By Rob Pegoraro
Sunday, January 25, 2009

QYou wrote that the digital-TV transition has nothing to do with cable TV going from analog to digital, but my cable company seems to disagree. What's the real story with digital cable?

ADigital cable, in which TV programs are compressed and encoded as a stream of ones and zeroes before being sent over cable lines, isn't new. Cable operators have been adopting it not because of the over-the-air DTV transition -- remember, they don't use the regular TV airwaves -- but for the same reason that wireless-phone carriers ditched analog cellular: digital uses much less of their bandwidth.

But the movement of many popular basic-cable channels from analog to digital is a more recent development.

This represents a problem for viewers with older cable-ready TVs, who now must rent a digital cable box. Many digital sets include a quadrature amplitude modulation (QAM) tuner that can receive unencrypted digital cable signals without a box, but these sets can have problems detecting available channels on a cable system's digital feed.

A second problem arises when cable companies suggest that their digital transition has been forced by the over-the-air DTV switch -- an argument as illogical as blaming digital migrations on the Redskins' late-season collapse. Herndon-based RCN, which provides service in the District, Montgomery County and Falls Church, has been the source of many such complaints from readers. RCN spokesman Michael Houghton said the company has "had relatively few issues of this type," considering the magnitude of its move to an all-digital system.

"We've cautioned all our members . . . to be very clear about not using the broadcast transition as a way to justify the migration of cable channels," wrote Brian Dietz, a vice president for the National Cable and Telecommunications Association.

Rob Pegoraro attempts to untangle computing conundrums and errant electronics each week. Send questions to The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or Turn to Thursday's Business section or visit anytime for his Fast Forward column.

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