
Answer» Correct Answer - C The sky waves are the radiowaves of frequency between 2 MHz to 30 MHz.

Discussion

174.	What is the radiowaves signal called if it propagates from one place to another along the surface of the earth?A. Sky waveB. Ground waveC. Carrier waveD. Modulated wave
Answer» Correct Answer - B

Discussion

175.	Find out the maximum electron density of the ionosphere if the maximum frequency of the radiowaves which returns to the earth after reflecting from the ionosphere is 18 MHz.A. `8m^(-3)`B. `6m^(-3)`C. `4 m^(-8)`D. `2 m^(-3)`
Answer» Correct Answer - C Given , critical frequency ` (f_(c))=18MHz ` maximum electron density `(N_("max "))=?` As we know that ` f_(c)=9(N_("max")=?` `implies 18=9(N_("max"))^(1//2)` ` or N_("max")=[(18)/(9)]^(2) or N_("max")=4m^(-3)`

Discussion

176.	On a particular day, the maximum frequency reflected from the ionosphere is 10 MHz. On another day, it was found to increase to 11 MHz. Calculate the ratio of the maximum electron densities of the ionosphere on the two days. Point out a plausible explanation for this.A. `1.21 `B. `0.82 `C. `0.50`D. `0.25 `
Answer» Correct Answer - A As ` , f_(c)=9sqrt(N_("max"))` ` :. N_("max")=(f_(c)^(2))/(81)prop f_(c)^(2` `implies ((N_(2))_("max"))/(N_(1))_("max")=((11)/(10))^(2) =(121)/(100)=1. 21 ` The variation may be due to atmospheric disturbances .

Discussion

177.	Frequencies in the `UHF` range normally propagate by means of:A. ground wavesB. sky wavesC. surface wavesD. space waves
Answer» Correct Answer - D

Discussion

178.	Digital signals (`i`) do not provide a continuous set of values.(`ii`) represents values as descrete steps. (`iii`) can utillize binary system (`iv`) can utillize decimal as well as binary system. The true option is.A. (i) and (ii) onlyB. (ii) and (iii) onlyC. (i), (ii) and (iii) but not (iv)D. All of (i), (ii), (iii) and (iv)
Answer» Correct Answer - C

Discussion

179.	Statement-I : Television signals are received through sky-wave propagation Statement-II : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explanation of the assertion.C. If assertion is true but reason is false.D. If the assertion and reason both are false.
Answer» Correct Answer - D

Discussion

180.	Digital signals (`i`) do not provide a continuous set of values.(`ii`) represents values as descrete steps. (`iii`) can utillize binary system (`iv`) can utillize decimal as well as binary system. The true option is.A. only (i) and (ii)B. Only (ii) and (iii)C. Only (i),(ii) and (iii) but not (iv)D. all of the above (i) to (iv)
Answer» Correct Answer - D All of them are properties of digital signals

Discussion

181.	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 intex of 75 % ?
Answer» `mu` = modulation index `= (A_m)/(A_c)` `rArr A_m = mu xxA_c = 0.75xx 12` `= 9 "volts"`.

Discussion

182.	For an amplitude modulated wave , the maximum amplitude is found to be 10 V while has minimum amplitude is found to ve 2 V . Determine the modulation index , `mu`. What would be the value of m if the minimum amplitude is zero volt ?
Answer» Given , maximum amplitude `A_("max") = 10V` Minimum amplitude `A_("min") = 2 V` Let `A_(c)` and `A_(m)` be amplitudes of carrier wave and signal wave `A_("max") = A_(c) + A_(m) = 10 ` _____ (1) and `A_("min") = A_(c) - A_(m) = 2 ` _______ (2) Adding the equation (1) & (2) we get `2 A_(c) = 6V , A_(m) = 10 - 6 = 4 V ` Modulation index `mu = (A_(m))/(A_(c)) = (4)/(6) = (2)/(3)` When the minimum amplitude is zero , then i.e., `A_("min") = 0` `A_(c) + A_(m) = 10 " "` _____(3) `A_(c) - A_m = 0 " " ` ______(4) By solving (3) & (4) we get `2 A_(m) = 10 , A_(m) = 5 , A_(c) = 5` Modulation index `mu = (A_(m))/(A_(c)) = (5)/(5) = 1`

Discussion

183.	Digitals signals (i) do not provide a continous set of values (ii) represent values are discrete steps (iii) can utilize binary system and (iv) can utilize decimal as well as binary systems . Which of the above statements are true ?A. (i) and (ii) onlyB. (i) , (ii) and (iii) but not (iv)C. (ii) and (iii) onlyD. All of (i) , (ii) , (iii) and (iv) .
Answer» A digital signal is a discontinous function of time in constrast to an analogue signal . The digital signals can be stored as digital data and cannot be transmitted along the telephone lines . Digital signal cannot utilize decimal signals .

Discussion

184.	When electromagnetic waves enter the ionised layer of ionosphere, then the relative permittivity i.e. dielectric constant of the ionised layerA. does not changeB. appears to increaseC. appears to decreasesD. sometimes e appears to increase and sometimes to decreases
Answer» Correct Answer - C When electromagnetic wave enter the ionised layer of ionosphere , then the relative premittivity of the ionised layer appears to decrease .

Discussion

185.	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% ?
Answer» Given , Peak voltage `V_(0) = 12 V` Modulation index `mu = 75% = (75)/(100)` We know that Modulation index `(mu) = ("Peak voltage of modulating signal" (V_(m)))/("Peak voltage"(V_(0)))` So , peak voltage of modulating signal `V_(m) = mu xx` Peak voltage `= (75)/(100) xx 12 = 9 V`.

Discussion

186.	Is it necessary for a transmitting antenna to be at the same height as that of the receiving antenna for line-of-sight communication ? A TV transmitting antenna is 81 m tall . How much service area can it cover if the receiving antenna is at the ground level ?
Answer» No, it is not necessary for line of sight communication , the two antenna may not be at the same height . Given, height of antenna h = 81 m Radius of earth R = `6.4 xx 10^(6)` m . Area `= pid^(2) ` , Range , d = `sqrt(2hR)` `therefore` Service area = `pi xx 2h R = (22)/(7) xx 81 xx 2 xx 6.4 xx 10^(6) = 3258.5 km^(2)`.

Discussion

187.	Is it necessary for a transmitting antenna to be at the same height asthat of the receiving antanna for line of sight communication? A TV transmitting antenna is 81 m tall. How much service area can it cover, if the receiving antena is at the ground level?A. `3800 km^(2)`B. `3260 km^(2)`C. ` 7400 km^(2)`D. `3320 km^(2)`
Answer» Correct Answer - B Range `, d=sqrt(2hR )` `:.` Service area ` = pi xx 2hR ` `=(22)/(7) xx 2 xx 81 xx 6.4 xx 10^(6)` `= 3258.5 xx 10^(6) m^(2)= 3258.5km^(2)=3260 km^(2)`

Discussion

188.	A transmitting antenna has a height 30m and that of the receiving atenna is 52 m . What is the maximum distance between them for satisfactory communication in line of sight mode ? Given , radius of earth is `6.4xx10^(6) `m .A. 45. 4 kmB. 44. 5 kmC. 36.3 kmD. 33.6 km
Answer» Correct Answer - A Here , `h_(T)=30 m , h_(R)=52 m , R=6.4xx10^(6) m ` ` d_(M)=sqrt(2Rh_(T))+sqrt(2Rh_(r))` `=sqrt( 2 xx 6.4 xx 10^(6) xx 30)+ sqrt( 2 xx 6. 4 xx 10^(6) xx 52 )` `=45.4 xx 10^(3) m =45.4 km`

Discussion

189.	A transmitting antenna at the top of a tower has a height 32 m and the height of the receiving antenna is 50 m . What is the maximum distance between them for satisfactory communication in LOS mode ? Given radius of earth `6.4 xx 10^(6) `m .
Answer» `d_(m) = sqrt(2 Rh_(T)) + sqrt(2 Rh_(R))` `d_(m) = sqrt(2 xx 64 xx 10^(5) xx 32) + sqrt(2 xx 64 xx 10^(5) xx 50 m)` `= 64 xx 10^(2) xx sqrt(10) + 8 xx 10^(3) xx sqrt(10) m = 144 xx 10^(2) xx sqrt(10) m = 45.5` km .

Discussion

190.	What is the modulation index of an over modulated waveA. 1B. ZeroC. `lt 1`D. `gt 1`
Answer» Correct Answer - D

Discussion

191.	Sinusoidal carrier voltage of frequency `1.5 MHz` and amplitude `50V` is amplitude modulated by sinusoidal voltage of frequency `10kHz` producing `50%` modualtion. The lower and upper side-band frequencies in `kHz` areA. `1490, 1510`B. `1510, 1490`C. `(1)/(1490), (1)/(1510)`D. `(1)/(1510), (1)/(1490)`
Answer» Correct Answer - A

Discussion

192.	Television signal on earth cannot be recevied at distances greater than `100 km` from the transmission station. The reasion behind this is thatA. The receiver antenna is unable to detect the signal at a distance greater than `100 km`B. The TV programme consists of both audio and video signalsC. The TV signals are less powerful than radio signalsD. The surface of earth is curved like a sphere
Answer» Correct Answer - D

Discussion

193.	Television signal on earth cannot be recevied at distances greater than `100 km` from the transmission station. The reasion behind this is thatA. The receiver antenna is unable to detect the signal at a distance greater than 100 kmB. The TV programme consists of both audio and video signalsC. The TV signals are less powerful than radio signalsD. The surface of earth is curved like a sphere
Answer» Correct Answer - D

Discussion

194.	Television signal on earth cannot be recevied at distances greater than `100 km` from the transmission station. The reasion behind this is thatA. The receiver antenna unable to detect the signal at a distance greater than 100 kmB. the TV programme consists of both audio and video signalsC. The TV signals are less powerful than radio signals.D. The surface of earth is curved like a sphere
Answer» Correct Answer - D TV signal are line of sight communication.

Discussion

195.	Laser beams are used to measure long distances becauseA. They are monochromaticB. They are highly polarisedC. They are coherentD. They have high degree of parallelism
Answer» Correct Answer - D

Discussion

196.	Laser light is considered to be coherent because it consists ofA. Many wavelengthsB. Uncoordinated wave of a particular wavelengthC. Coordinated wave of many wavelengthsD. Coordinated waves of a particular wavelength
Answer» Correct Answer - D

Discussion

197.	Assertion: A dish antenna is highly directional. Reasion: This is because a dipole antenna omnidirectional.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explanation of the assertion.C. If assertion is true but reason is false.D. If the assertion and reason both are false.
Answer» Correct Answer - b

Discussion

198.	A sinusoidal carrier voltage of `80 "volts"` amplitude and `1MHz` frequency is amplitude modulated by a sinusoidal voltage of frequency `5 kHz` producing `50%` modulation. Calculate the amplitude and frequency of lower and upper side bands.
Answer» Amplitude of both `LSB` and `USB` are equal and given by `=(mE_(c))/(2)=(0.5xx80)/(2)=20"volts"` Now frequency of `LSB=f_(c)-f_(s)` `=(1000-5)kHz=995kHz` Frequency of `USB=f_(c)+f_(s)` `=(1000+5)kHz=1005kHz`

Discussion

199.	A transmitter supplies `9kW` to the aerial when unmodulated. The power radiated when modulated to `40%` isA. `5 kW`B. `9.72 kW`C. `10 kW`D. `12 kW`
Answer» Correct Answer - B (`2`) `P_(t)=P_(c)[1+(m^(2))/(2)]=9[1+((0.4)^(2))/(2)]` `=9[1+(0.16)/(2)]` (`Qm=40%=0.4`) `=9(1.08)=9.72 kW`

Discussion

200.	The load current in the transmitting antenna of an unmodulated `AM` transmitter is `6 Amp`. What will be the antenna current when modulation is `60%`.
Answer» Total power carried by `AM` wave `P_(T)=P_(C)(1+(m^(2))/(2))`……(`1`) Where `P_(c)` is the power of carrier component and `m` is the modulation factor. If `R` is the resistance, `I_(m)` the antenna load current when modulation is `60%` and `I_(c)` is the antenna load current when unmodulated, then `(P_(T))/(P_(C))=(I_(m)^(2)R)/(I_(c)^(2)R)`, `:. 1+(m^(2))/(2)=(I_(m)^(2))/(I_(c)^(2))` using (`1`) or `I_(m)=I_(c)sqrt({(1+(m^(2))/(2))})` Given `I_(c)=6Amp`, `m=0.6` `I_(m)=6[1+((0.6)^(2))/(2)]=6[1.086]=6.52Amp`

Discussion

Explore topic-wise InterviewSolutions in .

The short wave Radio broadcasting band isA. `7 MHz` to `22 MHz`B. `88MHz` to `108 MHz`C. `30 KHz` to `300 KHz`D. `3 GHz` to ` 30 GHz`

the FM Radio broad casting band isA. `5 MHz` to `30 MHz `B. `88 MHz` to `108 MHz`C. `30 KHz ` to `300 KHz`D. `3 GHz` to `30 GHz`

The higher frequency TV broad casting bands range isA. `54-72 MHz` and `76` to `88 MHz`B. `174-216 MHz` and `420` to `890 MHz`C. `896` to `901 MHz` and `840` to `935 MHz`D. `5.925` to `6.425 GHz` and `3.7` to `4.2 GHz`

In amplitude modulation, carrier wave frequencies are:A. lower compared to those in frequency modulationB. higher compared to those in frequency modulationC. some as in frequency modulationD. lower sometimes and higher sometimes to those in frequency modulation

In amplitude modulation, carrier wave frequencies are….. Than that compared to those in frequency modulationA. lowerB. higherC. sameD. lower or higher

Amplitude modulation is used for broad casting becauseA. it is more noise immuneB. it requires less transmitting powerC. it has simple circuitD. it has high fidelity(faithful reproduction)

In amplitude modulationA. only amplitude is changed but frequency remains sameB. both amplitude & frequency changes equallyC. both amplitude & frequency changes unequallyD. only frequency changes but amplitude remains constant.

Draw backs of Amplitude modulationA. During transmission extreneous noise creeps in.B. Most of the transmitting power is wasted, as it does not contain useful information.C. The reception is not clear in the case of weak signals due to noiseD. The receiver set is complex

An amplitude modulated wave is modulated to `50%`. What is the saving in power if carrier as well as one of the side band are suppressed?A. `70%`B. `65.4 %`C. `94.4 %`D. `25.5 %`

A radiowave that travels in a straight line from the transmitting antenna to the receiving antenna is know asA. sky waveB. ground waveC. space waveD. ionospheric wave

The antenna current of an `AM` transmitter is `8A` when only the carrier is sent but increases to `8.96A` when the carrier is modulated sinusoidally . The percentage modulation isA. `50%`B. `60%`C. `65%`D. `71%`

When the modulating frequency is doubled, the modulation index is halved and the modulating voltage constant the modulation system isA. Amplitude modulationB. Phase modulationC. Frequency modulationD. All of the above

Because of tilting, which waves finally disappear?A. MicrowavesB. Surface wavesC. Sky wavesD. Space waves.

When microwave signals follow the curvature of earth, this is known as:A. windowB. the Faraday effectC. ionospheric reflectionD. ducting

Choose correct statements in the followingA. A vibrating tuning fork produce analog signalB. A muscial sound due to vibrating sitar string prodduce analog signalC. Light pulse produce digital signalD. Out put of `NAND` Gate produce digital signal

The frequency response curve (Fig. `15.2`) for the filter circuit used for production of `AM` waves should beA. (`i`) followed by (`ii`)B. (`ii`) followed by (`i`)C. (`iii`)D. (`iv`)

The frequency response curve (figure) for the filter circuit used for production of AM wave should be A. (i) followed by (ii)B. (ii) followed by (i)C. (iii)D. (iv)

The sky wave propagation is suitable for radiowaves of frequencyA. upto 2 MHzB. from 2 MHz to 20 MHzC. from 2 MHz to 30 MHzD. `0.56 xx10^(12) m^(-3)`

What is the radiowaves signal called if it propagates from one place to another along the surface of the earth?A. Sky waveB. Ground waveC. Carrier waveD. Modulated wave

Find out the maximum electron density of the ionosphere if the maximum frequency of the radiowaves which returns to the earth after reflecting from the ionosphere is 18 MHz.A. `8m^(-3)`B. `6m^(-3)`C. `4 m^(-8)`D. `2 m^(-3)`

Frequencies in the `UHF` range normally propagate by means of:A. ground wavesB. sky wavesC. surface wavesD. space waves

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 intex of 75 % ?

For an amplitude modulated wave , the maximum amplitude is found to be 10 V while has minimum amplitude is found to ve 2 V . Determine the modulation index , `mu`. What would be the value of m if the minimum amplitude is zero volt ?

When electromagnetic waves enter the ionised layer of ionosphere, then the relative permittivity i.e. dielectric constant of the ionised layerA. does not changeB. appears to increaseC. appears to decreasesD. sometimes e appears to increase and sometimes to decreases

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% ?

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

A transmitting antenna has a height 30m and that of the receiving atenna is 52 m . What is the maximum distance between them for satisfactory communication in line of sight mode ? Given , radius of earth is `6.4xx10^(6) `m .A. 45. 4 kmB. 44. 5 kmC. 36.3 kmD. 33.6 km

A transmitting antenna at the top of a tower has a height 32 m and the height of the receiving antenna is 50 m . What is the maximum distance between them for satisfactory communication in LOS mode ? Given radius of earth `6.4 xx 10^(6) `m .

What is the modulation index of an over modulated waveA. 1B. ZeroC. `lt 1`D. `gt 1`

Laser beams are used to measure long distances becauseA. They are monochromaticB. They are highly polarisedC. They are coherentD. They have high degree of parallelism

Laser light is considered to be coherent because it consists ofA. Many wavelengthsB. Uncoordinated wave of a particular wavelengthC. Coordinated wave of many wavelengthsD. Coordinated waves of a particular wavelength

A sinusoidal carrier voltage of `80 "volts"` amplitude and `1MHz` frequency is amplitude modulated by a sinusoidal voltage of frequency `5 kHz` producing `50%` modulation. Calculate the amplitude and frequency of lower and upper side bands.

A transmitter supplies `9kW` to the aerial when unmodulated. The power radiated when modulated to `40%` isA. `5 kW`B. `9.72 kW`C. `10 kW`D. `12 kW`

The load current in the transmitting antenna of an unmodulated `AM` transmitter is `6 Amp`. What will be the antenna current when modulation is `60%`.