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Commonly Asked CLI and Form 320 Questions

Q:  How often do I need to perform the CLI test?
A:  You must perform CLI testing once a year and at an interval of no more than 12 months (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) must 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.  Form 320 must be filed electronically via COALS (Cable Operations and Licensing System) on the FCC website.

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:  Conduct a single CLI test for all communities served from a single headend (PSID) and all the leaks found must be combined on a single Exhibit B or Exhibit C.  The CLI result cannot be calculated on a CUID basis, unless the test encompasses only a single community.  The electronically filed FCC Form 320 should list all CUID's served from the principal headend headend (PSID).  Where a single community unit is served by multiple headends, the operator is required to register a separate CUID (and PSID) for the area within the community unit served by each headend.

Q:  Can I combine multiple headends for one test result?
A:  The signal leakage test must be performed for each cable system (PSID) — usually one headend, one test result.  A technically integrated system, however, may have more than one headend, but only one principal headend — and only one PSID.

Q:  What is a Physical System Identifier (PSID) and how is that related to Form 320?
A:  A PSID is a number that is assigned to each cable system's principle headend.

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.   The test, therefore, 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 prefer that the test frequency be in the 108-137 MHz band.  Because the strength of the leak is frequency dependent, use of any frequency outside of this band means that the strength of each leak must 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 formulas can be found in Section 76.611(a)(1) of the rules.  Click here for a sample calculation of 10 log I∞ or 10 log I3000.  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.  The hubs are considered part of the system to which they are technically integrated—receiving 75% or more video signals from the same 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.

FCC Media Bureau > Engineering Division

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