NCTI 2 Part 2

What is the expected DC voltage on most hybrid fiber coax (HFC) network equipment?

+24 VDCm +.05 V

what do nonlinear distortions of quadrature amplitude modulation (QAM) channels look like on a spectrum analyzer?

As noise-like bands without a defined signature

In an operational amplifier (op amp) summing amplifier circuit, how can unequal weights be given to the signals being summed together?

By using different value input resistors for each signal.

The forward path signal in a traditional tree-and branch architecture

Originates at the headend and is transmitted downstream through coaxial trunk cable and trunk amplifiers

In an HFC network

Processing equipment in the headend converts the forward RF signal to a light signal.

Why is the isolation between the output and input sections of a common base transistor configuration quite high?

The base is typically at signal ground.

when configuring the upstream return in a distribution amplifier with multiple upstream ports, the amplitude levels for which port should be adjusted first?

The distribution amplifier port with the most attenuation in its upstream path

What distinguishes an operational amplifier (op amp) configured as a voltage follower with gain from an inverter circuit?

The input signal in the voltage follower with gain goes to the non-inverting input (+).

In a basic step-up switcher circuit design, what is the relationship of the square-wave duty cycle to the output voltage?

The larger the duty cycle, the higher the voltage.

During aerial plant construction

The strand is tensioned so its sag profile matches that of the overhead utility power lines.

What is the FCC specification regarding repair of leakage of the 20 µv/m level?.

there is no FCC specified time.

What is the maximum allowable signal detectable in the airspace during flyover?

10 µv/m

How long must the leakage log be kept on file?

2 years

What is the voltage on the secondary of a transformer if the number of secondary windings is 25% of the primary windings?

25% of the voltage on the transformer's primary.

How many symbols are available at the output of a quadrature phase shift keying (QPSK) modulator?

4 symbols, each containing 2 bits of data.

CLI calculations do not include leakage below:

50 µv/m.

What cumulative leakage index (CLI) meets Federal Communications Commision (FCC) requirements?

64 or less

what is installed in the input stage of a distribution amplifier for a flat frequency response into the input amplfier when the input signal has negative tilt?

A cable equalizer with positive slope.

Which type of rectifier circuit uses two alternating current (AC) waveforms on the transformer secondary?

A full-wave rectifier with a center-tapped transformer secondary.

What geometric shape is a sine wave based upon?

A right degree triangle

In an N-channel enhancement mode metal oxide semiconductor field effect transistor (MOSFET), what effectively turns the P substrate between the two wells into an induced N-channel?

A suitable positive voltage placed between the gate and the source.

what are the three elements of a carrier wave that can be manipulated?

Amplitude, frequency, and phase.

What would be the likely cause of non-linear distortion in the broadband cable network?

An amplifier.

what information remains afer the intermediate frequency (IF) signal is detected, or demodulated?

Analog or digital baseband information.

What property of a capacitor enables it to be used with an operational amplifier (op amp) to create a filter circuit?

At very low frequencies, capacitive reactance is high.

how is the AC voltage seperated from the RF signal in a distribution a,plifier?

By a capacitor that passes RF but blocks the low frequency 60 hertz (Hz) AC voltage which finds a low resistance path through the RD choke that blocks RF.

How does feed-forward amplifier technology achieve distortion reduction that is better than power-doubling?

By introducing delay lines and error amplifiers.

which class of amplifier utilizes a push-pull amplifier configuration in which each transistor conducts current during opposite cycltes of the input signal?

Class B amplifier

standby power supplies

Continue providing an output voltage even during a utility power outage by using a backup power source.

The direct current (DC) power supply modules in fiber-nodes and distribution amplifiers do what?

Convert the network alternating current (AC) voltage to DC voltage used by the active devices within the weatherproof housing.

What enables the collector current in an operational amplifier's differential amplifier to be independent of the two input voltages, VI+ and VI-?

DC bias circuitry in the differential amplifier emitter circuit.

what is used in some receivers to remove all the attenuation before the amplifier until the received signal reaches a designed threshold?

Delayed automatic gain control (AGC).

what is used in set-top boxes (STB) to strike a balance between image rejection, the bandwidth of the intermediate frequency (IF) filter, and the frequency which modulation is done?

Double IF conversion.

In what application would a bipolar junction transistor (BJT) common base configuration be used?

For impedance isolation between a low-impedance device and a high-impedance amplifier.

Verifying plant reliability includes

Frequency response sweeping, which is adjusting RF amplifier circuits to amplify all frequencies in the bandpass spectrum as equally as possible

RF trunk amplifiers

Have attenuator pads, equalizers, and diplex filters that control and route the RF signals.

when transmitting broadband signals

In a two-way hybrid fiber/coax (HFC) network, two or more individual optical fibers are required for each optical node location.

Why can Carson's Rule be used to determine the bandwidth of a frequency modulation (FM) carrier?

In most cases, the amplitude of the sidebands furthest from the carrier frequency are so low that they can be ignored.

What term describes changes in output direct current (DC) voltage with changes in input alternating current (AC) voltage expressed as a percentage?

Input regulation.

In a basic step-up switcher circuit design, what does the inductor do when the switch is closed and conducting current to ground?

It stores energy in its magnetic field with the current lagging the voltage by 90 degrees

A dipole antenna is used for FCC tests because:

Its performance is well characterized.

what type amplfiers are designed and intended to provide the final boosting of amplitude to the downstream signals exiting the headend?

Launch amplifiers

What leakage level must be entered in the leakage log?

Leaks 20 µv/m or higher measured 10 feet from the cable.

What are the disadvantages of using an slm for leakage detection?

Less sensitive than a leakage detector and doesn't have an alarm.

In an operational amplifier (op amp), what is a common practice to minimize voltage offsets at the inputs to an inverter?

Make the net DC resistance the same on both inputs to the op amp.

calculating the signal voltage and current range on the output of a bipolar junction transistor (BJT) involve repeated applications of what?

Ohm's law.

centralized power configurations

Provide the advantage of increased reliability through sharing of expensive backup generators and sophisticated monitoring equipment among different power realms.

how would you find the input level to an amplifier if the specifications only give the amplifier output level at 1,002 MHz and the amplifier Operation Gain?

Subtract the amplifier operation gain from amplifier output level at 1,002 MHz

what type of bandpass filters offer the precision, stability, and bandwidth most suitable for TV and set-top box (STB) intermediate frequency (IF) sections?

Surface acoustic wave (SAW) filters.

under what principle do frquency modulation (FM) detector circuit designs operate?

That voltage is created when the signal frequency moves from the center frequency.

in a basic N-channel junction field effect transistor (J-FET), what when nrgativa bias is applied to the gate?

The J-FET depletion region is expanded, decreasing the current that is transported between the source and the drain.

what two significant signals go into the mixer to create the intermediate frequency (IF)?

The RF signal frequency at the output of the front end filter and the local oscillator (LO) signal.

what are the peaks and minima of the amplitude modulation (AM) waveform envelope related to?

The amplitude of the modulation signal.

In a feedback linear regulator, what enables a stable output voltage while enabling a wide range of output current through the load?

The current across the Zener diode is constant.

what value of interstage equalizer should be installed if the associated amplifier tombstone field is blank and the amplifier output slope is 7dB?

The factory default value

With underground plant construction,

The fiber-optic and coaxial cables are often placed underground with other utility lines to jointly share construction costs.

What part of a receiver has several functions that include limiting the number of signals that reach the amplifier and mixer?

The front end filter.

Which of the following is a repair order specification when measuring leakage levels?

The location of the leak.

What do the number of filter poles generally correspond to?

The number of inductors plus capacitances that are in a filter circuit.

why is the term "gain control" applied to amplifier gain and controls inaccurate?

The only way to vary the output of any amplifier is to adjust the amplitude level of the signal going into the amplifier.

what prevents the subcarriers in orthogonal frequency division multiplexing (OFDM) from interferring with each other?

The peak power of each subcarrier aligns with the minimum power of the adjacent subcarrier.

In an operational amplifier (op amp), what is open-loop gain?

The pre-determined gain of the op amp without feedback.

What is used to quantify the efficiency of an amplifier?

The ratio of how much direct current (DC) power is required for the useable power from the amplifier.

What characteristic of foldback limiting circuitry protects equipment if the load is accidentally shorted?

The supplied voltage and current drops to near-zero or zero when the maximum current limit is reached.

What determines the voltage gain of an operational amplifier (op amp) inverter?

The value of the input and feedback resistors.

In a circuit with pure inductance, what is the phase relationship between the current and voltage?

The voltage leads the current by 90 degrees.

Why do metal oxide semiconductor field effect transistors (MOSFET) have internal zener diodes from the gate to the source or substrate?

To prevent damage from static electricity.

In a distribution amplifier, why is the frequency response at the input of the second outpit stage sloped?

To reduce intermodulation distortion levels caused by amplifying high amplitude levels.

What benefit does a power-doubling configuration offer compared to a single cascade push-pull hybrid amplifier?

Twice the output with the same distortion.

In a conventional amplitude modulation (AM) transmission, how much power is in the sidebands and how much is in the carrier?

Two-thirds of the power is in the carrier with one-third in the sidebands.

How should the gain of a broadband TV amplifier, such as a line extender, be calculated?

Using either power or voltage formulas.

What characteristic of a ferroresonant power supply provides voltage regulation as the source voltage changes?

With the flux in the core saturated, then the secondary voltage remains constant as the primary voltage changes.

to meet design criteria for noise and distortion, where must an amplifier input levels be kept?

Within the dynamic range of an amplifier, abive the noise floor and below the saturation point.

which class of amplifier efficiency approaches, but never achieves 100%

class D amplfier

Which class of amplifier has an output that is very high in harmonics that must be attenuated by a filter network?

class c amplifier

what logic family of bipolar transistor logic circuits is used extensively where the fastest speeds are required at the expense of power dissipation?

emitter coupled logic (ECL)

what is another name for the bipolar junction transistor (BJT) common collector configuration?

emitter follower

what are harmonics from amplified quadrature amplitude modualtion (QAM) channels generally called?

intermodulation noise

What term describes the frequency spectrum into an amplifier having higher amplitude at low frequencies than the high frequencies.

negative tilt

What is a consequence of high-speed charging and discharging of the capacitance in a complementary metal oxide semiconductor (CMOS)?

power is dissipated at heat.

if the power out of a transformer must equal the power in, assuming zero efficiency loss, what happens to the output current when the transformed output voltage is 10% lower?

the current increases 10%

which stage in a hybrid fiber/coax (HFC) downstream amplifier maintains a uniform and high carrier-to-noise ration (CNR) across the amplifier operating frequency spectrum with low nonlinear distortion levels?

the first, preamplifier, stage

to maintain unity gain, what does the internal attenuation in an amplifier do when the temperature drops from degrees fahrenheit (F) to degrees fahrenheit?

the internal attenuation increases.

Applying Carson's Rule to determine the bandwidth of a narrowband frequency modulation (FM) carrier, what is the most significant factor?

the maxumim modulation signal frequency.

describe an application for a distribution amplifier in a hybrid/coax (HFC) network?

to maintain downstream amplitude levels to the addresses furthest from the fiber nodes

underwhat conditions is installation of a house amplifier appropriate?

when channel amplitude levels from the network are acceptable but too low for the number of outlets.

what is the thermal noise level used for reference in the broadband cable noise calculations?

-59.2 dBmV

What is done to an operational amplifier (op amp) to create a low-pass filter circuit?

A capacitor is placed in parallel with the feedback resistor that is connected to the op amp inverting input (-).

In a Hybrid Fiber Coax (HFC) network what type of crude amplitude (AM) detector causes common path distortion (CPD)?

An envelope detector.

What is the bias voltage setting of the transistors in a push-pull circuit configuration?

At the point that under quiescent (no-signal) conditions, the transistors are about to come on, conducting little if any collector (or emitter) current.

How is hysteresis added to an operational amplifier (op amp) comparator circuit to ensure the output is always either high or low?

By adding positive feedback from the op amp output to the non-inverting input.

In a radio receiver, what is almost universally used to conduct the energy between the antenna and the receiver tuner?

Coaxial cable

According to SCTE- and NCTA-recommended trunk system map symbols, fiber-optic cable is represented by

Double arrows within a small circle on a solid line

Which of the following problem(s) are caused by egress?

Interference with aeronautical navigation an communication, amateur radio, public service, and cellular communications.

How does complementary metal oxide semiconductor (CMOS) technology combat capacitance in a circuit?

It combines N-channel metal oxide semiconductor field effect transistors (MOSFET) onto a single substrate.

what characterizes N-doped silicon that is used in bipolar junction transistors (BJT)?

N-doped silicon has an excess of free electrons compared to P-doped silicon.

What benefit does applying negative feedback in an amplifier circuit provide?

Operating stability.

What is the bias voltage of a transistor without a signal present called?

Quiescent voltage.

In a series-pass transistor regulator, which component isolates the Zener diode from changes in the load for improved voltage regulation?

The emitter follower configured transistor (series-pass transistor).

when configuring the input stage of a distribution amplifier, what element values can vary from those in the amplifier tombstone, depending on the input amplitude measurements?

The input equializer and attenuator pad values.