So far, practically all the digital transition "buzz" has been focused on avoiding the trauma that would be suffered by the "poor little old ladies" vainly wiggling their rabbit ears atop their 1975 Zeniths and getting no picture (or sound) on February 17, 2009.

Yes, I'm sure there will be a few of those. But there will be a lot more, and very vocal, "little old ladies" who already have digital reception capability (HDTV or otherwise) who will be shocked on Feb. 17th to find out they are not receiving one of there favorite DTV channels, and many of these "little old ladies" will be us. This will be a small problem, and it will be easily fixed. Here is the scoop:

As we know, on February 17, 2009, virtually all TV stations will switch to the digital format (except for some LDTV stations and translators). What is not readily known is that some digital stations in a few major market areas will also switch digital channel frequency assignments. Some will also change transmitter sites and signal coverage parameters. But these are of minor significance relative to the digital channel assignment changes.

The source of this minor "glitch" surrounds the TV receiver's built-in automatic channel guide system. When first turned-on after installation, the initial channel search system places, either prompted or automatically, into memory all the received digital (and analog) channels. To maintain station numeric identity with that of their analog channels, the stations transmit mapping tables, along with other metadata, for each active digital channel.* So let's say, if a station's analog channel were 4 and its digital channel were 25, the transmitted tables "map" channel 25 to channel 4-1, or if there were more than one multiplex, to 4-1 and 4-2 etc. In this manner the user need not be required to remember a station's digital channel assignment number. When the user selects 4-1, the tuner automatically tunes to channel 25. These channel maps are stored in the set's tuner channel selection memory.

Now, if, on 2-17-09, our channel 4 assumes a new digital channel, say 41, the TV set still "thinks" that it should tune to 25, and the viewer gets a blank screen. Most alternate suppliers of TV signals (such as cable or satellite providers) will be prepared for any such channel change and will switch accordingly so the viewer will see no changes. However, most TV sets and, of course, other devices with digital tuners receiving off-air signals will require a "Channel Search" be initiated in order to detect the new channels and acquire new channel maps. "Channel Search" or "Channel Scan" is normally a secondary menu selection usually found under the Set-up menu list.

Of course, most digital channels will remain as they are now, and thus this re-mapping problem will be minor, but, no doubt, will generate a few panic calls.

* Technically these tables are part of a metadata package call "Program System Information Protocol" or "PSIP," (pronounced "pee-sip").

Posted by Ed Milbourn, June 19, 2008 9:38 AM