RF Technology: Doug Lung

Channel Election Choices Revealed

In early February, most broadcasters had to pick the DTV channel they will use once the DTV transition is complete, and analog broadcasting ends. Within a week, the FCC made available on CDBS the dtv_transition and dtv_agreement_group databases that show those elections. I analyzed station channel choices using the databases dated Feb. 23, 2005. You may be surprised at some of the results.

Fig. 1 shows the number of stations electing each VHF and UHF channel. From this, you will notice the high-VHF channels, 7 through 13, have approximately twice as many stations per channel than the UHF channels. Of course, a major reason for this is there are only seven high-VHF channels available compared to 37 UHF channels. As you can see from Fig. 2, based on the channel elections filed in February, there will be three times as many stations on UHF as on VHF.

Sixty-six percent of stations picking channel election option "A" (selecting their analog or digital channel) elected to keep their existing DTV channel. Other filers selecting option "A" either picked their NTSC channel, or had only one channel to begin with.

Let's take a more detailed look at the channel elections on a band-by-band basis.

LOW VHF

My columns on low-VHF TV channels for DTV generated a large e-mail response. The vast majority of comments, including some from engineers at stations transmitting on low-VHF DTV channels, were against the use of the low-VHF channels--2 through 6--for DTV.

Guess what? While only 15 stations (43 percent) that were already allocated a low-VHF DTV channel kept it, 28 stations picked their low-VHF analog channel as their final DTV channel, increasing the total number of low-VHF stations from an existing 35 (based on Form 381 filings) to 43! Channel 5 was the most popular channel, followed, surprisingly, by Channel 2.

Stations with a tentative DTV channel designation on a low-VHF channel will have a chance to change it in the third round of selections. For the sake of argument, if all stations electing low-VHF DTV channels keep them, will consumers buy the large antennas needed to receive them? To answer the question, it's worth looking at where these stations are located.

HOW STATES SELECTED

Twenty-three states had no stations electing low-VHF channels. No state had more than three stations electing low-VHF DTV channels, and only four states had that many--Alaska, Michigan, Montana, and South Dakota. Eight states had two stations electing low-VHF DTV channels--Colorado, Georgia, Nebraska, Nevada, Tennessee, Virginia, West Virginia and Wyoming.

You may have noticed many of these states have markets that include large rural areas. These would be difficult to cover with a single UHF DTV station. People in these areas are used to erecting large antennas for over-the-air TV, but interference from motors, broadband-over-power line and other stations could still cause reception problems. However, I've heard newer ATSC receivers do a better job handling impulse noise, which could help low-VHF DTV reception.

HIGH VHF

Seventy-four percent of the 178 stations with DTV channels in the high-VHF band (Channels 7-13) decided to keep them. A total of 427 stations elected high-VHF channels--18 of them through negotiated channel agreements, representing 25 percent of the channel elections made in the first round. Looking at Fig. 1, you will notice more stations elected Channel 13 than any other TV channel.

While there will still be more DTV stations on UHF, with the number of high-VHF DTV stations more than doubling, consumers will want their antennas to include elements for high-VHF. As I noted in my review of Kerry Cozad's paper on receive antenna measurements, many UHF antennas will do an acceptable job receiving high-VHF signals. However, if these antennas do not meet the gain and directivity parameters used in FCC OET-69 studies, interference-free coverage may not be as good as expected. The increasing number of high-VHF DTV stations should give manufacturers an incentive not to compromise high-VHF performance in new designs. One downside is that the popularity of high-VHF DTV channels could pose a problem for stations wanting to increase coverage beyond what they specified on Form 381.

UHF

The database showed 954 stations (62 percent) elected to keep their UHF DTV channels. More than 10 percent of the stations with UHF DTV channels couldn't keep their existing channel because it was out of core (above Channel 51). The most popular UHF DTV channel was 19, with 48 stations electing it. The least popular UHF DTV channel was 14, with only 18 stations choosing it. At the other end of the band, 26 stations elected channel 51, the same number that elected channel 38. Three channels--14, 41 and 50--were less popular.

ACCURACY?

You may be wondering how much we can tell about the final DTV channel landscape when there will be two more rounds of channel elections. All stations had to file their DTV coverage choices in the pre-election filing last November.

According to the dtv_transition database, 1,761 stations filed FCC Form 381 last November The Feb. 23, 2005 dtv_transition database showed 1,743 stations filed FCC Form 382 for first-round DTV channel elections in February. Of these 1,743 stations, 50 picked option "C" and elected to give up their in-core DTV channels and participate in the second round. Based on these numbers, only 68 stations have yet to make their final DTV channel election. Another 62 stations picked option "B" for negotiated channel agreements. While some of these agreements may fall through, many stations entered into agreements allowing other stations to use their in-core analog channel and will stay on their existing DTV channel, even if the agreement collapses.

If we assume half the stations entering into a DTV channel agreement don't get their choice, it leaves only 99 stations, or about 6 percent, to make channel elections in the next two rounds. As noted before, stations on low-VHF channels will get a chance to pick another channel in the third round. This could result in as many as 43 stations picking new channels. If all decided to move off the low-VHF channels, first-round election results would still reflect the choice of 92 percent of TV broadcasters.

These counts are based on the data from the CDBS tables. While working on this article, I found the dtv_transition.dat table showed multiple and conflicting DTV channel election filings for several stations. Using the application_id field, I manually deleted the older applications. While I checked the 1,700-plus channel election applications three times, it is possible I missed a duplicate. I've posted spreadsheets showing channel election and negotiated channel data at www.xmtr.com/fcc/dtvch.zip.

NAB2005

In the past, before the National Association of Broadcasters show, I listed some of the items I'd be looking for. When I started to do that this year, I realized I'd be looking for many of the same items I'd written about last year. If you don't remember last year's column, you can find it here.

I expect the Nextel-led transition to 2 GHz digital ENG to be a big topic this year. Consumer interest in DTV is growing rapidly and advertiser interest will soon follow. This will put more pressure on TV broadcast engineers to make sure their DTV signals are ATSC-compliant and easily receivable, leading to increased interest in test equipment, higher-power transmitters and new techniques like distributed transmission. Don't forget to check www.nabshow.com/bec.asp for the latest information on NAB Broadcast Engineering Conference sessions.

Look for my observations on NAB2005 in my June 2005 RF Technology column.

See you at NAB!

Your comments and questions on any RF topic are always welcome. Drop me an e-mail at dlung@transmitter.com. Your question may become the basis for my next RF Technology column!