“Cumulative Leakage Index”What? Why? Who? Where? When? And How?
Listen for answers to these questions…What is CLI? Why do I need to be concerned with CLI? FCC ---who are they and why are they involved? Why keep leakage logs? What’s a microvolt? What is noise and how can it impact customers? Is there a direct correlation between CLI and
other distortions? Why is the customer's home a major contributor
to system problems? Why is proper cable and connector craftsmanship
so important?
What is Leakage?*Cumulative Leakage Index (CLI)CLI is the net effect of the combination of all
the leaks in the system added together =the amount of radio frequency (RF) signal that escapes or infects the cable system
These cumulative leaks form an invisible cloud of unwanted RF energy over the cable system
Leakage results from:Improper cable installationcomponent corrosionpoor product designVandalismcable breakspoor connections
Two types of leakage: Egress and IngressEgress= RF signal leaking out of the cable system
Damaged cableImproperly installed cableSignal escapes and follows the path of least resistance
including free space (air), strand, power and phone linesIngress= RF noise or interference that leaks into the
cable system through a break or external leak (loose connectors)Hair dryers, microwaves, radios, etc.Feeds into the coax drop from bad TV’s, long center
conductors, amplifiers, jumpers, customer equipment (VCR)
Ingress/EgressIngress:RF signal leaking into the coaxial plant
Egress:RF signal leaking out of the coaxial plant
Why Is It Important to Determine Leakage?Cable television systems and licensed over-the-
air broadcasters use many of the same frequencies to transmit programming. Specifically, cable systems use TV, radio and aeronautical radio channels, among others, within their cable plant.
Cable operators are considered the secondary users of these frequencies; therefore they must not interfere with the licensed over-the-air users who are the protected (primary) users of these frequencies.
What Problems Can Signal Leakage Cause? Cable signal leakage can interfere with any of
the over-the-air services that happen to be using the same frequencies as the cable operator and that are within the vicinity of the cable system.
Such interference, especially on the emergency channels, can interfere with the communications of safety personnel or airplane pilots.
When such interference occurs, it can endanger the lives or hamper the rescue efforts of safety personnel.
What are the FCC Rules Governing Signal Leakage? The FCC (Federal Communication Commission)has
set maximum individual signal leakage levels for cable systems.
The FCC sets even more stringent limits for cable systems that may interfere with aeronautical and navigation communications.
As a further measure, the FCC requires cable operators to have a periodic, on-going program to inspect, locate and repair leaks on their systems. –FCC files include:CLI quarterly ride outs (100% of system & log all leaks)Annual Flyovers (report on form 320)Daily Leakage Logs (date found/date repaired)
Can the Cable Company be penalized if it fails to control CLI?
4/17/2012
Pays to keep the system clean… In this Notice of Apparent Liability for Forfeiture (NAL), we
find that Cebridge Acquisition, LP (Cebridge), operator of the cable television system in Honey Grove, Texas, apparently willfully violated Sections 76.605(a)(12) and 76.611(a)(1) of the Commission’s rules (Rules),[1] by failing to prevent excessive signal leakage in the Honey Grove cable system. We conclude that Cebridge is apparently liable for a forfeiture in the amount of eight thousand dollars ($8,000).
Quarterly CLI Drive Out Results
Unauthorized Connection 1333 44.7%
Loose F Connector 426 14.3%
Loose Terminator 185 6.2%
Replace Connector 142 4.8%
No Fault Found 415 13.9%
It is a shared responsibility across Operations and Engineering.
Five Steps in Leakage AbatementDetectionLocationMeasurementCorrectionRe-measurement
Detection (What do I need?)Carrier Generator- a unique frequency
inserted by the headend that can be recognized by the leakage detector tuned to the carrier’s frequency
Leakage Detector- (Seekers’, Searchers’, Sleuths’)-provided and used by all technicians to detect leaks in the free space where RF energy is encountered
Calibrating Leakage Equipment1.Connect calibrated signal source set at 20 uV/m.2. Position the dipole antenna.3. Adjust to read 20 uV/m.
Identify the precise Location of the leak with your Leakage Detector
Hand Held Detectors Check the battery voltage, insure the unit is
charged before you proceed to isolate the leakListen to the audible alarm indicator as you
proceed to isolate the leak sourceIncreases in the tone pitch indicate you are closer
to the sourceDecreases in the tone pitch indicate you are
moving away from the leak sourceFollow the manufacturers recommended mode to
identify the leak sourceOnce the leak is identified to a pole, cable, or a
home, follow standard troubleshooting procedures until the leak is within compliance
Measurement-rules of engagementOnce a leak is located it must be
measuredμV/M What is a microvolt per Meter?
Standard unit of measure for CLI 50 Ohm off air measurementVoltage developed in 1 meter of infinitely thin
section of wire submerged in a leakage field produces 1μV of energy
All leaks greater than 20 microvolt's MUST be repaired per FCC rules
Any leak greater than 50 microvolt's MUST be repaired IMMEDIATELY per FCC rules
Measurement-rules of engagement (cont.)
Only leaks above 50 μV/m are used in CLI calculation
All measurements taken outside 108-137 MHz must be converted as if they were taken within the band
Leakage Detector-measures the level of the leak Take the reading at about 10 feet (3 meters)Repair itRe-measure
Measurement-rules of engagement (cont.)
Use a calibrated halfwave dipole antennaAntenna must be elevated 3 meters off the
ground and positioned 3 meters from the leakage source
Antenna must be rotated 360º in the horizontal plane for maximum reading
Turn on your Leakage Detector!
Measurement-Why do we care?
1. Meet FCC Compliance2. Prevent Off-Air Interference
Aeronautical & Aircraft CommunicationsAmateur Communications Broadcast TV signals (Analog & Digital)Public and Emergency Communications Radio Mobile Communications
Measurement-Why do we care?
3. Improves System PerformanceReduces Repeat Service CallsLocate Physical problems
Correction of Leak80% of all leakage is caused by problems
from the tap to customer equipment Common Causes of Leakage-
Loose drop connectorsImproperly installed connectors Inferior quality coaxial cable, passives, or
connectorsPoorly-shielded drop cablesBad connectors at the tapsBad/loose port terminators Corroded connectors
CorrectionCommon Causes of Leakage-cont.Cracks in the trunk and feeder cablesAnimal chews Physical trauma to cables or connectorsAging and environmental stressLoose hard line connectors
CorrectionCommon Causes of Leakage-cont.Customer installed equipmentDamaged amplifier housingsLoose amplifier housing lidsBroken tap portsPoor installation of splices and connectors Poorly-shielded customer premise equipment
Ingress impacts on Digital ChannelsMacro Blocking (Tiling)Freeze FramePicture and Sound go to blackRobotic VoiceData Packet Loss or slower speedsRepeat Service Calls
Ingress impacts on Analog ChannelsLines in pictureGhostingPay-per-view problemsInterference with two-way radio services
using the same frequenciesRepeat Service Calls
CorrectionRepair the leak- determine the root cause and
use TWC procedures to implement proper restorationTighten or replace connectorsReplace cracked or damaged cableTerminate open ports with 75 ohm terminatorsCorrect customer created issues (replace
splitters, self-run inferior cable)Properly terminate unauthorized connections
and report theft of service to Audit/Security operations
Audit/Security ProcessInsert your local process and contact
information
Re-measurementTake a final reading using the same
equipment and record the corrected CLI calculation (reportable to the FCC)
If the leak is still above 20 microvolt's it is NOT repaired (incomplete diagnosis-reengage)
Work the issue backtracking all the cable and connections
Correct issue until leak is under 20 microvolt's
CLI tipsTurn on your CLI equipment and use
properlyRecord/Repair/Re-measure your leaksTighten all connectorsUse PPC Signal Tight Connectors indoorsProperly terminate open portsDisconnect unauthorized drops and properly
terminate
EX vs EX PLUS G2 Comparative.wmv
Benefits of CLI programReduced ingress/noise in the plant (SNR)Increased plant performance (FEC)Better CPE performance thus improved
Whole House CheckReduction in Trouble Calls (TC to RGU
and rework)Customer Satisfaction!
Be careful using the word “radiate.”
(Q & A’s from the FCC website)
FAQ’s from the customerDoes a Cable Operator Need to Come into My
Home to Monitor for Signal Leakage?Usually, no. Cable operators can use equipment to
locate the general area of a leak. To pinpoint a leakage source for subsequent repair, however, the cable operator may request access to your home.
Am I Required to Let the Cable Operator into My Home to Monitor for and Repair Signal Leakage? Homeowners have the right to deny access to their
premises. If a leak cannot be repaired without access to your home, however, a cable operator can disconnect your service for denied access.
FAQ’s from the customer (cont.)Can My Cable Operator Terminate My Service
Because of Signal Leakage? The FCC’s rules allow cable operators to
disconnect service in order to repair signal leakage that exceeds FCC standards. The operator restores service when the signal leakage problem is remedied, and may not charge you for service while it is disconnected.
Is the Cable Operator Responsible for Repairing Signal Leakage on Subscriber-owned Equipment? No.
FAQ’s from the customer (cont.)Can I Hook Up a Second Set Myself?
In terms of the signal leakage rules, yes, but because the cable operator is responsible for leakage from the wiring, the operator can either refuse to connect to it or terminate service if the hook up causes signal leakage problems.
Is Signal Leakage Biologically Harmful? The power levels used in a cable system are
low. Therefore, it is unlikely that cable signal leakage from a cable facility will exceed the FCC’s RF allowable limits for RF exposure.
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