TRIPLETT
CableRater
dB Loss Meter
Instruction Manual
84-875
6/08
TABLE OF CONTENTS
1. Introduction …………………....................... 2
2. Safety Rules and Warnings .......................... 2
3. Product Features ...................................... 3
4. Typical Uses ........................................... 3
5. Specifications ......................................... 4
6. Transmitter Front Panel .............................. 6
7. Receiver Front Panel ................................. 7
8. Preparing for Use ..................................... 8
9. Operation ............................................... 9
10. Maintenance ......................................... 26
11. Warranty .............................................. 27
1: INTRODUCTION
The Triplett CableRater is a revolutionary dB Loss Meter for measuring Loss or
Gain in Cable Television distribution systems.
It consists of a portable handheld battery operated Transmitter and Receiver
designed to generate and measure a test signal that is similar to a Cable TV
signal. The Transmitter’s test signal can be applied to the input of a Cable TV
distribution system consisting of coaxial cable, amplifiers, splitters, switches,
etc. and the Receiver connected to any outlet downstream of the Transmitter,
and the Loss or Gain between the Transmitter and Receiver measured with the
press of a button.
The CableRater is an invaluable tool for verifying the design of a Cable TV distribution system, prior to the connection of any Cable TV services. It can be used
to troubleshoot a newly installed distribution system prior to, or following, the
application of drywall.
Before the introduction of the CableRater, it was usually necessary to wait until
the Cable TV service was ‘turned on’ in order to perform any testing of the distribution system. An expensive “dB Level Meter” was usually needed to perform
the tests. The CableRater offers the wire installer a cost effective alternative to
the expensive and inconvenient solutions of the past. Now installation and testing can be completely quickly and efficiently, and post installation callbacks minimized or eliminated.
2: SAFETY RULES AND WARNINGS
The Transmitter and Receiver of the CableRater are designed to tolerate momentary unintentional application of 120VAC to its F connectors.
2
2.1) The CableRater is not designed to tolerate accidental application of voltages
exceeding 132VAC 60Hz. Applying higher voltages may cause damage to
the CableRater, and may injure the user.
2.2) Use care when connecting the CableRater to any wire or cable. An
unexpected dangerous voltage may be present, which may result in injury
to the user.
2.3) Do not operate the CableRater with any of the product’s covers open or
removed. A dangerous potential applied to the F connectors may appear on
the battery connector or other parts in the product. This could pose a shock
hazard to the user, if for example, a cable with 120VAC on it is connected
to the CableRater.
2.4) Use caution when working with any long unconnected wire or cable. Under
some conditions, unconnected wires may “float up” to dangerous potentials,
and touching them may result in user injury.
3: PRODUCT FEATURES
3.1) Measures dB Gain or Loss in Cable TV Distribution Systems (+/-20dB range)
3.2) Tests without requiring connection to Cable TV service
3.3) Verify installation before Cable TV service is connected
3.4) CableRater Transmitter simulates frequency and level of TV channel 3.
3.5) Large backlit (Blue EL) digital display for accurate low light testing
3.6) Lightweight and convenient
3.7) Locking power switch on the Transmitter prevents accidental turn on
3.8) Battery Test in Transmitter and Receiver
3.9) Efficient Transmitter design permits hours of tests without replacing battery
3.10) Real Time measurement
3.11) F connectors for easy connection to standard cable TV distribution system
3.12) Protected against 120VAC 60Hz line cross
3.13) Works with typical ‘power injector’ amplifier systems
3.14) Receiver is user configurable for continuous operation or auto-shutoff
3.15) Kit includes Transmitter, Receiver, Patch Cable, Carrying Case,
and 2 - 9V batteries
4: TYPICAL USES
4.1) Measure dB Loss (or Gain) from main entrance to each TV outlet, including
Loss in all cable, connectors, switches, splitters, and amplifiers in between.
4.2) Check for bad / lossy cables
4.3) Check for bad / lossy connectors and connections
4.4) Check for bad / lossy splitters
4.5) Check for bad / lossy switches
4.6) Check for bad amplifiers, verify amplifier gain
4.7) Check for excessive loss in cable (too long of a run)
4.8) Check for intermittent connections
4.9) Identify cables
3
5: SPECIFICATIONS
5.1) Transmitter
5.1.1) Output Level . . . . . . . . . . . . . . . . . . . . . Approx 10dBmV +/- 3dB
5.1.2) Output Frequency . . . . . . . . . . . . . . . . . Approx 61.25MHz (Channel 3)
5.1.3) Output Impedance . . . . . . . . . . . . . . . . . Approx 75 Ohms
5.1.4) Battery Required . . . . . . . . . . . . . . . . . . Standard 9 volt Alkaline
5.1.5) Battery Life . . . . . . . . . . . . . . . . . . . . . . Approx 200 Hours
5.1.6) Battery Test LED. . . . . . . . . . . . . . . . . . Flashes to indicate good battery
5.1.7) Output Connector . . . . . . . . . . . . . . . . . Female “F” connector
5.1.8) Size (including F connector & knobs) . . 2 3/8" W x 4 1/8" H x 1 3/8"T
5.1.9) Weight (w/o battery) . . . . . . . . . . . . . . . Approx 3 ounces
5.2) Receiver
5.2.1) Input Level . . . . . . . . . . . . . . . . Approx -10 to +30 dBmV, 50dBmV max
5.2.2) Input Frequency . . . . . . . . . . . . Approx 61.25MHz (Channel 3)
5.2.3) Input Impedance . . . . . . . . . . . Approx 75 Ohms
5.2.4) Loss / Gain Accuracy . . . . . . . . Approx +/- 2dB
5.2.5) Loss / Gain dB Resolution . . . . 0.1dB
5.2.6) Display . . . . . . . . . . . . . . . . . . 1" high High Contrast LCD w/ backlight
5.2.7) Backlight . . . . . . . . . . . . . . . . . Blue Electro Luminescent
5.2.8) Auto Shut-Off . . . . . . . . . . . . . 4 settings (approx 1 to 5 min
5.2.9) Battery Required . . . . . . . . . . . Standard 9 volt Alkaline
5.2.10) Battery Life . . . . . . . . . . . . . . . Approx 15 Hours w/o Backlight
5.2.11) Battery Test . . . . . . . . . . . . . . On Screen Annunciator
5.2.12) Input Connector . . . . . . . . . . . Female “F” connector
5.2.13) Size (including F connector) . . 3 1/4" W x 6 1/2" H x 1 3/8" T
5.2.14) Weight (w/o battery) . . . . . . . . Approx 8 ounces
operable by separate pushbutton
after last signal is measured)
Approx 5 Hours w/ Backlight on
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5.3) General Information
5.3.1) Cables tested:
The CableRater is intended to work with coaxial cables exhibiting a 75 Ohm
characteristic impedance. Common cables include all types of RG-59 and all
types of RG-6. The CableRater also works with RG-11, RG-12, and cables intended for aerial or direct burial applications.. as long as they are 75 Ohm cables.
Cables with connectors other than type F can be tested with the appropriate
adapters.
5.3.2) The CableRater Receiver is a sensitive Radio Frequency (RF) Power meter.
In some cases, the RF energy in the air (over-the-air signals) is more powerful
than the signals in a typical cable TV distribution system. Over-the-air signals
include RF from nearby TV or Radio stations, Cell Phone towers, Pager towers,
Ham Radio operators, Microwave links, etc.
A distribution system that is in proper operating condition ‘shields out’ these
over-the-air signals, so they don’t interfere with the cable TV signals.
However, a distribution system that has faults, for example, a shield(s) on a
coaxial cable is open, can allow over-the-air signals into the system. This is
called “ingress”. Ingress will often result in poor TV picture quality on specific
channels (whose frequency is the same as the ingress signal).
If the CableRater is connected to a distribution system with ingress, the ingress
signal might be measured by the CableRater, causing an error in the Loss measurement.
The distribution system will not operate properly if there is ingress. So, if ingress is detected by the CableRater this problem must be corrected before performing a Loss Test. Refer to section 9.3 for instructions on testing for ingress.
5
6: TRANSMITTER FRONT PANEL
A
UNLOCK
B
C
Figure 1
A) Battery Test LED
B) Unlock Button
C) ON / OFF Power Switch
D) Output Connector
E) Zero Calibrate Knob
D
E
6
7: RECEIVER FRONT PANEL
A
B
C
D
G
F
E
Figure 2
A) LCD Display with Backlight
B) Low Battery Annunciator
C) Auto Power Off (APO) Annunciator
D) Under Range Annunciator
E) Backlight Button
F) Power Button
G) Input Connector
7
8: PREPARING FOR USE
8.1) Installing Battery in Transmitter
8.1.1) Remove screw from the back of the Transmitter case.
8.1.2) Carefully remove the front panel of the Transmitter.
8.1.3) Install 9 volt battery.
8.1.4) Reassemble Transmitter.
8.2) Installing Battery in Receiver, Setting Auto Power Off (APO)
8.2.1) Remove 2 screws located on the back, bottom, of the Receiver.
8.2.2) Remove battery cover. This fits rather snuggly and is sometimes difficult
to remove.
8.2.3) If changing the settings of the APO, refer to Figure 3 to see the location of
the jumpers that control the settings. A small pair of pliers or tweezers may be
helpful to move the jumpers.
JP4 JP3 JP2 JP1
Figure 3
There are 4 locations for the jumpers: JP1, JP2, JP3, and JP4.
Only 3 jumpers are needed.
The product is initially set to the APO mode, with the shortest timeout. Jumpers
JP2, JP3, and JP4 will be in place.
Refer to the following table to change the APO mode (either ON or OFF) or the
Timeout Duration. The ‘X’ indicates that a jumper is in this location.
8
1PJ 2PJ 3PJ 4PJ NOITPIRCSED
X X X
X X
X X
X
X X X
tuoemiTtsetrohS,NOOPA
tuoemiT1muideM,NOOPA
tuoemiT2muideM,NOOPA
tuoemiTtsegnoL,NOOPA
Note:
Be careful not to drop the jumper inside the product when changing the settings.
8.2.4) After setting the jumpers as desired, install battery and replace battery
cover.
Refer to Figures 1 and 2 for locations of the controls.
9: OPERATION
9.1 Description of Transmitter
9.1.1 ON / OFF Power Switch and UNLOCK Button
When the Transmitter is not in use, the ON / OFF switch should be placed in the
OFF position to conserve the battery life.
To turn the Transmitter ON, depress the UNLOCK button while moving the ON /
OFF switch from the OFF to the ON position. Release the UNLOCK button. When
the switch is moved to the OFF position, it will lock in this position, requiring the
user to again press the UNLOCK button to turn the switch ON.
9.1.2 BATTERY TEST Indicator
The BATTERY TEST indicator is a green LED (Light Emitting Diode) that flashes
periodically when the battery is good. With a good battery, the indicator will
flash initially when the Power switch is moved from the OFF to the ON position,
and then it will flash at intervals to indicate that the battery is still good. Typically, the indicator flashes at intervals of 5 to 30 seconds. The speed of the
flashing is not critical, and does not indicate the remaining charge in the battery,
only that the battery is supplying adequate power to operate the Transmitter.
tceffeonevah4PJdna3PJ,FFOOPA
In brightly lit situations, such as in direct sunlight, the flashing of the indicator
may not be visible.
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9.1.3 ZERO CALIBRATE Knob
The ZERO CALIBRATE knob is used to ‘calibrate’ the Transmitter to the Receiver
(more on this later). It can be turned clockwise or counterclockwise to increase
or decrease the level of the test signal generated by the Transmitter.
9.1.4 OUTPUT Connector
The OUTPUT connector is a standard F connector (the kind commonly used for
cable TV installations). The test signal generated by the Transmitter comes out
of this connector or ‘jack’. This jack is usually connected to the input of the cable
TV distribution system being tested, or, if testing individual components (like a
Splitter or Amplifier), to the input of the device being tested. This sometimes
requires the use of a ‘patch cable’.
9.2 Description of Receiver
9.2.1 Meter Push On/Off Button
The Meter Push On/Off button is used to turn the Receiver On and Off. If the
Receiver is Off, pressing the button will turn it On. If the Receiver is On, pressing
the button will turn it Off.
When first turned On, the Receiver’s LCD display may momentarily show random numbers or symbols, but within a few seconds, the display should indicate
the correct level.
When turned Off, the Receiver goes into a low power standby mode waiting for
the next button press. It can remain in this mode for months without depleting
the battery. If the Backlight is turned On when the Receiver is turned Off, the
Backlight is turned off also.
9.2.2 Backlight Push On/Off Button
The Backlight Push On/Off button is used to turn the LCD display Backlight On
and Off. The button only works if the power to the Receiver is already On. If the
Receiver is On, pressing the button will turn the Backlight On. If the Backlight is
On, pressing the button will turn it Off.
The Backlight uses a lot of power, more power than the rest of the electronics in
the Receiver, and if left on will cut the battery life significantly. For this reason, a
separate button allows the user to decide if he needs the Backlight or not.
The Backlight is not bright, and may not be seen in normal room lighting, but it
is clearly visible in the dark, allowing the user to take readings in poorly lit surroundings.
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9.2.3 Input Connector
The Input connector is a standard female F connector (the kind commonly used
for cable TV installations). The Transmitter’s test signal is applied to this connector or ‘jack’. Usually the test signal has been passed through a cable TV
distribution system, and it is appearing at a ‘Cable TV outlet’. The ‘outlet’, if
configured as a cable terminated in a male F connector, can be connected directly to the Receiver’s Input jack. If terminated in a wall plate with a female F
connector, a patch cable will be required to connect the test signal to the Input
jack.
If testing individual components (like a Splitter or Amplifier), the output of the
device being tested is connected to the Input of the Receiver. This often requires
the use of a ‘patch cable’.
9.2.4 LCD Display
The LCD display reads Gain or Loss in dB (deciBels). It also provides information about the battery condition, the APO mode, and whether an adequate test
signal is being ‘received’.
9.2.4.1 Underrange Indication
If no test signal, or inadequate test signal is applied to the Receiver, the LCD
displays an Underrange condition (see Figure 4).
Figure 4
If the Receiver is turned On without a connection to the Input jack, the Underrange
indication is expected.
If a cable is connected to the Input jack, and the Underrange indication is observed when the Receiver is turned On, the cable is not connected to the test
signal (from the CableRater Transmitter), or something between the Transmitter
and Receiver is introducing so much Loss that the signal is unmeasureable.
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9.2.4.2 Gain or Loss Indication
When a test signal is measured, after having properly calibrated the Transmitter,
the Gain or Loss of the cable, device, or distribution system between the Transmitter and the Receiver, is displayed in dB.
Numbers preceded by a minus (-) symbol indicate that the displayed value is a
‘Loss’... which means the level of the test signal is lower than it is at the Transmitter. It is expected that Splitters and the cable itself will cause Loss between
the Transmitter and Receiver.
Numbers without a minus (-) symbol indicate that the displayed value is a ‘Gain’
which means the level of the test signal is higher than it is at the Transmitter.
This usually happens only when an Amplifier has been used to increase the signal level.
An indication of 00.0 means the signal level is the same as it is at the Transmitter... that is there is no Loss and there is no Gain.
9.2.4.3 Auto Power Off Indication
If the Auto Power Off (APO) feature is activated (see 8.2), APO will appear in the
display. The APO feature allows the product to remain on as long as a signal is
being measured. If a signal is not being measured, the product will turn itself off
after the preset timeout duration (see 8.2.3). The timeout duration is reset to its
full interval whenever a signal is measured.
9.2.4.4 Low Battery Indication
If appears in the display, the battery is low and should be replaced.
9.3 Ingress
9.3.1 Testing for Ingress
Ingress, and problems associated with it, are described in section 5.3.2. Before
performing any Loss or Gain tests with the CableRater, it is a good idea to test
for ingress.
An ingress test is performed without cable TV service connected to the cable TV
distribution system. If service is already connected, disconnect it temporarily to
perform the test. Do not connect the CableRater Transmitter to the cable distribution system.
To test for ingress, connect the CableRater Receiver to each cable TV outlet.
Turn On the Receiver by pressing and releasing the Meter Push On/Off button. If
desired, turn On the Backlight by pressing and releasing the Backlight Push On/
Off button.
12
Observe the reading on the CableRater. If any reading is obtained, other than the
Underrange indication, ingress is occurring. The higher the reading, the more
ingress. This condition must be resolved before testing for Loss.
9.3.2 Fixing Ingress
The common cause of ingress is a coaxial cable with an open shield. The cable
itself may be OK, but the shield may be losing its connection where the F connector screws on to the splitter or other device. If this connection is not clean
and tight, the shield may be losing contact and allowing ingress. Make sure the
screw-on part of the F connector is snuggly tightened. A small wrench can be
used, but do not overtighten and cause damage to the connector or the equipment to which its attached.
Ingress might occur if the F connector on the cable or the attached device has
been exposed to the weather, and surface corrosion has caused the connector to
lose contact. If this occurs, replace the connectors/devices involved.
An open shield can also be caused by improper installation of the F connector on
the end of a cable. Install the connector properly.
A cable that is flexed or stretched excessively can develop a break in the shield.
Replace the cable.
If the over-the-air signals are especially strong in the vicinity of the test, ingress
can occur if the ends of the cable are left unterminated. The small center conductor of the cable acts as an antenna, picking up over-the-air signals. There are
‘terminations’ that screw onto unused F connectors, preventing ingress and ‘reflections’ in the cable. The CableRater Transmitter can be used as a termination,
if left turned Off... but an actual Termination usually works better.
Searching for the ‘bad’ cable is relatively easy. When a good cable or device is
connected to the CableRater Receiver, the reading should be Underrange. Disconnect or reconnect cables until the source of the ingress is located. The
CableRater Receiver can be connected to any cable when searching for ingress...
even cables ends that are usually thought of as an input. Ingress can occur at
the input or the output, and any place within the distribution system.
Some old televisions are a notorious source of ingress. Old TV’s were not very
well shielded, and they can pick up over-the-air signals, and contaminate the
distribution system with ingress. If this is suspected, connect the CableRater
Receiver to the antenna connection of the TV, and see if the CableRater measures any ingress.
13
9.4 Calibrating the Transmitter
To calibrate the Transmitter, a patch cable is used to connect the
Output jack of the Transmitter to the Input jack of the Receiver. See Figure 5.
UNLOCK
Figure 5
Turn On the Transmitter by holding the UNLOCK button down and moving the
ON/OFF switch to the ON position. The BATTERY TEST indicator must flash, and
must continue to flash at intervals. If the indicator does not flash, replace the
depleted battery with a fresh battery.
Turn On the Receiver by pressing and releasing the Meter Push On/Off button. If
desired, turn On the Backlight by pressing and releasing the Backlight Push On/
Off button.
Observe the LCD display.
The Low Battery symbol must not be displayed. If it is, replace the depleted battery with a fresh battery.
APO may or may not be displayed, depending on the selection made by the user.
A value between -4.0 dB and 4.0 dB will usually be displayed. If a different reading is displayed, such as Underrange (see Figure 4), check the patch cable to
14
make sure it is making good connection. The nuts on the F connectors on the
patch cable should be snuggly tightened to the connectors on the Transmitter
and Receiver. If the patch cable turns freely on the connectors, the nuts are not
tightened properly. Observing the reading on the Receiver’s LCD display, rotate
the ZERO CALIBRATE knob on the Transmitter, either clockwise or counterclockwise, until the LCD reads 00.0 dB. The Transmitter is now ‘calibrated’. Do not
alter the setting of the ZERO CALIBRATE knob for the duration of the testing.
Important Note:
The level of the test signal from the CableRater Transmitter can change slightly if
the Transmitter temperature changes. Consider this behavior if moving the Transmitter from a warm to a cold location, or vice versa. The affect is generally less
than +/- 0.5dB, so it doesn’t make a big difference in the measurements. However, if trying to obtain the most accurate measurements, allow the Transmitter
to acclimate itself to the new temperature for at least 30 minutes before calibrating it to the Receiver.
A Simple Transmitter Test:
If the user suspects the Transmitter is not working properly, it can be tested by
connecting it to the antenna input of a television set to Channel 3. The TV should
display a ‘blank’ screen... no snow. Different TV’s will display a blank screen
differently. Common displays are a white, gray, black, or blue screen. The
CableRater Transmitter does not produce a ‘sound’ signal, so the TV may produce no sound or a hissing sound.
9.5 Testing Loss in a Cable
‘Loss’ is a pretty self descriptive term. It’s the amount of signal, in dB, that is
‘lost’ in a cable, splitter, or other device. All cables have Loss... some more than
others.
Two types of cable are commonly used in Cable TV distribution systems... RG59 and RG-6.
In general, all RG-59 cables share similar Loss characteristics, although there
are numerous variations that affect the cable’s durability, shielding, and quality
of construction. Some constructions can result in less Loss, but not dramatically.
RG-6 has less Loss than RG-59. Again, all RG-6 cables share similar Loss characteristics, and variation in constructions abound, with some types being slightly
less ‘Lossy’ than others.
Loss is usually expressed in dB per 100 ft. Loss varies with the test frequency,
with more Loss being experienced as the frequency rises. Cable TV systems
15
typically use frequencies from about 40 Mega Hertz (MHz) to about 900MHz.
The CableRater performs tests at about 60MHz.
There are many resources ‘on line’ (on the Internet) that give details on the Loss
of various types of cables.
Figure 6 shows some typical Loss figures for RG-59 and RG-6. Notice that the
Loss at 60MHz for 100ft of RG-59 and RG-6 is about the same (2.4dB vs 2.1dB).
Figure 6 is only intended to be representative of coax in general. Different brands
of coax can have more or less Loss than shown in Figure 6.
95-GR 6-GR
YCNEUQERF
tf001 tf002 tf003 tf001 tf002 tf003
zHM06
zHM009
Bd4.2 Bd8.4 Bd2.7 Bd1.2 Bd2.4 Bd3.6
Bd2.01 Bd4.02 Bd6.03 Bd3.9 Bd6.81 Bd9.72
Figure 6
Typical Cables Losses
So, you can expect about 2dB of Loss per 100 ft of cable or about 1dB for 50 ft.
or 4dB for 200 ft. Cables less than 50 ft long should have Losses of less than
1dB.
To check the Loss of a cable, first Calibrate the Transmitter as described in 9.4,
then connect one end of the cable to be tested to the Transmitter Output. and the
other end of the same cable to the Receiver Input (similar to Figure 5, but using
the cable you are testing instead of the patch cable). Press the ‘Meter’ button on
the Receiver and read the Loss on the LCD display. Loss is displayed as a negative or ‘minus’ value in dB.
Referring again to Figure 6, notice that the Loss at 900MHz is substantially greater
than at 60MHz. 900MHz is the frequency of cable TV channel 142. If the cable TV
distribution system being tested is expected to work at these frequencies, then
the 900MHz Loss is of great interest, and should be considered when designing
a system.
In general, most devices designed to work on a cable distribution system have a
relatively flat frequency response. That is, they exhibit about the same amount
(within a few dB) of Loss or Gain at all frequencies (that they are designed to
operate at).
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Coaxial cable, however, always has increasing Loss as frequency increases. This
effect must be considered, and compensated for if necessary. Various methods
of compensation are available... like amplifiers with frequency ‘tilt’ adjustments,
or inline tilt compensators. Tilt compensation is often used when cable runs
exceed several hundred feet.
Important Note:
Occasionally, the CableRater may indicate that a longer cable has less Loss. This
is possible if the longer cable in question is made with premium materials and
superior construction techniques. However, if the cable is less than 30ft long, its
more likely that the CableRater is “lying”. “Standing Waves” can occur when
measuring the cable Loss. These Standing Waves in the cable can make the
Loss appear to be a little higher or lower than it really is. Usually, the effect
causes less than 2dB of error in the measurement, often less than a few tenths
of a dB of error.
If a measurement indicates that several cables of slightly different length (for
example 10, 11, and 12ft) show losses that seem contradictory to their length,
the likely cause is Standing Waves. This is a well documented phenomenon, and
not a reason for concern (i.e. the cables are not bad).
9.6 Testing Loss in a Splitter
Splitters are used to ‘split’ one Cable TV signal into multiple signals. They are
manufactured in different shapes and sizes, and are commonly available to split
the signal in as many as 16 ways. When the signal is split, the resulting multiple
signals are lower in level than the original signal. The splitters have Loss. In
general, the Loss for all types of splitters is about the same for a given number
of outputs. Figure 7 shows some typical Losses experienced by splitters with
different numbers of outputs.
epyTrettilpS BdnissoL
yaw2 5.3
yaw3 5.5
yaw4 7
yaw6 9
yaw8 11
yaw61 61
Figure 7
Typical Splitter Losses
17
To test a splitter with the CableRater, first calibrate the Transmitter as described
in 9.4, and then connect the Transmitter and Receiver to the splitter as shown in
Figure 8. To get the most accurate results, a 75 Ohm termination should be
placed on any unused outputs... but even without the termination, the Loss should
be similar to the Loss shown in Figure 7. Note: The CableRater displays Loss as
a negative or ‘minus’ value in dB. So a 2 way splitter would read about ‘-3.5dB’
on the CableRater display. Notice that the smallest splitter, a 2 way, has more
loss than 100 ft of cable (at 60MHz).
UNLOCK
2 Way Splitter (with a termination on the unused output) being tested
Figure 8
Note:
Some splitters have different losses on their outputs. This is most commonly
seen on 3 way splitters. These splitters are usually marked with the expected
loss for each output.
9.7 Testing Amplifier Gain
There are many types of amplifiers. Only amplifiers intended for use on a Cable
TV system should be tested. The CableRater will not damage other types of amplifiers, but it may not test them correctly either. For example, ‘antenna’ amplifiers or ‘satellite dish’ amplifiers, which can both have F connectors on them,
cannot be properly tested.
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The CableRater is limited to testing Gain up to about 40dB. Attempting to measure higher gains will produce inaccurate results.
To test the Gain of an amplifier, first calibrate the Transmitter as described in 9.4.
Then connect the CableRater Transmitter’s output to the amplifier’s input, and
the amplifier’s output to the CableRater Receiver’s input, as shown in Figure 9.
Press the ‘Meter’ button on the Receiver and read the Gain on the LCD display.
UNLOCK
Transmitter, Amplifier, and Receiver
Figure 9
The maximum output level that an amplifier can produce must be considered.
Most common amplifiers cannot produce output levels exceeding about 40dBmV.
Since the output level of the CableRater Transmitter is 10dBmV, an amplifier
with a 30dB gain connected directly to the Transmitter output will produce a
40dBmV (10dBmV + 30dBmV = 40dBmV) signal at the amplifier output... if the
amplifier doesn’t ‘saturate’. “Saturation” occurs when an amplifier can’t pro-
19
duce any more output level. In such a case, the CableRater will measure the Gain
as being lower than expected. If saturation is suspected, reduce the input level
to the amplifier with an attenuator, then measure the gain of the amplifier with
the CableRater, adding the attenuator loss to the Gain displayed on the CableRater
to obtain the correct amplifier gain. For example, insert a 10dB attenuator between the Transmitter’s output and the amplifier’s input, then measure the output signal of the amplifier with the CableRater, and add 10dB to the CableRater’s
reading to obtain the actual Gain.
Important Note:
Some amplifiers may be excessively noisy or may oscillate if they are operated
with their input disconnected. This does not damage them, but it can cause
unusual readings when measuring amplifier gain. For example, the amplifier can
appear to be amplifying a signal, because a CableRater Receiver connected to
the amplifier output indicates a signal is present... but the Transmitter test signal
is not being applied to the amplifier’s input... the amplifier input is open. Try
connecting a termination to the input of the amplifier to see if it behaves correctly... i.e. the CableRater connected to its output reads Underrange or a value
less than -15dB. If appropriate behavior is obtained, the amplifier may be OK
once it is incorporated into the cable distribution system.
Some amplifiers can become unstable when the CableRater Receiver is connected to their output. The CableRater Receiver does not have a ‘wideband’ 75
Ohm input impedance (75 Ohms is the standard impedance of a cable TV distribution system). The CableRater Receiver uses a ‘narrowband’ 75 Ohm input
impedance. This sometimes causes an amplifier to oscillate or be overly noisy. If
the CableRater Receiver indicates the presence of a signal on the output of an
amplifier, and the input has been terminated as previously described, the Receiver may be causing the amplifier to oscillate. Usually, when this occurs, it is
necessary to properly terminate the amplifier so it won’t oscillate. The amplifier
can be terminated, and the CableRater connected to the amplifier to perform a
measurement, by inserting an in-line attenuator between the output of the amplifier and the input of the CableRater Receiver. Use whatever attenuator is handy,
in the range of 3 to 10dB. Assuming that this hookup makes the amplifier stable,
a gain test can be performed as previously described, but now the loss of the inline attenuator is added to the CableRater reading to obtain the amplifier Gain.
For example, if the CableRater reads 14.0dB, and a 6dB in-line attenuator was
used, the amplifier’s Gain is 20.0dB.
9.8 Testing Distribution System Loss
9.8.1 Signal Level
A Cable TV distribution system is usually designed to apply a signal of 0dBmV to
10dBmV to each TV, VCR, STB (Set Top Box), or other device.
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A 0dBmV signal is the minimum amount allowed by the FCC (Federal Communications Commission). This will produce a good to moderate quality TV picture,
depending upon the specifications of the TV connected to the signal. Some TV’s
can provide good pictures with a -10dBmV signal.
A +10dBmV signal is a ‘hot’ signal, and should provide more than adequate
signal level to any TV and in some cases, may provide too much signal level,
resulting in ‘overload’ of the TV’s tuner. This won’t damage the TV, but it may
produce various interference patterns between different channels (channel bleeding or ghosting), or cause distortion in the picture or sound.
A good signal that will work with almost all TV’s is in the +5 to +10dBmV range.
The distribution system for the TV signal should be designed to place the signal,
at all outlets, in this optimum range. If you are an experienced installer, and
know the typical levels that provide good picture to a TV, you may expand the +5
to +10dBmV range to a range that works well based on your experience. For
example, you may decide that a range of 0dBmV to +15dBmV is acceptable or
-10dBmV to +18dBmV is OK. The wider the acceptable range, the simpler the
system will be to implement. It is also important to know the typical signal level,
measured at the connection to the building, that is acceptable to your Cable TV
Provider. In many localities, it is in the +10dBmV to +15dBmV range.
9.8.2 How much Loss is acceptable?
If the Cable TV Provider typically delivers a +14dBmV signal to the premises,
and a minimum of +5dBmV is desired all outlets the maximum Loss is 9dB
(14dBmV - 9dB = 5dBmV). If the cable runs are relatively short, then a 6 way
splitter (see Figure 7) could be added to supply 6 outlets with a signal of approximately +5dBmV. To test the system for the appropriate Loss, first calibrate
the CableRater Transmitter to the Receiver, then connect the Transmitter to the
splitter input and measure each outlet for Loss with the Receiver. The Loss should
measure about 9 or 10dB.
If a +3dBmV signal is acceptable at the outlets, and cable runs are short, an 8
way splitter can be used (+14dBmV - 11dB = 3dBmV). If cable runs are long,
and more outlets are needed, then an amplifier may be necessary.
9.8.3 How many TV’s are to be connected at once?
Many new houses have cable TV outlets in every room. It is not expected that
every room will have a TV, but it is not unusual for households to have 3 or more
TV’s. Outlets in every room allow the TV’s to be placed anywhere in the household without having to run new wires.
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A ‘star’ or ‘home run’ scheme is often used. A coaxial cable (coax) from each
room is run back to a common point, where the splitters and amplifiers are
located. This might be a Structured Wiring panel or a board attached to a basement wall. In some localities, all of the coaxes exit the side of the house, to a
patch panel that can be serviced without requiring entrance to the house.
It is usually desirable to use a splitter with the minimum number of required
outputs. That is, if you have 3 TV’s, it is usually desirable to install a 3 way
splitter instead of, for example, an 8 way splitter. Because a 3 way splitter has
less loss than an 8 way splitter, using a 3 way splitter will provide a stronger
signal to each TV. An instance in which you may want to use a splitter with more
outputs than is necessary, is if your cable TV provider supplies a very strong
signal that causes your TV to overload. If this happens, installing a splitter with
more outputs will reduce the signal level on each output. Alternately, an in-line
attenuator can be used to reduce the signal level.
9.8.4 Is an amplifier needed?
If a large number of outlets are to be used, a large splitter, like a 16 way or more
may be needed. Use of a large splitter may reduce the signal level below the
minimum acceptable level at each outlet. For example, if the level provided by
the cable company is +10dBmV, and a 16 way splitter is used, with 16dB of Loss
on each output, then, neglecting any cable loss, the level at each TV outlet will be
-6dBmV (+10dBmV - 16dBmV = -6dBmV). If cable Loss is included, the level at
each outlet will probably be a few dB lower. A -6 to -8dBmV signal will probably
produce a poor quality (snowy) TV picture.
There are several solutions to this problem. The Cable TV Provider may be able
to increase the signal level delivered to the premises. Or, an amplifier can be
used to raise the +10dBmV signal level to a higher level before applying it to the
splitter. Figure 10 shows an example of an amplifier connected between the
Provider’s signal and the splitter.
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Figure 10
Amplifier and 16 Way Splitter
The amplifier must have the appropriate Gain to place the signal levels in the
appropriate range. A level towards the top end of the range is desired. Amplifiers
are available in several Gains, or in Variable Gain. Typical Gains are 10dB, 12dB,
15dB, or 20dB. A 15dB amplifier would be a good choice . This would raise the
level at each outlet to about +7 to +9dBmV.
To use the CableRater to test this system, first without the amplifier.. connect
the Transmitter to the input of the 16 way splitter. Then, connect the Receiver to
each outlet and measure the Loss. Its expected to read about -16dB. Next add
the amplifier to the circuit, connect the Transmitter to the input of the amplifier,
and measure the Loss at each outlet. It should read about -1dB.
So, if +10dBmV is applied to the input of the amplifier, about +9dBmV can be
expected at each outlet.
9.8.5 Long Cable Runs
If the length of the coaxial cable run exceeds about 50 feet, from the Cable
Provider’s connection on the outside of the building to the inside TV outlet, the
coax’s Loss must be considered. There may, or may not be splitters or amplifiers in the line. The total length of the cable is what’s important.
Figure 6 shows that the Loss for 100 feet of RG-59 at 60MHz is about 2.4dB.
This amount of Loss is usually tolerable. However, the 900MHz Loss of 10.2dB
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(at 100 feet) must be considered if the Provider has channels reaching up to 100
or more. The difference between the 60MHz and 900MHz levels is called ‘tilt’. In
this case, the tilt is about 8dB in 100ft of RG-59. 50ft of RG-59 would exhibit
about 4dB of tilt.
It is not unusual for the Cable TV Provider to have already introduced tilt compensation to the TV signals. That is, the higher frequencies (channels) will already be adjusted higher in level when delivered to the customer premises. A tilt
of +4dB is typical.. which would compensate for about 50ft of coax. If one considers the AGC circuit (Automatic Gain Control) in all modern TV appliances, the
tilt of an additional 50ft of coax is automatically compensated for. So, depending
on the signal coming from the Provider, it may not be necessary to introduce
any special compensation on up to 100ft of coax... even on a 100 or 150 channel
system.
Systems with a lower number of channels, like 78 or 80 channel systems, often
don’t require special compensation until the coax is longer than 200ft.
If tilt compensation is required, an in-line tilt compensator or an amplifier with a
tilt adjustment can be used. Use the instructions provided with the compensator
for proper use and adjustment.
9.9 Identifying Cables
When a large number of cables have been installed and are unmarked, the
CableRater can aid in identifying the cables. The typical distribution system layout has the ends of all of the cables routed to a central location, and the far ends
of these cables located in the areas where televisions will be connected.
Calibrate the Transmitter as described in 9.4. Estimate the length of cable to be
tested and estimate its loss. For example, a 100 foot cable will have about 2 or
3dB of Loss (see Figure 6). Turn on the Transmitter and connect it to the TV end
of the cable. At the central location, turn on the Receiver and experimentally
connect it to various cable ends. All of the cables, except the one with the Transmitter signal, should measure Underrange.
The measured signal from the Transmitter should show the loss of the cable. If
the loss is higher than the amount attributable to the estimate of cable length,
then there may be a splitter or other device inserted somewhere in the cable... or
the cable may be faulty. If there is a splitter in the cable, then the Transmitter’s
signal may appear on more than one cable. Once you believe you have identified
the cable, turn off the Transmitter and verify that the Receiver reads Underrange.
If you obtain unexpected readings on the Receiver, you may be seeing the effects of Ingress. See section 9.3.
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9.10 Comparing CableRater Readings to Signal Level Meter Readings
The CableRater Receiver is not intended to accurately measure the signal level
of TV signals on a cable system. It is not as accurate as a Signal Level Meter
(SLM) intended for this purpose.
The CableRater does not have the selectivity to measure a single TV channel. It
measures TV Channel 3 and several adjacent TV channels. Because it measures
several channels at once, the measured level is higher than an SLM measurement.
Also, because the CableRater uses a reference level of 10dBmV for its 0dB indication, it starts off reading 10dB lower than an SLM.
In general, because of the difference in selectivity and the reference level, the
CableRater usually reads about 6 to 8dB lower than the actual level of TV channel 3. For example, if the CableRater Receiver reads 0.0dB when connected to an
operating cable TV system, the level of Channel 3 is probably about +6 to +8dBmV.
There are many variables that can affect the reading, so it should be understood
that the reading is a ‘guestimate’.
It is not appropriate to compare the readings of an SLM and a CableRater. The
SLM will undoubtedly be more accurate for measuring the signal level on the
cable. However, if an SLM is not available, the CableRater can be used to make a
comparison measurement between a location known to have good signal level,
and a location in which the signal level is unknown. This will give the user a
rough idea of how the unknown signal level compares to a known good signal
level.
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10: MAINTENANCE
The CableRater contains no user serviceable parts.
To clean the outside of the CableRater, use a cloth dampened with a mild detergent solution. Do not use abrasive cleansers or chemical solvents that may damage the case.
TRIPLETT PRODUCT RETURN INSTRUCTIONS
In the unlikely event that you must return your Triplett equipment
for repair, the following steps must be taken.
1) Call 1-800-TRIPLETT to obtain a Return Material
Authorization (RMA) number from Customer Service.
2) Enclose a copy of the original sales receipt showing
date of purchase.
3) Clearly print the RMA number on the outside of the
shipping container.
4) Return to: Jewell Instruments
850 Perimeter Road
Manchester, NH 03103
ATTN: Repair Dept.
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Triplett One Year Limited Warranty
Triplett / Jewell Instrument s warrants instruments and test equipme nt manufactured
by it to be fr ee f rom defective material or wo rkmanship and agrees to repa ir o r
replace s uch products w hich, under no rmal use and se rvice, discl ose the defect to
be the fault of o ur ma nufacturing , wit h no charge within on e yea r of the d ate o f
original pur chase for par ts a nd labor. If we are unable to rep air or replace the
product, we will make a refund of the purchase price. Consult the Instruction Manual
for instructio ns regardin g the proper use and servicing o f instrument s and test
equipmen t. Our obli gation unde r this warra nty is limit ed to repai ring, replac ing, or
making refund on any in strument or test equipme nt which proves to be d efective
within o ne year fro m the date of original purchase.
This w arranty d oes not apply to any of our products which have been repa ired or
altered by unauthorize d persons in any way so as, in our sole jud gment, to injure
the ir stab ili ty or rel iabil ity, or whi ch hav e bee n subj ect to mis use, ab use ,
misappli cation, neglig ence, accident or which have had the serial num bers altered,
defa ced, or remove d. Acce ssori es, includ ing batter ies and fuses, not of our
manufact ure used wi th this pro duct are no t covered b y this warr anty.
To register a claim under the pro visions of this warranty, contact Triplett / Jewe ll
Instruments’ Customer Service Department for a Return Authorization Number (RMA)
and return instructions. No returned product will be accepted without an RMA
number. Upon our inspec tion of the product, we will advis e you as to the disposition
of your claim.
ALL WARRANTI ES IMPLIE D BY LAW ARE HEREBY LIM ITED TO A PERIO D OF
ONE YEAR FROM DATE OF PURCH ASE, AND THE PROVISI ONS OF THE
WAR RANT Y A RE EXP RESS LY IN LI EU OF A NY OTH ER WAR RAN TIES
EXPRESSE D OR IMPLIE D.
The purchaser agrees to as sume all lia bility for any damages and bodily injury
which may result from the use or m isuse of the product by the purchaser, his
employee s, or others, and the remedies pro vided for in this warranty are exp ressly
in lieu of any other liability Triplett / Jewell Instruments may have, including incidental
or conse quential da mages.
Some states (USA ONLY) d o not allow the excl usion o r limita tion of inciden tal or
conseque ntial damages , so the above limit ation or exclusi on may not apply to yo u.
No represe ntative of Triple tt / Jewell Inst ruments or any other person is authorized
to exte nd the li ability of Triplett / Jewell In struments in connect ion with the sale of
its prod ucts beyond the terms hereof.
Triplett / Jewell Instruments reserv es the right to discontin ue models at any time, or
change specificat ions, price or design, without notice and wit hout incurring any
obligati on.
This war ranty gives you specif ic legal ri ghts, and y ou may have other right s
which va ry from sta te to state .
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