Trilithic SST R4 User Manual
9581 SST R4
OPERATION
MANUAL
COMPANY PROFILE
Trilithic, Inc. was founded in 1986 as an engineering and assembly company providing
customized communications and routing systems for business and government
applications. As business expanded, Trilithic broadened its offerings by acquiring
components manufacturer Cir-Q-tel and instruments manufacturer Texscan, adding
broadband solutions to the product line.
Today, Trilithic is comprised of three major divisions, Broadband/CATV Instruments &
Systems, Wireless & RF Microwave Components, and Field Technical Products The
Instruments Division specializes in the design and manufacturing of portable RF and
digital test equipment and integrated test systems performing in a wide range of
Broadband and LAN applications. The Wireless division provides components and
custom solutions for companies specializing in cellular, military and other wireless
applications. The Field Technical Products Division is a leading supplier of governmentmandated Emergency Alert Systems used by Broadband service providers. An industry
leader providing telecommunications solutions for major broadband and wireless
markets around the world,
Trilithic is dedicated to providing quality products, services and communications
solutions meeting or exceeding our customers’ expectations. Today, from our worldwide
headquarters in Indianapolis Indiana, we provide over 1500 measurement products and
communications components to thousands of customers around the world.
TWO YEAR WARRANTY
Trilithic, Inc. warrants that each part of this product will be free from defects in materials
and workmanship, under normal use, operating conditions and service for a period of two (2)
years from date of delivery. Trilithic, Inc.’s obligation under this Warranty shall be limited, at
Trilithic, Inc.’s sole option, to replacing the product, or to replacing or reporting any
defective part, F.O.B. Indianapolis, Indiana; provided that the Buyer shall give Trilithic, Inc.
written notice.
Batteries are not included or covered by this Warranty.
The remedy set forth herein shall be the only remedy available to the Buyer under this
Warranty and in no event shall Trilithic, Inc. be liable for incidental or consequential damages for
any alleged breach of this Warranty. This Warranty shall not apply to any part of the
product which, without fault of Trilithic, Inc., has been subject to alteration, failure
caused by a part not supplied by Trilithic, Inc., accident, fire or other casualty,
negligence or misuse, or to any cause whatsoever other than as a result of a defect.Except
for the warranty and exclusions set forth above, and the warranties, if any, available to the
Buyer from those who supply Trilithic, Inc., there are no warranties, expressed or implied
(including without limitation, any implied warranties of merchantability of fitness), with respect
to the condition of the product or its suitability for any use intended for it by the Buyer or by
the purchaser from the Buyer.
TRILITHIC
9710 Park Davis Drive
Indianapolis, IN 46235
(317) 895-3600
(800) 344-2412
GENERAL INFORMATION ................................................................................................ 3
Introduction ..................................................................................................................... 3
SST Headend Unit.......................................................................................................... 3
Equipment.......................................................................................................................4
OPTIMIZING THE RETURN PATH ................................................................................... 5
Introduction ..................................................................................................................... 5
Return Path Performance Parameters ...........................................................................5
SIGNAL-TO-NOISE RATIO ............................................................................................ 5
SIGNAL-TO-INGRESS RATIO ....................................................................................... 5
A Balanced System ........................................................................................................ 6
ABOUT YOUR 9581SST R4 ..............................................................................................7
9581R4 System Overview .............................................................................................. 7
Theory of Application ...................................................................................................... 7
BALANCING THE RETURN PATH............................................................................ 7
MEASURING INGRESS AND NOISE........................................................................ 7
INSTALLING THE 9581R4................................................................................................. 9
Introduction ..................................................................................................................... 9
SST Headend Unit Installation........................................................................................ 9
REVERSE TEST CARRIERS .................................................................................... 9
FORWARD DATA CARRIER ................................................................................... 10
INSTALLATION PROCEDURE................................................................................ 10
Forward Connections ........................................................................................... 11
Reverse Connections........................................................................................... 11
SST WITH TWO INPUT PORTS ......................................................................... 11
SST WITH TEST POINT MANAGER OPTION.................................................... 11
SETTING UP THE 9581SST R4....................................................................................... 13
Introduction ................................................................................................................... 13
9581R4 SST Onscreen Help ........................................................................................ 13
Power Up ...................................................................................................................... 13
Set Up ........................................................................................................................... 14
BASIC OPERATION......................................................................................................... 17
Introduction ................................................................................................................... 17
Sweep Mode................................................................................................................. 17
Gain/Tilt Mode............................................................................................................... 18
Spectrum Mode............................................................................................................. 18
Fast Spectrum Mode .................................................................................................... 19
ADVANCED OPERATIONS............................................................................................. 21
Introduction ................................................................................................................... 21
FEATURE NOTES............................................................................................................ 27
Interoperability ..............................................................................................................27
Extending the Measurement Range ............................................................................. 27
RECONFIGURE SST FOR GREATER RANGE .......................................................... 27
Increase Sensitivity and Range .................................................................................... 28
EFFECT OF OFFSET ON SSR AND 860 UNITS ........................................................ 28
EFFECT OF OFFSET ON RSVP UNITS .....................................................................28
SPECIFICATIONS ............................................................................................................ 31
INDEX
TRILITHIC 9581SST R4 Operation Manual 1
2 TRILITHIC 9581SST R4 Operation Manual
GENERAL INFORMATION
Introduction
Any CATV operator who maintains a two-way CATV distribution system knows that many factors can
affect the performance of that system. Cumulative noise, signal ingress, incorrect gain or bad flatness all
conspire to harm the return path which can lead to loss of service and customer complaints.
You have taken an excellent step toward alleviating the problems of your return path with your purchase
of this 9581R4 Return Path Maintenance System. Trilithic’s 9581R4 is the next generation of the 9581.
It is designed to monitor all of the troublesome parameters in a single, simple to use system. The 9581R4
is part of Trilithic’s Guardian II Return Alignment System which includes the 9581R4 SST, 9580 SSR,
860 DSP, RSVP Installer Return Test Units and Isometer (for more information, refer to the operating
manuals for the 9580 SSR, 860 DSP, RSVP and Isometer).
The 9581R4 differs from the 9581 in several ways:
• Nominally twice as fast ingress capture capability.
• Addition of many new security features and functional enhancements.
The 9581R4 is designed with two forward telemetry transmitters which makes it appear as two 9580
SSTs. This ensures that the unit is compatible with the earlier versions of the 9580 system. The setup
parameters for nominal level, coupler value and detector mode are common for the SSTs. Test
frequency, link frequency, and gain/tilt frequencies are treated independently for each SST.
It is more than just a return alignment system, however. The system also monitors the total performance
of the return path by evaluating ingress and return noise. In any of the 9581R4’s Modes of operation, you
can catch the transient events. In the SSTs FAST Mode, the scan rate is doubled so that you can catch
smaller duration transients. PEAK HOLD enables the Unit to display the highest ingress points in NORM
or FAST Modes. This makes the SST a powerful tool for capturing transient ingress. The AVERAGING
feature is included and can be used to reduce the noise floor displayed on the SST when measuring CW
or common path. The digitizer for the 9581R4 handles 42 MHz in a single band and 65 MHz in two bands.
The 9581R4 SST is also equipped with TraffiControl. This feature enables the 9581R4 SST to measure
and plot the ingress spectra of bands occupied by return traffic. TraffiControl automatically filters all the
“desired” signals from scanned return spectra so that only the ingress spectrum remains.
The basic 9581R4 system consists of two types of equipment:
• SST Headend Unit (contains two SSTs in one enclosure)
• 860 DSP(i) with SSR or RSVP option, or SSR Field Unit
A system may include more hardware including additional 860 DSP(i) with SSR or RSVP options, SSR
Field Units, RSVP Installer Return Test Units and a variety of headend options.
SST Headend Unit
The SST Headend Unit is compact; occupying only 3.5" of rack space. It is easy to set up and operate. A
single SST Headend Unit can support up to twelve SSR Field Units at a time with no loss of operating
speed.
When it is equipped with two optional Test Point Managers (TPM8), the SST analyzes sweep and ingress
signals from up to sixteen separate test points individually. It sends the appropriate ingress spectrum and
sweep data to each SSR Field Unit to which it is connected.
TRILITHIC 9581SST R4 Operation Manual 3
Even when it is not supporting the SSR Field Units, the SST can function as a monitor for return path
quality. In attended headends, the personnel can observe noise and ingress patterns using the SST’s
built-in LCD display panel as an aid to trouble-shooting. Unattended locations can be monitored since the
SST, when equipped with the Communications Manager option (ECM), can send ingress and sweep
measurement data via Ethernet or fiber to a PC located in a central office (see INGRESS MANAGER
3.X OPERATION MANUAL for more information).
Equipment
The 9581R4 Return Path Maintenance System comes with the following standard items:
• SST Headend Unit (2 units in one enclosure)
• Operation Manual: 9581R4 SST (1)
• SST Configure Software CD (1)
In addition to the standard equipment, you can also purchase the following:
• Additional SST Headend Units
• 860 DSP Field Units (Carrying Bags included)
• SSR Field Units (Carrying Bags included)
• RSVP Installer Return Test Units
• Communications Manager option (ECM)
• SNMP Agent option
• Test Point Manager option - equips SST so that it can monitor up to 8 individual Headend test
points - each 9581SST can handle two TPMs for a total of 16 test points
• Replacement NiCad battery pack (SSR Field Unit)
• Replacement Power Cube (SSR Field Unit)
4 TRILITHIC 9581SST R4 Operation Manual
OPTIMIZING THE RETURN PATH
Introduction
Before you begin using your 9581R4 system, let’s review the theory behind return path alignment and
maintenance. To provide complex interactive services on cable, operators must ensure that they provide a
reliable return path or customers won’t have access to pay services, which will result in a loss of business. The
high power transmissions from CB, ham radio and shortwave operators in the 5 to 30 MHz range, as well as
other RF noise generating devices, present a threat to the return path as they can enter the cable system and
interfere with upstream traffic. Additionally, the ever present signals from AM broadcast can enter the cable
system and increase the power loading on the return laser to problematic levels.
As the return paths converge on their way to the headend or node, they act as interference concentrators. The
various sources of ingress tend to add together and these independent sources of noise can merge to form a
single strong ingress where the branches converge.
Since return path problems get worse as the branches converge, the best place to measure return path performance
is at the headend; just before the upstream data is recovered. Return path performance monitored at the
headend needs to be available to the technician in the field for alignment and troubleshooting. The 9581R4
system simplifies this process as follows:
The SST Headend Unit measures the system ingress as well as the test signals from the SSR Field Unit(s) and
then transmits the results as data back to the SSR Field Unit(s), thus enabling the field technician to align the
system and trouble shoot ingress problems from anywhere in the system.
Return Path Performance Parameters
Reliable upstream performance depends upon:
• Proper Gain and Tilt
• Adequate signal-to-ingress ratio
It is important to balance Gain and Tilt in order to get the optimum performance from your system. Refer
to Figure 1 Balance Gain and Tilt.
SIGNAL-TO-NOISE RATIO
Gain in a particular branch, if set either high or low, can adversely affect the signal-to-noise ratio in some
part or the entire return path.
If set low, signals on this branch could be “swamped” by the noise of other branches.
If set high, noise on this branch might be amplified enough to interfere with signals on other branches.
To minimize noise-induced communications errors, upstream data systems use robust modulation
schemes like Quadrature Phase Shift Keying (QPSK), which typically operates at a data rate of 1.544 Mbps.
However, even when using QPSK as the modulation format, your return system must provide a signal-tonoise ratio of at least 10 dB, as measured in a 1 MHz bandwidth around the data carrier center frequency to
provide a marginally adequate Bit Error Rate (BER) of 10E-5
Incorrect gain settings, in some or all of the return paths, degrade the signal-to-noise ratio and increase
the BER of the return path system.
SIGNAL-TO-INGRESS RATIO
When using QPSK, the sum of all ingressing signals lying within the data signal bandwidth (approximately 1
MHz for the data signal as discussed in SIGNAL TO NOISE RATIO above) should be at least 20 dB below
TRILITHIC 9581SST R4 Operation Manual 5
the level of the data signal. As the sum of ingressing signals exceeds this level, the BER performance of the
return path system is degraded. If ingress levels approach – 10 dBc, communication may be seriously
degraded.
A Balanced System
When the system is balanced, a signal on one branch is degraded equally by noise on ALL branches to the
same node.
If, however, the gain of one path is set
HIGHER than the others, its noise could disrupt traffic on ALL other paths.
others, its signals are disrupted by the noise of ALL other paths.
Figure 1 Balance Gain and Tilt
If the gain of one path is set LOWER than the
6 TRILITHIC 9581SST R4 Operation Manual
ABOUT YOUR 9581SST R4
9581R4 System Overview
Your 9581R4 Return Path Maintenance System is a single test system that enables you to deal with all
aspects of return path upkeep; including both ingress control and system balancing. At the core of the
system is the SST Unit, a 0.3 to 65 MHz digitizing spectrum analyzer, which is installed at the headend of
your cable system.
The SST Headend Unit monitors all signals arriving at the headend, including reverse signal “traffic”, noise,
ingress and test carriers from the SSR Field Unit(s).
A single SST Unit can monitor up to sixteen separate headend test points simultaneously which enables you to
analyze the condition of each. The SST analyzes test signals and the return spectra separately. It packages
measurement results into a data stream that it transmits to the 860 DSP(i) or SSR Field Unit(s).
The 860’s and SSR’s are addressed individually (A - F) which allows six of these units to be in operation on
each TPM-8 at any one time. Each of these Field Units transmits up to eight test carriers at user-settable
frequencies. The SST measures these test carriers to compute the gain and tilt of the return path. The 860s and
SSRs can store up to 24 sweep displays which can be reviewed at a later time or uploaded to a PC.
During system testing, the SST sorts out the test carrier measurements for each field piece and tags the data
with the individual addresses (A – F) so that each field piece displays the appropriate information. When
the field piece receives its data, it displays the response of the return path as either a line graph or as numeric
values for gain and tilt. Ingress and noise data are presented as a spectrum analyzer display. For more
information, refer to the manual that came with your particular field piece.
Theory of Application
The 9581R4 test system can be used to:
• Balance the return path
• Measure the return path’s ingress and noise
BALANCING THE RETURN PATH
In the basic test architecture, test signals are injected upstream by the field piece. The SST measures
these signals automatically at the headend. Then, the measurement data is transmitted back to the field
piece for display.
In order to balance the return path of your system, you need to consider several alignment objectives. You need to
set the fiber return path link to the system’s design specifications. You must also set each line amplifier so that it will
compensate for the gain and tilt of the cable and passives to the next amplifier.
The 860 and SSR have two types of displays, which will accommodate amplifier adjustment differences:
• Eight-carrier line graph for amplifiers that require screwdriver adjustments.
• Calculated gain and tilt values for amplifiers that use pads and equalizers.
MEASURING INGRESS AND NOISE
In the basic test architecture, the SST Headend Unit’s spectrum analyzer measures the incoming ingress
and noise. It then transmits this measurement data to the field pieces. The field pieces display the ingress
data as a spectrum pattern.
TRILITHIC 9581SST R4 Operation Manual 7
REMINDER: If your 9581 is equipped with the Test Point Manager option, you can analyze sixteen
return paths individually.
When you are analyzing the return path, you need to determine if the return frequencies carrying “traffic”
have an adequate signal/ ingress ratio. To do this, you must first calculate the effective ingress power.
For narrow band ingress, such as CB or shortwave, measure the ingress power directly.
For broadband ingress, such as interference from machinery, treat the ingress as noise and correct for video
or data bandwidth. In the formulas below, Measured Power (MP) equals the reading from the 9581 and IP equals the
effective Ingress Power.
• compute the effective noise in a 4 MHz video bandwidth, take the reading from the 9581R4 and add 10.3
dB. IP = MP + 10.3 dB
• compute the effective noise for data bandwidth, take the reading from the 9581R4 and add 10 times the
log (data BW divided by .375MHz).
• IP = MP + 10 x log (data BW/.375 MHz)
• maintain good picture quality, video signals require narrow band ingress to be between – 40 to 60
dBc, depending on the offset from the video carrier and broadband ingress to be at least – 40 dBc.
Quadrature Phase Shift Keying (QPSK) should have an effective ingress power of – 20 dBc for either type of
ingress for a Bit Error Rate (BER) of approximately 1 x 10E-6.
HOT TIP
When the SST is setup according to this manual, it reserves
about 15 dB of its amplitude measurement range to prevent the
digitizer from being overloaded by powerful ingress transients.
10 dB of this “guard band” is visible as the top division on the
SST’s spectrum display with an additional 5 dB above that.
Experience has indicated that 15 dB is much more margin than
is needed in all but the “dirtiest” systems. Up to 10 dB of the
“guard band” can be reassigned to extend the SST’s measurement
dynamic range. For more information, see Extending the
Measurement Range on page. 27
8 TRILITHIC 9581SST R4 Operation Manual
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