NCT4 Tools and Test Equipment 16

Question 1

SLM

Answer 1

Signal Level Meter

Question 2

Signal Level Meter

Answer 2

A frequency selective receiver capable of tuning in a desired frequency/channel with a display showing the RF signal strength (dBmV).

Question 3

The minimum signal level at the input to the customer’s television is

Answer 3

0 dBmV, with a maximum of 15 dBmV.

Question 4

5 points to maintaining an SLM

Answer 4

Keep the battery charged.
Clean the battery terminals regularly.
Keep the SLM clean by wiping it gently; dry the display screen to prevent spots.
Do not use any type of cleanser or polish on the display.
A regular calibration should be made and logged.

Question 5

DSAM

Answer 5

Digital Service Activation Meter

Question 6

In miniscan mode, the Digital Service Activation Meter (DSAM) monitors up to

Answer 6

12 channels at a time.

Question 7

MER

Answer 7

Modulation Error Ratio

Question 8

MER is an

Answer 8

overall quality measurement that can be performed on a digital QAM carrier.

Question 9

Ingress:

Answer 9

Passage of an outside signals into the cable; can result in noise and disruption of the desired signal.

Question 10

BER

Answer 10

Bit Error Rate

Question 11

BER detects

Answer 11

erorred bits in the system.

Question 12

The DSAM measures BER by

Answer 12

tracking the bits sent, the number of errored bits (pre-FEC), and the number of bits that cannot be fixed by forward error correction (post-FEC).

Question 13

Constellation Mode

Answer 13

displays a pattern of data points on a graph for easy interpretation, letting you detect and quickly diagnose sources of digital video problems.

Question 14

DQI

Answer 14

Digital Quality Index

Question 15

DQI is a simple indicator of

Answer 15

the overall quality of a QAM digital stream. This JDSU exclusive measurement is extremely effective in tracking intermittent problems.

Question 16

DQI Signal quality readings of 6 or 7 indicate

Answer 16

that impairments are detected, but are most likely corrected by FEC and interleaving.

Question 17

DQI Readings of 1 to 4 indicate

Answer 17

that the subscriber service is most likely being adversely affected by the impairments.

Question 18

DQI Readings of 8 and higher are typically

Answer 18

not detected by FEC BER.

Question 19

DQI also catches errors sometimes missed by BER and errored seconds measurements. To help troubleshoot intermittent issues, the index is plotted on a

Answer 19

180-second graphical history display.

Question 20

DQI is a statistical measure of

Answer 20

the signal impairments that can cause uncorrected bit errors, resulting in packet loss. It also detects impairments that have not yet caused any pre-BER errors.

Question 21

Because it samples QAM symbols, the decoder must acquire and maintain what?

Answer 21

QAM lock in order to obtain DQI readings.

Question 22

A sweep trace reveals

Answer 22

every physical error in the network that influences transmitted signals.

Question 23

The majority of all transmission errors can be detected by measuring the

Answer 23

frequency response of the network

Question 24

sweep results are independent of transmission methods and formats, it is the most effective method to set up the right…

Answer 24

gain versus frequency.

Question 25

Referencing active carriers, instead of transmitting sweep signals over active carriers, lets the meter sweep without…

Answer 25

degrading service quality.

Question 26

DMM

Answer 26

Digital Multimeter

Question 27

RMS

Answer 27

Root Mean Square Meter

Question 28

Root Mean Square Meter

Answer 28

The RMS accurately measures AC voltages of signals other than pure analog sine waves.

Question 29

Digital Multimeter

Answer 29

The DMM is a digital meter, which usually uses a LCD or LED display.

Question 30

In general, signal leakage detectors have the following characteristics and functions:

Answer 30

Portable and powered by batteries
Usually fragile and expensive
Could have audible sound, LEDs, or a leakage strength meter/display when a leak is detected
May detect leaks at various frequencies, or on one specific frequency as determined by the operator
Usually has sensitivity control for finding the exact location of a leak
Uses a dipole antenna to detect a signal leak and determine its direction

Question 31

Cable locators are used to find the

Answer 31

location or path of underground cables.

Question 32

Most locators work by

Answer 32

inducing a tone into the cable. The technician then follows the direction of the cable with a receiver that monitors the tone.

Question 33

A cable locator is made up of two parts:

Answer 33

Transmitter

Receiver

Question 34

TDR

Answer 34

Time Domain Reflectometer

Question 35

Impedance:

Answer 35

The resistance of a circuit (cable, passive devices are examples) to alternating current. Although impedance is measured in ohms, it can’t be measured with the ohm portion of a volt-ohm meter.

Question 36

Impedance Mismatch:

Answer 36

The condition that results when two components of a system are operating at different impedance.

Question 37

The TDR is used to determine the

Answer 37

distance of a known fault from a specific location.

Question 38

A TDR is used to locate:

Answer 38

Bad or unknown splices 
Opens 
Shorts
Kinked cable
Crushed cable
Water in the cable
Any type of impedance mismatch

Question 39

A short is a situation where the

Answer 39

center conductor comes in contact with the shield

Question 40

A reflection with the opposite polarity indicates

Answer 40

that the fault is a short.

Question 41

The worse the fault,

Answer 41

the larger the reflection will be.

Question 42

A properly terminated cable will absorb all the TDR’s pulse energy, resulting in

Answer 42

almost no reflection.

Question 43

Dead Zone:

Answer 43

A dead zone can be found at the beginning of the cable caused by the time lag needed for the pulse width to launch into the cable.