[GetReal]

Think of the digital signals as something like a compressed data stream somewhere in your computer, if a single data bit is munged (missing or overlayed by a bit of static, then when received by the TV or STB and uncompressed, the hardware doesn't know what to do with the info containing a munged bit because it no longer passes testing (CRC etc.) so it is rejected = no picture or momentarily frozen picture. This compression sequence allows the broadcaster to add more features to the signal (more audio/ and/or language channels, different picture formats, messaging, etc.) while at the same time signicicantly reducing on-air bandwidth. In February it's going to be all about antennas, somewhere. Either conventional in your backyard (most people), satellite on your property or satellite on your cable providers property, so buy as big and hi-tech as your budget allows if the broadcaster is farther away from you than 15-25 miles. But also be aware that some antennas sold as "designed for digital" etc., are marketing hype, there is no way to design an antenna to select between digital and analog---all that matters is received signal strength.
Part of that saving in bandwidth has already been auctioned off by the US Federal Communication Commission, giving the government a massive chunk of cash. Thankfully, the Gov is returning part of that chunk of $$ to the people in that it is offereng 2 free "upgrade" cards per houshold to buy converter box's, valued at $40 each card, just search "converter rebate" on the web and then sign up to receive yours in about a month. Converter box's are available at Walmart and elsewhere for $55 and up, and these are the same type box's being provided by comcast etc., so, own your own---inexpensively. Theses converters work with any digital source, converting back to analog for older TV's.

[ivorycruncher]

"And, unless I'm
mistaken, digital signals actually use more bandwidth per channel. It's
just that when it's done via "landline" rather than over the air,
there's no worry about allocation conflicts with other services (like
airplanes, police, cell phones, etc)"



I think you're a bit confused there. The new digital broadcast signals are still broadcast over the air, not via a wire. The transmitter is just sending a digital format signal, not an analog one. However, as far as my understanding goes, digital signals do not interfere with analog signals in the same frequency range, so the analog bandwidth is cleared out for other uses, such as emergency services and other things that the spectum has bene auctioned off for.

As for the fuzzy stations you may get now, not only will they probably not be watchable, but stations that just barely come in now will not come in at all, due to the fact that digital broadcast signals can't travel nearly as far as analog signals without degrading beyond use. With analog, it gets distorted, but digital is either on or off, it works or it doesn't. So, what does this mean? Well, for people who live out in the middle of nowhere with no cable service available, and all you can pickup are fuzzy channels, even with a digital converter, you probably won't be able to receive any channels at all anymore after the switch. That pretty much means you're stuck with a satellite service, or nothing at all. For others, even in a city, you may lose a few channels. I know, this really bites, but what can you do?



The thing I can't figure out is, if these digital signals are supposed to be so great and clear, why don't the emergency services use them instead? ;)

[JimH443]

I'm finding it difficult to nail down sources that aren't conflicting and/or confusing, but from what I can tell the main reason the FCC can sell off the frequencies it has been is not so much because digital uses less bandwidth as much as it is that DTV will use different frequencies of the radio spectrum. If true, this is yet another reason for people who rely on over-the-air transmissions to get a new antenna. Antennas are designed for specific frequencies. An antenna that gets great reception now may not work very well after the transition.

[GetReal]

Some but not all emergency services do use mixed digital now (municipal services such as police, fire, ambulance. Militare is ALL digital). It's only within the past decade or so that electronics has been able to produce the circuits necessary to compress high-density data fast enough to make digital use effective. Compression of signals makes the benefits of digital services just sufficiently economical to be"cutting-edge", aka save $$$. But a decade is short time for all consumers & emergency users to spend money. Expect to see every broadcast service converted to compressed digital most quickly, even your AM & FM music broadcasts! Anyway! The industry just needs you to spend more... :^)
Also note that a TV transmitter is just producing a signal, what is in that signal doesn't matter, all will interfear with anything else on the same frequency, also that yes TV frequencies are changing in that the whole TV allocation is becoming less, but what remains will be somewhere within the original range so older antennas probably will still work to an extent. Also note that conversion of a specific service is not the simple thing of just deciding to do it, the USA belongs to the International Telecommunications Union, which means that any changes anywhere must first be approved internationally...time and politics!

[dlgreen]

Too little is being said regarding the real problem with 8VSB Over The Air reception. The FCC shackled us with a defective system in their haste to auction off those extra channels. Payback to special interests were put ahead of protecting the public interests. I did some lobying for reserving some of that spectrum for the public utilities, and it was clear that the auction schedule was more important than getting things right. The bank regulators are not the only ones selling us out in Washington DC. Better systems came along; but the FCC refused to admit their mistake stalling until it is too late to fix it. It was more important that the patent be held locally (i.e., a campaign contributor) than to give us the best system.

Signal strength is not the problem. The problem is ghosting - especially unstable ghosts. I live a mere three to six miles from all of the local stations for the Detroit area, but I cannot use rabbit ears to watch half of the eight channels. I have plenty of signal, so amplified antennas won't help. With the least wind blowing, the swaying trees on my property cause shifting ghosts that are annoying on analog but fatal to digital. The most sensitive part of the signal is the audio. The audio is the first to go and the last to recover from a picture freeze. It is easy enough to mentally interpolate during a frame freeze, but long gaps in the sound make watching a talk show hopeless. An outdoor antenna may be essential to continue OTA service, but the geniuses at the FCC scheduled this switch in the worst possible month for installing roof-top antennas, and much of the country already has had above average snowfall.

Digital service gave the cable companies an excuse to charge extra. Even if you have a QAM TV compatible with digital cable, they block the channels that are not free over the air, so it's not just about bandwidth. HD is another excuse to charge more.

[rgreen4]

You are wrong Ivorycruncher. When the Tallahassee stations started converting (well over 2 years ago), the stations that had been analog only, I could not pick up or picked up so poorly they were unwatchable. Now I had this nice big fringe antenna, but it didn't help. Then when they were dual broadcasting I could pick up the same stations as digital. Not only that, in some cases there was one or two alternate feeds so instead of one station, I got two or three. They were clear and steady. I live about 60 miles north east of Tallahassee. If it were clear flat land I could have gotten a good analog signal, but the pine trees suck it up.

Then lightning stuck and took out the antenna, satellite box and DVR. I just replaced the satellite box with a DVR and have been 100% satellite ever since. I may replace the antenna this spring so I can get other stations than just the main local ones on satellite.

[coastie65]

Verizon went to full Digital in April of this year. My TV has an ATSC tuner, so will pick up digital signals. I haven't tried it through a direct connection yet.When I had DirecTV, they only charged for the first Box and the second one was free. I didn't hook up the third TV, but would been charged for a box on that one I think. All the local stations have got their digital service up as well as HD channels. coastie65

[GetReal]

Dlgreen you might be on to something there. Years ago when the FCC sent out its Request For Proposal on new TV broadcasting, I was then working for a separate division of Harris Corp., which eventually submitted one of the 5 proposals finally undertaken for consideration by the FCC. Not being directly involved I am sure I missed much of that activity but I do know that Microsoft wanted one of the picture formats to be identical to something used on computers, giving needed compatability. So Harris included 800x600 i/p as one format their proposal would support, along with compatability to existing formats and to various 16/9 wide screen, audio, etc. Also knowing digital broadcasts would be more difficult to receive (Harris was then already producing digital radios & video for the military), their proposal included lots of error correction and other compensation/fallback capability. This was rejected with the excuse that it would be to costly to produce TV's---humbug, as new technology is always initially expensive but then the volume manufacturing process soon compensates! So now we have expensive TV's that oftenly have difficulty displaying anything or anyway giving reliable service to viewers.


In my h-opinion, the Harris proposal provided much better formats and capability than what was actually accepted by the FCC after "testing." So one might conclude that FCC selection criteria were biased in favor of some other considerations!

[GetReal]

Rgreen4 you might be into an anomoly or something there, or I am. Like you all local channels started the switch to digital about 2 years ago, by broadcasting two signals. Not then being on Sat-TV I had a modest $65 radio shack antenna in the back yard at about 25 feet high. I could/can get 11 locals on analog but only get one channel of digital consistantly and one other marginal/unwatchable, this about 45 miles SE from Orlando Fl., with a then near new Toshiba "digital ready" TV, confirmed with a new "Xmas" delivery of a Sony 46" TV. So after experimenting variously I gave up on the idea of antennas, rejected cable service as expensive and then got DirecTV. With them, for $5 monthly over standard service, I get 26 of what they call locals. Florida has lots of scrub pine trees everywhere, including adjacent to me, I am sure this was part of my problem in reception but does not compare with your experience. Digital TV service is still so new that I don't think it is well understood yet but do think in February there are going to be very many people disappointed in what they can receive. Since digital uses less bandwidth per signal than analog, then at same transmitter power it should automatically provide a better signal to noise ration (better reception) but the digital format (with me) seems to reduce any advantage significantly.

[mjd420nova]

Adama: Well, it goes like this. My digital box is using the analog video/audio outputs and the TV set has the PIP feature, so I can watch two shows at once with a split screen instead of the small frame in the corner conventional setup. I am also not the only one in the house paying for a digital hookup, one set has the DVR option to allow me to record another show and the other box has it's video output going to a PC with a video capture card with a DVD burner, so that gives me another option there. I've done some playing around and found it pretty amazing what options I do have, thankfully I don't pay for the other two boxes as they are in the kids rooms and it only cost an additional $15 each for the other boxes.

[rgreen4]

Of course the fact that my antenna was almost 20' high may explain the better digital reception and the fact that it made an excellent lightning rod.

Like you, all my reception today is over DirecTv and I get 6 "local" channels out of Tallahassee, three are HD (currently both HD and SD are listed for those three). The HD versions have just recently shown up.

[dlgreen]

Tv antennas had to cover up to channel 83. The switch to digital is eliminating channels above 53, which eliminates a few elements and the resulting length. A "digital" antenna would be less expensive if it weren't for the inflation in the price of aluminum. Some early model digital antenna included only the UHF band with the temporary digital channels. Since many stations will go back to their original channel, these antenna may not work while, ironically, the old analog antenna that cover all channels will work!

[dlgreen]

GetReal, you are mixing two issues. Formats, such as 800x600 are a separate issue, and are mainly a question of how much complexity to mandate in receiver displays. The information in the bits is one things. Receiving all of the bits via an antenna is another. The issue with 8VSB (8 vestigial side bands) is that it is like 8 separate signals spaced over the 6 MHz TV channel. Early color TV has similar issues with ghosting causing color shifts from the color carrier shifting phase/arrival time. Each sideband is a different frequency and can react differently to reflections (ghosts). 8VSB is sensitive to relative shifts between those 8 carriers, and an error means faild number crunching and a black screen rather than an annoying color shift. Fringe antennas are more directional, which is why people with the snowy pictures will be the winners. 8VSB testing looked at fringe areas and urban areas, but I didn't see any mention of suburban areas with trees that sway in the wind.

Superior systems, like CODFM, made the leap from theory to practice just as the FCC started to pour concrete on the issue. If they were an auto company, the first shipment would have been recalled. They are now working on stealing another chunk of bandwidth in each TV channel (more degradation of the HD's ability to keep up with motion) to create a sub-standard definition (YouTube quality) channel of a new format (CODFM?) that works with cell phones and other non-stationary devices.

[GetReal]

My comment about picture formats is probably irrelivant but was intended to be background to the fact that the FCC probably did not select an optimum standard, for whatever reason. Comments about bits were intended to be taken at imbedded propagation level as some form of modulated RF signal (aka, if some brief or recuring instant of signal reception is munged by static, fading or whatever), not after decoding to some point by the TV or STB, where the sidebands would then be more apparent and have whatever good or bad effects. So called "ghosting" is an effect of either fading and/or of signal reflections on different frequencies within wide-band signals, regardless of modulation format. The military well understand this and correct for it by diversity reception (using 2 or more widely separated antennas and some form of combiner), not a viable solution for TV reception. Anyway, my statements in this thread support my own experience and that of things I have read, both technical and personal info. My TV antenna is mounted high, very directional, large and with many elements, requiring a rotator to receive various channels, but still substandard only with digital. Also as previously stated, I don't think conditions effecting digital broadcasting are yet well understood at our level and people should expect surprises