Practice Test Geeks(SBCA) Satellite Broadcasting and Communications Association Certification Practice Test
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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

  1. What is the purpose of a 'splash plate' or subreflector in a Cassegrain antenna system?

    Answer: To redirect the reflected signal from the main dish back toward a secondary focus near the vertex

    In a Cassegrain system, the convex hyperboloidal subreflector reflects energy from the main dish back through a hole at the vertex to a feed located behind the main reflector.

  2. Which specification defines the minimum angular separation an antenna can maintain between the desired satellite and an interfering adjacent satellite?

    Answer: Half-power beamwidth (HPBW)

    The half-power beamwidth (HPBW) is commonly used to characterize antenna selectivity, and the FCC uses antenna size and beamwidth requirements to enforce minimum orbital arc discrimination.

  3. An antenna's gain is measured at 45.5 dBi at 14.0 GHz. If the operating frequency drops to 12.0 GHz with the same dish diameter, what happens to the gain?

    Answer: Gain decreases because the effective aperture area is inversely proportional to frequency squared

    Antenna gain is proportional to (πD/λ)², and since λ increases at lower frequency, gain decreases when frequency drops while dish size remains constant.

  4. What is 'antenna depolarization' in the context of satellite communications, and what causes it?

    Answer: Rotation of the signal polarization plane caused by Faraday rotation or rain

    Depolarization is the conversion of polarized signal energy into the orthogonal polarization, commonly caused by rain (differential attenuation) or ionospheric Faraday rotation.

  5. In a receive-only C-band earth station, what is the primary reason larger dish sizes (e.g., 4.5 m vs. 1.8 m) are often preferred over smaller dishes?

    Answer: Larger dishes provide higher G/T ratios necessary to overcome C-band's lower satellite EIRP levels

    C-band satellites typically operate at lower EIRP than Ku-band, so receive-only terminals need larger dishes to achieve sufficient G/T for acceptable carrier-to-noise ratios.

  6. What does the 'figure of merit' G/T represent in a satellite receive system?

    Answer: The ratio of antenna gain (dBi) to system noise temperature (K) in dB/K

    G/T (gain-to-noise temperature ratio) in dB/K is the key figure of merit for a receive system, combining antenna gain and system noise temperature into a single performance metric.

  7. A satellite dish is installed at a site with 35°N latitude targeting a satellite at 101°W longitude. The site longitude is 87°W. Which tool is most appropriate to calculate the required azimuth and elevation angles?

    Answer: A satellite look-angle calculator using the geographic coordinates of both site and satellite

    Look-angle calculators use site latitude/longitude and satellite orbital longitude to compute precise azimuth, elevation, and polarization skew angles.