SBE Certified Broadcast Technologist (CBT) — Questions and Answers

Question 1: According to FCC regulations, what is the minimum required content for a legal station identification announcement?

Call letters and city of license (Correct answer)
Frequency and licensee name
Station slogan and city of license
Call letters, frequency, and station slogan

Correct answer: Call letters and city of license

FCC rule § 73.1201 states that the official station identification must consist of the station's call letters immediately followed by the community or communities specified in its license. While other information like frequency or licensee name may be inserted between the call letters and city of license, they are not the minimum requirement.

Question 2: Which of the following statements best describes the fundamental principle of the SMPTE ST 2110 suite of standards for professional media over IP networks?

It separates video, audio, and ancillary data into individual, independently-timed essence streams over IP. (Correct answer)
It is primarily designed for transmitting compressed video over the public internet to consumers.
It encapsulates the entire SDI signal, including video, audio, and data, into a single IP stream for simplified transport.
It uses a proprietary compression algorithm to transmit 4K video over standard 1 Gigabit Ethernet networks.

Correct answer: It separates video, audio, and ancillary data into individual, independently-timed essence streams over IP.

The core concept of SMPTE ST 2110 is the separation of video, audio, and ancillary data into individual 'essence' streams. Each stream is independently packetized and timed using Precision Time Protocol (PTP), which provides immense flexibility in routing and processing signals within a production environment.

Question 3: A broadcast FM antenna has a gain of 6 dBd. Approximately how many times greater is its effective radiated power compared to a dipole radiating the same transmitter power?

4 times (Correct answer)
2 times
6 times
8 times

Correct answer: 4 times

6 dBd corresponds to a power ratio of 10^(6/10) ≈ 4, meaning the antenna focuses energy to produce four times the ERP of a reference dipole.

Question 4: What does VSWR stand for in transmission line theory?

Variable Signal Wave Response
Voltage Standing Wave Ratio (Correct answer)
Voltage Surge Waveform Rating
Vector Signal Wave Reflection

Correct answer: Voltage Standing Wave Ratio

VSWR (Voltage Standing Wave Ratio) describes the ratio of maximum to minimum voltage on a transmission line due to reflected waves from an impedance mismatch.

Question 5: A broadcast engineer is setting up a new SMPTE ST 2110 facility. What is the critical role of the Precision Time Protocol (PTP / IEEE 1588) in this environment?

To compress video and audio streams to conserve network bandwidth.
To manage user access and security credentials for network equipment.
To monitor the network for hardware failures and send alerts.
To provide a high-accuracy, common time reference for synchronizing all separate media essence streams. (Correct answer)

Correct answer: To provide a high-accuracy, common time reference for synchronizing all separate media essence streams.

In an ST 2110 system, video and audio are separate IP streams. Precision Time Protocol (PTP) is essential for providing a highly accurate master clock reference to all devices on the network. This allows the separate essence streams to be precisely aligned and synchronized at their destination, which is the IP-based equivalent of traditional black burst or tri-level sync.

Question 6: For maximum signal transfer between a transmitting antenna and a receiving antenna in a line-of-sight system, which property of the antennas must be aligned?

Bandwidth
Polarization (Correct answer)
Physical height
Voltage Standing Wave Ratio (VSWR)

Correct answer: Polarization

Polarization refers to the orientation of the electric field of the radio wave. For optimal signal reception and maximum power transfer, the transmitting and receiving antennas must have the same polarization (e.g., both vertical or both horizontal). A mismatch in polarization can cause significant signal loss.

Question 7: In digital logic, what is the purpose of a Schmitt trigger input?

To provide hysteresis and prevent false triggering from noisy signals (Correct answer)
To amplify weak digital signals
To convert analog signals to digital
To synchronize signals to a clock edge

Correct answer: To provide hysteresis and prevent false triggering from noisy signals

A Schmitt trigger uses hysteresis (different threshold voltages for rising and falling edges) to cleanly convert slow or noisy signals into crisp digital transitions.

Question 8: A technician at a television station notices that during periods of heavy icing, the transmitter's VSWR reading initially improves (decreases) before eventually worsening (increasing) as the ice accumulates further. What is the most likely reason for this initial improvement?

The ice acts as a lens, focusing the RF energy more efficiently.
The ice changes the antenna's polarization to circular, which is more robust.
The ice insulates the antenna, preventing power loss due to thermal radiation.
The antenna was originally tuned for a frequency slightly higher than the operating frequency, and the initial ice accumulation effectively 'lengthens' the elements, bringing them closer to resonance. (Correct answer)

Correct answer: The antenna was originally tuned for a frequency slightly higher than the operating frequency, and the initial ice accumulation effectively 'lengthens' the elements, bringing them closer to resonance.

Broadcast antennas are often tuned to have their minimum VSWR at a frequency slightly above the actual operating channel. As ice builds up, it dielectrically loads the antenna elements, making them appear electrically longer. This 'lengthening' can shift the resonant frequency downward, moving the point of minimum VSWR closer to the operating frequency, thus temporarily improving the match before further accumulation makes the antenna electrically too long and worsens the VSWR.

Question 9: What is the Q factor of an inductor primarily a measure of?

The inductor's resonant frequency
The number of turns in the winding
The ratio of energy stored to energy dissipated per cycle (Correct answer)
The inductor's maximum current rating

Correct answer: The ratio of energy stored to energy dissipated per cycle

Q factor (quality factor) measures the ratio of reactive power stored to real power dissipated, indicating how 'ideal' the inductor is.

Question 10: What is a frame synchronizer used for in broadcast?

To buffer video for time-delay broadcast compliance purposes
To correct lip sync errors in live productions
To convert between interlaced and progressive scan formats
To synchronize an asynchronous incoming signal to the facility's house sync (Correct answer)

Correct answer: To synchronize an asynchronous incoming signal to the facility's house sync

A frame synchronizer captures an incoming video signal and re-clocks it to match the local house sync, allowing asynchronous signals (like satellite feeds) to be cleanly integrated.

Question 11: Which unit is used to measure electrical resistance?

Watt
Ohm (Correct answer)
Volt
Ampere

Correct answer: Ohm

The Ohm (Ω) is the SI derived unit of electrical resistance, named after German physicist Georg Ohm. Resistance is a measure of the opposition to the flow of electric current in an electrical circuit. A higher resistance means less current will flow for a given voltage.

Question 12: What is the -3dB frequency of a low-pass RC filter with R=1kΩ and C=0.1μF?

15920 Hz
159.2 Hz
1000 Hz
1592 Hz (Correct answer)

Correct answer: 1592 Hz

The cutoff frequency fc = 1/(2πRC) = 1/(2π × 1000 × 0.0000001) ≈ 1592 Hz.

Question 13: What is the primary advantage of using a differential amplifier in broadcast audio equipment?

Lower output impedance
Rejection of common-mode noise on balanced lines (Correct answer)
Higher voltage gain
Wider frequency response

Correct answer: Rejection of common-mode noise on balanced lines

A differential amplifier rejects signals common to both inputs (common-mode noise) while amplifying the difference signal, making it ideal for balanced audio connections.

Question 14: What is the significance of the vertical interval in a video signal for broadcast switching?

It carries closed caption data and cannot be used for switching
It is the blanking period between video frames, the preferred point to perform clean video switches (Correct answer)
It contains the color burst reference and must be protected during transmission
It determines the frame rate of the video signal and cannot be altered

Correct answer: It is the blanking period between video frames, the preferred point to perform clean video switches

The vertical interval is the blanking period between frames; switching during this interval avoids visible glitches because no active picture data is being transmitted.

Question 15: A broadcast station receives a Required Weekly Test (RWT) of the Emergency Alert System (EAS). What is the station's primary obligation regarding this test?

Re-transmit the test to the public immediately.
Log the receipt of the test. (Correct answer)
Notify the State Emergency Communications Committee (SECC) of successful receipt.
Originate a new RWT within the hour.

Correct answer: Log the receipt of the test.

FCC rules require that EAS participants log the receipt of Required Weekly Tests (RWTs). Unlike Required Monthly Tests (RMTs), stations are not required to re-transmit RWTs to the public. The purpose is to verify that the equipment can receive the alert.

Question 16: What is the purpose of pressurizing a coaxial transmission line with dry nitrogen?

To lubricate the inner conductor for easier installation
To prevent moisture ingress that would increase line losses and cause arcing (Correct answer)
To raise the characteristic impedance from 50 to 75 ohms
To increase the dielectric constant and reduce signal velocity

Correct answer: To prevent moisture ingress that would increase line losses and cause arcing

Dry nitrogen pressurization keeps moisture out of the transmission line, preventing increased dielectric losses, corrosion, and potential arcing at high power levels.

Question 17: What is the primary purpose of a transmission line in a broadcast RF system?

To transfer RF energy from the transmitter to the antenna with minimal loss (Correct answer)
To amplify the RF signal before it reaches the antenna
To filter out unwanted harmonics in the transmitted signal
To match the antenna impedance to the studio equipment

Correct answer: To transfer RF energy from the transmitter to the antenna with minimal loss

A transmission line's primary role is to efficiently transfer RF energy from the transmitter output to the antenna while minimizing losses due to reflection and attenuation.

Question 18: What does the term 'dBm' represent in RF and broadcast engineering?

Decibels relative to 1 millivolt
Decibels relative to 1 milliwatt (Correct answer)
Decibels of modulation
Decibels per meter

Correct answer: Decibels relative to 1 milliwatt

dBm is a unit of power expressed in decibels relative to a reference of 1 milliwatt.

Question 19: According to Kirchhoff's Current Law (KCL), what is the relationship of currents at a junction (or node) in a circuit?

The total current entering a junction is greater than the total current leaving it.
The current is the same through all components in any circuit configuration.
The total current leaving a junction is equal to the total current entering it. (Correct answer)
The algebraic sum of all voltages around a closed loop is zero.

Correct answer: The total current leaving a junction is equal to the total current entering it.

Kirchhoff's Current Law (KCL) is based on the conservation of charge and states that the algebraic sum of currents entering a junction must equal the algebraic sum of currents leaving that junction.

Question 20: What is the impedance of a series RLC circuit at resonance?

Equal to the inductive reactance
Equal to the capacitive reactance
Zero
Equal to the resistance only (Correct answer)

Correct answer: Equal to the resistance only

At resonance, inductive and capacitive reactances cancel, leaving only the resistance as the circuit impedance.

Question 21: What is the primary function of a bypass capacitor in an amplifier circuit?

Filter RF interference from the input
Regulate supply voltage
Increase DC gain
Block DC while passing AC signals to ground (Correct answer)

Correct answer: Block DC while passing AC signals to ground

A bypass capacitor shorts AC signals to ground at a specific frequency, effectively removing the emitter resistor from the AC signal path to increase gain.

Question 22: Which network switch feature is most critical for efficiently managing multicast traffic in a media-over-IP environment by preventing streams from being sent to all network ports unnecessarily?

Spanning Tree Protocol (STP)
Power over Ethernet (PoE)
IGMP Snooping (Correct answer)
Link Aggregation (LACP)

Correct answer: IGMP Snooping

By default, a standard switch floods multicast traffic to all ports, which can overwhelm the network and connected devices. IGMP (Internet Group Management Protocol) Snooping allows the switch to 'listen' to the IGMP messages between devices and the router. The switch builds a table of which ports have devices that have requested a specific multicast stream and then forwards that stream only to those ports, drastically reducing unnecessary traffic.

Question 23: What is the maximum permissible exposure (MPE) limit for RF radiation at broadcast frequencies as defined by the FCC for general population/uncontrolled environments?

0.1 mW/cm² at all frequencies
1.0 mW/cm² at all frequencies
Power density varies by frequency per OET Bulletin 65 (Correct answer)
5 mW/cm² flat limit regardless of frequency

Correct answer: Power density varies by frequency per OET Bulletin 65

FCC OET Bulletin 65 specifies frequency-dependent MPE limits for uncontrolled environments, not a flat value.

Question 24: What generation of ATSC standard introduced support for HEVC video compression and mobile broadcasting?

ATSC 4.0
ATSC 2.0
ATSC 1.0
ATSC 3.0 (Correct answer)

Correct answer: ATSC 3.0

ATSC 3.0 (NextGen TV) introduced HEVC compression, OFDM modulation, and native IP delivery with mobile reception capability.

Question 25: Which audio measurement unit is standardized for normalizing broadcast audio levels by taking into account human perception of loudness over time?

LUFS (Correct answer)
VU
dBu
dBFS

Correct answer: LUFS

LUFS (Loudness Units Full Scale), also known as LKFS, is the standard unit for measuring and normalizing audio loudness in broadcast. Unlike peak (dBFS) or voltage (dBu) measurements, LUFS is designed to measure perceived loudness over a period of time, which more closely aligns with human hearing.

Question 26: A broadcast technologist notices hum bars rolling through a video monitor. The hum frequency is 60 Hz. What is the MOST likely cause?

Incorrect video termination resistance
Ground loop introducing AC power-line interference into the video path (Correct answer)
Incorrect horizontal sync frequency
Defective chroma demodulator

Correct answer: Ground loop introducing AC power-line interference into the video path

60 Hz hum bars in video are a classic symptom of a ground loop where different ground potentials create a current path through the video cable shield.

Question 27: In broadcast infrastructure, what is the purpose of a patch bay (jackfield)?

To provide a centralized, flexible point for interconnecting and re-routing signals between equipment (Correct answer)
To test signal levels at multiple points in the signal chain simultaneously
To patch software-defined routing changes into hardware routers
To provide regulated power distribution to broadcast equipment racks

Correct answer: To provide a centralized, flexible point for interconnecting and re-routing signals between equipment

A patch bay provides a normalized wiring point where signals flow through by default but can be easily re-routed by inserting patch cables for troubleshooting, maintenance, or special routing needs.

Question 28: A transmitter's forward power reads 10 kW but the reflected power meter reads 2 kW. What is the net delivered power to the antenna?

8 kW (Correct answer)
10 kW
12 kW
5 kW

Correct answer: 8 kW

Net delivered power equals forward power minus reflected power: 10 kW − 2 kW = 8 kW.

Question 29: A technician is setting up a new high-definition video router. A signal labeled as 'SMPTE 292M' is being used. What is the nominal data rate of this HD-SDI signal?

270 Mbit/s
1.485 Gbit/s (Correct answer)
3 Gbit/s
12 Gbit/s

Correct answer: 1.485 Gbit/s

The SMPTE 292M standard defines the High-Definition Serial Digital Interface (HD-SDI). This standard specifies a nominal data rate of 1.485 Gbit/s, which is capable of carrying uncompressed high-definition video signals like 720p and 1080i.

Question 30: What is the minimum safe working distance from an energized AM broadcast antenna base for an unprotected worker, according to IEEE C95.1?

It depends on the station's ERP and frequency (Correct answer)
10 feet at all times regardless of power
There is no IEEE-specified distance for AM antennas
5 meters from the base insulator

Correct answer: It depends on the station's ERP and frequency

IEEE C95.1 RF safety distances are calculated based on the specific power level and frequency, so the safe distance varies by station.

Question 31: A broadcast engineer discovers the station's Emergency Alert System (EAS) equipment has not been tested in over 60 days. What is the violation?

EAS equipment only needs testing during actual emergencies
Required weekly tests must occur at least once per week (Correct answer)
EAS tests must occur daily
Monthly tests are sufficient so no violation has occurred

Correct answer: Required weekly tests must occur at least once per week

FCC rules require Required Weekly Tests (RWT) of EAS equipment at least once per week, so missing 60 days constitutes multiple violations.

Question 32: Which type of capacitor is commonly used in high-frequency RF circuits due to its low parasitic inductance?

Electrolytic capacitor
Tantalum capacitor
Mylar film capacitor
Surface-mount ceramic chip capacitor (Correct answer)

Correct answer: Surface-mount ceramic chip capacitor

Surface-mount ceramic chip capacitors have extremely low parasitic inductance and are ideal for high-frequency RF bypass and decoupling applications.

Question 33: What does OSHA require for employees working at heights above 6 feet?

Rubber gloves
Ear protection
Fall protection equipment (Correct answer)
Eye wash station

Correct answer: Fall protection equipment

The Occupational Safety and Health Administration (OSHA) mandates specific safety measures to protect workers from falls. For employees working at heights of 6 feet or more, OSHA requires employers to provide and ensure the use of appropriate fall protection equipment, such as guardrails, safety nets, or personal fall arrest systems, to prevent serious injuries or fatalities.

Question 34: A broadcast engineer is selecting an antenna for a new FM station. The antenna specification sheet lists its gain as 5 dBd. What is the equivalent gain expressed in dBi?

2.85 dBi
5.00 dBi
7.15 dBi (Correct answer)
10.00 dBi

Correct answer: 7.15 dBi

The gain of an antenna can be expressed relative to a theoretical isotropic radiator (dBi) or a half-wave dipole antenna (dBd). A standard dipole antenna has a gain of 2.15 dBi. To convert from dBd to dBi, you add 2.15 dB. Therefore, 5 dBd + 2.15 dB = 7.15 dBi.

Question 35: When streaming live, real-time video over a managed IP network, why is the User Datagram Protocol (UDP) typically preferred over the Transmission Control Protocol (TCP) for transporting the media packets?

TCP is an older protocol that is not compatible with modern video formats.
TCP's guaranteed delivery mechanism introduces latency that is unacceptable for live video. (Correct answer)
UDP has a much larger packet size, allowing for higher video quality.
UDP includes native, high-level encryption which is required for broadcast content.

Correct answer: TCP's guaranteed delivery mechanism introduces latency that is unacceptable for live video.

TCP guarantees the delivery of every packet by requiring acknowledgements and retransmitting lost packets. This process of waiting for acknowledgements and retransmissions adds significant delay (latency), which would cause a live stream to pause or buffer. UDP, by contrast, sends packets without requiring acknowledgement, prioritizing speed and low latency over guaranteed delivery. For live video, it is better to have a momentary, imperceptible glitch from a dropped packet than to have the entire stream halt.

Question 36: In a DC circuit, what does the power formula P = V × I represent?

Power equals voltage divided by resistance
Power equals voltage times current (Correct answer)
Power is current divided by voltage
Power is resistance minus current

Correct answer: Power equals voltage times current

In a DC circuit, the power (P) dissipated by a component or circuit is calculated by multiplying the voltage (V) across it by the current (I) flowing through it. This fundamental formula, P = V × I, is crucial for determining the rate at which electrical energy is consumed or converted in a circuit. It is a cornerstone of electrical engineering calculations.

Question 37: In a broadcast facility, three resistors with values of 100Ω, 200Ω, and 300Ω are connected in series. What is the total resistance of this combination?

1100Ω
54.5Ω
200Ω
600Ω (Correct answer)

Correct answer: 600Ω

When resistors are connected in series, the total resistance is the sum of the individual resistances. Therefore, RT = R1 + R2 + R3 = 100Ω + 200Ω + 300Ω = 600Ω.

Question 38: A broadcast facility is implementing a new IP-based video system to distribute a single live camera feed to 25 separate monitoring destinations within the plant. Which IP transmission method is the MOST efficient for this purpose?

Multicast (Correct answer)
Unicast
Broadcast
Anycast

Correct answer: Multicast

Multicast is the most efficient method because the source sends a single packet stream to a specific multicast group address. Network switches then intelligently replicate the stream only to the ports connected to devices that have requested to join that group, saving significant bandwidth compared to other methods.

Question 39: What is the primary function of a circulator in a high-power broadcast transmitter output stage?

To combine signals from two separate transmitter chains
To convert horizontal polarization to circular polarization
To boost the carrier frequency before reaching the antenna
To protect the transmitter PA from damage caused by high reflected power (Correct answer)

Correct answer: To protect the transmitter PA from damage caused by high reflected power

A circulator directs reflected power (from antenna mismatches) into a dummy load, protecting the transmitter's final amplifier stage from potentially damaging high VSWR conditions.

Question 40: A broadcast station must conduct an RF exposure evaluation when it applies for a new license. Which FCC document provides the methodology for this evaluation?

OET Bulletin 65 (Correct answer)
FCC Public Notice DA 03-2550
FCC Form 302
ANSI/IEEE C95.3

Correct answer: OET Bulletin 65

FCC OET Bulletin 65 provides the methodology and worksheets for evaluating RF exposure compliance at broadcast stations.

Question 41: Which component resists the flow of current in a circuit?

Capacitor
Transistor
Diode
Resistor (Correct answer)

Correct answer: Resistor

A resistor is a passive two-terminal electrical component specifically designed to resist the flow of electric current in a circuit. It introduces a controlled amount of electrical resistance, converting electrical energy into heat. Resistors are used to limit current, divide voltage, and terminate transmission lines, among other functions.

Question 42: When measuring AC voltage with a true-RMS meter, what value is displayed for a 170V peak sine wave?

120V (Correct answer)
85V
170V
240V

Correct answer: 120V

RMS voltage of a sine wave = Vpeak / √2 = 170 / 1.414 ≈ 120V, which is the effective heating value equivalent to that DC voltage.

Question 43: In a common-emitter BJT amplifier, what is the phase relationship between input and output signals?

180° phase shift (Correct answer)
270° phase shift
In phase (0°)
90° phase shift

Correct answer: 180° phase shift

A common-emitter amplifier inverts the signal, producing a 180° phase shift between input and output.

Question 44: Which ATSC standard defines the rules for closed captioning in digital television broadcasts?

ATSC A/65
ATSC A/53 Part 4 / CEA-708 (Correct answer)
ATSC A/52
ATSC A/72

Correct answer: ATSC A/53 Part 4 / CEA-708

CEA-708 (referenced in ATSC A/53 Part 4) defines digital closed captioning for DTV, replacing the analog CEA-608 standard used in NTSC.

Question 45: A technician is working on an AC circuit for a transmitter and needs to calculate the capacitive reactance (Xc) of a 10µF capacitor at a frequency of 60Hz. What is the approximate capacitive reactance?

377 Ohms
265 Ohms (Correct answer)
600 Ohms
1.67 Ohms

Correct answer: 265 Ohms

The formula for capacitive reactance is Xc = 1 / (2πfC). Plugging in the values: Xc = 1 / (2 * 3.14159 * 60Hz * 0.000010F), which calculates to approximately 265 Ohms.

Question 46: What is the result of connecting resistors in series?

Resistance cancels out
Current increases
Total resistance increases (Correct answer)
Voltage drops to zero

Correct answer: Total resistance increases

When resistors are connected in series, their individual resistances add up to form a larger total resistance. This means that the equivalent resistance of the series combination is the sum of all the individual resistances. This configuration effectively increases the overall opposition to current flow in the circuit.

Question 47: What is the primary function of a diode in an electronic circuit?

To amplify the input signal.
To resist the flow of current equally in both directions.
To store electrical energy in a magnetic field.
To allow current to flow in only one direction. (Correct answer)

Correct answer: To allow current to flow in only one direction.

A diode is a semiconductor device that acts as a one-way switch for current. It allows current to flow easily in one direction (forward bias) but severely restricts current from flowing in the opposite direction (reverse bias). This property is fundamental to processes like AC to DC rectification.

Question 48: What is the maximum data rate of a single ATSC 1.0 6 MHz broadcast channel?

25 Mbps
12 Mbps
38 Mbps
19.39 Mbps (Correct answer)

Correct answer: 19.39 Mbps

An ATSC 1.0 channel provides approximately 19.39 Mbps of usable payload data rate within a 6 MHz channel.

Question 49: In a parallel RC circuit, what happens to total impedance as frequency increases?

Impedance increases
Impedance remains constant
Impedance decreases (Correct answer)
Impedance becomes purely resistive

Correct answer: Impedance decreases

As frequency rises, capacitive reactance decreases, reducing the overall parallel impedance of the RC circuit.

Question 50: What does an Optical Time-Domain Reflectometer (OTDR) measure in a fiber optic plant?

Optical carrier frequency
Location and magnitude of losses and reflections along a fiber (Correct answer)
Modulation depth of optical signals
Chromatic dispersion only

Correct answer: Location and magnitude of losses and reflections along a fiber

An OTDR sends light pulses down the fiber and analyzes backscatter to pinpoint splices, connectors, breaks, and their associated losses.

SBE Certified Broadcast Technologist (CBT)

The CBT exam, administered by the Society of Broadcast Engineers, certifies technicians on the technical knowledge required to operate and maintain broadcast equipment across AM/FM and TV systems. It covers broadcast systems, RF transmission, digital standards, FCC regulations, and safety.

Questions

180 min

Time Limit

70%

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