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.

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  1. Which modulation technique is used in DVB-S2 to achieve higher spectral efficiency compared to DVB-S?

    Answer: 8PSK and 16APSK

    DVB-S2 supports higher-order modulations including 8PSK and 16APSK, enabling greater spectral efficiency than DVB-S which uses QPSK.

  2. What is the primary purpose of a Reed-Solomon outer code in a digital satellite transmission chain?

    Answer: Correcting burst errors after Viterbi decoding

    Reed-Solomon outer coding corrects burst errors that remain after the inner Viterbi decoder, providing a concatenated error correction scheme.

  3. In MPEG-2 transport stream, what is the fixed packet size?

    Answer: 188 bytes

    MPEG-2 transport stream packets are fixed at 188 bytes, consisting of a 4-byte header and 184 bytes of payload.

  4. What does the term 'spectral efficiency' measure in satellite digital transmission?

    Answer: Bits transmitted per second per hertz of bandwidth

    Spectral efficiency is measured in bits/s/Hz and indicates how effectively a transmission system uses available bandwidth.

  5. Which DVB-S2 feature allows the uplink to adapt modulation and coding in real time based on link conditions?

    Answer: Adaptive Coding and Modulation (ACM)

    ACM (Adaptive Coding and Modulation) dynamically adjusts modulation order and FEC rate per terminal based on real-time link margin.

  6. What is the function of an energy dispersal scrambler in a satellite uplink chain?

    Answer: Spreading signal energy to avoid spectral lines

    Energy dispersal randomizes data patterns to prevent strong spectral lines that would cause interference and violate regulatory power spectral density limits.

  7. In DVB-S2 framing, what is a BBFRAME (Baseband Frame) used for?

    Answer: Encapsulating input stream data before LDPC/BCH encoding

    The BBFRAME is the baseband framing structure that encapsulates input stream data and a header before applying BCH and LDPC forward error correction.