Correct Answer : Heinrich Hertz
Explanation : The German physicist, Heinrich Hertz, first applied the theory given by Maxwell to prove the existence of radio waves in 1887. To honor him the unit of frequency is given his name.
Correct Answer : Transmitter
Explanation : A transmitter is an electronic component that converts the electric signals into a signal that is suitable for transmission in any given medium. It could be wires, air, water, land or even space.
Correct Answer : Digital
Explanation : In digital communication, the information can be quantized and transmitted. In time division multiplexing the information or digital data is quantized and transmitted in time slots which can be put together to get the original information.
Correct Answer : Half duplex
Explanation : Ia a walkie talkie the communication is two way but at a given time only one way communication is allowed. This type of communication is called as half duplex communication.
Explanation : The communication between an aircraft and an ATC is half duplex meaning only one can speak at a time. The ATC asks or gives guidance for the aircraft, which the pilot has to fully hear before he can respond. If he responds before, the signal is not received by the ATC.
Correct Answer : SONAR
Explanation : SONAR or SOund Navigation and Ranging is the transmission of information using sound waves. Since seawater is saline, it shorts out the electrical field in the radio waves and hence radio communication cannot be used.
Correct Answer : Duplexer
Explanation : A transceiver is a device that contains the necessary electronic components for both transmission and receiving in the same medium. They have a common power supply and a common antenna for transmitting and receiving.
Correct Answer : Permeability and permittivity of medium
Explanation : Since the EM waves are made of electric and magnetic fields, the resistance given by the medium to conduct electric and magnetic waves determine the speed of the EM wave. This is given by the permeability and the permittivity of the medium.
Correct Answer : Walkie talkie
Explanation : A simplex communication is when signal is sent from one end and is received at the other end. The communication in a walkie talkie is a two way communication.
Correct Answer : Modulation
Explanation : Modulation is the process of making the information signal more compatible with the medium. Modulation is the reason why we can have different channels on radio.
Correct Answer : Baseband signal
Explanation : The information signal, regardless of analog or digital type, is referred to as baseband signals. It could be voice, video or digital data and is modulated before transmission. In some case, baseband signals can be transmitted without modulation.
Correct Answer : Pulse modulation
Explanation : Modulation is of three types, frequency modulation, amplitude modulation and phase modulation. Pulse modulation is a type of amplitude modulation.
Correct Answer : Time division multiplexing
Explanation : In serial buses, time division multiplexing is used to split the digital data, which is in binary numbers, into individual bits which occupy a particular time slot and is transmitted. The use of serial buses increases the limit on transmission speed and reduces noise.
Correct Answer : Less noise
Explanation : Although AM is much simpler and has a wider range due to atmospheric propagation, one of its major disadvantages is due to noise. Noise directly affects the amplitude of the signal and its hard to retrieve the original information.
Correct Answer : Amplitude of the carrier wave
Explanation : In amplitude modulation, the amplitude of the carrier wave is modulated with respect to the information signal. The frequency and the phase of both the carrier and the information signal remain constant.
Correct Answer : Code division multiplexing
Explanation : In code-division multiplexing, the signals to be transmitted are converted to digital data that is then uniquely coded with a faster binary code. The signals modulate a carrier on the same frequency. All use the same communications channel simultaneously. The unique coding is used at the receiver to select the desired signal.
Correct Answer : Multiplexing
Explanation : Multiplexing is the process of transmitting more than one signal via a common transmitting medium. A device called a multiplexer is used for this purpose. The signal can be demultiplexed at the receiver end to retrieve the original information.
Correct Answer : Frequency
Explanation : Cps or cycles per second is an alternative unit for the frequency of an EM wave. The other unit for frequency is Hertz which is more commonly used around the world.
Correct Answer : EM spectrum
Explanation : The range of electromagnetic signals encompassing all frequencies is referred to as Electromagnetic spectrum. It includes radio waves, microwaves, optical waves, x-rays, gamma rays and cosmic waves.
Correct Answer : Wavelength
Explanation : The wavelength of a wave is the distance the wave travels in one cycle. The wavelength of a signal is represented by the Greek letter λ (lambda) and has the same units as length.
Correct Answer : ITU
Explanation : The International Telecommunications Union (ITU), an agency of the United Nations that is headquartered in Geneva, Switzerland, comprises 189 member countries that meet at regular intervals to promote cooperation and negotiate national interests. The ITU brings together the various countries to discuss how the frequency spectrum is to be divided up and shared. Because many of the signals generated in the spectrum do not carry for long distances, countries can use these frequencies simultaneously without interference.
Correct Answer : 60Mhz
Explanation : Bandwidth = upper frequency – lower frequencyUpper frequency = bandwidth + lower frequency = 54Mhz + 6Mhz = 60Mhz.
Correct Answer : 26Mhz
Explanation : Bandwidth = upper frequency – lower frequency = 928Mhz – 902Mhz =26Mhz.
Correct Answer : Bandwidth
Explanation : Bandwidth is that portion of the electromagnetic spectrum occupied by a signal. It is also the frequency range over which a receiver or other electronic circuit operates. More specifically, bandwidth is the difference between the upper and lower frequency limits of the signal or the equipment operation range.
Correct Answer : Stopped by ionizing effects
Explanation : X-rays are not stopped by ionizing effects and that was the only reason they were ever thought they could be used in communication. In re-entry vehicles, a temporary communication cut off is experienced due to ionizing effects. X- rays were hard to modulate and focus and hence gradually let down.
Correct Answer : 2m
Explanation :
Correct Answer : 2.5Ghz
Correct Answer : Books
Explanation : Infrared radiation is generally associated with heat. Infrared is produced by light bulbs, human bodies, and basically any physical equipment that generates heat.
Correct Answer : Satellite communication
Explanation : SHFs or Super High Frequency EM waves are those which lie between the frequency range of 3 to 30GHz range. These microwaves frequencies are widely used in satellite communication and radar.
Correct Answer : 1477.8Mhz
Explanation : Wavelength =8 in.= 0.203 mFrequency = 300/0.203 = 1477.8Mhz.
