|Hawes Mechanical Television Archive||
DTV Changeover FAQ, Part 6
Frequency shift and coverage. Many stations are shifting to new frequencies. Some, but not all VHF stations will move to UHF frequencies. The local coverage area of the new frequencies usually matches the coverage of the old frequencies. (The typical match is 90 percent or better.) I suspect that fringe-coverage conditions of widely-separated frequencies probably don't match as well. For instance, lower frequencies tend to travel further. Higher frequencies tend to be less noisy. In an analog picture, noise makes "snow." Yet noise can destroy a digital picture. Add this fact into the bargain, though: Digital signals have a higher average signal strength than analog signals do.
QUESTION. How well do these DTV converters perform?
ANSWER. In Chicago-area tests, a Zenith DTT900, ATSC converter picked up 11 extra stations. Some of these are multicasters with three or more subchannels. Analog sets here receive about 19 stations. Our digital test pulled in 30. Add to those the UHF stations that we could never before see on this particular set. Now they come in fine. For the test, we never re-aimed the roof antenna. In fact, the test antenna is very old, and missing a few elements.
Despite our inadequate setup, the pictures seemed sharp, ghost-free and clear. The color was extremely saturated. Some might like this effect, but to us it seems unnatural. We also noticed frequent digital artifacts. The artifacts are a definite step down from analog. A common problem is that digital pictures often don't fill the screen. We were glad that the Zenith includes a "Zoom" button that fixes this problem. Yet the Zenith doesn't work through a switchbox. That's another minus.
Analog problem. Some stations might not convert to digital broadcasting. Of course, you won't see these stations through a decoder box. The Zenith doesn't have a passthrough switch to allow analog television viewing after conversion. An external switchbox would fix this problem, but the Zenith refuses to operate through a switchbox. Our test switch is a Radio Shack unit. The only way to watch analog shows is to reconnect the antenna to the TV.
The Upshot? After the fourth crash, the DTV box looks a little different to me: These converters work well. Yet they aren't as simple, reliable or easy to use as analog tuners are. At least converters aren't that expensive. Use your NTIA coupon and buy one. Try it out. Maybe you'll be satisfied with the result. You can always return the box for your out-of-pocket expense. In that case, you'll lose the coupon. But, if you venture nothing, you gain nothing.
For converter reviews, see these sites...
QUESTION. I want to upgrade to a DTV set. What should I do with my old TV, VCR, TiVo, DVD player, etc.?
ANSWER. Sell it to your uncle in Mexico. (Honestly, someone could make a good business of remarketing used TVs in Mexico!)
There are many other good uses for your analog TV set...
Or recycle your equipment the green way. See...
QUESTION. My converter worked when I installed it. Now all I get is snow. What should I do?
ANSWER. Follow these steps...
Still doesn't work? Check these connections...
QUESTION. After the analog stations shut off, my converter stopped receiving a few digital channels. How can I get these stations back?
ANSWER. Rescan your channels. To do that, follow your converter's instruction manual. If you lost the manual, click the <MENU> button on the remote control. Then follow the onscreen instructions.
Before the analog station shutdown, some digital stations operated on temporary channels. After the shutdown, these temporary digital stations went off the air. Afterward, the channels that you miss moved to their final locations.
Rescanning the stations allows your converter box to find the new channel locations. In about five minutes, you'll be watching your favorite stations again.
Oh, one more item: When you tune in those new channels, you want the picture to fill the screen. Don't forget to reset the <ZOOM> control. (On some sets, this is the <ASPECT RATIO> control.)
QUESTION. My converter only displays a still picture. The TV screen is full of numbers. Did I break this thing?
ANSWER. Your converter probably isn't broken, but it definitely crashed. Computers do that, and your converter is a computer. You'll notice that none of the controls work, either. I've seen crashes where you can't even turn off the unit!
QUESTION. What are some drawbacks to DTV?
QUESTION. I watch sporting events, and I'm concerned about digital artifacts. What does an artifact look like?
ANSWER. You have reason for your concern. Sporting events are among television's finest programs. These programs push the limits of the technology, and they provide some of the best pictures. This point is especially true of live events such as football and automobile races. Sports enthusiasts are television's "power users" and also its strongest critics.
A digital artifact might involve the whole screen, or just a part. In the worst digital artifacts, the picture freezes and breaks up into a panel of squares. The screen might stay this way for several seconds. Of course, you miss the action. You might have seen such digital artifacts with analog reception of digital shows, such as shows from a satellite. (In these shows, the program is digital up until the transmitter.)
Digital artifacts tend to occur when a large part of the picture changes. For example, when a foreground football player dashes across the screen. Or when the scene changes. Since sports involve a lot of motion and scene changes, expect to suffer through many digital artifacts.
In sports television, the worst problem of artifacts is that they obscure rapidly- changing events. Such events are the essence of sports! Also during and after a digital artifact passes, the sound often goes out of sync.
Except for digitally-originated shows, analog TV has no digital artifacts. We might as well say it: Digital artifacts are a terrible drawback of digital TV. The lack of digital artifacts is a serious advantage of analog TV.
QUESTION. What are the digital channel assignments for my area?
ANSWER. For the national list (by state), click Digital Channels.
The links below help you to find all the stations in your area. You can also find the distance to the station antenna. This information will help you to aim your receiving antenna for the best picture...
QUESTION. My converter has two (or three) types of outputs. Which connectors do I use?
ANSWER. The coax output is the one that most people use. That's why most manufacturers provide a coaxial cable. Connect the coaxial cable between the converter box output and the TV's antenna input.
The RCA jacks provide an AV output that bypasses part of the TV. Result: A better picture. Very few qualifying converters (such as Channel Master) provide a DIN jack output. This jack is for S-video. The DIN output bypasses more of the TV circuit and offers you the best picture. Of course, your TV must also have an AV or a DIN jack. Here's a summary...
QUESTION. Will the new ATSC, digital standard last as long as NTSC did?
ANSWER. Not likely. Digital devices become obsolete much faster than analog devices do. Think about how many PCs or cellphones you've had in the past 10 or 15 years. Other digital devices have come and gone, too. For example...
DTV didn't just pop up. Engineers began designing it in the 1980s. By the 1990s, the standard was complete. DTV is 20-year-old technology.
Due to Moore's Law and economics, the digital product design cycle is about three months long. For example, as soon as they hit the assembly line, PCs are obsolete. By then, three generations of replacements are well developed. Your new PC might serve you for 18 months. By then, you've installed a couple of service packs to keep the software alive. Eventually, the memory becomes insufficient. Or the feature set is incompatible with the rest of the world. The same will happen for DTV (ATSC) products.
QUESTION. What's the evidence of DTV's coming demise?
ANSWER. Of course, we don't have a crystal ball. But note these facts...
QUESTION. What's inside my DTV box?
ANSWER. A digital computer. For those who know computer hardware: The computer includes an MC68360 microprocessor, SDRAM, ROM, an I/O port and a bus system. The processor divides down the crystal clock frequency to produce necessary outputs. One of these is the 3.58 MHz color burst frequency.
Computer system. The LG converter boxes use a 32-bit computer system. The MC68360 microprocessor is a descendant of the famous, Motorola MC68000 processor. The 68000 was the brains of the original Apple Macintosh and Commodore Amiga computers. Today, Freescale manufactures this processor family.
Processor design. Engineers designed the MC68360 for communications. Its other name is QUICC, for quad integrated communication controller. Onboard the chip are four serial communications controllers (SCC). The chip also includes two serial-management controllers (SMC) and a serial peripheral interface (SPI).
Peripherals. Your converter box includes some very useful peripherals...
QUESTION. Is the box hackable?
We haven't investigated inside the box, and don't know if the factory potted the components. We also don't know how much proprietary hardware is in there. I've read that at least the early boxes don't include writable flash memory. Too bad. But, hey, a converter's a computer, and computers are universal machines. Then in some sense, these boxes are hackable! Plus, in a few years, converters will start turning up at resale shops and rummage sales.
By now, hackers are planning to replace the converter program with their own code. Maybe they'll figure out how to play converter Pong, Space War or Tank. After all, if the firmware is accessible, the box could run other applications. Food for thought, you guys: Since it includes video peripherals, the box is particularly well suited to graphic-display applications.
At one time, Agilent produced an emulator for MC68360 applications. Amateur developers might have some use for the Agilent manual. See... Agilent book.
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Copyright © 2008 by James T. Hawes. All rights reserved.