Digital TV conversion -- pshaw!

I was trying to explain the difference between analog and digital signals to the kids today because the digital TV conversion deadline is right around the corner (Feb. 17) and we're some of the last hold-outs with a bunny ear antenna.

G: "Are we going to get one of those box thingies for our TV?"

Mom: "No, probably not."

L: "Why are they making us have to have that box."

Mom: "Because the TV stations are changing the way they broadcast their signal."

G: "How?"

Mom: (trying to remember my college radio station DJ days that feel like a lifetime ago) "Well, analog signals are waves that are sent from the antenna at the TV station and our TV antenna picks them up. Digital signals are more like polka dots coming out of the TV station's antenna and our TV doesn't understand polka dots. It only understands waves."

L. "Why are they broadcasting polka dots instead of waves?"

Mom: "Well, the government decided they needed those waves for other things and now we need our TV to understand polka dots and the only way it can do that is to get one of those special converter boxes."

G. "So we need a polka dot box."

L. "I like waves better. I like my old TV. I don't need no stinkin polka dots."

And as much as I enjoyed this conversation, I did do a better job of explaining the issue in more detail, with the help of <a href=http://howstuffworks.com>HowStuffWorks.com</a> a little later.

Basically, the real reason for this change (or so the web reports, I'm a bit of a conspiracy theorist on occasion) is because TV broadcasters have to move their signals to another part of the sound spectrum so that space can be freed up for police, fire and other public safety communications as well as wireless services for the general public. And as we discovered, bandwidth really is needed after the technology problems people had <a href=http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/01/21/BU0P15DOF5.DTL target=new>with the inauguration yesterday</a>).

So although I do not like the idea of being forced to buy a converter box (even with a rebate, <a href=https://www.dtv2009.gov/ target=new>which are no longer available</a>, there is still an out-of-pocket cost), there are actually some very good reasons why the government has required this change.

But the question the kids, and I (who couldn't remember nearly enough about those DJ days), wanted to know was what frequencies were used for TV (i.e., the sound spectrum) so we did a bit of research (which truth be told, I found much more interesting than they did).

Basically there are bands of frequencies on the sound spectrum.

<img src="http://seen.mainetoday.com/gallery_photos/2009/01/21/313/3792_radio-spectrum_580.jpg" class="">
Megahertz, which means "millions of cycles per second," is how strong the frequency transmitter at a broadcast station is oscillating. So if you are listening to FM radio -- we'll use 97.9FM as an example (the girls favorite station) -- the radio station's transmitter oscillates at a frequency of 97,900,000 cycles per second. To hear that transmission, you simply tune your radio, which is set up to "hear" frequencies in the FM range, to that specific frequency to listen to its broadcast.

All FM radio stations transmit frequencies between 88 megahertz and 108 megahertz on the band. A different bandwidth is assigned to AM radio as well as many other things. And all of this is assigned and monitored by the FCC.

HowStuffWorks.com explains the different frequencies on the spectrum and how they are used by modern day society, which the girls and I found really interesting.<UL>* AM radio - 535 kilohertz to 1.7 megahertz
    * Short wave radio - bands from 5.9 megahertz to 26.1 megahertz
    * Citizens band (CB) radio - 26.96 megahertz to 27.41 megahertz
    * Television stations - 54 to 88 megahertz for channels 2 through 6
    * FM radio - 88 megahertz to 108 megahertz
    * Television stations - 174 to 220 megahertz for channels 7 through 13
    * Garage door openers, alarm systems, etc. - Around 40 megahertz
    * Standard cordless phones: Bands from 40 to 50 megahertz
    * Baby monitors: 49 megahertz
    * Radio controlled airplanes: Around 72 megahertz, which is different from...
    * Radio controlled cars: Around 75 megahertz
    * Wildlife tracking collars: 215 to 220 megahertz
    * MIR space station: 145 megahertz and 437 megahertz
    * Cell phones: 824 to 849 megahertz
    * New 900-MHz cordless phones: Obviously around 900 megahertz!
    * Air traffic control radar: 960 to 1,215 megahertz
    * Global Positioning System: 1,227 and 1,575 megahertz
    * Deep space radio communications: 2290 megahertz to 2300 megahertz</UL>So as I understand this conversion from analog to digital TV, the FCC is changing the bandwidth we've historically used for television. I guess they have to in order to make room somewhere on the spectrum to expand the cell phones and emergency response system frequencies.

Then there's also the added benefit of digital TV that involves "multicasting," which allows several shows within a single frequency to be broadcast simultaneously.

I can see the advantages there for the TV station. More shows = more advertising = more money for broadcasters.

There might be a conspiracy theory in this after all.

But there's a lot more to this change - and how it works - than I understand. But I did find my bit of research into the basics of it fascinating.

The kids however brought me back to the bottom line.

"Are we going to be able to watch Dancing with the Stars after Feb. 17?"

"Not on the regular TV."

"But we can watch it on the computer right?"

After a search on abc.com and a quick download of their <a href=http://abc.go.com/player/index?pn=index target=new>full episode player</a>, we discovered that yes in fact, we can watch that TV show after this conversion as well as any other recent episode of that channel's prime time shows.

"So we do have polka dots after all mom. They're just not in the TV."

And so I ask again, <a href=http://raisingmaine.mainetoday.com/blogentry.html?id=5179>why pay for a new TV (or a converter box)?</a>

Maybe what we really need is a bigger computer monitor.