Antenna Systems Flashcards
7 cards from real SBCA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Antenna Systems flashcards as text
What is the primary advantage of a phased array antenna over a traditional parabolic dish for satellite communications?
Answer: Electronic beam steering without mechanical moving parts
Phased arrays steer their beam by adjusting the phase of signals at individual antenna elements electronically, enabling rapid beam repositioning without mechanical actuators.
During antenna system commissioning, a technician measures a receive signal level 3 dB lower than the link budget predicts. Which is the LEAST likely cause?
Answer: The satellite's EIRP being 3 dB higher than specified in the link budget
A satellite transmitting 3 dB more than specified would cause the received level to be higher than predicted, not lower — it is the least likely cause of a 3 dB deficit.
What is 'antenna gain roll-off' in the context of wideband satellite systems?
Answer: The reduction in antenna gain observed at frequencies near the band edge compared to the center frequency
Gain roll-off describes how antenna gain decreases toward the edges of the operating bandwidth, which must be accounted for in wideband link budget calculations.
Which grounding practice is most critical for protecting a satellite dish installation from lightning damage?
Answer: Installing a dedicated ground rod at the dish base and bonding all metallic components to a single-point ground
Proper grounding requires a dedicated earth ground at the antenna structure and bonding all metallic components (dish, mast, coax shield) to a single common ground point.
An antenna's beamwidth is measured at 0.7° at 14.25 GHz. A neighboring satellite is located 2° away in orbital arc. What is the approximate isolation advantage provided by the antenna's directivity?
Answer: The interfering satellite falls outside the half-power beamwidth, providing significant sidelobe attenuation
Since the 2° separation is nearly 3× the 0.7° HPBW, the interfering satellite falls well into the sidelobe region where antenna gain is substantially reduced.
What is the purpose of 'autotracking' systems on large earth station antennas used for non-geostationary (NGSO) satellites?
Answer: To continuously repoint the antenna to track the satellite as it moves across the sky
NGSO satellites move relative to the Earth's surface, so autotracking systems continuously monitor the beacon signal and servo the antenna mount to maintain peak gain alignment.
Which material property is most important when selecting a radome to cover a satellite dish antenna installation?
Answer: Low RF dielectric loss to minimize signal attenuation through the radome material
Radome materials must have low dielectric loss (low loss tangent) to avoid attenuating the RF signal as it passes through on both transmit and receive paths.