DTV: Rabbit Ears and FUD

Posted by: Stephen Wildstrom on February 05, 2009

rabbit earsSpreading FUD—fear, uncertainty, and doubt—is an old marketing technique in the tech business—and Washington policy debates. The discussion of the now-postponed digital TV transition has been mired in an unusual amount of FUD. You’d think that television might get a story that so intimately concerns itself right, but not if you read headlines like “ Rabbit ears get reprieve” used by CNN both on the air and on its Web site.

So here’s the nitty-gritty on what will happen to over-the-air TV signals when the DTV transition finally occurs. (If you get all your TV content from cable or satellite, you can stop here; you’ll probably never notice the transition.)

Currently, television stations broadcast on three bands, VHF-low (Channels 2-6), VHF-high (Channels 7-13), and UHF (Channels 14-69). Most UHF tuners go up to 83, but channels 70-83 were converted to cell phone use in the 1980s. Once analog broadcasting is shut down, channels 52-69 will also be repurposed, mostly for wireless data and public safety, and all of the digital stations will operate on channels 2-51.

How well an existing antenna, either set-top "rabbit ears" or a rooftop rig, will work for digital signals is going to vary a lot from situation to situation, and the results you get testing digital broadcasts today is not necessarily indicative of what will happen June 12, the new cutoff date. Some digital stations will continue operating as they do today, but some will move to new frequencies and some will be broadcasting from new tower locations; either change could affect your reception and may require, at a minimum, adjustment of your antenna. There is, by the way, no such thing as a digital antenna. Digital vs. analog makes a big difference to the circuitry in a TV set, but to an antenna, FM radio waves--that's what TV signals are--are just FM radio waves. Antennas are turned for the frequencies they receive, not the nature of the signals.

The other crucial difference is what a weak signal means for your viewing experience. Analog signals degrade gracefully. As the signal weakens, the picture gets snowy and the sound may get fuzzy, but it's up to the viewer to decide just when it becomes unwatchable. Digital TV is much more of a go-no go proposition. With a weak signal, the picture breaks down into big pixelated blocks before disappearing altogether. Even worse, the audio breaks up like a bad wireless phone connection. Most people quickly find the effects of even a moderately poor digital signal intolerable. That means that some people who got by with rabbit ears may have to go to an outside antenna and some people with rooftop antennas may have to upgrade them for higher gain.

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Reader Comments

tom

February 6, 2009 06:52 AM

Indeed. Not enough attention have been given to the antenna, leaving consumers open for manipulation by electronics salespeople. A couple of my neighbors were told they had to have new, digitial TV antennas costing several tens of dollars, when all they needed were simple UHF bowties.

Mike

February 6, 2009 02:09 PM

Yes, in the beginning there was so much confusion. Retailers were telling some consumers they would have to purchase a NEW TV with a built-in digital turner, which we know isn't the case, as their old analog would not work

For my situation, I do not have cable or satellite nor do I want them. One TV will be hooked up to a converter box, and my other two, which both have built-in digital tuners, are connected to an inexpensive ($9.99) indoor antenna and work fine. Sure, you'll have to move the "ears" for best reception, but with nearby towers near my home, I'm fine

Karl

February 6, 2009 02:53 PM

The other difficulty is that currently, many stations are broadcasting in digital at a reduced strength, until they discontinue analog broadcasting. So if your reception is marginal in digital, you don't know for sure if you have a problem, because it might get better when analog broadcasting is ended.

Micheal Todd

February 6, 2009 03:13 PM

Digital TV signals are AM, not FM ( Analog TV video was AM; sound was FM ) Also, VHF channels 2 thru 6 will be lost in the transition to all digital.

Steve Wildstrom

February 6, 2009 04:03 PM

@Michael Todd--You're right. Actually, digital TV (ATSC) uses something called 8VSB modulation, which I don't pretend to understand. The basic point, though, is right, there's no such thing as a "digital" or "analog" antenna. According to the FCC's final DTV allotment table, channels 2-6 remain in the digital mix after some controversy, but they seem to want to move as many broadcasters as possible off of that VHF-low band.


Ken Z

February 6, 2009 06:49 PM

Actually, analog TV is a mixture of AM and FM signals. The analog video signal is broadcast using vestigial sideband broadcasting (VSB). Regular AM broadcasts transmit two side-bands and a carrier. VSB transmits only one complete side-band and the complete carrier wave but truncates the 2nd side-band in order to make the total signal bandwidth fit within 4.5MHz allocated for a TV channel. Also, the sound is transmitted using FM and must also fit in the 4.5MHz channel allocation. Digital TV in the United States does use 8VSB as is related to the current analog transmissions but only in how the radio waves are sent out (i.e. vestigial sideband broadcasting). The video and audio of a 8VSB signal uses trellis encoding (think of an orchestra with each instrument transmitting a portion of the digital data) to layer on top of the radio signal.

Hank

February 7, 2009 08:54 PM

If anyone wants to check to see what channels they can get the strongest and what type of antenna,they might need.Go to www.tvfool.com
and click on tv signal locater tab on left of page under TOOLS.Put in your address and click on find local channels tab below that.You might want to use Coordinates Option also.Find those at http://www.batchgeocode.com/lookup
Read below that what it says the colors mean for the antenna type you need.
You can see opinons on TV antennas at http://www.highdefforum.com under Local HDTV info link and deep fringe reception.Good luck
Also TVfool.com site has downloadable Coverage maps of your local TV stations which shows location of tv towers and signal strength.TV stations advertise antennaweb.org but that site is useless compared to tvfool.com .See for yourself.

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BusinessWeek writers Peter Burrows, Cliff Edwards, Olga Kharif, Aaron Ricadela, Douglas MacMillan, and Spencer Ante dig behind the headlines to analyze what’s really happening throughout the world of technology. One of the first mainstream media tech blogs, Tech Beat covers everything from tech bellwethers like Apple, Google, and Intel and emerging new leaders such as Facebook to new technologies, trends, and controversies.

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