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TRAINEE GUIDE
Sheet 1 of 1
FOR TRAINING USE ONLY 1
INFORMATION SHEET 1-1
ACTIVITY
A. INTRODUCTION
In this lesson, you will learn about the TDR's purpose and function, safety, controls and indicators,
and operation. This activity is designed to stimulate prior knowledge and interest in the topics
covered in this lesson.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
2. Navy Safety and Occupational Health (SOH) Program Manual for Forces Afloat, Volume
II, Surface Ship Safety Standards, OPNAVINST 5100.19 (series)
C. INFORMATION
For each item listed in the Topic column, write a brief statement in the Knowledge column that
describes what you know about the topic.
When you complete the activity, you will discuss your findings with the class.
No. Topic Knowledge
1 TDR purpose and function
2 TDR safety
3 TDR controls and
indicators
4 TDR operation
TRAINEE GUIDE
Sheet 1 of 2
FOR TRAINING USE ONLY 2
OUTLINE SHEET 1-2
OPERATE THE TIME-DOMAIN REFLECTOMETER (TDR)
A. INTRODUCTION
The TDR is a piece of electronic test equipment used to locate faults in metallic cables (e.g.,
coaxial cable). It is important to know how to operate the TDR to identify degraded cable
conditions, determine if a cable is impaired, and determine how far away the fault is.
B. OBJECTIVE
Upon successful completion of this section, you will be able to:
GIVEN APPLICABLE TECHNICAL DOCUMENTATION AND DIRECTIVES OPERATE
THE TIME-DOMAIN REFLECTOMETER (TDR) IAW ESTABLISHED SAFETY
REQUIREMENTS, APPLICABLE TECHNICAL DOCUMENTATION AND DIRECTIVES
C. SECTION OUTLINE
1. Section Introduction
2. Purpose and Function
3. Safety
4. Front Panel Controls and Indicators
5. Rear Panel Controls
6. Menus
7. Dialog Box Navigation
8. Cable Test Preparations
9. Relative Distance Measurement
10. Measuring VSWR
11. Common Cable Faults
12. TDR Procedures
TRAINEE GUIDE
Outline Sheet 1-2 Sheet 2 of 2
FOR TRAINING USE ONLY 3
13. Practice
14. Section Review
TRAINEE GUIDE
Sheet 1 of 2
FOR TRAINING USE ONLY 4
INFORMATION SHEET 1-3
GLOSSARY
A. INTRODUCTION
The following is a list of acronyms, abbreviations, and key terms used in this lesson.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
2. Navy Safety and Occupational Health (SOH) Program Manual for Forces Afloat, Volume
II, Surface Ship Safety Standards, OPNAVINST 5100.19 (series)
C. INFORMATION
Term Definition
AC Alternating Current
BNC British Naval Connector; a miniature quick-
connect/disconnect RF connector used with
coaxial cable
CCW Counterclockwise
CG Guided Missile Cruiser
CIC Combat Information Center
CW Clockwise
H Horizontal function button
IS International System of Units; a system of
physical units based on the meter, kilogram,
second, ampere, kelvin, candela, and mole,
together with a set of prefixes to indicate
multiplication or division by a power of 10
LPO Leading Petty Officer
Mb Megabit
M-FUNC Multifunction
M-FUNCTION Multifunction
ns Nanosecond
PC Personal Computer
RF Radio Frequency
TRAINEE GUIDE
Information Sheet 1-3 Sheet 2 of 2
FOR TRAINING USE ONLY 5
Term Definition
RJ-45 Registered Jack-45
rVSWR Reflective Volts Standing Wave Ratio
TDR Time-Domain Reflectometer
USB Universal Serial Bus
V Vertical function button
VDC Volts Direct Current
VoP/Vp Velocity of Propagation
VSWR Volts Standing Wave Ratio
Δ Absolute distance measurement
Ω Ohms
TRAINEE GUIDE
Sheet 1 of 1
FOR TRAINING USE ONLY 6
INFORMATION SHEET 1-4
PURPOSE AND FUNCTION
A. INTRODUCTION
The TDR is a piece of electronic test equipment that uses time-domain reflectometry to
characterize and localize faults in metallic cables used in microwave, RF, and digital systems.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
The TDR can scan and detect subtle cable faults, which include:
1. Minor conductor or insulation damage
2. Water ingress
3. Loosened, corroded, or poor-quality interconnects
The TDR has an array of built-in software tools to simplify common measurements such as cable
length, local impedance (i.e., resistance of an electric circuit), and return loss.
The TDR tests cables for defects by creating and sending a signal down the cable and measures
the time it takes for the signal, or part of the signal, to return (i.e., reflection).
The signal’s reflection begins at the fault point of the cable. The more severe the flaw, the more
energy is reflected back, resulting in easier identification of imperfections.
The resulting measurement allows the operator to identify changes in impedance within the cable
that indicate the presence of a short, a partial short (crimps), an open, a partial open (nicks in the
cable), a defect in the shield or conductor, a foreign substance (e.g., water), or thermal damage.
The TDR allows the operator to save frequently used test configurations to minimize setup time.
The TDR can store waveforms for later analysis or historical comparison.
The TDR is especially helpful in locating defects in long, intricately routed, and inaccessible cable
runs.
TRAINEE GUIDE
Sheet 1 of 2
FOR TRAINING USE ONLY 7
INFORMATION SHEET 1-5
SAFETY
A. INTRODUCTION
Some electrical measuring instruments are used to measure electrical voltages or signals that can
be dangerous and may be fatal if you come in contact with energized circuits or equipment while
performing testing procedures. Exercise extreme caution when working with the TDR and
energized equipment.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
2. Navy Safety and Occupational Health (SOH) Program Manual for Forces Afloat, Volume
II, Surface Ship Safety Standards, OPNAVINST 5100.19 (series)
C. INFORMATION
General Safety
You must observe the following general safety precautions at all times:
1. Never work alone on energized electrical or electronic equipment.
2. Use the one-hand rule when turning on electrical equipment. Never operate a switch with the
other hand on a metal surface, which would provide a path to ground through the body.
3. Remove or snugly secure any loose clothing.
4. Remove all jewelry.
5. Never use outlets that appear to be burned or damaged.
6. Report all hazards. If at any time you detect a hazard, it is your responsibility to report the
hazard to ensure that it is corrected.
7. Make sure there is plenty of light in the work area. Never work with tools in dark areas where
you cannot see clearly.
8. Do not use any equipment that has a frayed cord, or a broken or damaged plug.
9. Do not touch a conductor until it is properly tagged out of service and tested, to be sure it is de-
energized or discharged.
10. Obey all warning signs; read equipment warning labels before use.
11. Always de-energize and tag out installed electrical equipment with red DANGER,
DO NOT OPERATE tags before starting any maintenance or repair. Test for energized
circuits.
12. Use an authorized voltage indicator to test if equipment or circuits are energized.
13. Do not use aluminum or metal portable ladders when working on electrical equipment.
TRAINEE GUIDE
Information Sheet 1-5 Sheet 2 of 2
FOR TRAINING USE ONLY 8
14. Always connect electrical equipment cords to the extension cord before the extension cord is
inserted into an energized receptacle.
TDR Safety
To avoid possible electric shock or personal injury, follow these guidelines when using the
TDR:
1. Only use the power cord supplied with the TDR, and then only if the cord is in good condition.
2. To reduce the risk of electric shock, disconnect all external cables before connecting the 24
VDC external power supply.
3. Never use the TDR to test any cable or device carrying a non-zero electrical potential relative
to earth ground, as this could cause an electric shock.
4. Upon loss of the protective-ground connection, all accessible parts, including the screen,
knobs, and connectors, can give an electric shock.
5. Do not operate the TDR in an explosive atmosphere unless your unit has been specifically
certified for that condition.
6. To avoid personal injury and risk of electric shock, do not open the TDR case, and do not
operate unless the case is fully intact.
7. The TDR should never be used to test any cable or device carrying live electrical signals, as
this carries a risk of electric shock.
8. Always properly ground the conductor(s) of any cable or wiring to remove any static charge
prior to connecting it to the TDR.
9. Do not proceed beyond a DANGER, WARNING, or CAUTION notice until the indicated
conditions are fully understood and met.
TRAINEE GUIDE
Sheet 1 of 1
FOR TRAINING USE ONLY 9
DIAGRAM SHEET 1-6
FRONT PANEL CONTROLS AND INDICATORS
Front Panel Controls and Indicators
1 Power button 13 LIBRARY button
2 H1 function button 14 SELECT button
3 H2 function button 15 CURSOR button
4 H3 function button 16 SCAN button
5 H4 function button 17 AUTOFIT button
6 Menu button 18 M-FUNC button
7 VERTICAL POSITION knob 19 M-FUNCTION knob
8 VERTICAL SCALE knob 20 V1 function button
9 HORIZONTAL POSITION knob 21 V2 function button
10 HORIZONTAL SCALE knob 22 V3 function button
11 CABLE connector 23 V4 function button
12 Host USB port
TRAINEE GUIDE
Sheet 1 of 3
FOR TRAINING USE ONLY 10
INFORMATION SHEET 1-7
FRONT PANEL CONTROLS AND INDICATORS
A. INTRODUCTION
To accurately operate the TDR, it is essential that you are able to identify and understand the
function of the buttons, knobs, connectors, and ports on the TDR's front panel.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
The TDR front panel controls and indicators provide the functionality to scan and filter cable
defects and characterize their failings. The table below describes the function of each control and
indicator on the TDR’s front panel.
Control/Indicator Function
Power button Selecting the power button applies power to the TDR
when the power switch on the rear panel is in the on
position.
Selecting the power button when power is applied to the
TDR displays the shutdown menu. The shutdown menu
options are as follows:
1. The Vacuum Database option cleans the unused
records from the TDR, freeing space in memory.
2. The Clean Shutdown option turns the TDR off and is
the preferred method for shutting down the TDR.
3. The Cancel option exits the shutdown menu.
CABLE connector This BNC allows you to attach the test cable to the TDR.
Ensure the test cable is properly grounded before
connecting to the BNC. This prevents electrostatic
damage to the internal circuitry of the TDR.
TRAINEE GUIDE
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FOR TRAINING USE ONLY 11
Control/Indicator Function
Menu button The Menu button accesses and navigates through the
TDR’s internal menus.
The button activates the on-screen help function when
held down while selecting any other button on the TDR.
H1-H4 function buttons The H1 through H4 buttons provide different functions
based on the menu selected (e.g., set the horizontal
calibration by selecting button H4).
V1-V4 function buttons The purpose of these function buttons depends upon the
selected menu (e.g., set the vertical calibration by
selecting the V4 function button).
M-FUNCTION knob The M-FUNCTION knob implements the function
selected by the M-FUNC button.
M-FUNC button The M-FUNC button displays the current operation on
the screen. The function of the M-FUNCTION knob is
corrected by this button.
SCAN button The SCAN button displays a specialized soft-menu scan
and trace menus.
The SCAN button contains menus for saving, deleting,
hiding, and performing mathematical operations on
selected traces.
This button also allows you to perform automated scans
of an entire cable when detected by the AUTOFIT
button.
SELECT button The SELECT button is used to choose between traces on
the screen. Selecting the button has no effect if no
scanned traces are loaded.
TRAINEE GUIDE
Information Sheet 1-7 Sheet 3 of 3
FOR TRAINING USE ONLY 12
Control/Indicator Function
AUTOFIT button The AUTOFIT button displays the entire length of the
test cable and allows you to zoom in and inspect the
cable.
The TDR display will indicate terminations in the cable
caused by a short (e.g., crimps) or an open or break
(e.g., nicks), or the location of the last cursor position.
CURSOR button The CURSOR button allows you to toggle between the
two available on-screen cursors to display the distance,
return loss, or other measurements between the two
cursors.
By selecting and holding the CURSOR button for 1
second, you can move cursors that are not on the screen
to the display.
LIBRARY button The LIBRARY button opens the library menu, which
contains a database of previously named configurations,
saved cable records (scans), and the records of known
cable types.
Host USB port This USB 1.1 port allows the TDR to interface with USB
devices such as a barcode reader, keyboard, or thumb
drive.
VERTICAL controls The VERTICAL POSITION knob controls the vertical
position of the selected trace, moving it up or down.
The VERTICAL SCALE knob controls the display’s
vertical scale. It is displayed numerically on the bottom
of the screen.
HORIZONTAL controls The HORIZONTAL POSITION knob controls the
horizontal position of the cursor (i.e., left to right) and
the displayed trace relative to the start position of the
cable scan.
The HORIZONTAL SCALE knob controls the
horizontal scale of the displayed trace, and can be
displayed in either English or IS.
TRAINEE GUIDE
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FOR TRAINING USE ONLY 13
DIAGRAM SHEET 1-8
REAR PANEL CONTROLS
Rear Panel Connectors and Switches
1 Power switch
2 Client USB connector
3 RJ-45 Ethernet port
4 External 14.4 VDC battery pack connector
5 24 VDC power adapter plug
TRAINEE GUIDE
Sheet 1 of 1
FOR TRAINING USE ONLY 14
INFORMATION SHEET 1-9
REAR PANEL CONTROLS
A. INTRODUCTION
To accurately operate the TDR, it is essential that you are able to identify and understand the
function of each control on the TDR's rear panel.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
The table below describes the function of each control on the TDR’s rear panel.
Control Function
Power switch The power switch turns the TDR off and
prevents it from powering on.
Client USB connector The client USB connector allows you to
connect the TDR to a host computer for data
transfer and PC control.
RJ-45 Ethernet port The 10/100 Mb RJ-45 Ethernet port can be
used for data transfer and remote PC control.
External 14.4 VDC battery pack connector The external 14.4 VDC battery pack connector
allows you to select whether the external
battery or the internal battery is charged. By
default, the internal battery is preferred for
charging. The secondary battery will be
charged when the preferred battery is detected
to be at full charge.
24 VDC power adapter plug The 24 VDC power adapter plug allows you to
connect the 24 VDC AC adapter.
TRAINEE GUIDE
Sheet 1 of 3
FOR TRAINING USE ONLY 15
PROBLEM SHEET 1-10
CONTROLS AND INDICATORS ACTIVITY
A. INTRODUCTION
Troubleshooting a cable to ensure it is performing as expected and meets the desired specifications
is a critical task. The TDR allows you to identify subtle changes in cable impedance that indicate a
fault. Properly setting up the TDR is essential in this task.
B. EQUIPMENT
None
C. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
D. DIRECTION
Identify and define each of the controls and indicators numbered in the graphics below.
E. PROBLEM
TRAINEE GUIDE
Problem Sheet 1-10 Sheet 2 of 3
FOR TRAINING USE ONLY 16
TRAINEE GUIDE
Problem Sheet 1-10 Sheet 3 of 3
FOR TRAINING USE ONLY 17
1. Name:
Function:
2. Name:
Function:
3. Name:
Function:
4. Name:
Function:
5. Name:
Function:
6. Name:
Function:
7. Name:
Function:
8. Name:
Function:
9. Name:
Function:
10. Name:
Function:
11. Name:
Function:
12. Name:
Function:
TRAINEE GUIDE
Sheet 1 of 2
FOR TRAINING USE ONLY 18
INFORMATION SHEET 1-11
MENUS
A. INTRODUCTION
Key TDR functions are presented in a menu format. Interpreting the menus will assist you in
successfully operating the TDR.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
The TDR features an array of built-in menus and analysis tools that allow the operator to locate
cable faults. The table below describes the TDR’s menus and their functions.
Menu Function
CABLE LEN menu The CABLE LEN menu allows you to select
predefined short, medium, and long cable
lengths while measuring the pulse period of
the cable.
Display menu The Display menu turns on-screen display
items on or off using the soft-menu
buttons to show or remove a variable. For
some items, selecting the button once shows
the display item, and selecting it again hides
the item. Some items may disappear
automatically when scanned traces are
selected.
Power menu The Power menu allows you to adjust the
power save options, power display, and
battery charging preference.
Connections menu The Connections menu allows you to change
the way the TDR connects to an external
source.
Measurement menu The Measurement menu allows you to change
units, Vp control, and reflection coefficient
calculation methods.
TRAINEE GUIDE
Information Sheet 1-11 Sheet 2 of 2
FOR TRAINING USE ONLY 19
Menu Function
Diagnostics menu The Diagnostics menu allows you to obtain
information on the software and hardware
versions for the TDR and diagnose potential
performance issues.
Info menu The Info menu provides you with information
regarding the TDR and its installed software.
Math menu The Math menu contains frequently used
mathematical operations.
TRAINEE GUIDE
Sheet 1 of 2
FOR TRAINING USE ONLY 20
INFORMATION SHEET 1-12
DIALOG BOX NAVIGATION
A. INTRODUCTION
Recognizing the different dialog boxes and their functions will facilitate operating the TDR and
prompt a faster response time.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
Use the M-FUNCTION knob to scroll through the different entry boxes.
1. With an entry box selected, press the Keyboard menu option to call up an on-screen keyboard.
2. Select the desired characters with the M-FUNCTION knob, selecting the Select menu option
for each one.
3. Select the Shift menu option to get more characters.
4. To delete a character, use the Back menu option.
5. With the on-screen keyboard open, accept the current entry with the OK menu option, or return
to the original entry with the Cancel menu option.
6. With the keyboard off the screen, select the OK menu option to accept all changes to the
current dialog box and close the dialog box.
7. Select the Cancel menu option to clear all changes.
With a USB keyboard attached, entries can be changed directly by using the following steps:
1. Use the Tab key to scroll down through entry boxes; hold down Shift and select Tab to scroll
up through entry boxes.
2. Use the Backspace key to delete a character, and use the arrow keys to move the cursor left or
right.
3. Select Enter for OK or Escape for Cancel.
TRAINEE GUIDE
Information Sheet 1-12 Sheet 2 of 2
FOR TRAINING USE ONLY 21
Some dialog boxes present a list of selectable items. Use the M-FUNCTION knob to highlight
individual items for selection. Then, use the Select option to choose the highlighted item.
Where appropriate, multiple items can be marked for selection using the options on the right-side
menu:
1. Toggle selected
2. Clear all
3. Mark all
4. Toggle all
TRAINEE GUIDE
Sheet 1 of 2
FOR TRAINING USE ONLY 22
INFORMATION SHEET 1-13
CABLE TEST PREPARATIONS
A. INTRODUCTION
The TDR is a useful tool in finding and examining cable faults. To prepare a cable for testing, you
must navigate through several layers of TDR menus.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
When testing a cable, you must perform several preliminary steps before beginning the cable trace.
Determining Vp
Vp, also sometimes abbreviated VoP, is the measure of the velocity of an electrical signal within a
cable expressed as a fraction of the speed of light in a vacuum.
Vp can be set in ranges between 0.25 and 1.0.
An accurate Vp is necessary for accurate cable length and distance-to-fault measurements.
The current setting for Vp appears on the lower center of the screen.
For cables of a known type, you can approximate the Vp by using the minimum Vp for that cable
type. To find that Vp value, use the TDR’s built-in library of cable types.
You can also approximate the Vp by testing a known cable of the same length and type as the one
you want to test.
Changing Vp
To change the Vp, select the M-FUNC button until the top-center information indicator reads Vp.
Two Vp indicators, Coarse Vp and Fine Vp, will be separately available:
1. Coarse Vp allows for the modification of the first three significant digits.
2. Fine Vp allows for the modification of the last three significant digits.
TRAINEE GUIDE
Information Sheet 1-13 Sheet 2 of 2
FOR TRAINING USE ONLY 23
Measurements and traces are automatically updated on the display to reflect the new Vp.
Finding an Unknown Vp
Follow these steps to find the Vp for a cable under test where the Vp is entirely unknown. It
requires a sample cable of the same type that can be measured physically.
Step Number Step
1 Measure the length of the test cable. Make sure the test cable is of the same
type as the cable for which you need to determine the Vp. If there are any
adapters used while connecting the cable, include their length in the
measurement or set one of the cursors at the end of the adapter before
attaching the cable.
2 Attach the test cable to the CABLE connector.
3 Select the AUTOFIT button. The TDR will now show the beginning and the
end of the test cable.
4 Position the active cursor (the last cursor selected) at the end of the test
cable. Use the HORIZONTAL SCALE knob to zoom in on the end of the
cable and get an accurate placement.
5 Adjust the Vp until the TDR distance measurement to the active cursor
equals the physical measurement. The final Vp value is the true Vp value of
the cable.
TRAINEE GUIDE
Sheet 1 of 1
FOR TRAINING USE ONLY 24
INFORMATION SHEET 1-14
RELATIVE DISTANCE MEASUREMENT
A. INTRODUCTION
To reduce time and expense, the TDR can accurately measure the relative distance to a fault.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
The TDR displays the absolute distance from cable start and the relative distance from the passive
cursor to the active cursor.
The Vp must be set accurately for the section of cable between the cursors in order for the TDR to
accurately measure relative distance.
To measure the relative distance between two points in a cable, perform the following:
1. Access and set the Display menu to distance and ns.
a. Select the menu button.
b. Select the Display button.
c. Select the Distance ns button. The data appears in the top right corner of the display.
2. Exit the menu.
a. Select the menu button. The Display menu closes and the top-level menu appears.
b. Select the menu button. The top-level menu closes.
3. Select the AUTOFIT button. The TDR will now show the beginning and the end of the test
cable.
4. Select the CURSOR button to change the active cursor.
5. Turn the HORIZONTAL POSITION knob to move the active cursor to the beginning of the
section to be measured.
6. Turn the HORIZONTAL POSITION knob to move the newly active cursor to the end of the
section to be measured.
The TDR displays the distance measured between the two cursors as a Delta value below
the absolute distance measurement.
TRAINEE GUIDE
Sheet 1 of 1
FOR TRAINING USE ONLY 25
INFORMATION SHEET 1-15
MEASURING VSWR
A. INTRODUCTION
The Navy requires its cables to meet or exceed performance standards at a certain level across a
broad spectrum of operating frequency ranges. The TDR uses these specifications, which include
VSWR, to determine if the cable passes or fails its performance requirements.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
VSWR is defined as the maximum reflected voltage over the minimum reflected voltage at a given
frequency.
To understand what VSWR is, consider this example: A voltage wave is traveling down a cable to
an antenna. In some cases, part of this voltage wave is reflected back down the cable in the reverse
direction toward the source. The VSWR is a measure of what is happening to the forward and
reverse voltage waveforms and how they compare in size.
A VSWR value of 1.2:1 denotes a maximum standing wave amplitude that is 1.2 times greater
than the minimum standing wave value. For example, a 50 Ω coax cable would have 9% of its
voltage reflected and 0.8% of its power reflected.
If there is no reflection, VSWR will be 1.
If all energy is reflected, VSWR goes to infinity.
The TDR displays two different VSWR values:
1. The first VSWR value is calculated from the total reflection relative to the output impedance
of the TDR (50 Ω).
2. The second VSWR value, labeled rVSWR, is calculated as the reflection between the two
cursors.
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FOR TRAINING USE ONLY 26
INFORMATION SHEET 1-16
COMMON CABLE FAULTS
A. INTRODUCTION
When a possible cable fault occurs (e.g., a break, a short circuit, moisture, or a bad connector),
signal power is compromised and the cable falls below specified performance specifications.
Knowing the different types of cable faults is crucial to locating faults in all cable systems aboard
ship.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
Faults are mostly found at cable terminations and joints, or other locations where there has been
disruption in the cable’s route.
Each change in a signal has a different effect on the trace displayed on the TDR. A positive
reflection shows a higher impedance (i.e., the trace curves up); a lower reflection shows a lower
impedance (i.e., the trace curves down).
Examples of common cable faults:
1. A short shows as a curved negative trace to the bottom of the screen.
2. An open conductor shows a large positive trace to the top of the screen.
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Information Sheet 1-16 Sheet 2 of 3
FOR TRAINING USE ONLY 27
3. A cable splice or joint shows a small positive trace followed by a small negative trace.
4. A T-joint shows a negative trace followed by a long positive trace.
5. A bridge tap shows a small positive trace followed by, after a short distance, a small negative
trace.
6. A split shows a short positive trace followed by a negative trace.
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FOR TRAINING USE ONLY 28
7. A wet splice in water shows a short positive trace followed by a negative trace.
8. Water ingress shows a long, irregular trace.
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INFORMATION SHEET 1-17
INITIALIZATION PROCEDURE
A. INTRODUCTION
It is important to know how to set up and verify proper operation of the TDR to accurately
measure cable lengths, troubleshoot, and identify faults on cables.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
Follow the steps below to initialize the TDR:
1. Select the power button and observe the display.
2. Attach the cable to be tested to the CABLE connector.
3. Set the Vp to match the Vp of the cable under test.
a. Select the LIBRARY button.
b. Select the H2 function button to select the Cable Types menu. The Cable Type menu
appears.
c. Turn the M-FUNCTION knob CW or CCW to select the cable type.
d. Ensure the cable type of the cable under test is highlighted in the Cable Type menu.
e. Select the H3 function button to select the Select button. The Cable Type menu closes.
4. Exit the menus.
a. Select the menu button. The top-level menu appears.
b. Select the menu button. The top-level menu closes.
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INFORMATION SHEET 1-18
MEASURING CABLE LENGTH
A. INTRODUCTION
The ability to quickly measure cable length helps to ensure efficient test measurements during
troubleshooting procedures. Precise measurements also provide quantitative confirmation of
adherence to the Navy's cabling standards.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
Follow the steps below when using the TDR to measure cable length:
1. Perform the TDR Initialization Procedure.
2. Select the AUTOFIT button to ensure the entire length of the cable fits on the display.
3. Access and set the Display menu to distance and ns.
a. Select the menu button. The top-level menu opens.
b. Select the V2 function button to select the Display menu.
c. Select the V3 function button to select the Distance ns menu. The distance is displayed in
the upper right corner of the display.
d. Select the V3 function button to select *Distance* *ns*.
4. Exit the menus.
a. Select the menu button. The Display menu closes and the top-level menu appears.
b. Select the menu button. The top-level menu closes.
5. Select the CURSOR button to position the active cursor.
6. Access the Display menu to close the distance function.
a. Select the menu button.
b. Select the V2 function button to select the Display menu.
c. Select the V3 function button to select *Distance* ns.
d. Select the V3 function button to select Distance *ns*.
7. Exit the menus.
a. Select the menu button. The Display menu closes and the top-level menu appears.
b. Select the menu button. The top-level menu closes.
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Sheet 1 of 2
FOR TRAINING USE ONLY 31
INFORMATION SHEET 1-19
MEASURING DISTANCE TO A FAULT AND IDENTIFYING THE FAULT
A. INTRODUCTION
Many components can cause problems for electrical systems. Cable lines are typically the most
common failure point. These failures can cause unwanted signal reflections. Using the TDR, the
root cause of an RF problem can be identified and isolated, thereby saving time and expense.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
Follow the steps below when using the TDR to measure distance to and identification of a fault:
1. Perform the TDR Initialization Procedure.
2. Select the AUTOFIT button to ensure the entire length of the cable fits on the display.
3. Access and set the Display menu to distance and ns.
a. Select the menu button.
b. Select the V2 function button to select the Display menu.
c. Select the V3 function button to select the Distance ns menu.
d. Select the V3 function button to select *Distance* *ns*.
4. Exit the menus.
a. Select the menu button. The Display menu closes and the top-level menu appears.
b. Select the menu button. The top-level menu closes.
5. Select the CURSOR button to position the active cursor.
6. Measure the distance to the fault and identify the fault.
a. Rotate the HORIZONTAL POSITION knob CW or CCW to move the active cursor to the
beginning of the first fault.
b. Rotate the VERTICAL SCALE knob CW or CCW to zoom in and identify the fault.
c. Rotate the HORIZONTAL SCALE knob CW or CCW to get an accurate distance
measurement to the fault.
d. Identify the type of fault.
7. Access the Display menu to close the distance function.
a. Select the menu button.
b. Select the V2 function button to select the Display menu.
c. Select the V3 function button to select *Distance* ns.
d. Select the V3 function button to select Distance *ns*.
8. Exit the menus.
a. Select the menu button. The Display menu closes and the top-level menu appears.
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Information Sheet 1-19 Sheet 2 of 2
FOR TRAINING USE ONLY 32
b. Select the menu button. The top-level menu closes.
Note: Repeat step 6 if the distance for additional faults is needed.
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Sheet 1 of 1
FOR TRAINING USE ONLY 33
INFORMATION SHEET 1-20
MEASURING VSWR
A. INTRODUCTION
Measuring VSWR is important in understanding the efficiency of a system and how well the
components of the RF network are matched in impedance. When impedance is improperly
matched, you lose signal power, which results in weak transmissions, poor reception, or both.
B. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
C. INFORMATION
Follow the steps below when using the TDR to measure the VSWR:
1. Perform the TDR Initialization Procedure.
2. Select the AUTOFIT button to ensure the entire length of the cable fits on the display.
3. Access and set the Display menu to VSWR.
a. Select the menu button. The top-level menu appears.
b. Select the V2 function button to select the Display menu. The Display menu appears.
c. Select the V4 function button to display more menu functions. Page 2 of the Display menu
appears.
d. Select the V1 function button to select VSWR.
4. Exit the menus.
a. Select the menu button. The Display menu closes and the top-level menu appears.
b. Select the menu button. The top-level menu closes.
5. Turn the HORIZONTAL POSITION knob CW or CCW to move the active cursor along the
cable trace.
6. Access the Display menu to close the VSWR function.
a. Select the menu button. The top-level menu appears.
b. Select the V2 function button to select the Display menu.
c. Select the V4 function button to display more menu functions. Page 2 of the Display menu
appears.
d. Select the V1 function button to select *VSWR*.
7. Exit the menus.
e. Select the menu button. The Display menu closes and the top-level menu appears.
f. Select the menu button. The top-level menu closes.
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Sheet 1 of 2
FOR TRAINING USE ONLY 34
PROBLEM SHEET 1-21
OPERATE THE TDR PRACTICE
A. INTRODUCTION
This exercise allows you to practice operating the TDR. You will set up the TDR, measure cable
length and VSWR, and identify and measure distance to a fault.
B. EQUIPMENT
None
C. REFERENCES
1. Automated Metallic Time-Domain Reflectometers Operator's Manual, CT100 and
CT100HF
D. DIRECTION
For each scenario, use the job and information sheets in your Trainee Guide to practice performing
the procedures to operate the TDR. Record your test measurements in the spaces provided.
E. PROBLEM
During pre-underway check-offs, your LPO assigns you the task of troubleshooting a possible cable
fault on a newly installed RG-58/U cable. You are to measure the length of the RG-58/U cable.
Measuring Cable Length
Measurement Answers
Cable lengths 1. ft
2 ns
3. ∆ft
4. ∆ns
TRAINEE GUIDE
Problem Sheet 1-21 Sheet 2 of 2
FOR TRAINING USE ONLY 35
Your LPO suspects one or more faults in an RG-58/U cable. You are to troubleshoot for a possible
fault. If a fault(s) is found, you are to measure the distance to the fault(s) on the cable and identify
the type of fault.
Measuring Distance to a Fault and Identifying the Fault
Measurement Answers
Distance to fault #1 1. ft
2. ∆ft
Distance to fault #2 3. ft
4. ∆ft
Type of fault 5.
Vp 6.
The LPO needs to know the reflection of an RG-58/U cable used in a single antenna installation.
You are to measure the VSWR and rVSWR of the RG-58/U cable.
Measuring VSWR
Measurement Answers
VSWR 1. VSWR
rVSWR 2. rVSWR