SBCA Satellite Theory & Signal Transmission 3

Question 1

Rain fade affects satellite signals primarily in which frequency band and above?

Accepted Answer

Above 10 GHz (Ku-band)

Answer

Rain attenuation becomes significant above approximately 10 GHz because raindrops are comparable in size to the wavelength, causing scattering and absorption.

Question 2

What is the purpose of uplink power control (UPC) in satellite earth stations?

Accepted Answer

To compensate for rain fade and maintain a constant signal level at the satellite

Answer

UPC dynamically increases transmit power during rain events to maintain a stable received signal level at the satellite, counteracting uplink attenuation.

Question 3

Polarization isolation between cross-polarized transponders is measured by which parameter?

Accepted Answer

Cross-Polarization Discrimination (XPD)

Answer

XPD quantifies how well a system isolates signals on orthogonal polarizations; rain can degrade XPD, causing interference between co-frequency cross-pol transponders.

Question 4

In DVB-S2 (Digital Video Broadcasting – Satellite, 2nd generation), which modulation scheme offers the highest spectral efficiency under good signal conditions?

Accepted Answer

32APSK

Answer

32APSK carries 5 bits per symbol and is the most spectrally efficient DVB-S2 modulation, used when the link margin is high enough to support it.

Question 5

Which orbital region is designated for geostationary satellites, and at what altitude above the equator does it exist?

Accepted Answer

Clarke Belt, approximately 35,786 km

Answer

The Clarke Belt (named after Arthur C. Clarke) at ~35,786 km is where satellite orbital period equals Earth's rotation period, making the satellite appear stationary.

(SBCA) Satellite Broadcasting and Communications Association Certification Practice Test

(SBCA) Satellite Broadcasting and Communications Association Certification Practice Test

SBCA Satellite Theory & Signal Transmission 3