Electronic Design

The DTV Transition: Will It Happen? What Can We Expect?

Since 2005, we have been hearing that analog TV will go off the air on February 17 and that high-definition digital television (DTV) will replace it. The government and the television stations have been preparing since then, and everything is in place. But will it happen?

President Obama has asked Congress to postpone the switch to give consumers more time to get a converter or a DTV set. The Federal Communications Commission also supports a delay. While the Senate approved a new June 12 deadline last month, the measure failed to get the twothirds vote it needed to pass in the House of Representatives. (As of this writing, no new legislation has been suggested.) Less than 20% of U.S. homes still get TV over the air (OTA). Many of these viewers are seniors and members of low-income families who rely solely on OTA TV.

One of the main problems is that the National Telecommunications and Information Administration (NTIA) has run out of the $40 converter box rebate cards that it has been sending to citizens who request them. Some officials in the Obama administration feel that there has been insufficient funding for the DTV education program and DTV transition despite the near $1 billion already spent.

Another concern is the difference in coverage areas. In most tests, well over 90% of those viewers who switched to DTV have no problem getting adequate reception on their new DTV set or with a converter box attached to an older analog set. Yet for those viewers out near the fringes of a transmitter’s coverage area, poor reception to no reception at all is a reality. If the total coverage area is smaller with DTV, there will be fewer viewers compared to legacy analog coverage. TV stations could lose substantial ad revenue if their viewing audience is smaller.

The outliers are viewers in these fringe areas and beyond. These folks get their TV OTA by choice or because there is no local cable TV or Internet Protocol (IPTV) service available. Many of them have access to satellite TV but may not be able to afford it. In any case, fringe reception is common for these viewers, who most likely use outdoor TV antennas, attic antennas, or amplified rabbit ears.

These antennas work well with analog TV, but they may be insufficient for digital TV. Analog TV signals degrade gracefully with attenuation. The picture remains on the screen but gets snowier with distance or with interference in the line of sight (LOS). With digital TV, attenuation produces pixilation before the signal drops out entirely. With a weak signal, you won’t get a snowy picture. You’ll get nothing.

Whose problem is it? In the past, viewers used a higher antenna or bought an amplifier. Today, many consumers will blame the government. There is little the TV stations can do, as they are stuck with their capital investment in high-power TV transmitters as well as the towers, antennas, and ground they occupy. They want viewers, but they aren’t in any position to subsidize consumers. So, they better map their coverage areas and let people know their practical range.

According to Jon Hammarstrom and Darren McCarthy of Tektronix, better mapping is the key to understanding the real range and quality of a DTV signal. Mapping involves plotting the electromagnetic field strength as a function of distance from the transmitter. This information provides a useful guide to consumers, who can better assess their need for an improved antenna, amplifier, or other solution. The station or a subcontractor can use a receiver/spectrum analyzer like Tektronix’s SA2600 to measure and map the signals (see the figure).

The government has been generous with its converter box rebate cards. If the transition is delayed, the government may or may not make more rebate cards or offer help for a better bigger, better, or higher antenna, which is the ultimate solution to most problems.

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