Avionics Multiple Choice Questions on “Satellite Applications”.
1. What is the primary use of communication satellites?
a) Telephone service
b) Surveillance
c) Research
d) GPS
Answer: a
Clarification: 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.
2. Which of the following is not a reason for redistributing TV signals through satellites rather than skywaves or spacewaves?
a) High frequency signal
b) Long distance communication
c) Economically feasible
d) Power requirements
Answer: d
Clarification: 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.
3. What type of satellite TV service uses compressed data transmission to beam signals directly to every home?
a) Direct broadcast satellite
b) Mobile satellite service
c) Broadcasting satellite service
d) Fixed satellite service
Answer: a
Clarification: 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.
4. Which frequency band does the direct broadcast satellite system use?
a) C band
b) X band
c) Ku band
d) MF band
Answer: c
Clarification: 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.
5. What technique does DSP use to double the number of channels by using helical antennas?
a) Spatial isolation
b) Frequency reuse
c) Multiplexing
d) Modulation
Answer: b
Clarification: 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.
6. What is the number of satellites present in the Iridium system?
a) 72
b) 51
c) 66
d) 32
Answer: c
Clarification: 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.
7. Which frequency band is used for connecting the satellite system with the public switched telephone network?
a) L band
b) Ku band
c) C band
d) Ka band
Answer: d
Clarification: 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.
8. What provides the sufficient drive to the final power amplifier?
a) Intermediate-power amplifier
b) Operational amplifier
c) Power driver circuit
d) Up converter
Answer: a
Clarification: 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).