What technique does DSP use to double the number of channels by using helical antennas?

A)
Modulation
B)
Frequency reuse
C)
Multiplexing
D)
Spatial isolation

Correct Answer :   Frequency reuse

Explanation : 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.

Recently Updated in Avionics Questions
Which frequency band is used for connecting the satellite system with the public switched telephone network?
A)
Ka band
B)
L band
C)
C band
D)
Ku band

Correct Answer : Option (A) :   Ka band

Explanation : 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.

What provides the sufficient drive to the final power amplifier?
A)
Up converter
B)
Power driver circuit
C)
Operational amplifier
D)
Intermediate-power amplifier

Correct Answer : Option (D) :   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).

What is the number of satellites present in the Iridium system?
A)
72
B)
66
C)
51
D)
32

Correct Answer : Option (B) :   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.

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