Practice Test Geeks(SBCA) Satellite Broadcasting and Communications Association Certification Practice Test
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Digital Transmission 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 Digital Transmission flashcards as text

  1. What is the Nyquist sampling theorem's requirement for lossless digital sampling of an analog signal?

    Answer: Sample at least twice the highest frequency component

    The Nyquist theorem states the sampling rate must be at least twice the highest frequency in the signal to allow perfect reconstruction.

  2. Which parameter directly determines the symbol rate (baud rate) of a satellite carrier?

    Answer: Occupied bandwidth and roll-off factor

    Symbol rate is set by the transponder's occupied bandwidth and the roll-off factor of the Nyquist filter shaping the signal.

  3. What does a BER (Bit Error Rate) of 10⁻⁶ mean in a digital satellite link?

    Answer: One error per one million bits

    BER of 10⁻⁶ means one bit error occurs for every one million bits transmitted, which is an acceptable threshold for many satellite services.

  4. In satellite broadcasting, what is the advantage of using statistical multiplexing over fixed bit-rate multiplexing?

    Answer: It dynamically allocates bandwidth to maximize overall picture quality

    Statistical multiplexing allocates more bits to complex, fast-moving scenes and fewer to static scenes, improving overall video quality within a fixed total bit rate.

  5. What is the role of an LDPC (Low-Density Parity-Check) code in DVB-S2?

    Answer: Providing powerful inner forward error correction near Shannon limit

    LDPC codes in DVB-S2 provide near-Shannon-limit error correction performance, enabling operation at very low Eb/No with high reliability.

  6. Which measure describes the minimum Eb/No required to achieve error-free communication as defined by information theory?

    Answer: Shannon limit

    The Shannon limit defines the theoretical minimum Eb/No (-1.6 dB) below which reliable communication is impossible regardless of coding complexity.

  7. What causes inter-symbol interference (ISI) in a digital satellite transmission system?

    Answer: Multipath or bandwidth limiting causing symbols to overlap in time

    ISI occurs when a signal's bandwidth is excessively limited or when multipath causes delayed copies of symbols to interfere with adjacent symbols.