Sunday, June 14, 2009

The TV Rapture

It’s true. It really happened. It was not like judgment day, or the rapture, which never really happen. Analog TV was actually turned off on the announced date, and now, all TV broadcasts will be digital.

Anticipation of this had caused concern for audio people like me. Our wireless systems share the same spectrum of airwaves as TV, and since digital channels use their bands more thoroughly than analog, we expected there to be fewer “cracks” for us to slip in a wireless signal.

Our wireless systems come in “blocks,” with each block being a certain range of frequencies. The range of frequencies for a block overlaps the bands of about 4 TV channels. For a given city, some TV channels will have a broadcast on them, and some will be empty. So, when ordering a new wireless system, the buyer or helpful dealer needs to research what blocks have the fewest TV stations broadcasting in the city where the wireless system will be used. In our area, block 28 of Lectrosonics brand wirelesses used to be the best. But in recent years, more TV stations were put in 28, and 22 became the best, followed by 24, then 27, then 29.

You can use a wireless receiver to scan within its block and show you where the TV broadcasts are. Then, you can set your system to use a frequency that is not already used by a TV station.

Problems arise if you already own wirelesses on a certain block and new TV stations start broadcasting on that block. Your available frequencies are reduced. Also, when traveling to another city, you have to check where that city’s TV stations are and see if your block will work there, or if you need to rent systems on other blocks.

In the all-analog days, even if a block was mostly filled with TV channels, there would be a few empty frequencies at the bottom and top edges of a channel’s range. These were called “guard bands.” An audio recordist forced to use a wireless system on an already crowded block could probably find some open frequencies in these guard bands.

But digital TV uses all the frequencies within its band and leaves no guard bands. We were afraid that the conversion to all-digital would crowd the ariwaves more and leave us fewer options.

But in the past year, as the big analog cut-off approached, people started to realize that when all the analog stations went away, they would not necessarily all be replaced by digital stations. This would mean a net decrease in the number of TV stations we have to compete with. This likelihood was enhanced by the fact that one digital “channel” can carry more than one TV program. So if a station could broadcast 4 programs in the band formerly of 1, then it would do that rather than buy 4 whole different bands. Furthermore, it's a lousy economy anyway where advertising can hardly be sold on the broadcasts that do exist.

On the big cut-off day, June 9, I was reading facebook when one friend announced that her analog TV had gone away, right in the middle of Sarah Palin’s interview with Matt Lauer. It was a shame to her that this was the last thing her TV was ever able to show, but I find it symbolically appropriate.

I wondered, “Are the airwaves clearer on my blocks?” I went to my audio bag and set the receivers to scan, and sure enough, the block 24’s, which had once shown the fully-used bands of at least 2 TV channels, now showed only a few weak spikes. And the block 27’s, which had shown a single TV channel, were empty. Nothing was on them, except for maybe one tiny little weak signal at one end. It was very strange looking at the empty scan. It was like the end of the world, perhaps the rapture after all, with human activity suddenly squelched. Alone at home on a street where everyone else was at work, I could have been the last person on earth.

Now, unless TV networks find a reason to create so many new digital channels that they need to buy up the vacated analog channels, it should actually be easier for audio recordists to find emtpy frequencies.

1 comment:

Marsosudiro said...

"I could have been the last person on earth."

Just don't do like Burgess Meredith in the Twilight Zone.