TechnoBabble

In another blog, FarmTruk asked two questions about digital converter boxes and the answers turned into a blog of their own so instead of eating up comment space, I have decided to just create a new blog entry since these are such great questions that others may have as well.

FarmTruk askes:

Q. Will the new digital signals and converter box improve fringe area reception?

A. Yes and no. One of the great things about digital TV is that the picture is always perfect. No static or snow. If you are receiving the signal you have a perfect picture.

One of the bad things about digital TV is if you do not have a good signal, you do not have a watchable signal unlike analog TV where you can still see a picture, it just may not be very clear (in digital it is called the "Cliff Effect" it is either there or it is not.)

Now having said all of that, I have played with several generations of digital turners with good success over the past 5 years and I can tell you that while signal strength is important, (like with analog, you have to have a signal to begin with before you can receive anything) but the "quality" of that signal is more important.

For example, when FOX8 first went on the air in digital in 2002, we were transmitting a whopping 4200 watts. That was 0.0042% of our allocated 1 million watts! I live in north Greensboro and with our tower at Randleman, signal strength was very low, to say the least, but I had a viewable picture 99% of the time with a modest wire mesh antenna (Channel Master 4228) on my single story house. Digital receivers have greatly improved since then as well has our power output. We are now broadcasting at 1 million watts and we now get reports of reception from Martinsville, Sanford, The Wilksboro's and north Charlotte which is the same as our channel 8 analog coverage.

From north Greensboro I get the Roanoke digital stations as well as the Raleigh stations with no problem using the same wire mesh antenna I put up in 2002, which comes in handy when the local stations pre-empt a network show I want to watch. People in Winston-Salem regularly pick up the Charlotte stations and people in High Point pick up both the Raleigh and the Charlotte stations.

For those looking for a more "technical" explaination, strap in, here comes digital TV 101!

So what does a "good quality signal" mean in digital TV? Unlike analog TV that is made up of two signals, one visual, one aural, that increases and decreases in strength as well as width over the spectrum depending on the content of the picture, digital is the same strength and width no matter whether it is a stand def or high def picture and it is actually a square signal as in the following picture.

So as long as the signal quality is good (in technical terms called the signal to noise ratio) you will have perfect picture and perfect sound no matter how close or far you are from the tower meaning as long as the receiver basically sees this shape signal, the signal level doesn't really matter. Of course you don't want this signal to be greatly tilted on either side because that will cause a loss of picture (Cliff Effect). Receivers very close to transmitters will have a deformed signal that will not decode properly because of too much signal into the receiver (receiver overload) to the point that the signal doesn't look like this anymore (squashed or tilted or many valleys as the receiver tries to reduce and deal with too much signal) and there will not be any picture displayed on your set.  You would have to reduce the signal strength coming into the receiver so the signal will be square again by using attenuators or removing an antenna booster.

As as you see, in digital, signal level isn't as important as the signal quality. Just  because you are close to the transmitter doesn't mean you will automatically get a picture! Common sense goes a long way even if your technical knowledge is limited.

Q. Will this new box work equally well on the currently VHF and UHF stations?

Yes it will. Because of the way TV waves work, lower channel numbers carry farther with less power than higher channel numbers. In the digital world, our 1 million watt channel 35 digital signal only needs 15,000 digital watts at channel 8 for the same coverage. It is as easy for receiver manufactors to build receivers in the lower channels as it is for the upper channels. There isn't any real difference these days between the VHF and UHF channels on any TV tuner.

Keep the great questions coming!