NAB Broadcasting Technology & Equipment 3 — Questions and Answers
Question 1: What does the acronym EAS stand for in broadcasting?
- Enhanced Audio System
- Emergency Alert System (Correct answer)
- Electronic Automation Server
- Encoded Audio Standard
Correct answer: Emergency Alert System
The Emergency Alert System (EAS) is the national public warning system that requires broadcasters to interrupt programming to broadcast emergency alerts.
Question 2: A broadcast engineer notices the video waveform monitor shows the luminance signal peaking at 110 IRE. What is the problem?
- The signal is too dark and needs gain
- The signal is over-modulated and may cause illegal broadcast levels (Correct answer)
- The chroma phase is shifted 90 degrees
- The audio is clipping in sync with video transients
Correct answer: The signal is over-modulated and may cause illegal broadcast levels
Legal broadcast luminance levels must not exceed 100 IRE (with sync at -40 IRE); exceeding this causes over-modulation and FCC compliance issues.
Question 3: Which type of microphone element uses a thin metallic diaphragm whose capacitance changes with sound pressure?
- Dynamic (moving coil)
- Ribbon
- Condenser (capacitor) (Correct answer)
- Piezoelectric
Correct answer: Condenser (capacitor)
Condenser microphones use a charged capacitor whose capacitance varies with diaphragm movement, requiring phantom power or a battery to maintain the charge.
Question 4: What is the purpose of a 'gen-lock' signal in a broadcast facility?
- Lock the transmitter output power to a reference level
- Synchronize multiple video sources to a common timing reference (Correct answer)
- Encrypt digital video for conditional access
- Align closed caption data with video frames
Correct answer: Synchronize multiple video sources to a common timing reference
Gen-lock (genlock) synchronizes the horizontal and vertical timing of cameras and other video equipment to a common house sync signal, enabling glitch-free switching.
Question 5: In FM broadcasting, what is the maximum permissible frequency deviation for a monaural signal?
- ±25 kHz
- ±50 kHz
- ±75 kHz (Correct answer)
- ±100 kHz
Correct answer: ±75 kHz
The FCC specifies a maximum frequency deviation of ±75 kHz for FM broadcast stations, which corresponds to 100% modulation.
Question 6: What is the function of a 'router' in a broadcast facility's signal infrastructure?
- Convert IP data packets for the internet
- Switch any input signal to any output destination under control (Correct answer)
- Amplify weak RF signals from the antenna
- Decode compressed video streams for monitoring
Correct answer: Switch any input signal to any output destination under control
A broadcast router (routing switcher) provides flexible any-in to any-out signal switching, typically controlled by a control panel or automation system.
Question 7: Which SMPTE standard defines the timecode format widely used in professional broadcast production?
- SMPTE ST 259
- SMPTE ST 12-1 (Correct answer)
- SMPTE ST 292
- SMPTE ST 2110
Correct answer: SMPTE ST 12-1
SMPTE ST 12-1 defines Linear Timecode (LTC) and Vertical Interval Timecode (VITC) formats used for hours:minutes:seconds:frames synchronization.
NAB Broadcasting Technology & Equipment 3
What does the acronym EAS stand for in broadcasting?