If your grandma’s TV goes dark on Feb. 17, you can thank Republicans in the House of Representatives, who have effectively killed off an attempt to postpone the switch to all-digital television by four months.

The measure, already approved unanimously by the Senate, had plenty of votes to pass in the House under normal circumstances. But yesterday’s  215-to-168 margin, largely split along party lines, was shy of the two-thirds majority needed to pass the bill immediately as a special measure.

If House Democrats backed by the Obama administration decide to try again, the measure delaying the switchover till June 12 could come up again next week as a regular bill – with passage virtually assured. If it doesn’t, the analog TVs in an estimated 6.5 million households will become doorstops on Feb. 17 when broadcasters turn off their analog transmitters in favor of a new generation of digital broadcasts.

Congress set the official Feb. 17 deadline back in 2005, when it also established a $1.34 billion program to provide $40 coupons to help Americans offset the cost of converter boxes that will allow  existing analog TVs to receive digital broadcasts.

This was not exactly an act of largesse, considering that the entire switchover scheme was forced on an unsuspecting public in 1996 by a bipartisan cabal of lawmakers, bureaucrats, cell phone companies, broadcasters and overseas TV equipment makers who saw an opportunity to pick our pockets in the name of technological progress. There was virtually no consumer demand for digital TV, and the most of the billions of dollars consumers have spent on new digital equipment to deal with the switchover have gone to bolster the bottom lines of foreign manufacturers — and increase an already staggering U.S. trade deficit.

Making a bad situation worse, the coupon program ran out of money — or depending on how you look at things, the program can’t use a big chunk of the money appropriated for it until unused coupons it has already issued reach their 90-day expiration date. New coupons can then be sent to millions on of Americans who found themselves on a waiting list, but few are likely to get them by the Feb. 17 cutoff.

Most of the 6.5 million households that will go dark are occupied by the poor and elderly. These constitutencies haven’t exactly turned out in droves for Republicans in recent elections, which may explain the GOP’s willingness to cut them off. In fact, Republicans opposed Democratic attempts to provide more money back in 2005 when the transition legislation was enacted. So it seems ab it strange that a group of GOP lawmakers has sponsored a bill providing an extra $250 million for converters now that it’s too late. Conscience money? Or am I just a cynic?

On the other side of the issue are most of the nation’s commercial broadcasters, who have been transmitting on both analog and digital systems for years and are anxious to turn off their expensive, power-hungry analog equipment. Many haven’t budgeted money to continue dual transmissions after Feb. 17 (although a lot of skeptics like me have predicted just the kind of imbroglio that’s now occurring).

Caught in the middle are the nation’s public television stations. Like their commercial counterparts, they’re spending big bucks they’d rather use elsewhere on electricty to keep both broadcast systems running. But since the elderly make up a disproportionate chunk of their audience (they love PBS news and watch it over analog TVs with antenannas), public stations are likely to suffer the largest proportional loss of viewership when the switchover actually occurs.

Meanwhile, no one knows how many millions of sets — either native digital models or analog sets with converters — will lose at least one of the stations its owners now receive. When you get to the bottom line, digital signals aren’t as powerful as analog broadcasts — and they’re more subject to crosstalk and interference from hills, towers and tall buildings. In my tests with a variety of equipment in several locations around Baltimore and Washington, I couldn’t find a single combination of TV, indoor antenna and coverter box that consistently brought in all the digital stations that were available in analog. That may generate even more complaints than the lack of converter boxes.

Stay tuned!