Remember television? For most of its history, TV wasn't cable, satellite or YouTube. It was radio with low-res moving pictures. On the transmitting side it was an extension of radio, with transmitters on towers, mountains and high buildings, serving viewers with signals within a range limited by frequency and terrain. Like FM radio, TV was on VHF bands. In the U.S., channels 2-6 were spread from 54 to 88MHz (ending just below the FM band) and channels 7-13 ran from 174-216Mhz.
Not all TV signals are the same. For a signal with a given power and antenna height, range varies with frequency. Higher frequencies have less bending properties than lower ones. Energy is also more quickly absorbed by atmosphere and reduced or halted by buildings and terrain. This is why (again in the U.S.) visual signals for channels 2-6 had maximum powers of 100,000 watts, while those from 7-13 had "equivalent" maximum powers of 316,000 watts.
Range for a given power became more critical when TV expanded to the UHF band in the 1950s. UHF was problematic from the beginning. Receiving it required a new or expanded tuner, plus a new kind of antenna specially designed for the very short UHF waves. This is why TVs from the 50s to the 90s came with little "loop" or "bowtie" antennas, in addition to rabbit ears. The latter were for UHF while the former were for VHF.
For TV stations and networks, VHF channels were much more desirable than UHF ones — not just because VHF channel numbers were lower and more easily remembered, but because UHF signals had much less range than VHF ones. To compete with VHF signals, UHF stations could operate with a maximum power of 5,000,000 watts. And even those signals were never equivalent. If you're looking to push signals out past the horizon, VHF is much better than UHF.
In recent years the UHF band has also become more cramped. UHF TV originally ran from channels 14-80 (470-894Mhz). Since then everything upwards of channel 51 (698-869MHz) has been lopped off for a variety of other uses. Pagers use the 806-824MHz band (formerly TV channels 70-72). Analog mobile phones got 824–849 MHz (formerly TV channels 73-77). Public safety got the 849-869MHz band (formerly TV channels 77-80). And the "700MHz" band (formerly TV channels 52-69) was auctioned off in March of this year.
Yet UHF is winning, by federal mandate. On February 17, 2009, all U.S. television stations will be required to switch off their analog transmitters and use digital transmission exclusively. Nearly all of that will happen on what's left of the UHF band. Most stations will maintain their old channel branding, and still be known as "Channel 2" or "Channel 12", but their signals will in nearly all cases be coming in on a new UHF channel. For example, WNBC-TV in New York will move from Channel 4 to Channel 28. WABC-TV will move from Channel 7 to Channel 45. Both are already broadcasting on those channels in digital form. Come next February, all of them will, even if all they're doing is putting out low-def pictures over a high-def signal. In the Boston area, where I live most of the year, only one of the four major commercial networks broadcast their evening news in HD. The rest put SD (standard def) pictures on an HD signal.
If you have an HDTV and live within sight of New York TV station transmitters on the Empire State Building, you can probably pick them up over an antenna on your set or your roof. In fact, a loop or bowtie antenna will do. So will length of wire about 5 inches long, attached to the center conductor of your coaxial connection on the back of your set.
But if you live farther away, good luck. Your old VHF TV station not only won't have the range it did on VHF, but will probably not have the same range as an old analog signal on the same UHF frequency. It certainly won't have the same behavior. The signals tend to be either there or not-there. They don't degrade gracefully with increasing "snow", as analog signals did. They break up into a plaid-like pattern, or disappear entirely. Read through the photo essays here and here for more about how that works, and what a confusing mess this move is making out of the familiar old local channel rosters.
Adding to that confusion is the persistence of some DTV stations on the VHF band. Many more stations are applying for VHF channels, because they know the signals will be better, and in most cases will stay on familiar channels. When I look at FCC data for Los Angeles, San Diego, Washington and New York, I see lots of new activity by stations trying to keep their VHF signals. (When looking at that data, note that LIC is for license, APP is for application, CP is for construction permit, CP-MOD is for CP modification and DT after a channel indicates a digital signal.)
While the Program and System Information Protocol (PSIP) will cause stations to publish (and display) whatever channel they choose on the receiving set, the fact remains that most will still radiate on channels other than those they have long been associated with.
Digital signal transmission is also very different from the analog sort. For a variety of arcane technical reasons, many (perhaps most) digital signals are directional. That is, they operate at their full licensed power in only a few (or perhaps only one) direction, and have big dents or "nulls" in other directions. In the old analog days directionality was the exception rather than the rule, and was usually intentional, to protect other signals on the same or adjacent frequencies, or to pull back on the signal in the direction of a mountain that might cause unwanted reflections or places (such as the sea) where nobody lived anyway. Not the case with DTV. Lots of new DTV signals are directional just anyway.
It's interesting to see how this plays out where we live in Santa Barbara (and where I'm writing this now).
On my old roof antenna and its rotator, I got just about every analog TV station between Santa Barbara and San Diego. That included both VHF and UHF signals. With that antenna (the top one from Radio Shack) I even got little K35DG, a low-power UHF station at UC San Diego with a signal that puts a deep null in our direction (west-northwest, nearly 200 miles across the Pacific ocean). I sent them emails reporting reception and they were amazed.
In our new house (next door to the old one that had the big roof antenna) I anticipated the digital switchover and installed a high-gain Winegard HD-9022 UHF antenna. For analog reception it gets every UHF in Santa Barbara, Los Angeles and San Diego/Tijuana in nearly all weather, at nearly all times of year. But that's analog. What about digital?
For DTV, the Winegard does the best it can, but it's not enough. The slight terrain shadowing between here and Broadcast Peak (where most our local TV stations radiate from) makes the two digital signals from there KPMR and KEYT almost impossible to receive. I haven't seen KPMR at all (could be it's not on the air yet), and KEYT's signal on Channel 27 is barely there. In fact the signal is so bad that I can't keep it visible long enough for me to shoot a picture of it. That's a far cry from KEYT's old analog signal on Channel 3, which was crystalline on our old roof antenna and is still okay with rabbit ears on our old Trinitron in the basement.
As it happens, the only clear DTV pictures we get are from 200+ miles away: from San Diego/Tijuana. That's because there's a clear signal path across the ocean between those transmitters and our house. While signals on UHF frequencies are characterized as "line of sight" (clearly the case with our local KEYT signal), they do bend slightly. Across the gently curved ocean between San Diego and Santa Barbara, UHF TV signals bend just enough to make it most of the time with a watchable signal in analog. Not so with digital, which is much more demanding of the receiver. (Specifically, it demands a high signal/noise ratio.) As you see here and here, reception is either perfect or gone. In fact it's gone most of the time. Setting up the DVR ro record programs is almost pointless, given the crap-shoot nature of reception.
(Yet reception across those distances is to some degree predictable. For that I rely on William Hepburn's
Radio & TV DX Information Centre. With layout and graphics as retro as the practice of DX (fishing for faraway radio signals a preoccupation that ate way too many hours of my early years as a techie*), Hepburn's is a site for sore distant-TV-watchers' eyes. His tropospheric forecasts are very helpful for predicting when "tropo ducting" will favor the San Diego/Tijuana stations. All this fun tech stuff is of little relevance to ordinary viewers, but I figure will be less boring to our technical readership here at Linux Journal.)
- For many viewers, the digital signals aren't going to be there, no matter what the viewer does (other than hunt them down on cable or satellite).
- The stations themselves in most cases are giving up viewers, including (as in WECT's case -- see below) whole regional markets.
It's all a big new game of hard-to-get.
Of course, what you get from the FCC and the TV industry is pure propaganda. If you watch TV at all you have surely seen many reassuring messages about what's going to happen in February. If all you watch are cable or satellite, you won't notice the difference. But if you watch over the air signals, the difference will possibly be huge, regardless of what the promotional messages say. So will the disconnect between the whole concept of television and its origins as a live terrestrial medium. Hey, what's the "range" of a YouTube video? Or of anything you send over the Net, including live video streams?
For one propaganda example, take the DTV.gov site. It begins, "On February 17, 2009 all full-power broadcast television stations in the United States will stop broadcasting on analog airwaves and begin broadcasting only in digital. Digital broadcasting will allow stations to offer improved picture and sound quality and additional channels. Find out more about whether or not you will be impacted by the digital TV (DTV) transition. Go now." Go there and you'll find a section that begins "Analog TVs Will Need Additional Equipment to Receive Over-the-air Television When the DTV Transition Ends", followed by a Converter Box Coupon Program that rewards getting a converter box. Among the top links there is this one to Wilmington, NC - First in Digital.
Washington, DC — Federal Communications Commission (FCC) Chairman Kevin Martin today announced Wilmington, North Carolina, will be the first market to test the transition to digital television (DTV) in advance of the nationwide transition to DTV on February17, 2009. The commercial broadcasters serving the Wilmington television market have voluntarily agreed to turn off their analog signals at noon on September 8, 2008. Beginning at 12:00 pm on September 8, 2008, these local stations, WWAY (ABC), WSFX-TV (FOX), WECT (NBC), WILM-LP (CBS), and W51CW (TrinityBroadcasting) will broadcast only digital signals to their viewers in the five North Carolina counties that comprise this television market.
...This test market will be an early transition that will give broadcasters and consumers a chance to experience in advance the upcoming DTV transition. The Commission is coordinating with local officials and community groups to accelerate and broaden consumer education outreach efforts. The outreach will focus on the special transition date for Wilmington and the steps viewers may need to take to be ready by September.
Okay, let's take the case of WECT, which has been on Channel 6 for the duration. WECT is sort-of-famously one of the first stations in North Carolina to broadcast from a 2000-foot tower. Here's what Wikipedia currently says about it:
WECT TV6 Tower is a 2000 ft (609.6 m) tall mast used as antenna for FM- and TV-broadcasting. It was built in 1969 and is situated at Colly Township, North Carolina, USA at 34°34'44.0" N and 78°26'12.0" W. WECT TV6 Tower is, along with several other masts, the seventh tallest man-made structure ever created; it is not only the tallest structure in North Carolina, but also the tallest in the United States east of the Mississippi River.
(Actually, WECT is tied for first among ten TV towers in North Carolina that are among the world's tallest structures.)
The WECT tower in Colly Township is halfway between Wilmington and Fayetteville,. The latter is a bigger city than Wilmington, which is why WECT's builders put it there. The WECT analog signal on Channel 6 is huge, and local to both Fayetteville and Wilmington. Back when I lived in North Carolina, north of Chapel Hill, we could get it with my roof antenna any time, even though it was well over 100 miles away. And the audio was always audible just below the bottom of the FM band on a car radio, over pretty much all of central and eastern North Carolina.
WECT's digital signal, however, won't be coming from the old tower. I'm not sure why, but I'm sure it's just too far away. Instead WECT's new DTV signal is currently licensed for Channel 44, and transmitting with a directional pattern from the WUNJ (NC Public Television) tower southwest of Wiilmngton. I see by an fccinfo.com query that WECT also has an application for a Channel 44 signal on a higher tower. The site is where WWAY now sits, along with WUNJ (same tower). Since WECT's bug-splat directional pattern with that application is nearly identical to WWAY's digital one on Channel 46, along with WSFX's on Channel 30 -- and they all have the same antenna height -- I am sure we are looking at a new master antenna for WWAY, WECT and WSFX, with WUNJ broadcasting from a lower antenna on the same 2000-foot tower (which is already standing).
In any case, WECT loses Fayetteville.
Recently I visited the site of another Channel 6, and put a photo essay up on the Linux Journal Flickr Site. This Channel 6, WLNE-TV, also has an audio signal I can hear in Boston on any radio, even though the transmitter is southeast of Providence, in Rhode Island. The tower is 1000 feet high, and otherwise occupied only by a small Spanish-language FM station. The facility will surely be mothballed while the new digital signal comes from a antenna structure shared with other DTV stations in Providence.
How many more of these huge TV structures will be abandoned in the digital switchover, I wonder? Whatever the number, it will help accelerate the end of TV as We Know it.
Which is my point. This essay, and a shorter one in an upcoming Linux Journal, are swan songs for my expiring expertise (such as it is, or was) in analog broadcast engineering. Knowing this kind of stuff will be as useful to me as the Morse code I haven't used in close to 50 years. And I'm looking forward to it.
Because the failures of the DTV switchover will bring into sharp relief the obsolescence of official notions about What TV Is.
What we called TV has already become nothing more than a form of data that can be carried over the Net at nearly zero cost, and stored anywhere for about the same. Live transmission is a demanding thing, but not once the pipes get fat enough. Where they aren't, we have podcasting and variations in file size to avoid bandwidth hoggery.
Already anybody can produce high-def TV. As devices such as the Red camera come down in price, along with processing, data storage and render farming, Hollywood-grade video production quality will no longer be exclusive to Hollywood. Collaboration and distribution over the Net will inevitably follow.
As it does, it will become ever more clear that "TV stations" will be repositioned as doomed mainframes.
There will always be a need for local and regional news, and coverage of events by organizations and individuals whose interest and expertise is also local and regional. But "range" will be determined by interest, not by transmission medium. The lack of capacity for new program sources on one-way cable and satellite systems will expose the antique natures of those systems as well.
For example, the fiber coming to my house has "bandwidth" in excess of a terabyte in both directions. It's great that Verizon (through FiOS) gives me 20Mb symmetrical bandwidth; but -- as Bob Frankston started asking three years ago -- Why Settle for Just 1%? More to the point, why settle for TV when you can do anything with video files or streams of any size? Trust me, the time is coming when that's a very serious question.
At some point the need for that capacity outruns the need for television. When that happens, vast new markets will open. Including ones far bigger than what we've had with TV alone for the last sixty years.
Until then, we'll just have to imagine them. But don't worry, they'll become real soon enough.
* As a kid in New Jersey, I logged more than 800 stations on the AM band, mostly using my Hammarlund HQ-129X ham radio receiver (yes, I had a transmitter too a Johnson Viking I). That's about eight stations per channel. Not bad considering that I could see the towers of most New York City AM stations from my bedroom window. Later, as an adult living in North Carolina, I received more than 1200 FM stations, mostly through "tropo" ducting and sporadic E-layer skip. My antenna was a Finco FM-5 that I rotated by hand, and my tuner was a little KLH Model 18
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