NCT4 Leakage Flashcards
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?
1990
Define CLI
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.
76.610
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.
76.611
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 must
be offset by 25 KHz, ± 5 KHz.
76.612
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.
76.613
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.
76.614
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.
76.615
What section of the Code of Federal Regulations is this?
This section covers restrictions on carriers near certain emergency radio frequencies.
76.616
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.
76.617
What is a closed system with regard to CLI?
A system in which transported signals are completely contained within the medium.
