Today, most sets sold still receive only analog broadcasts, missing out on the visual and sonic excellence of high-def TV.

The plasma and LCD HDTVs that dominate high-end electronics stores are sometimes scarce at mass-market retailers– at the Target store in Seven Corners on Thursday night, a measly one HD set was on display.

But if you’re buying a TV set, it’s now time to think about getting a digital model.

One reason is the steady march of TV technology, which has driven prices of tube-based digital sets to below $500. HDTVs are becoming more of a commodity, so you’re no longer in serious danger of buying a set and finding that next year’s model works radically better.

Another reason is the increasing quantity and availability of HD programming via cable, satellite or free, over-the-air broadcasts. (Digital TV can be provided in lower-quality forms than HD, but those lesser formats are little used, making “HD” essentially synonymous with “digital.”)

But the biggest reason to think digital is that analog television’s days are numbered. Those signals almost certainly will vanish from the airwaves by the end of the decade, and possibly a lot sooner.

The rush to ax analog comes because digital and analog broadcasts use different frequencies, and the government won’t let TV stations keep both. It plans to auction some analog frequencies to other telecom users — thus covering a tiny bit of the ballooning federal debt — and hand others over for use by police, firefighters and paramedics. Congress originally placed a conditional Dec. 31, 2006, deadline that no one in the industry thinks will happen, but is now looking at ways to set a later, unconditional deadline.

If TV sets had the life spans of computers, that wouldn’t be a problem. But people routinely keep TV sets for a decade or more. An analog set bought today will easily spend more than half its life needing to be hooked up to a converter box to receive any over-the-air broadcasts.

It will still work with cable or satellite boxes as before — but as high-definition content inevitably becomes a standard feature instead of a premium add-on, you’ll wind up paying for things you cannot watch.

A digital TV will cost more now, but it should be a better value over time. Unfortunately, picking out a digital set still requires detective work. Four important factors are either well-hidden or absent entirely in ads and retail presentations.

More here.