SBCA Satellite Theory & Signal Transmission 2 — Questions and Answers
Question 1: What is the primary advantage of using Ku-band frequencies over C-band for direct-to-home (DTH) satellite broadcasting?
- Smaller dish antennas are required (Correct answer)
- Less susceptibility to rain fade
- Lower atmospheric absorption
- Greater orbital arc coverage
Correct answer: Smaller dish antennas are required
Ku-band's shorter wavelength allows smaller receiving dishes (typically 45–90 cm) compared to C-band's larger 1.8–3 m dishes, making DTH practical for residential installations.
Question 2: In satellite communications, EIRP stands for Equivalent Isotropic Radiated Power. What two factors determine EIRP?
- Transmit power and antenna gain (Correct answer)
- Receiver sensitivity and noise figure
- Orbital altitude and inclination
- Transponder bandwidth and modulation depth
Correct answer: Transmit power and antenna gain
EIRP = transmit power (in watts or dBW) multiplied by the antenna gain, representing the effective power radiated in a given direction.
Question 3: Which orbital parameter describes the point in a satellite's elliptical orbit where it is closest to Earth?
- Perigee (Correct answer)
- Apogee
- Inclination
- Argument of latitude
Correct answer: Perigee
Perigee is the closest point to Earth in an elliptical orbit, while apogee is the farthest point.
Question 4: A satellite transponder with a 36 MHz bandwidth operating in bent-pipe mode retransmits signals without which process?
- On-board signal regeneration or demodulation (Correct answer)
- Frequency conversion
- Amplification
- Polarization switching
Correct answer: On-board signal regeneration or demodulation
Bent-pipe transponders perform frequency conversion and amplification but do NOT demodulate or regenerate the signal; regenerative (processing) transponders do.
Question 5: What phenomenon causes satellite signals to experience a rotation of polarization as they pass through the ionosphere?
- Faraday rotation (Correct answer)
- Fresnel diffraction
- Doppler shift
- Scintillation
Correct answer: Faraday rotation
Faraday rotation occurs when electromagnetic waves interact with free electrons in the ionosphere in the presence of Earth's magnetic field, rotating the polarization plane.
Question 6: In a satellite link budget, the term G/T (figure of merit) refers to what ratio?
- Receive antenna gain to system noise temperature (Correct answer)
- Transmit gain to transponder bandwidth
- Ground station gain to satellite EIRP
- Gain to thermal noise power spectral density
Correct answer: Receive antenna gain to system noise temperature
G/T (dB/K) is the ratio of receive antenna gain (dBi) to system noise temperature (dBK), measuring the earth station's receive efficiency.
Question 7: Which multiple access technique assigns each earth station a unique frequency slot within the transponder bandwidth, regardless of whether the station is actively transmitting?
- FDMA (Frequency Division Multiple Access) (Correct answer)
- TDMA (Time Division Multiple Access)
- CDMA (Code Division Multiple Access)
- SDMA (Space Division Multiple Access)
Correct answer: FDMA (Frequency Division Multiple Access)
FDMA pre-assigns fixed frequency slots to each station; the slot remains occupied even during idle periods, which can reduce efficiency compared to demand-assigned methods.
SBCA Satellite Theory & Signal Transmission 2
What is the primary advantage of using Ku-band frequencies over C-band for direct-to-home (DTH) satellite broadcasting?