Are indoor digital TV antennas directional?

Yes, but to a very limited extent.

The most common indoor antennas generally may have rabbit ears, discs, and dials. The rabbit ears, contrary to popular belief, get the best directional signal when they are laid flat with both sides sticking straight out, perpindicular on a plane parallel with the earth, and perpindicular to the line from the broadcasting tower.

The length matters, too, but it depends upon which station is being received. You can set the length in the middle, to the stations you like best, or adjust it for optimum reception for each channel.

Loops should be arranged so that the plane that intersects the entire loop is perpindicular to the line from the broadcasting tower. Discs generally are plastic covered loops and should be arranged the same way.

Dials make some adjustment in the electrical properties of the antenna. Try each dial position, do a full channel scan, and mark the positions that pull in maximum channels. Then narrow it down from there by watching the channels for a while.

Now with that said, these rabbit-ear, loop, disc, dial antennas are not particularly directional because they do not make up for shadow signals that bounce off mountains and trees and buildings (whereas truly directional antennas, outdoor antennas and higher quality directional indoor antennas make compensations for these extra signals.). If the reception is still not satisfactory, then look for an antenna that is truly directional, omnidirectional, outdoor, or has a signal boost.

Tuning for digital transmissions is complicated because the picture comes in perfect, not at all, or perfect with sporadic corruptions, which you don't see right away when tuning. For more about selecting an antenna and tuning it, read on...

Going by outdoor antennas (which have definite directionality), antennas specifically marketed as directional have a gun shape to them that you just point. Other indoor antennas are specifically marketed as omni- or multi-directional. With these, there is no problem with aiming. Although they may not be the optimal antennas when all stations are in one direction, they are probably just fine (as I believe they are usually of higher quality than the uni-directional ones.) The information below may also be helpful for aiming and fine-tuning indoor antennas for digital TV reception: After finding the direction and distance of all the transmitting towers for digital television in the area (from the customized map at www.antennaweb.org), the next step would be to choose an antenna, hook it up, and aim it.

The antenna does not have to be "digital ready". Antennas are pretty much the same for analog and digital TV. (However, it is smart to know the characteristics of digital broadcasts in your area because of the difficulty in tuning to them.) You can start with whatever antenna you have, and if it does not work well enough, then research and buy a more appropriate one for your area. If you have no antenna at all, then try sticking the center wire tip of a cable TV cable into a potato or an orange--just to get an idea of the basic reception in your area. It will last a couple weeks until the vegetable dries out.

You need to be particularly choosy about your antenna if you want to receive channels 2-6, and to a lesser extent for channels 7-13. Channels 14-83 are the easiest to receive digitally, and most any antenna may do for those depending upon the distance and direction. If you are not satisfied with your reception on 2-13, but get 14-83 just fine, then you may want to just be patient rather than investing in an antenna: because of the large degree of difficulty with tuning these stations for digital transmissions, most stations are soon moving to the UHF band, channels 14-83. If you cannot wait, then focus on antennas designed specifically for both VHF and UHF (not only UHF in this case). In deciding whether you need a VHF antenna or not, you must realize that the stations have been renumbered and no longer represent the frequencies they broadcast on. For example, Digital channels 2-1, 2-2, 2-3, 2-4, 3-1, 5-1, 8-1, etc., are not necessarily broadcasted on VHF channels 2-8. To find out the broadcasted channels you must refer to a list like the one at www.antennaweb.org. (However, that website seems to only show the analog and dash-1 digital channels, not the dash-2 thru 5 channels, so another source must be sought).

If all the stations that you want are in the same direction from your house (within 20 degrees or so), then you can use a directional antenna and aim it right at the middle of the stations. Outdoor antennas come in 2 basic types, directional and multidirectional. Multidirectional antennas do not have to be aimed. To aim a directional outdoor antenna, follow the directions from the manufacturer. Indoor antennas are another story. They often come with no documentation, either in the box or on the manufacturer's website regarding tuning or aiming. They may only say turn the antenna until you get the best reception. This works fine for analog broadcasts because you can see the difference in quality when you turn the antenna. But digital broadcasts are different because the picture is either perfect or non-existent, or it corrupts at odd times and stops for a while (closed captioning may turn to gibberish, blocks of the picture turn colors or look like lower resolution, the screen freezes, and then a few seconds later it may restart). To tune an indoor antenna for digital reception the best method may be to try different positions of the rabbit ears, disc, and dial, and write them down methodically, doing a new complete scan for channels each time, and then count and write down how many channels are found each time. This is a better method for digital because the number of channels found is a better indication of signal quality than the visible picture quality. Be sure not to do manual scans because those function only to add new channels not to count the number of channels receivable. This method would work best when all towers are in one direction. If stations are broadcasting from different directions, then you should write down not only how many stations are detected, but which ones. Then your job is to come up with multiple settings combinations that get all the different stations you want at different times. After you have discovered them all, then do manual scans in each setting (if your TV has that function) to add all the stations. Then, keep a note close to your TV about which settings to use when actually watching each station. You may need only 2 settings to cover all your favorite stations (and in most areas only one setting will probably be satisfactory).

Since modern digital TVs have computers, one function really missing from them (exists in some models?) is a function to evaluate the tuning quality. Wouldn't it be great if your TV reported the signal quality it is receiving for each channel? I am not an engineer, but from what I know of the way digital TV works, it seems like such an easy function that I wonder if it is not already built in to TVs, but just not publicized. I am definitely looking for this function to appear soon.