NCT4 Tools and Test Equipment 16 Flashcards Preview

2016 Master > NCT4 Tools and Test Equipment 16 > Flashcards

Flashcards in NCT4 Tools and Test Equipment 16 Deck (43):
1

SLM

Signal Level Meter

2

Signal Level Meter

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

3

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

0 dBmV, with a maximum of 15 dBmV.

4

5 points to maintaining an SLM

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.

5

DSAM

Digital Service Activation Meter

6

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

12 channels at a time.

7

MER

Modulation Error Ratio

8

MER is an

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

9

Ingress:

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

10

BER

Bit Error Rate

11

BER detects

erorred bits in the system.

12

The DSAM measures BER by

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).

13

Constellation Mode

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

14

DQI

Digital Quality Index

15

DQI is a simple indicator of

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

16

DQI Signal quality readings of 6 or 7 indicate

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

17

DQI Readings of 1 to 4 indicate

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

18

DQI Readings of 8 and higher are typically

not detected by FEC BER.

19

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

180-second graphical history display.

20

DQI is a statistical measure of

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.

21

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

QAM lock in order to obtain DQI readings.

22

A sweep trace reveals

every physical error in the network that influences transmitted signals.

23

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

frequency response of the network

24

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

gain versus frequency.

25

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

degrading service quality.

26

DMM

Digital Multimeter

27

RMS

Root Mean Square Meter

28

Root Mean Square Meter

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

29

Digital Multimeter

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

30

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

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

31

Cable locators are used to find the

location or path of underground cables.

32

Most locators work by

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

33

A cable locator is made up of two parts:

Transmitter
Receiver

34

TDR

Time Domain Reflectometer

35

Impedance:

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.

36

Impedance Mismatch:

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

37

The TDR is used to determine the

distance of a known fault from a specific location.

38

A TDR is used to locate:

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

39

A short is a situation where the

center conductor comes in contact with the shield

40

A reflection with the opposite polarity indicates

that the fault is a short.

41

The worse the fault,

the larger the reflection will be.

42

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

almost no reflection.

43

Dead Zone:

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.

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