DTV TUTORIAL: OCTOBER 30, 2007
Hey Kids, Time For A Game Of Musical Chairs!
All DTV stations broadcast on UHF channels, right? Wrong! What’s more, on February 17, 2009, many of them will move back to VHF channels.
There seems to be a common misperception among consumers and DTV manufacturers that all terrestrial digital TV stations have been assigned and will stay on UHF TV channels. While that’s certainly the case in major markets like New York and Los Angeles, it’s definitely not the case in smaller markets like Binghamton, NY or Scranton, PA, or even in a large market like Atlanta or Dallas.
In fact, all existing VHF and UHF TV channels from 2 up to 51 are available for ATSC (digital terrestrial) broadcasting. It just so happens that most of the major TV markets have a full complement of VHF analog stations on the air, so the FCC assigned mostly UHF channels to be used during the transition years (1997 through 2008). The final choice of channel is largely up to each station, provided that another broadcaster hasn’t grabbed its desired resting place.
One thing that seems constant is that broadcasters are abandoning low-band VHF channels like rats leaving a sinking ship. In most markets, high-band VHF (7-13) or UHF (14-51) channels are preferred for post-DTV transition operation. Notable exceptions that I am aware of include WPVI-6 (Philadelphia, PA) and WRGB-6 (Albany, NY).
The FCC has given broadcasters several chances to pick their final digital channel once the analog transmitters go dark on 2/17/09. In more than one case, a station with an analog high-band VHF assignment (like WABC-7 in New York) has opted to give up its UHF assignment (in this case, channel 45) and move back to that old, familiar VHF channel.
In other cases, stations didn’t move quickly enough to keep their old analog VHF channel, like WCAU-10 in Philadelphia. Since VHF 10 has been allocated to a station in nearby Harrisburg, WCAU will shut down their digital station on UHF 67 (a channel they would have lost anyway, as it’s out of the DTV “core”) and park their semi on UHF 34, currently occupied by WYBE-DT, who will move back to their original UHF channel 35.
In yet other markets, a new digital station can’t even begin broadcasting until its FCC-assigned channel is vacated by another temporary DTV station. (Remember playing musical chairs as a kid?) WNYA-DT in Albany, NY has been assigned VHF 13. Unfortunately, it’s currently in use by WNYT-TV, who also operates an ATSC station on neighboring VHF 12. Once WNYT-TV (analog) goes dark, WNYA-DT can light up.
Figure 1. As you can see, some TV stations will have to play
a game of “musical chairs” before February 17, 2009.
None of this should be a mystery to anyone. The FCC has all of this information and more in its Final Channel Election Tables, available for your perusal at http://www.fcc.gov/dtv/. These tables can be downloaded in Excel format, which allows you to quickly sort stations by city, state, and even channel assignments.
For the most part, the tables have been turned from the good old days of the 1940s and 1950s when everyone wanted to broadcast near the low end of the VHF band. Channels 2 through 6 were highly coveted, while getting a UHF channel assignment was the equivalent of being exiled to Siberia.
Nowadays, those low-band VHF slots aren’t as popular due to impulse noise interference and sporadic enhancement of VHF signals (DX) from other parts of the country during summer months. The FCC data shows only 43 stations electing to use channels 2, 3, 4, 5, or 6 at the end of the transition.
The conventional engineering wisdom is that it takes 2x as much transmitter power to achieve the same coverage area on UHF as with a VHF transmitter. But VHF antennas use circular polarization, whereas UHF antennas use horizontal polarization and have much smaller wavelengths. An argument could be made that less power is needed on UHF to achieve similar coverage, as long as the viewer has a directional antenna in place.
Everyone has their own technical and/or financial reasons for moving or staying put. So while we can say goodbye to KCBS-2 in Los Angeles, KYW-3 in Philadelphia, and WNBC-4 in New York, we'll still have WPIX-11, KCAL-9, WUSA-9 in Washington DC, and KGO-7 in San Francisco — they'll just be digital, not analog.
Figure 2a. After 2/17/09, you may have to replace this antenna…
Figure 2b. …with one of these for DTV reception,
although something smaller will probably do the trick.
What does this game of musical chairs mean to you? Simply that you’ll probably need to change the type of antenna you’re currently using to receive terrestrial DTV and HDTV programs, and you definitely shouldn’t wait until the night before 2/17/09 to do it.
Fortunately, the current crop of DTV receivers work umpteen million times better than their 1st-generation ancestors, so conventional multi-band antennas should be able to do the trick without you having to breaking the bank.
That’s not to say you can’t receive VHF high-band signals on a UHF antenna, but you’d have to be pretty close to the transmitter, as your UHF-only stick won’t have very much gain at those frequencies. As for low-band VHF, a UHF antenna might as well be disconnected for all the good it will do.
You’ve probably also seen how all of the PC-based DTV tuner “sticks” and modules all come with tiny, collapsible whip antennas that won’t be of much use unless you’re within a couple miles of a TV transmitter. If you travel a lot and want to watch DTV on the road, you may want to look into a combination VHF/UHF antenna; one that combines collapsible whips with a tunable UHF loop of some kind.
I tested a couple of these at Chicago’s O-Hare Airport earlier this year and was pleasantly surprised with the results as I was able to pull in all of the local UHF digitals plus WBBM-DT on VHF-3 (one of the dumbest frequency assignments the FCC has ever made).
In a nutshell, forewarned is forearmed, as one sage remarked years ago. Download and check the tables to see who’ll be switching seats in your market. You may even want to call the station’s engineering department to confirm the final DTV channel assignment. If everyone is planning to stay on UHF channels (like Syracuse, NY), then you’re probably home free.
But if one or more of your favorite local stations is moving back to VHF, you’ve got some antenna work ahead of you…
