Reader Question: Digital TV Reception

Q: We recently purchased two digital converter boxes for our analog TVs. Although the pictures are generally very good, occasionally the picture freezes or distorts, as does the sound. This happens on both TVs. Each set is connected to its own antenna. Do I need a different type of antenna to receive the digital signal consistently or do you know what I need to do to fix this problem? Thank you for any help you can give.
L. H. OConnell

A: The likely cause of your problem is that your signal reception is marginal. It’s possible that this may improve when the February 17, 2009 changeover occurs, as some of the broadcasters may switch their digital broadcasts to transmitters with more power. But it’s probably a good idea to address the problem now, just to be safe.

With a weak analog signal, the image and sound are processed, but with static and “snow” and other distortion, sometimes to the point where the image is impossible to see. Digital signals are different; they “fall off the cliff” when they get too weak. You will get an excellent picture — as clear as a DVD — until the signal falls below the threshold, and then it will freeze, break up into large blocks, or just go altogether blank. Unfortunately, a weak analog signal can still be good enough to watch, but a weak digital signal won’t work.

What can you do about this? First, if you are using a directional antenna (such as one of those large, branching types typically mounted on the roof), you want to make sure that it’s pointed straight at the transmitter for the station you’re trying to receive. If the local stations are in different directions, you’ll need a rotor. If you go to www.antennaweb.org, you can find out the compass headings and distance for the stations in your area. It’s a free service, and very useful.

If this does not solve the problem, then you may need an antenna with more gain, which means that it captures more of the broadcast signal. www.antennaweb.org will give you some guidance about the type of antenna that may work best for your location.

The other step you can try is to get a signal amplifier. This connects between your antenna and your converter box, and will boost the signals received from your antenna. Note that inexpensive models tend not to be very effective, so you’ll probably need to get a good quality unit in order for it to help.