Campus Cable TV Signal Leakage:
What’s The Story,
and What Should We
Be Doing About It?
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Disclaimer:
The opinions expressed by the presenter during this
presentation do not necessarily reflect those of The
Georgia Institute of Technology, Campus Televideo,
The Association of Higher Education Campus
Television Administrators, or the Peabody Hotel.
(But they should.)
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Signal Leakage: Types
• Don’t use the “R” word. (Radiation)
• Ingress:
Unwanted RF signals getting INTO the Cable System.
• Egress:
Unwanted RF signals getting OUT of the Cable System.
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Signal Ingress:
• RF signals outside the cable at or near the same
frequency of the RF signals on the cable will
cause problems with the RF signals on the cable
if they can get in.
Analog
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Digital
Cable TV Shares the Spectrum With Off-Air
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Signal Egress:
Channels 95 through 22 added in the 1970’s
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Signal Egress: Air Distress Frequency
(121.5 MHz)
1984 FCC begins Signal Leakage Monitoring
Requirements for Franchised Cable TV Systems
Frequency offsets added in 1989.
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Signal Leakage: (CLI) Cumulative Leakage Index
FCC begins CLI in the 1990’s.
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Signal Leakage: Cumulative Leakage Index
What does this have to do with Me?
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Signal Leakage: Cumulative Leakage Index
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Signal Leakage: Cumulative Leakage Index
(MVPD=Multichannel Video Programming Distributor)
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Signal Leakage: Cumulative Leakage Index
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Signal Leakage: Cumulative Leakage Index
So what does this
mean?
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Signal Leakage: Cumulative Leakage Index
CFR 47 Part 76, 76.605(a)(12), 76.610-76.614,
76.616, 76.617, 76.1706, 76.1803, 76.1804
Prior to the use of signals in the aeronautical radio
bands, and at least once each calendar year,
CATV systems, MVPDs, and Non-Cable MVPDs
must comply with FCC requirements for
signal egress.
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Aeronautical Frequencies
108 MHz
137 MHz
Channels 98, 99, 14, 15, & 16
225 MHz
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Channels 24 thru 53
400 MHz
Aeronautical Frequencies
• CFR 47 76.616 (b)…”The transmission of digital
signals in this range is limited to power levels
measured using a root-means-square detector of
less than 10-5 watts (+34 dBmV) in any 30 kHz
bandwidth over any 2.5 millisecond interval.”
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Signal Leakage: Cumulative Leakage Index
What do I
need to do?
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Signal Leakage: Cumulative Leakage Index
If you are going to use the
aeronautical channels…
Consult with your Legal department.
Get FCC forms 320 & 321 in order.
(More on this later)
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Signal Leakage: Cumulative Leakage Index
If you are already using the
aeronautical channels…
Consult with your Legal department.
Get FCC forms 320 & 321 in order.
(More on this later)
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Signal Leakage: Cumulative Leakage Index
• Acquire Commercial Signal
Leakage detection equipment.
(Make a “calibrated leak”.)
• FM Radio
• Contracted Fly-Over
or Ride-Out
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Signal Leakage: Cumulative Leakage Index
At least 75% of the oldest part of the cable system
needs to be tested every year.
All Signal Leaks measured at more than 20 micro/V
per meter @ 3 meters (10 feet) must be repaired.
All Signal leaks measured at greater than 50 micro/V
per meter @ 3 meters must be logged for CLI
calculation.
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Calculating CLI
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Calculating CLI
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Egress:
Where does Egress come from?
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Signal Leakage: Egress:
How does it get out?
• A lack of proper System Maintenance.
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Signal Leakage: Egress:
How does it get out?
• Loose or improperly made connectors.
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Signal Leakage: Egress:
How does it get out?
Cracks in the Cable Shield.
• How old is your mainline coax?
(Coax older than 15 years is very prone to shield defects.)
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Signal Leakage: Egress:
How does it get out?
Attempted signal theft.
Roughly 75% of all cable signal leakage occurs
between the Tap and the Television.
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In case you’re Wondering…..
“What if I don’t comply?”
(aka: “I’ll take my chances.”)
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Reminder…
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Q&A
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Penalties
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The Bottom Line…
File it.
(FCC Form 321)
Find it.
Fix it.
Report it.
(FCC Form 320)
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Questions?
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