MT1-2 2022 SCTE
How many states does the binary numbering system offer?
2
Line power supplies output:
60 VAC or 90 VAC
A modulation scheme that depends on varying amplitude sidebands is called:
Amplitude modulation
The bridge rectifier and filter capacitor convert the AC input voltage to:
An unregulated DC voltage
reliability of an HFC architecture increases ( Choose 2 )
As the number of active devices decreases As the number of customers decreases
A customers installation is not working correctly. Where should the first RF reading be taken?
At the wall plate
What is the problem associated with the donut constellation?
Coherent (discrete) interference
Frames are located at the _ layer of the OSI model.
Data-link
A way of multiplexing several groups of carriers at different frequencies onto a single piece of coaxial cable for transmission in the forward path
FDMA
An analog signal uses AM for video and this type of modulation for audio:
FM
A linear power supply is generally more efficient than a switching power supply
False
In a digital return, if you see activity above the normal upstream band, it must be laser clipping
False
Laser clipping distortion products on the upstream are confined to the normal upstream frequency range in all cases
False
True or false: when coax lines are close together, the signal from the locator is induced onto the parallel conductor making accurate location easy.
False
True or false: when no RF is available at a set top box or cable modem, check levels at the station cabinet or tap plate.
False
The number of waves that pass a fixed point per unit of time defines:
Frequency
A modulation scheme that varies the frequency of a carrier is called:
Frequency modulation
A line power inserter has
Three ports
MPEG specifies different degrees of compression vs. quality by specifying
profiles and levels
What is the common stream type for MPEG - 2 video ?
02
What is the channel bandwidth of a return signal?
1.6 MHz 3.2 MHz 6.4 MHz
1011 is equivalent to a decimal____
11
Which is the TSID for video?
1110 1111
As per the module, how many cable channels fall into the LTE spectrum?
18
Which is NOT an access method used by cable operators in the upstream portion of the network?
Quadrature Phase Shift Keying
The output of a line power supply is a:
Quasi-square wave
Name a way of multiplexing seceral groups of carriers at different slots onto a single piece of coaxial cable for transmission in the return path. (Allows cable modems to communicate with the CMTS)
ATDMA/ TDMA/ SCDMA
Which MPEG - TS field is concerned with the 27MHz program clock reference ?
Adaptation
Which is NOT an issue to consider when preparing a network for new or additional upstream signals ?
RF channels are shared by means of modulation
A signal leakage reading of 5 uV/M at 271 MHz has been detected from 30 feet away. What should you do?
Re-measured from a distance of 10 feet
What is the first step of A / D conversion ?
Sample
What is the first step of A/D conversion?
Sample
A_ is a device that is used to measure the amplitude of a forward path signal
Signal level meter
What statement describes a PMT ?
This entry contains the PID values of each of the elementary streams ( video audio , data ) which make up a program
Which statement describes a PMT?
This entry contains the PID values of each of the elementary streams (video, audio, data) which make up a program
Typical switching power supply switching frequencies are in the:
KHz range
Which of the following is NOT an off air user of the return path RF spectrum?
LTE
Which of the following is NOT a general recommended procedure for making return path measurements on cable systems?
LTE leakage characterization
What is going on with the constellation?
Too much noise, interference, or non-linearity
Output current limit prevents damage due to a failure that draws excessive current from the power supply
True
The 115 VAC power input to a line power supply has a peak voltage higher than 115 volts.
True
The antenna radiation pattern changes based on the antenna type used for leakage detection
True
True or False : BER is defined as the ratio of bits containing errors relative to the number of bits sent and received in a given time interval .
True
True or false: Modulation symbol rate is sometimes called the baud rate
True
True or false: Modulation symbol rate is sometimes called the baud rate.
True
True or false: in upstream modulation, 6 bits per symbol is known as 64 QAM
True
An architecture in which a common signal source is distributed to many municipalities is referred to as :
Point to Multi - point
What is the DOCSIS specified maximum group delay variation?
200 an/MHz
Analog leakage detectors are designed with a very narrow measurement bandwidth making them undabke to measure digital leakage. What is the bandwidth that can be measured by an analog leakage dectector?
25 KHz
The color burst signal is __ MHz above the video carrier
3.58 MHz
The audio carrier in an NTSC channel is located _MHz above the video carrier .
4.5
What is upstream frequency range for a high - split architecture ?
5 to 200 MHz
Whag is the return path spectrum used by a non-EuroDOCSIS sub-split architechture?
5 to 42 MHZ
Digital channels are typically carried___ lower in power than analog channels.
5 to 6 dBmV
What is the symbol rate of 256 QAM ?
5.36 MS / s @ 6MHz and 6.95 MS / d @ 8MHz
Analog PAL uses a channel bandwidth of 8 MHz and analog NTSC uses a channel bandwidth of__ MHz
6
What is the bandwidth of a signal with an upper frequency limit of 275MHz and lower frequency limit of 267MHz ?
8 MHz
How many symbol bits are in a 256 QAM ?
8 bits / symbol
How many symbol bits are in a 256 QAM?
8 bits/symbol
What are the components of an MPEG - 2 macroblock ?
8 x 8 blocks
When using the divide and conquer (or half split method) troubleshooting method, if the signal level at a tap indicates a signal level below minimum, the next place to check would be:
The output of the amplifier upstream
What type of filter blocks a band of frequencies?
Band rejection filter
Which MPEG frame type offers the best compression ratio ?
Bi - directional frame
Which of the following would best indicate that excessive upstream attenuation is present?
Cable modem transmit power at the maximum
When using a VOM on a feeder/distribution coax, the amount of resistance measured in ohms across the center conductor and outer metal shield when a short circuit is present will likely be:
Close to zero
What is the optical form of FDM in the return path?
WDM
When using a handheld digital signal analyzer (H-DSA) or signal level meter (SLM) the difference between an analogs video and audio carrier levels are expressed as a ratio of dB called the:
Delta
What is one of the primary reasons why LTE cellular service is impacted by digital leakage?
Digital leakage looks like boise that effectively covers the entire LTE spectrum
Why is digital leakage hard to measure?
Digital leakage looks like white noise Loss of measurement sensitivity at 6MHz bandwidth
Wht type of antenna has a gain of 2.14 dB?
Dipole
An HFC network is typically designed with :
Fewer active devces as compared to a tremand branch system architecture .
The HFC access network is similar to the coaxial tree and branch topology except that long coaxial trunk runs are replaced by ___links .
Fiber
The technique of varying the ___of a carrier based on the characteristics of the baseband signal by referencing two carriers .
Phase
Contains the optical reciever which recieves the light from the outside plant optical return transmitter.
Headend
Which return / forward split offers the most amount of upstream bandwidth ?
High
Which interference type is more likely to lead to upstream laser clipping if the laser has insufficient margin for interference?
Impulse and/or burst noise
Which of the following is NOT a stationary impairment on the return path?
Impulse/ burst noise
The resistance of a short piece of coax cable will read approximately ___ on an ohm-meter.
Infinity
The technique of varying the of a carrier based on the characteristics of the baseband signal by referencing two carriers .
Phase
How might you observe laser clipping with a spectrum analyzer on a fully loded upstream network?
Look for activity out of band above the upstream maximum frequency
Which ATSC PSIP base table extensions provides version , size and carries PIDs for all other tables ?
MGT
One million Hz is
MHz
Which of the following is the best way to prevent aliasing of measurements with digital oscilloscopes?
Make sure the sample rate is at least twice the maximum bandwidth of the input signal
What are two aspects of a dipole antenna that can be used for directional information?
Maximum gain portion of the radiation pattern and the null point
Which 2 way RF configuration uses 104 MHZ up to 1000 MHZ for the downstream?
Mid-split
Audio and video information are superimposed on an RF carrier by a process called:
Modulation
What is the name of the headend or hub device that produces 6 MHZ QAM signals ?
Modulator
What is the name of the headend or hun device that produces 6MHz QAM signals?
Modultor
Layer 3 of the OSI model is called __
Network
Layer 3 of the OSI model is called__
Network
What is the table that has a PID value of Ox1FFF ?
Null
A crowbar circuit monitors
Output voltage
Which MPEG frame type uses data from the previous frames to reconstruct the MPEG video ?
P - frame
What does the controller in a switching power supply vary in order to control the output voltage?
Switching frequency and duration
What is the designation used by cable operators for a digital signal frequency (e.g., QAM)?
The center frequency
What is the initial indicator used by LTE service providers to determine that a cell site has interference?
The uplink recieved strength signal indicator (RSSI)
Which of the following measurments is not provided by proactive network maintenance technology?
They are all provided by PNM technology
How could you determine if a raised noise floor on the lower upstream frequencies is there continuously or only intermittently?
Use a sampling oscilloscope and do an FFT on the samples between strong impulses.
Impulse noise is caused by:
Vehicle ignitions, neon signs, static from lightning, power line switching transients, household appliances.
After connecting the drop to the set top box, no digital picture appears on the TV. What course of action should be down next?
Verify hookup- component, HDMI, composite, etc
