There are many myths and misconceptions floating around about the upcoming digital television transition in the US, which will be completed in February of 2009. Having spent quite a lot of time experimenting with reception from my location in Washington, DC, I thought it'd be of use to others to write about my successes and failures, as well as clarify some of the misconceptions as I understand them. I am not a broadcast engineer or RF expert by any means; I am writing from my experiences and from what I understand about RF and related physics. YMMV. Updated, 9/21/2008: Trying to clear up further and expand on the problems a preamp can cause.
If you read this guide and find it confusing, please let me know. I can be reached at leitec [a] leitec [d] org.
Please note my experience involves only standard broadcast reception; I do not have cable or satellite and thus have no experience with them. The transition affects only people like me who receive broadcasts with a regular antenna.
That last sentence clears up two of the misconceptions:
That said, antennas do vary in quality, and an appropriate antenna is required for good digital television reception. An antenna or antenna system that works well for analog TV may not work well for digital, or vice-versa. This is highly location-dependent, not only on your local broadcasters but also on your reception location, terrain, etc. There are a few general facts:
The latter two highlight the importance of proper antenna selection and positioning and good wiring. Your current antenna may be pointing in the wrong direction and picking up too many reflections that your receiver cannot correct, or (or perhaps additionally) your cabling is in bad shape. The antenna itself may be fine, so a good first point in troubleshooting a current antenna is replacing the connections to the antenna. At this point you can check for obvious problems like rust, bent masts, etc. Replace the cabling with quality RG-6 coaxial cable (especially if you currently have 300Ω twin-lead) and use a good matching transformer (also called a balun) to connect to your antenna's feed terminals. Also read the section on preamplifiers below, as it may be helpful in some situations, especially if the cable to the TV is long.
If this does not improve digital reception, try re-aiming the antenna towards the transmitters. Sites like TV Fool can indicate the direction to the towers in your area. TV Fool is also useful for finding out the actual digital transmission channel being used by a particular station. Prior to the transition in 02/09, all stations are transmitting their digital signals on different channels than their analog signals, since the two cannot coexist on a single channel. ATSC allows for remapping; this means that on your TV the digital channel will appear under the same number as you already know, despite being transmitted on a completely different frequency. Digital channels also have a subchannel number since more than one program stream can be transmitted in the same physical channel. Most tuners nowadays allow you to manually enter the actual RF channel, so you can adjust your antenna until you can get a good signal.
Once/if stations change frequencies you will need to re-scan the channels on your receiver.
An important point to note is that digital television does not degrade into snow as the signal weakens like analog television does. As I said before digital receivers can generally work with weaker signals and still receive the full signal, but it is a digital transmission subject to the cliff effect. Basically, the receiver either has a good signal or it doesn't. You won't get snow or ghosts if your signal isn't strong or is distorted; you will either lose the signal completely or have visual or audio artifacts or freezeups. ATSC has forward error correction and newer tuners are much better at handling certain forms of distortion (like multipath) but some errors cannot be corrected.
Note also that all of this is independent of the resolution of the digital TV signal. ATSC tuners can decode all formats, whether standard-, enhanced- or high-definition. The TV station decides what resolution to broadcast in. If you get the signal at a point your receiver can decode it, you will get the picture in whatever resolution it was sent. There is no mechanism currently in ATSC whereby you receive a lower-resolution signal if your signal isn't strong enough. Don't let anyone fool you into buying a certain "HD" antenna promising a better picture; that is a lie. And remember, the "D" in DTV and HDTV do not stand for the same word. DTV is digital television; HDTV is high-definition television. HDTV broadcasts use DTV transmission, but you do not need an HDTV to get DTV. Conversely, not all HDTV is digital; component video as found on consumer HDTV sets (YPbPr, or the red-green-blue jacks) is analog but can provide high-definition video. You will be able to watch high-definition programming on a standard-definition set or converter. It won't be high-definition, but it may very well look better even on a standard-definition screen.
Current-generation DTV tuners can tune in signals from an indoor antenna in many cases. Most of my experience is in fact using an indoor antenna as I rent my house. The good news is that if you can get TV with an indoor antenna now the odds are you will get great digital reception indoors as well, with the added benefit of high-definition (if you have an HDTV) or at the very least a picture without snow, ghosting or other visual distortions.
Even so, an outdoor antenna is almost always better if your location allows for it. If you own your property the FCC protects your right to install an antenna for TV reception. The regulations override any bans by homeowners' associations, city councils and other such regulatory bodies in almost all cases. There are also some protections for renters, but your landlord will still have a say in permanent modifications.
If you must stick to indoor reception, again all is not lost and you may very well be surprised by the results. The caveats are the signal you receive is undoubtedly weaker than with an outdoor antenna, and distortions from moving cars, people, pets, etc. can cause errors. These can be seen with analog TV, of course, but as discussed before the results of distortions are different between the two formats. Where you place the antenna is also a factor, just as it is with an outdoor antenna. The process of positioning the antenna is more trial and error than with an outdoor antenna, though, since most indoor antennas are less directional than outdoor antennas and there may be reflections within your house. Experimentation is really the best way to determine optimum placement. Generally the signal is stronger near a window in the direction of the transmitter tower, and generally the higher you are in the house (if you have the option) the stronger the signal. These are not universal due to factors most likely beyond your control, but are good rules of thumb.
If you have no antenna at all (indoor or outdoor) and want to try off-air DTV reception, the most sensible way to start is with an unamplified rabbit ears and loop combination antenna. These can be purchased for $10 or less, and will give you an indication of what is needed. In some cases that may be in fact all you need. Experiment with placement; if you have a small TV you can try different places in the house, but try to keep the cable short when first determining a good location. The rabbit ears are for VHF, and the loop for UHF; again consult the local channel tables to determine what you need to adjust.
If your reception is satisfactory with just the cheap antenna, great; you are done. If not, things get a bit more complicated. In all likelihood there is not that much difference between small indoor antennas, even the more expensive models. Many are further examples of marketing at work. I will go as far as to place the entire line of amplified set-top antennas in this category. There may be exceptions, but amplification is generally not going to play a part in what you can receive and the built-in amplifiers are most often of poor quality. Stick to unamplified antennas and use an external preamplifier if necessary. I will discuss that later. Some are less kind on internal antennas than I.
If you have the room to hide a bigger antenna (or simply don't mind the visual) there are some bigger antennas that can be easily used indoors. Two popular examples are the Antennas Direct DB-2 and Channel Master 4220. These have higher gain figures and more directionality than most indoor antennas, but both are UHF-only. You'll still need rabbit ears for VHF, and can use a VHF/UHF combiner to join both on a single cable to feed to your TV. Rabbit ears are about as good as it gets for indoor VHF antennas. Outdoor VHF antennas are very large again due to the longer wavelength compared to UHF. You can probably take up half of an average bedroom with an antenna designed to go down to channel 2 (54-60mhz). A Silver Sensor equivalent at VHF frequencies would be huge. Rabbit ears are strongest on the broad side; that is, point the "V" towards the station. The same applies for UHF loops, and for the bigger UHF antennas I mentioned the "whiskers" are pointed towards the station. For all of these you may replace "towards the station" with "towards the strongest reflection" if that is your case (read my example below).
If you find that a position farther away from your set works best, you can place the antenna there and run a cable to your set. Use high-quality RG-6 coaxial cable to minimize interference and loss. The longer the cable, the higher the loss, and the higher the channel, the higher the loss. If your reception is worse with the antenna at the same spot but with a longer cable, this is where a preamplifier can come in handy. Preamplifiers vary greatly in quality. You want a low-noise preamplifier with a sufficient amount of gain to offset the cable loss. These are placed as close to the antenna as possible to amplify the signal before too much is lost or too much noise is introduced. The two I have used are the Winegard HDP-269, a medium-gain, fairly low-noise amplifier intended for locations with strong signals, and the Channel Master 7777, a high-gain, low-noise VHF/UHF amplifier. Amplifiers, particularly higher-gain amplifiers, can overload and actually worsen reception; the effect is akin to speaking closer or louder into a microphone to be heard louder, but in result being less understandable due to distortion (that's not an exact analogy but it's close). Noisy amplifiers can also do little to improve, since the noise they create may be stronger than the amount of signal you are losing due to the cable, or noisier than the signal being received at the antenna. Low-noise preamplifiers (the CM7777 has a 2.0db noise floor) can theoretically improve the signal-to-noise ratio for weaker stations in addition to the offset in cable loss. But don't count on a preamplifier to receive something you can't receive at the antenna with a short cable; this may happen, but you are more than likely going to be disappointed unless you are shopping for preamplifiers in the $500 range with noise floors around 0.5db. Even then it's still not a guarantee. But all this noise-floor business is difficult to measure and what you need is difficult to assess. Published figures may not represent actual results, either.
Another note about preamps: beware of nearby FM stations. Even if your TV stations are 50+ miles away, a great many places have local FM stations that'll cause overload problems on your amplifier. Check FM Fool to see what's close to you. Nearby FM's can be a problem even if your preamp has an FM trap. If this the case in your area, try either passing VHF unamplified (since the signals degrade less over the same cable length verus UHF) or by employing filtering. If you want to amplify only UHF, you can use a VHF-UHF combiner, commonly referred to as an UVSJ, with the VHF side terminated with a 75Ω terminator. If you are in an area where no broadcasts occur below physical channel 7, you can use a high-low combiner (HLSJ in common parlance) similarly, terminating the VHF-low input. Since most HLSJ's also pass UHF on their high side it can be an easy way to filter FM stations from your system. It might be worthwhile even without a preamp.
A further warning about preamps: beware of other radio services that use frequencies in or near the TV bands. I have one preamp that is still designed for when TV went up to channel 83. Channels 70-83 were reallocated for cell phone use, and you could likely have a close-by cell phone tower that your UHF antenna is picking up; some actually have positive gain on those frequencies. The same will be true for channels 52-69 after the transition next year. There are also other radio services that are authorized to use unallocated TV frequencies. The lesson out of all of this is that preamps are really tricky to get right, and should not be on your shopping list immediately. If you do indeed find that connecting right up to the antenna with a short cable works then you might make good use of one, but keep these non-TV sources of interference in mind.
Filters to eliminate these unwanted signals from going into your TV antenna system, but can be hard to find. I do not know of a off-the-shelf solution for anything other than FM. If you are serious and convinced you need a preamp you could investigate further.
If you have a good position and want to run cables to two or more sets, you can use a splitter. Splitters themselves cause the signal to be lost, as does the additional length of cable. This is another situation where you may need a preamplifier. Another option is a distribution amplifier, though I have not used these and cannot make recommendations. Try without amplification first.
A further option if your situation allows is an attic-mounted outdoor antenna. This is, generally speaking, better than a small indoor antenna and worse than an outdoor-mounted antenna. Construction materials cause signal loss and reflections, with some materials worse than others. However, it can be worthwhile in a lot of situations and allows you to get the antenna out of sight if that is important for you. The same wiring guidelines for outdoor antennas apply, and a good preamplifier may help, but the same warnings above apply.
Since installing an outdoor antenna, a Winegard HD-1080, I have not needed the Samsung tuner and have reverted to my TV's built-in tuner. Despite the terrible marketing name, the HD-1080 is a good performer in my situation, providing the necessary VHF-HI coverage for the stations reverting to 7 & 9 next year, and good UHF reception for the rest. (Although the manufacturer's specs show poor VHF-HI performance, my proximity to the transmitters makes this more or less irrelevant. It's doing a good job bringing in the only local VHF digital station, the low-power, 200W WMDO-LD 8.) That's a good sign for 7 and 9 next year. It's split at the rooftop to service upstairs and downstairs and still has a very strong signal with no amplifiers. It was installed by Fairfax Antenna, which I'd recommend to anyone in the DC area wanting a professional install.
I had the installer mount my CM4220 on the roof as well, pointing towards Baltimore, but due to severe multipath this is not working well--the digital doesn't lock, and the analog is also a complete mess. You can see two equally-strong images, plus some more, weaker ghosts. This antenna is on a separate coax run only to the Insignia tuner. I believe with a bit of further tuning it might work well; I didn't want the installer to waste too much time on it. I suspect the same reflection I took advantage of to make indoor reception possible is what's killing the more direct, rooftop reception. In this case the reflection is nearly as strong as the direct signal. It does get WMPT-DT 42 very well, though, which has more or less been impossible from indoors lately, though I recently found a good indoor position that works well with my Silver Sensor. Other recent experiments make me believe that even the largest and longest beam antennas (like the narrow-lobed 91XG, which I have experimented with indoors) will have trouble here due to excessive multipath.
The following is my old indoor setup, left for reference:
I have two tuners in my small, two-story house. The tuner upstairs (Insignia NS-DXA1) is more sensitive and seems better at handling multipath than my downstairs tuner (Samsung DTB-H260F), which is itself an improvement over the built-in tuner on my very cheap downstairs HDTV ("Polaroid" 15-inch POS). I live within the city of Washington and thus have many reflections to deal with but the signal is strong since I am only a few miles from the towers. I can only use indoor antennas since I rent. A small indoor antenna I bought for $8 works to receive all the DC channels perfectly, with small adjustments occasionally required. Actually, a mere paperclip inserted into the antenna jack on the tuner picks up almost everything, but that is of course not exactly reliable.
Being only about 30 miles to Baltimore I explored the possibility of getting its TV stations. I found a position in my house that picks up a reflection from a source unknown that gives me strong reception of almost all the Baltimore digital stations. But since the signals are weak compared to the local DC stations, and because splitters and long cable runs can cause you to lose much of what you have it's problematic to get this signal to both TV's, upstairs and downstairs. I have a 25 foot cable run from this location to the TV upstairs, and 50 feet to the TV downstairs. Running both into a splitter causes the Baltimore stations to go away. I've resorted to manually switching between the two, and keeping an antenna downstairs for mostly solid DC reception.
I experimented with preamplifiers before the splitter, and while they do generally work to get the signals to both TV's they are problematic. The Winegard HDP-269, which has a high signal tolerance but relatively low gain, works well with almost all stations but can't get at least one weak station past the splitter and long cables. The Channel Master 7777 does not have the high signal tolerance and instead has super-high gain, as it is intended for weak-signal areas. Even with the indoor antenna it was overloading slightly, and although it got the channel in question (WMPT DT-42, from Annapolis, MD) past the splitter it was still very weak and the signal output was so strong on some channels that my upstairs TV's front-end overloaded when watching analog channels. I eventually decided the bulk of the additional equipment and the overall unreliability was not worth the hassle. The antenna is now hooked up to the upstairs TV with no amplifier on the 25' cable, and I can swap it for the downstairs cable if I really want to watch something from Baltimore in HD. An additional note is that since the signals at that location are reflections, both of the DC and Baltimore stations, they are more prone to distortion from passing airplanes and fade out more easily during bad weather.
The actual antenna has changed pretty often. At first I used Channel Master 4220 since all channels are currently UHF. This worked fine but I needed to move it from side to side on the windowsill where it was placed. I tried a CM4221, but found it actually worsened reception; I lost some of the Baltimore stations. Reception is often a mystery and things don't always make sense as you expect them to. Furthering the trend of downsizing I tried a Radio Shack UHF bowtie antenna (item 15-234), soldered a matching transformer (15-1140) directly to it, eliminating the twin-lead cable completely and connected it to the preamplifier, while I was still using one. This was a good setup, and I could watch most channels on both TV's without moving the antenna around. Note that the modification I made was very important; reception with the twin-lead cable caused interference. By connecting the coaxial cable as close as possible I eliminated this interference. I used a 2' RG-6 cable between the antenna/transformer and the preamp. Still, as noted above, the reflected signals plus the fact that the bowtie picks up signals (and thus interference from moving objects) from the back this isn't the ideal setup.
My current antenna for the upstairs TV, now hooked up without a splitter or preamplifier and running only to said TV, is a homemade log-periodic for the UHF band. It seems to be relatively flat across the band, but has lower gain than, say, the CM4220. Nevertheless, I can narrow in on the reflections and pick up very strong signals for Baltimore and DC. The Insignia converter box's tuner is very good at correcting errors so this is quite reliable. For downstairs, I went with the "Silver Sensor" antenna, which I decided to try since you can now get the unamplified version for under $15 online. Pointed just right even my TV's built-in tuner can get all the DC stations, but the Samsung tuner is more forgiving. A recent round of severe weather prompted me to put something more effective for local reception at the expense of the out-of-market stations.
The stations I get from my house (zip 20002) with the current setup are:
Written by Claudio Leite. Last modified 2008-06-13.