FCC Form 320 contains a snapshot of the interference potential to aircraft communications and navigation over a cable system's distribution plant. Cable operators have the option of performing either the ground based Basic Signal Leakage Report (CLI) (10 log Iinfinity  or 10 log I3000 ) or airspace measurement. In either case, the test result should show compliance with the basic signal leakage criteria outlined in 47 CFR Section 76.611. The test equipment used must be capable of measuring leaks of 20 µv/m @ 3 meters or its equivalent, and the test frequency must be within the VHF aeronautical band of 108-137 MHz or a frequency in which the results can be correlated to that band. The test signal used shall carry an average power equal to the average power level of the strongest carrier on the system. The accompanying exhibits shall include a list of all aeronautical frequencies used (Exhibit A) and information on the test measurements including a list of all leaks 50µv/m or greater detected for ground based measurements, (Exhibit B) or information on airspace tests (Exhibit C).
- Click Here for On-line CLI Calculations 
- File Form 320 Electronically 
- Commonly Asked CLI and Form 320 Questions 
- Basic Signal Leakage (CLI) rules 
If you have any questions on Signal Leakage report (CLI), please call (202) 418-7000.
- Registrations and operational change inquiries: Jerilyn Harris 
- Basic signal leakage and non-cable MVPD inquiries: Carol Thomas 
- Aeronautical frequency notification inquiries: Jerilyn Harris 
- Cable Television Relay Service (CARS) inquiries:
- MVPD technical inquiries only: Walid Kassem 
- Non-MVPD technical inquiries: FCC Bureaus 
If you have been contacted by FCC staff by phone or by letter regarding a registration, aeronautical frequency notification, basic signal leakage performance report (CLI) or CARS application requesting more information, unless otherwise directed, please send all requested information to the address below with the reference number and the name of the person requesting the information for faster processing.
Name of Person Requesting Information
Federal Communications Commission
Media Bureau, Engineering Division
Washington, D.C. 20554