The end of broadcast television was always going to happen eventually, but thanks to the FCC and the vagaries of a little-known modulation format known as 8-VSB, it may happen before the end of this decade. As of February of 2009, analog television signals will be shutdown across in America. The signals which have been on in some form or another for the past 80 years, which brought the whole country together to watch fuzzy images of the moon landings, the Nixon “Checkers” speech, and the first shuttle launch, will suddenly stop. In their place will be digital high definition broadcasts. If you can receive them.
Despite the hype about digital, there are some very nice things about analog, most notably its graceful failure in the presence of noise. If interference degrades your signal, or a bus drives by your house, causing changing power levels, an analog picture will just get a bit fuzzy or maybe you’ll see a ghost image. Either way, you’ll still comprehend what’s going on, and it will be a minor annoyance. In a sense, the beauty of analog transmission is that it leverages the massive ability of the human brain to decipher noisy inputs, making the world’s best signal processor (you!) part of the transmission system. Digital television, however, is all or nothing. Either you get a perfect signal, or you get a black screen. And I predict that it will be the latter for a surprising number of people.
The modulation format chosen for our brave new world of digital television was not decided by engineers as much as by committees of bureaucrats. Their choice, 8-VSB, has two big positives going for it. One, it is power efficient, allowing less energy to be used by the transmitters. And two, and perhaps the biggest reason it was chosen, it relies on patents owned by Zenith, an American company. The downside, and the reason the Europeans don’t use it, is that 8-VSB is very susceptible to something called multi-path interference (MPI). Simply put, MPI happens when there are things—like mountains or buildings, or even buses—off of which the signal can reflect on route to your TV. 8-VSB is especially bad in changing environments, such as when people walk around a room or a plane flies over your house.
The origin of this sensitivity is the tremendous amount of data that must be squeezed into the 6 MHz channel spacing used by existing analog channels. The full data rate of a digital TV signal is almost 20 Mb/s, an astounding amount of data to be sending over the air. It’s even more astounding when you consider that it has to be squeezed into the 6 MHz channels used since the early days of television. To accomplish this feat, the information is spread over the full 6 MHz without any redundancy whatsoever. To be power efficient, it only uses one “carrier.” However, when multiple transmission paths interfere, certain parts of the spectrum (certain frequencies) will destructively interfere, causing loss of signal at those frequencies. This frequency-dependent attenuation has to be removed by equalization before the whole signal can be reliably deciphered. As you can imagine, doing this when the equalization needed is constantly changing is very difficult. In practice, the screen will go black while the receiver tries to figure out what to do. The Europeans, to their credit, use a modulation system called COFDM that is akin to having hundreds of independent radio stations each with a tiny bandwidth transmitting simultaneously, each carrying a simpler part of the more complicated signal. This is much less susceptible to interference, as each low-bandwidth subchannel only has to be equalized relative to itself, and there’s not much that can happen over a very narrow bandwidth signal. (There was actually quite a bit of “drama” over our choice of schemes, as partly detailed in this article.)
My skepticism about the switch to digital comes from forced experience with it, as I’m not allowed to have cable where I live. Most Boston stations have been broadcasting in digital for some time (in addition to their analog signals) and I can attest that it’s very difficult to get good reception where we are in Cambridge, due to all the buildings. We are a scant 5–7 miles from the transmitters, very close by most standards, and yet our digital signals are flaky and will go out completely if a bus drives by or a person walks by our window. We’ve becomed conditioned to expect the picture to go black whenever we hear a bus approach. And this is with a top-of-the-line antenna and a TV with a fifth generation receiver chip.
The reason I’m writing about all of this is not to complain for the sake of complaining. That is something I would never do! Nor do I think it would be the end of the world if we can’t all watch Knitting with the Stars or Survivor XXIV, Staten Island. I decided to write about this because the switch to digital could potentially be such a disaster that it could cause an interesting shift in our nation’s media consumption. It could also be a potentially lucrative shift if you invest in companies who stand to benefit, like Comcast or DirecTV.
In terms of social impact, the (few) people who were on the edge regarding TV, who maybe had an old analog TV around for news or the occasional football game, will probably end up giving up broadcast TV entirely, switching to Internet-based media. However, tens of millions of others will be driven to cable or satellite TV, many simply due to confusion over what the switch means. (A majority of people surveyed thought that they would have to buy a new TV once the switch occurs.) A high proportion of people still using OTA TV are poor—predominantly living in urban apartments, the worst possible situation for digital TV reception—and will no longer be able to receive any television. The result is that they will become even less connected to mainstream American media and news, for good or bad.
In terms of business, I think this will finally put the stake in the local affiliate system, as the need for local broadcast facility was one of the reasons they existed to begin with. Along with them will go the curious phenomenon known as the local news broadcast. (So at least one good thing will come of it.) National television networks will still exist, but unemcumbered by contracts with local affiliates, distribution will become entirely on demand through cable and satellite, and increasingly through the Internet. I would guess Apple will play a major role, offering a box (a la Apple TV) that allows one on-demand access to programs with targeted (and non-optional) advertising. (Microsoft will try to do the same, offering a set top box based on Windows, and will fail miserably.) The move to on-demand programming will bring the final demise of the network news departments. Nobody will be willing to sit through an on demand full news broadcast when there is always a sitcom to be had. We will realize, too late, that the imposed schedule of broadcast television was the last bit of social discipline we had, forcing us to at least sit through the news before we got Seinfeld at 8.
All because somebody in the government decided vestigial sideband modulation was the way to go.
