Viavi HST-3000 Parts list manual

Revision 9.0
March 2012
Technical Assistance: 1-866-228-3762 [e-mail]
© 2012 JDSU. All rights reserved.
HST-3000 VDSL QUICK CARD
WIDEBAND ,038/6(NOISE

Revision 9.0
February 2012
2Technical Assistance: 1-866-228-3762 [e-mail]
© 2012 JDSU. All rights reserved.
VDSL2 QUICK CARD
Wideband Testing - Wideband Noise
Wideband Testing Definitions
Before beginning description of the Wideband test feature found on the HST-3000 it is important the techni-
cian has a basic understanding of two main principles.
• Frequency
• Noise
Frequency: Many technicians are surprised to learn the XDSL signals while on the cable are a series of analog
tones. is is an oversimplication of the technology but a very good explanation from a repair standpoint.
XDSL technologies occupy groups or “spectrums” of frequency according to the technology.
For example, ADSL1 utilizes frequencies between roughly 20 kHz (20000 Hz) to 1.1 MHz (1.1000000 Hz).
ADSL2+ doubles the frequency range to 2.2 MHz and VDSL2 is capable, depending on prole, of going to
30 MHz
Ideally, these spectrums of frequencies would travel from end to end on the circuit all at the same “loudness”
or amplitude. However, in reality, frequency loses amplitude at a linear rate. is means that as frequencies
increase, they lose signal strength faster over the same distance.
Consider the following table, which shows loss per kilometer for three frequencies, 1000 Hz, 300kHz, and
772kHz -- as the frequencies increased their corresponding amplitude decreases.
Table: 1 - Frequency vs Loss per Kilometer
Frequency Loss per Kilometer
1000 Hz 1.27 dB
300,000 Hz 17.87 dB
772,000 Hz 22.56 dB
HST-3000 Test Interface
Connect dual tip & ring + ground leads to the mini-banana connectors on the top of the HST as shown be-
low.
Plug in mini-banana
connectors as shown
n

Revision 9.0
February 2012
3
Technical Assistance: 1-866-228-3762 [e-mail]
© 2012 JDSU. All rights reserved.
VDSL2 QUICK CARD
Wideband Testing - Wideband Impulse Noise
Purpose
 e purpose of this test is to identify the presence of intermittent wideband noise that could cause loss of
synch or degrade the performance of the VDSL circuit. is is the same measurement provided in the VDSL
Good Pair Check except that it is performed manually allowing for continuous analysis of noise level. If the
VDSL Good Pair Check fails for Impulse Noise, it is recommended that the manual Impulse Noise test (be-
low) be run for at least 15 minutes for further troubleshooting.
is test is typically run from the SAI / cross box towards the customer premises. Typically, this test is per-
formed with the pair terminated to the same impendence that will be present when the VDSL2 circuit is in-
stalled (100 Ohms). Because impulse noise is intermittent in nature, this test is typically run over a period of
time – again, usually at least 15 minutes or more if an Impulse Noise problem is suspected and requires further
troubleshooting.
Procedure
1. Connect the Tip and Ring test leads from the HST-3000 to the
desired pair. Connect the ground lead to a valid earth ground
reference (connected to HST as shown in the gure on Page 1).
2. Press the Home navigation key, press the Copper soft key and then
selected Wideband TIMS from the menu and press OK.
3. Press the Display soft key on the lower left of the display; select
WB2 TIMS from the pop-up menu and then Impulse Noise from
the cascaded menu as shown to the right.
4. e Wideband Noise measurement screen should now be displayed
(Stopped indication shown at the top of the screen). Before starting
the measurement, follow the next 3 steps.
5. For VDSL loops, the Filter should be J-20K8. To change the lter
selection, press the Actions soft key, select Filter from the pop-up
menu and choose J-20K8 from the cascaded menu.
6. For VDSL loops, the Termination should be 100 Ohms. To change
the termination, press the Actions soft key, select Termination from
the pop-up menu and choose 100 Ohms from the cascaded menu.
7. For VDSL loops, the reshold should be 52 dBr n (-38 dBm). To
raise or lower the reshold, use the Up / Down arrow keys. To
change from viewing the reshold in dBr n to dBm (or visa versa),
press the Action soft key and select Set reshold in dBm (or dBr
n as applicable). e equivalent reshold in mV will always be dis-
played on the screen.

Revision 9.0
February 2012
4Technical Assistance: 1-866-228-3762 [e-mail]
© 2012 JDSU. All rights reserved.
VDSL2 QUICK CARD
Wideband Testing - Wideband Impulse Noise
Procedure (continued)
8. Press the Start soft key to begin the test the test will run continuously
until the Stop soft key is pressed.
9. e measurement will count the number of hits against the resh-
old recorded in the window directly to the left of the programmed
threshold. It will also count the number of hits 3 dB above and 3
dB below the threshold.
10. If enabled, an audible “Beep” will sound with each hit counted. is
feature can be turned on / o by pressing the Action soft key and
selecting Enable / Mute Sound Eects. e status of this feature is
shown by the speaker icon on the screen.
11. e elapsed time of the test is shown in the window in the upper left
hand of the display.
Run for 15 minutes against a reshold of 52 dBr n (-38 dBm), there
should be < 3 hits. If a greater number of hits occur, a problem exists.
e display of hits 3 dB above and below the programmed threshold
assist in further diagnosis of the problem by giving additional clues as
to the relative magnitude of the hits in reference to the programmed
threshold. For example, if only 3 hits occurred against the 52 dBr n
threshold but there was 1 hit at the 3 dB point above the threshold and
a signicant number of hits at the 3 dB below point, strong consider-
ation should be given to assessing the pair as marginal and investigating
further.
Unwanted impulse noise “spikes” typically come from external sources such as AC power equipment (trans-
formers, generators, etc.) but plant related issues like pair imbalance or potential bonding & grounding prob-
lems are often the root causal factors behind unacceptably high levels of impulse noise. For further trouble-
shooting, the Impulse Capture and Spectral Analysis functions should be used.
Wideband Testing - Wideband Impulse Noise

Revision 9.0
February 2012
5
Technical Assistance: 1-866-228-3762 [e-mail]
© 2012 JDSU. All rights reserved.
VDSL2 QUICK CARD
Understanding and Testing Impulse Noise
Impulse Noise can be dened as any burst of noise that exceeds the RMS (Root Mean Squared) level of the
background noise by 12dB (4 times the voltage). A typical noise impulse is much larger than the data signal,
and can destroy successive bits of data. More data is destroyed in a high speed data stream than a low speed
one.
An impulse noise measurement is made by counting the number of impulses exceeding a preset threshold.
Often it is desirable to measure the amplitude distribution of the noise impulses. is is done by counting the
impulses exceeding three dierent thresholds.
Impulse Noise resholds can be measured with either a dBm or dBrn scale
• dBm measures absolute power
• 0 dBm equals 1 mW to the appropriate load
• If the dB power level is doubled the resulting
• reading on the dB scale goes up 3dB
• If the dB power level is halved the resulting
• reading goes down 3dB
• dBr n measures dB above reference noise:
• Reference noise 0 dBr n = -90 dBm
• Scale shows the relationship between dBm and dBrn
e HST-3000 WB2 SIM can measure Impulse Noise resholds by using either a dBm or a dBrn scale.
Either scale is congured for a
• Center reshold - Metallic Standard is -38 dBm or 52 dBr n
• +3/-3 dB above and below center resholds
• Termination - 100 or 135 Ohms - Metallic Standard lter is 100 Ohms
• Filter Types - G or J Filters - Metallic Standard lter is J-20K8