Flashcards in leakage Deck (38)
What 3 things can disturb shielding in coaxial cable to cause leakage?
Damage, corrosion or faulty installation
In what city and year did an incident occur that prompted the FCC to establish new rules regarding leakage?
Harrisburg, PA, 1976
In what year did the FCC begin to require cable systems to perform annual CLI tests?
A figure of merit derived mathematically from the number and severity of signal leaks in a cable system.
What recourse does the FCC possess to enforce compliance with leakage rules?
They can impose fines and shut down portions of the bandwidth.
In what document does the FCC describe signal leakage rules?
Code of Federal Regulations, Title 47, Telecommunication, Part 76, Cable Television Service
What section of the Code of Federal Regulations is this?These rules cover the basic requirements for the aeronautical frequency bands 108 to 137 MHz and 225 to 400 MHz. The rules in this section apply to anyone using these frequencies and that have carriers at a level of +38.75 dBmV or higher.
What section of the Code of Federal Regulations is this?These are special requirements over and above the general requirements. This section spells out the CLI requirements by stating that a cable system must either use a ground based test and measurement system, or perform a flyover once a year. If the ground based system is used, it must cover at least 75 percent of the entire network. It must also include older portions of the network that might be expected to have a higher level of signal leakage. The flyover would include the entire system.
What section of the Code of Federal Regulations is this?The rules in this section establish the frequency offset requirements. Because the aeronautical radio communications bands' operating frequencies are spaced at 25 KHz intervals, the cable carriers must be offset by 12.5 KHz, ±5KHz in order to fall midway between those channels. The aeronautical navigation frequency carriers are spaced at 50 KHz between carriers. For this reason, the cable signals using this portion of the spectrum mustbe offset by 25 KHz, ± 5 KHz.
What section of the Code of Federal Regulations is this?This section covers harmful interference caused by a cable system, and states that a system must take immediate measures to correct a problem, or shut off the offending carriers.
What section of the Code of Federal Regulations is this?This section tells us that a substantial portion of the network must be monitored every 90 days. It also states that every leak in excess of 20 microvolts per meter should be entered into a signal leakage log that must be kept of file for a minimum of 2 years. The Signal Leakage Log includes the location of each leak, date found, cause, and date repaired.
What section of the Code of Federal Regulations is this?Whenever the cable operator adds a channel or changes the frequency offset of a channel in the aeronautical bands, the operator must notify the FCC prior to making these changes. The operator must also file an annual report on each channel carried in the aeronautical bands. This information is included in the FCC form 320 that must be completed annually. The operators must also submit either a CLI report or a flyover test result that includes descriptions of testing methods used, and the method used to calibrate the test equipment.
What section of the Code of Federal Regulations is this?This section covers restrictions on carriers near certain emergency radio frequencies.
What section of the Code of Federal Regulations is this?Here, we are told the cable operator accepts responsibility for ensuring that any devices attached to the cable system meets the requirements of the FCC rules. This includes hotel distribution system, customer owned devices, etc. If the customer does not correct the problem, the cable operator must disconnect service from that device if it is causing an out of tolerance leak.
What is a closed system with regard to CLI?
A system in which transported signals are completely contained within the medium.
What are the most common services impacted by excessive ingress?
Upstream online and telephony services.
How can connectors cause leakage in a cable system?
They can become loose or corroded over time, or they were improperly installed in the first place.
In order to prevent signal leakage and physical damage to the network, you should have a maintenance program that includes what?
Checking the insides of devices for moisture or water damage whenever they are open, and tightening all hard line and F-connectors whenever you are working on the coaxial plant.
Name 5 environmental factors that affect signal leakage.
Lightning, UV rays, solar emissions, temperature fluctuations and static electricity
What is the maximum variation that can be caused by seasonal and diurnal temperature changes?
How does UV radiation impact the durability of cable in our system?
It breaks the bonds holding the molecules together in the jackets of coaxial and fiber optic cable.
What is the impact of solar emissions in cable systems?
It can cause the noise floor to rise, and may induce mirror currents in coaxial cables.
What is the impact of lightning in cable systems?
It may induce an electrical surge in the cable, which must be shunted to earth ground.
What frequency range does LTE operate in?
700 to 800 MHz
What FCC protections does Comcast have with regards to LTE ingress?
What can a LTE provider do if they discover LTE egress coming from our system?
They will contact us, and if we do not repair it, they can file a complaint with the FCC.
What can make a STB or modem susceptible to LTE interference?
Plastic cases with air holes for circulation.
What is a passing Figure of Merit CLI Score?
Anything less than or equal to 64.
What form is used to file the Annual CLI Calculation?
What is the minimum leakage level that a leakage meter must be able to detect?
20 ìv/m @ 3 meters, or its equivalent
What should the power level be of the CLI test signal?
The test signal should have an average power level equal to the average power level of the strongest carrier on the system
Name 3 methods to calibrate a leakage meter.
Performed by manufacturer, direct coupling, or antenna
What is the preferred method for leakage meter calibration?
Performed by manufacturer
Per FCC specification, where should the dipole be located to accurately measure a leak?
10 feet from the cable plant, 10 feet from the ground, at least 10 feet from other conductors
What 7 things should a System Leakage Log include about a leak?
Date found, location, cause, strength, distance to leak, date repaired, strength after repair
What is the FCC standard for percentage of plant to be tested on a ground based test?
What is the Comcast standard for percentage of plant to be tested on a ground based test?