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Correct CHOICE is (a) Intermediate-POWER amplifier

Explanation: The power amplifier USUALLY BEGINS with an initial stage called the intermediate-power amplifier (IPA). This PROVIDES sufficient drive to the final high-power amplifier (HPA).

The CORRECT answer is (d) Ka band

To EXPLAIN: The satellites communicate with ground stations called gateways that connect the system to the public switched TELEPHONE network. The satellites also communicate among themselves. Both gateway and intersatellite COMMUNICATION TAKES place over Ka band frequencies.

Correct OPTION is (b) Frequency reuse

The explanation is: The digital SIGNAL is transmitted from the satellite to the receivers using circular polarization. The DBS satellites have right-hand and left-hand circularly polarized (RHCP and LHCP) helical antennas. By TRANSMITTING both polarities of signal, frequency reuse can be incorporated to double the channel CAPACITY.

Correct answer is (c) 66

Explanation: The satellite systems use low-earth-orbit satellites to perform the relay services to the main TELEPHONE system or to make a connection directly between any TWO cellular telephones USING the system. One of the oldest and most widely used is the Iridium system. It uses a CONSTELLATION of 66 satellites in six polar orbits with 11 satellites per orbit 420 mi above the earth.

Correct choice is (C) Ku band

The best EXPLANATION: The DBS satellite uses the Ku band with a frequency range of 11 to 14 GHz. UPLINK SIGNALS are usually in the 14- to 14.5-GHz range, and the downlink usually covers the range of 10.95 to 12.75 GHz.

The correct CHOICE is (a) Direct broadcast satellite

The best explanation: The direct broadcast satellite (DBS) system is an all-digital system. Data compression techniques are used to reduce the data rate in ORDER to produce high-quality picture and sound. They uses special broad COVERAGE SATELLITES with high power to transmit cable-TV-like SERVICES direct to homes equipped with the special DBS receivers.

The CORRECT option is (d) POWER requirements

Easiest explanation: TV signals are being TRANSMITTED through satellites for redistribution. Because of the very high-frequency signals involved in TV transmission, other long-distance transmission methods are not technically or economically FEASIBLE.

Right CHOICE is (a) Telephone service

Explanation: The PRIMARY use of communication satellites is in long-distance telephone service. Satellites greatly SIMPLIFY long-distance CALLS not only within countries but ALSO worldwide.

Correct choice is (a) MICROWAVE COMBINER

To EXPLAIN: Individual up CONVERTERS are used on each modulated CHANNEL. At the output of the up converters, all the signals are combined in a microwave combiner, which produces a single output signal that is fed to the final amplifiers.

Right ANSWER is (a) True

Easy EXPLANATION: In digital systems, ANALOG signals are first digitized with PCM converters. The resulting serial digital OUTPUT is then used to modulate a QPSK modulator.

Correct answer is (b) RF frequency synthesizer

For explanation I would SAY: In RF TUNING, a mixer FED by a fixed-frequency local oscillator performs an initial up conversion to 700 MHz. Then a sophisticated RF frequency synthesizer applied to a second mixer provides up conversion to the final MICROWAVE frequency.

Right answer is (c) Klystron amplifier

To elaborate: The signals to be sent to the satellite MIGHT be TV programs, multiple TELEPHONE calls, or DIGITAL data from a COMPUTER. These signals are used to modulate the carrier, which is then amplified by a large traveling-wave TUBE or klystron amplifier.

The correct option is (b) Up converter

To ELABORATE: The transmit subsystem consists of two BASIC parts, the up CONVERTERS and the POWER amplifiers. The up converters translate the BASEBAND signals modulated on to carriers up to the final uplink microwave frequencies.

Right option is (a) True

To elaborate: It must be possible to adjust its AZIMUTH and elevation so that the antenna can be properly ALIGNED with the satellite. Earth stations supporting geosynchronous satellites can generally be fixed in position, HOWEVER, azimuth and elevation adjustments are necessary to initially PINPOINT the satellite and to permit minor adjustments over the satellite’s life.

Right choice is (b) FREQUENCY SYNTHESIZER

Easiest explanation: In RF tuning, the first local oscillator is made adjustable. Generally, a frequency synthesizer is USED in this application. The frequency synthesizer GENERATES a HIGHLY stable signal at selected frequency increments.

Correct option is (a) True

To EXPLAIN I would say: The telemetry system is used to report the status of the onboard subsystems to the ground station. The telemetry system typically consists of various ELECTRONIC sensors WHOSE data are SELECTED by a multiplexer and then converted to a digital signal, which then modulates an internal TRANSMITTER. This transmitter sends the telemetry information back to the earth station, where it is recorded and monitored.

Right option is (b) When in orbit, solar POWER is always available

Best explanation: When a SATELLITE goes into an ECLIPSE or when the solar panels are not properly POSITIONED, there is a temporary cut in solar power supply. In situations like this the batteries take over temporarily and keep the satellite operating. The batteries are not large enough to power the satellite for a long time; they are used as a backup system for ECLIPSES, initial satellite orientation and stabilization, or emergency conditions.

Right option is (b) High power OUTPUT over wideband is not POSSIBLE

Explanation: it is generally not possible to generate very high output power over such wide bandwidth. The FACT is that no components and circuits can do this well. The high-power amplifiers in most transponders are traveling-wave tubes that inherently have limited bandwidth. They operate well over a small RANGE but cannot DEAL with the entire 500-MHz bandwidth allocated to a satellite.

Correct OPTION is (c) 24

The explanation is: Since in frequency REUSE each channel can be used TWICE the numbers of transponders are also DOUBLED. 12 x 2 = 24 transponders, two for each frequency.

The correct choice is (a) True

The BEST explanation: A regenerative REPEATER demodulates the uplink SIGNAL after the frequency is translated to some lower intermediate frequency. The RECOVERED baseband signal is then used to modulate the downlink signal.

Correct choice is (b) Dual conversion transponders

The BEST I can explain: A dual-conversion TRANSPONDER makes the FREQUENCY translation in two STEPS with two MIXERS. No demodulation occurs.

Correct choice is (c) Transponder

The EXPLANATION is: The uplink SIGNALS from EARTH are amplified, translated in frequency, and re-transmitted on the downlink to ONE or more earth STATIONS. The component that performs this function is known as a transponder.

Right answer is (c) Voice, video, computer DATA

Best EXPLANATION: An earth station takes the signals to be transmitted, known as baseband signals, and MODULATES a microwave CARRIER. The three most common baseband signals are voice, video, and computer data.

Correct option is (a) Reduce interference

For explanation I would say: Because of the CLOSE proximity of the transmitter and the receiver in the satellite, the high transmitter output power for the downlink is picked up by that satellite receiver. Naturally, the uplink SIGNAL is totally obliterated. Furthermore, the transmitter output FED back into the receiver input causes oscillation. To avoid this PROBLEM, the receiver and transmitter in the satellite TRANSPONDER are designed to operate at separate frequencies. In this way, they will not interfere with each other.

Correct answer is (a) True

Easiest explanation: SPATIAL-division multiple access uses spatial isolation technique. Earth stations in each segment may actually USE the same frequency, but because of the very narrow BEAM widths of the antennas, there is no INTERFERENCE between adjacent segments. This technique is referred to a spatial-division multiple access (SDMA) in that access to the satellite depends on location and not frequency.

Correct ANSWER is (b) Frequency reuse

Easy explanation: In the frequency reuse technique two systems use the same frequency, although operating on exactly the same frequencies, they are isolated from each other by the use of special antenna techniques. For example, a VERTICALLY POLARIZED antenna will not respond to a horizontally polarized signal and vice versa. Or a left-hand circularly polarized (LHCP) antenna will not respond to a right-hand circularly polarized (RHCP) signal and vice versa.

Right option is (a) Ground station

Explanation: The communication subsystem is the most IMPORTANT part of the satellite. It requires VARIES additional systems like the POWER system, propulsion system, telemetry system for its proper FUNCTIONING. The ground system HOWEVER is not one of the satellite subsystem and is independent of the satellite. It is just a transponder to monitor and command the satellite.

Right answer is (a) Spatial isolation

The explanation is: By USING narrow beam or spot beam antennas, the area on the earth covered by the SATELLITE can be divided up into smaller SEGMENTS. Earth stations in each segment may actually USE the same FREQUENCY, but because of the very narrow beam widths of the antennas, there is no interference between adjacent segments.

Correct CHOICE is (b) 72Mpbs

For explanation: For binary transmission, the maximum theoretical data RATE or CHANNEL capacity C for a given BANDWIDTH B isC = 2B = 2(36) =72Mpbs.

The CORRECT answer is (a) MF

To explain: MF is a LOWER frequency band than Ku, C and X BANDS and does not LIE in the microwave spectrum. Microwaves are used for satellite communication SINCE the lower bands get reflected by the ionosphere.

Right answer is (c) Are not diffracted by the IONOSPHERE

The EXPLANATION is: VHF, UHF, and MICROWAVE SIGNALS penetrate the ionosphere with little or no attenuation and are not refracted to earth. Lower frequencies undergo total internal refraction and GET reflected back to earth.

The CORRECT option is (d) Overcrowding

To elaborate: Most new communication satellites will operate in the Ku band. This upward shift in FREQUENCY is happening because the C band is overcrowded. MANY communication satellites are in orbit now, most of them operating in the C band. However, there is some difficulty with interference because of the heavy usage. The only way this interference will be minimized is to shift all future satellite communication to higher frequencies.

The CORRECT ANSWER is (B) Communication satellites

The explanation is: Communication satellites are not originators of information to be transmitted. If a transmitting station cannot communicate directly with one or more receiving stations because of line-of-sight restrictions, a satellite can be used. The transmitting station SENDS the information to the satellite, which in turn re-transmits it to the receiving stations.

Right choice is (a) More number of OPERATING channel

Easy explanation: To be economically feasible, a satellite must be capable of handling SEVERAL CHANNELS. As a result, most satellites contain multiple TRANSPONDERS, each operating at a different frequency. Each transponder represents an INDIVIDUAL communication channel.

Right answer is (c) Transponder

Explanation: The transmitter-receiver COMBINATION in the satellite is known as a transponder. The BASIC FUNCTIONS of a transponder are amplification and frequency TRANSLATION. The reason for frequency translation is that the transponder cannot transmit and RECEIVE on the same frequency.

Correct ANSWER is (B) Subsatellite point

To elaborate: The satellite location is specified by a point on the surface of the EARTH DIRECTLY below the satellite. This point is known as the subsatellite point (SSP). The subsatellite point is then located by using conventional latitude and LONGITUDE designations.

Correct answer is (a) True

The explanation is: The original signal being transmitted from the EARTH station to the SATELLITE is CALLED the uplink, and the re-transmitted signal from the satellite to the RECEIVING stations is called the downlink. Usually, the downlink frequency is lower than the uplink frequency. A TYPICAL uplink frequency is 6 GHz, and a common downlink frequency is 4 GHz.

The correct CHOICE is (b) Angle of elevation

Best explanation: The angle of elevation of a satellite is the angle that APPEARS between the line from the earth station’s antenna to the satellite and the line between the earth station’s antenna and the earth’s horizon. If the angle of elevation is too small, the signals between the earth station and the satellite have to pass through MUCH more of the earth’s atmosphere. Because of the very low powers USED and the high absorption of the earth’s atmosphere.

The correct choice is (c) GEOSYNCHRONOUS orbit

Best explanation: The best SOLUTION is to launch a synchronous or GEOSTATIONARY satellite. In a geosynchronous earth orbit. Since the satellite remains apparently fixed, no special earth station tracking antennas are REQUIRED. The antenna is simply pointed at the satellite and remains in a fixed position. With this ARRANGEMENT, continuous communication is possible.

Right option is (d) 40

To elaborate: Most COMMUNICATION satellites in USE today are of the geosynchronous variety. Approximately 40 percent of the earth’s SURFACE can be “seen” or accessed from such a satellite. Users INSIDE that area can use the satellite for communication.

The correct option is (a) 0°

For EXPLANATION: Another DEFINITION of inclination is the angle between the equatorial plane and the satellite ORBITAL plane as the satellite enters the northern HEMISPHERE. When the angle of inclination is 0°, the satellite is directly above the equator. Orbits with 0° inclination are generally called equatorial orbits.

Correct answer is (a) synodic PERIOD

Explanation: ANOTHER method of expressing the time for one orbit is the revolution or synodic period. One revolution (1 r) is the period of time that elapses between the successive passes of the SATELLITE over a given meridian of earth LONGITUDE. Naturally, the synodic and sidereal periods differ from each other because of the earth’s ROTATION.

Right option is (c) Sidereal PERIOD

The best I can explain: The period is the time it TAKES for a satellite to complete one ORBIT. It is also called the sidereal period. A sidereal orbit uses some external fixed or apparently motionless object such as the sun or star for REFERENCE in determining a sidereal period.

Correct answer is (B) False

Easiest explanation: Satellites that are near earth have to move at HIGHER SPEEDS to sustain their orbit since the gravitational pull is much higher. Since the EFFECT of gravity is less at higher altitudes, satellites that far away REQUIRE less speeds.

Right CHOICE is (c) Perigee

The explanation is: In an elliptical orbit, the speed changes depending upon the height of the satellite above the earth. Naturally, the speed of the satellite is greater when it is CLOSE to the earth than when it is far AWAY. The CLOSEST POINT is called the perigee.

Correct OPTION is (b) Posigrade

For explanation: The direction of SATELLITE rotation may be either in the same direction as the EARTH’s rotation or against the direction of earth’s rotation. In the former case, the orbit is said to be posigrade, and in the latter case, retrograde. Most ORBITS are posigrade.