Twenty-five years ago, with regulators and the cable industry struggling to agree on an acceptable use of the aeronautical band, signal leakage was a very hot topic.

The rules that emerged from those days turned leakage into what editors call an "evergreen" topic – suitable for discussion in any of the four seasons.

But change is in the air. Attention to leakage is warming up, if not dangerously cooling down.
All digital? The status quo is well-understood. Cable Leakage Technologies VP Engineering Ken Eckenorth summarized the regulatory regime in the March 2007 issue of CT:

"Since 1985, cable operators must completely drive out their plant four times a year, logging all leaks 20 µV/m and above. Since 1990, we must conduct a drive-out of at least 75 percent of the plant and file a CLI (cumulative leakage index) report to the FCC showing all leaks 50 µV/m and above, indicating which leaks are repaired and their locations. As an alternative to the annual rideout, a flyover of the plant is permitted."

(For more, click here.)

Operators can now file Form 320 electronically, but the meat of these rules hasn’t changed.

What happens, however, in an all-digital world, or in a scenario where channels within the aeronautical band go digital?

"When signals are digitized, they use more of a spread spectrum type of signaling modulation," said ComSonics Director of Marketing Ken Couch. "What happens is the signaling level falls below the general FCC requirements."

Will all digital lineups accordingly presage an end to concern over leakage from these particular (108-137 MHz and 225-400 MHz) frequencies?

Not so fast, said Couch. First, the FCC may stay involved, perhaps with network health requirements that incorporate leakage measurements. Second, as is generally recognized, a cleaner pipe and tighter (with minimal signal egress or ingress) plant correlates with more and better services. Just a sliver of analog Proactive maintenance is an even bigger hurdle than quarterly filings. "The technology is easy; it’s the process that’s hard," said Couch. "Sometimes we’re successful in helping the MSO, and sometimes it’s a real slow, grinding process because they’re … often not able to quickly migrate resources and change over."

A crucial component of the currently "easy" technology that enables operators to measure the health of their plant could be at risk of disappearing. Couch is on a mission to remind operators who are allocating spectral use in ongoing analog reclamation projects not to eliminate every analog signal capable of triggering their installed infrastructure of test equipment.

"By the way, it’s not even a channel, it’s a sliver of a channel," Couch said.

Admitting that he would love to sell millions of dollars’ worth of equipment to solve the problem of testing digital signals, Couch said the reality is that operators can’t afford that approach, and that all it takes is a little proactive thinking now.

For more on leakage testing, see the November and forthcoming December issues of CT.

– Jonathan Tombes

Read more news and analysis on Communications Technology‘s Web site at

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