NAB Broadcasting Technology & Equipment 2 — Questions and Answers
Question 1: What is the primary function of a distribution amplifier (DA) in a broadcast facility?
- Amplify audio signals from microphones
- Split and amplify a single signal to multiple destinations without level loss (Correct answer)
- Convert analog signals to digital format
- Regulate power supply voltage to transmitters
Correct answer: Split and amplify a single signal to multiple destinations without level loss
A distribution amplifier splits one input signal into multiple isolated outputs while maintaining proper signal levels.
Question 2: Which modulation technique does ATSC 3.0 (NextGen TV) use for its physical layer?
- 8-VSB
- OFDM (Orthogonal Frequency Division Multiplexing) (Correct answer)
- QAM-256
- COFDM with MPEG-2
Correct answer: OFDM (Orthogonal Frequency Division Multiplexing)
ATSC 3.0 uses OFDM, which provides better multipath rejection and mobile reception compared to the 8-VSB used in ATSC 1.0.
Question 3: In digital audio, what does the term 'bit depth' determine?
- The number of audio channels recorded
- The sample rate frequency
- The dynamic range and resolution of audio samples (Correct answer)
- The data compression ratio applied
Correct answer: The dynamic range and resolution of audio samples
Bit depth determines the number of amplitude levels available per sample, directly setting dynamic range (approximately 6 dB per bit).
Question 4: What is the purpose of a frame synchronizer in broadcast video routing?
- Synchronize audio channels to video frames
- Lock an incoming video signal to the local house sync reference (Correct answer)
- Convert interlaced video to progressive scan
- Compress video for transmission over IP networks
Correct answer: Lock an incoming video signal to the local house sync reference
A frame synchronizer buffers an incoming signal and re-clocks it to align with the facility's house sync, preventing roll or tearing when switching sources.
Question 5: What is the standard impedance of a coaxial cable used for broadcast video (SDI)?
- 50 ohms
- 75 ohms (Correct answer)
- 110 ohms
- 300 ohms
Correct answer: 75 ohms
Broadcast SDI video uses 75-ohm coaxial cable, which is also the impedance of the BNC connectors used throughout the industry.
Question 6: Which of the following best describes 'loudness normalization' as required by the CALM Act?
- Limiting peak audio levels to -3 dBFS
- Maintaining average program loudness at -24 LKFS/LUFS (Correct answer)
- Compressing all audio to a uniform dynamic range
- Setting audio sample rate to 48 kHz
Correct answer: Maintaining average program loudness at -24 LKFS/LUFS
The CALM Act requires broadcasters to maintain average dialog loudness at -24 LKFS, measured using the ITU-R BS.1770 algorithm.
Question 7: In an HD-SDI signal, what is the total bit rate for 1080i/59.94?
- 270 Mb/s
- 1.485 Gb/s (Correct answer)
- 3 Gb/s
- 6 Gb/s
Correct answer: 1.485 Gb/s
HD-SDI (SMPTE ST 292-1) carries 1080i at 1.485 Gb/s (or 1.4835 Gb/s for 59.94 Hz systems).
NAB Broadcasting Technology & Equipment 2
What is the primary function of a distribution amplifier (DA) in a broadcast facility?