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Signal Leakage              

 Signal Leakage Report (Form 320)     Filing Instruction      Where to send Form 320     CLI Rules
 Multichannel Video Prog. Distributor (MVPD)     filing CLI (Form 320) for MVPD     Where to send Form 320     MVPD Rules

      Commonly asked CLI and FCC Form 320 questions.

     Q: How often do I need to perform the CLI test?

     A: CLI testing must be performed once a year and at an interval of no more than 12 months apart (i.e. the next CLI test must always be completed within 12 months of the completion date of the previous years test).

     Q: When must the FCC Form 320(s) be filed with the Commission?

     A: FCC Form 320(s) are to be filed once each calendar year. This means that a cable system has until the end of December each year to file the FCC Form 320. However, FCC Form 320(s) should be filed within 45 days of completion so that the most current CLI information is on record at the Commission.

     Q: If my headend serves multiple community units (CUIDs), how should the CLI test be performed and how should the FCC Form 320s be filed?

     A: A single CLI test must be conducted on all communities served from a single headend and all the leaks found must be combined on a single Exhibit B or Exhibit C . The CLI result can not be calculated on a CUID basis, unless the test only encompass a single community. The same Exhibit A and Exhibit B /C can be attached to the completed FCC Form 320's for all CUID's served from the common headend. All testing information on the FCC Form 320s should be identical (i.e. testing dates, miles of plant and miles of plant tested, etc). Where a single community unit is served by multiple headends, the operator is required to register a separate CUID for the area within the community unit served by each headend .

     Q: Can I combine multiple headends for one test result?

     A: In general, the signal leakage test must be performed for each cable system (i.e. one headend, one test result).

     Q: What is a Physical System Identification (PSID) and how is that related to Form 320(s)?

     A: A PSID is a number that is assigned to each cable system's principle headend. Since CLI demonstrates signal leakage compliance for the cable plant, ALL community units served by the same headend should be included in the CLI calculation.

     Q: How much time am I allowed to perform my CLI test?

     A: The CLI test represents a summation of all leaks found from a cable system at a moment in time. Therefore, the test should reflect only the time that it takes to drive out the system plant, find leaks and record them. The maximum time allowed is 90 days which coincides with the time period for a quarterly monitoring drive out.

     Q: What frequency should I use for CLI testing?

     A: The Rules require the test frequency to be in the 108-137 MHz band. Because the magnitude of the leak, measured at 3 meters (10 feet), is frequency dependent, use of any frequency outside of this band requires that the magnitude of each leak be correlated to what the leak size would be if measured with a carrier in the 108-137 MHz band.

     Q: Should I offset the test frequency?

     A: Yes, because the test frequency could potentially interfere with aircraft and other over-the-air communications.

     Q: Show me how 10LogI infinity and 10LogI3000 is calculated?

     A: There are two methods for calculating the ground-based Cumulative Leakage Index (CLI). The formulae can be found in CFR Part 76.611(a)(1). Click here for a sample calculation of 10LogI infinity or 10LogI3000. Or, use the CLI calculator to get results on line.

     Q: Can I separate out microwave hubs?

     A: That depends on whether the hubs are served from a common headend. Special circumstances may exist where an AML receive area should be viewed as a separate CLI testing area. In these cases you will need to include in the filing your reasons for separating the tests. Also, you may want to contact the Commission to determine whether you have a proper justification for performing separate tests.


For comments or questions pertaining to Engineering Division web pages, send e-mail to the Media Bureau, Engineering Division Webmaster at: Walid.Kassem@fcc.gov. Questions can also be answered by calling the FCC's National Call Center, toll free, at 1-888-Call FCC (1-888-225-5322).

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