DTV Reception Guide (2)

Digital TV Antenna Requirements

Your digital TV antenna plays a critical role in the reception of DTV broadcasts. Discover all you need to know on indoor, outdoor, and smart DTV antennas, and see what you can do to help improve DTV reception.

Philips Amplified Indoor DTV Antenna

DTV Reception Facts

It is an unfortunate fact that the TV antenna and its downlead are often taken for granted by almost everyone, and few realize the importance of a good TV antenna installation.

The irony is that while people are ready to spend even thousands of dollars on a big screen LCD or plasma HDTV, yet many are unwilling to spend any more than is the bare minimum on their antenna installation.

Yet, the extra cost involved to set up a good digital TV antenna using a full size multi-element outdoor system is nothing compared to the cost of the average TV.

This is even more so when it comes to digital TV reception. A good digital TV antenna can literally make or break the picture since it can give you that little extra decoding margin to remain above the so called digital cliff referred to in our introductory article to digital TV.

The above may be better understood in the light of a study released by research firm Centris which says that 9.2 million of the 17 million U.S. households that receive over-the-air TV reside in what they refer to as 'challenging areas'. This means that these households would receive only four or fewer broadcast TV stations if they use an indoor digital TV antenna or a small to medium omidirectional rooftop antenna.

The top 10 cities cited by Centris as having the most limited digital TV coverage are:

New York

Boston (Manchester)

Philadelphia

Los Angeles

Washington, DC (Hagerstown)

Seattle-Tacoma

San Francisco-Oakland-San Jose

Minneapolis-St. Paul

Atlanta

Cleveland-Akron (Canton)

We are sure that TV broadcasters will somehow have to reinforce their DTV transmission network, but the study shows that many households will also have to upgrade their TV antennas.

You see, DTV does provide a clearer picture and sound than its analog TV equivalent but... this holds true as long as you can receive it.

Specifically, you will receive digital television as long as you have enough decoding margin for your set-top box to reconstruct the image. This level of signal corresponds to the 'digital cliff'.

The subject of digital TV antennas and DTV reception is complex and would necessitate a whole discussion on its own. As such, in this short guide to DTV reception, we would limit ourselves to a few TV reception basics but that may make a whole difference when it comes to the reception of weak DTV signals.

Digital TV Antenna Basics

Digital terrestrial television operates within the same VHF/UHF bands assigned to analog TV. This means that the same type of television antennas apply. Yet in view of the broadcast channel re-allocations we referred to in our introductory article on digital television, you may need to use a different antenna for the reception of DTV.

Digital TV antennas may be divided into outdoor and indoor. Furthermore, outdoor antennas may be further sub-divided into grouped antennas and wideband.

Grouped antennas - like Yagi antennas (consisting of a main boom with a number of arms running perpendicular to it) are tuned to cover only a portion of the respective VHF or UHF band. This means that when it comes to grouped antennas, you may need more than one antenna to cover the full range of TV broadcast channels covering your area. On the other hand, grouped antennas provide a far greater forward gain than wideband multi-directional antennas (such as bowtie type antennas), and therefore are more suitable for long-range reception.

Outdoor and Indoor Antennas

Philips PHDTV1 Silver Sensor UHF/HDTV Digital Indoor TV Antenna

Philips PHDTV1 Silver Sensor UHF Indoor Digital TV Antenna

As long as you live in a primary DTV reception area, a good inexpensive indoor digital TV antenna such as the Philips PHDTV1 Silver Sensor UHF/HDTV Indoor Antenna, should help you receive most of the available DTV channels in your area.

The Philips is a 'directional' type antenna. This means that for best DTV reception, you will have to direct your indoor DTV antenna with its long boom pointing in the same direction as the transmitting TV station.

Directional type antennas provide a much higher gain in the forward direction; the Philips provides 6-7 dB of forward gain. This helps minimize DTV interference from other broadcast stations (as long as these does not fall within the same line-of-sight) due to a narrow acceptance angle.

This higher gain along the forward path also helps make up for the significantly higher signal loss associated with the indoor reception of DTV RF signals.

However...

The Channel Master 4228 UHF antenna is a long-range wide-band (Channels 14-69), 8-way bowtie dipole design directional antenna with a maximum gain of 15.8dB and a beam width of 15 degrees.

Designed for use outdoors, though it can also be used indoors (e.g. in the attic), it provides exceptional performance especially in fringe DTV reception areas up to 60 miles away from DTV transmitters.

Antenna size: 39.5"W x 5.3"D x 36.4"H

To make the most out of your digital TV reception, you have to go outside! VHF and UHF signals travel in straight lines and therefore can be obstructed by hills and tall buildings.

This means that ideally, you should place your antenna outside, positioned as high as possible and pointing towards the transmitting station covering your area. However, keep in mind that outdoor antennas do suffer from deterioration due to their exposure to the elements; they should therefore be checked periodically.

Mounting your digital TV antenna inside the attic, while providing total protection from the elements, can lead to weak reception as roof tiles, insulation, water tanks, etc., can screen the antenna from the incoming signal.

In general, depending on building construction, you can expect to lose anything between 30% to 70% of the signal when mounting your digital TV antenna inside. The signal loss can even reach 100% in houses with metal (aluminum) siding.

This means that the use of indoor digital TV antennas - whether in the form of a full size antenna mounted in the attic, or a specifically designed indoor DTV antenna such as the Philips Silver Sensor featured above - is recommended only in good reception areas. Outdoor installation is always best.

Masthead Amplification and Distribution Amplifiers

If you live in an area where the signals are weak, or need a very long downlead to feed your TV, you may require amplification either through the addition of a separate masthead amplifier, or through the use of an active digital TV antenna. The latter is a TV antenna with a built-in amplifier situated within the antenna junction box itself.

Masthead amplifiers should be mounted close to the antenna to avoid amplification of noise and other interference picked up via the downlead.

Channel Master 7777 High Gain Masthead Amplifier

Furthermore, both masthead amplifiers and active DTV antennas require a power feed that is provided via the antenna downlead itself.

While in general, it is best to avoid amplifiers for digital TV reception, yet if used properly, masthead amplification can be beneficial. Their use is mainly recommended if the signal level received when using a passive digital TV antenna is too low to achieve the necessary decoding margin to enable your DTV converter box or digital TV tuner to constitute the image.

However...

If you are already experiencing interference, or ghosting (multiple images of the same picture superimposed on each other as a result of signal reflections from tall structures, trees, etc.), the use of amplification will further aggravate these problems since interference signals will be amplified as well.

In addition, if a masthead amplifier is used to boost signals from a distant station in the presence of strong local signals, the local signal may eventually overload your system. In this case, the masthead amplifier will need to incorporate specially designed notch filters to block or attenuate the local signals.

In other words, while masthead amplification can make up for weak reception signals, yet it cannot correct poor signal quality resulting from multiple image reflections and interference.

And what about Distribution Amplifiers?

In general, it is possible to run up to two TV receivers off the same digital TV antenna by using a simple passive signal splitter - which as its name implies, divides the RF signal between the receivers. This means that each TV will get half the original signal received via the antenna.

However, if the signal is not strong enough to support passive splitting, or if you wish to run more than two receivers and long feeding leads, then you will need a distribution amplifier. Various types are available for domestic use; these normally can serve anything between four and eight receivers.

Electroline 8-port RF distribution amplifier

The Electroline EDA-FT08100 featured here is an 8-port RF distribution amplifier with a forward gain of 3dB per port.

Like masthead amplifiers and active digital TV antennas, distribution amplifiers are mains powered - normally via one of the downleads and by the same power box used to drive the masthead amplifier. Distribution amplifiers power consumption is minimal and are designed for continuous running.

And as with masthead amplifiers, the use of distribution amplifiers may lead to interference problems - mainly in the form of patterning interference. If this is the case, try to substitute the distribution amplifier with a lower gain one; alternatively, you may need to use specially designed filters. You will need to consult with the manufacturers' installation instruction.

DTV Reception Made easy - Smart Antennas

DTV reception is not as easy as analog TV reception and once the signal is lost, it is not always obvious how to get it back!

To make DTV reception easier on the consumer, the Consumer Electronics Association had adopted a standard - referred to as EIA/CEA-909A - that allows the DTV tuner to control the position and gain of intelligent antennas. These TV antennas are often referred to as 'Smart Antennas'.

A DTV receiver or digital TV converter box with an EIA/CEA-909-based compliant interface can select any one of up to 16 antenna positions and up to four gain settings for an EIA/CEA-909 compliant smart antenna. Control is achieved either through a special Smart Antenna port on the DTV tuner box itself, or over the same RF antenna connection.

Unfortunately, at present there is not much choice for Smart Antennas - possibly because these are considered as slow movers by retail outlets due to their relatively slightly higher cost.

We are only aware of one such model - the DX Antenna DTA-5000 TV Smart Antenna. The DTA-5000 is a compact VHF/UHF multi-directional antenna designed for outdoor use. It has a CEA - Green zone certification and a maximum gain of 25 dB over the full UHF band.

DX Antenna DTA-5000 DTV Smart Antenna

Note: In your search for a smart-type EIA/CEA-909 compliant digital TV antenna, you may come across the Channel Master SMARTenna 3000A. Despite the 'SMART' label, and despite that various online resources point to the Channel Master 3000A as a 'smart' digital TV antenna, yet this is not the case.

The SMARTenna specifications clearly indicate that the 3000A does not come with a smart antenna interface. Instead, this is basically a small outdoor VHF/UHF multi-directional antenna (CEA - Yellow Zone rating) with a maximum gain of 20dB for use in areas of strong TV reception. In other words, the SMARTenna label is just a product name.

Being an omnidirectional antenna implies that the 3000A represents a convenient solution in applications where off-air TV signals come from different compass directions, yet this TV antenna is not suitable for use in areas with high multi-path (ghosting) problems.

The GE 22730 Converter box with smart antenna support

Unlike smart antennas - which as stated are somewhat more expensive than standard digital TV antennas, DTV set-top boxes with Smart Antenna support fall within the same price bracket as other DTV converter boxes.

This means that opting for a DTV box with smart antenna support may be worth considering even if you do not have a smart antenna since it gives you the option of adding one later.

Note however that when it comes to smart digital TV antennas, some converter boxes will work only with their own brand smart antenna i.e. as a smart antenna - converter box pair. A case in point is the GE 22730 converter which will only work with the GE smart digital antenna.

DTV converter boxes worth considering with Smart Antenna support include the RCA DTA800, the Tivax STB-9, and the MaxMedia MMDTVB03.

Antenna Box Labeling - CEA Certification

Not sure which digital TV antenna is right for you? Help is on the way. The CEA had come up with a color coding certification system for outdoor antennas. All you have to do is to match the CEA-certified antenna color mark with the color of your station.

This CEA-certified antenna mark for outdoor antennas is divided into six different zones - each corresponding to a different color - yellow, green, light green, red, blue, and violet. These zones identify the different types of antennas that are required for a consumer to receive optimal reception.

For example, a large directional digital TV antenna such as the Channel Master 4228 featured above, can be used to cover any color code area - with amplification and roof mounting for blue and violet colors, and without amplification for yellow color codes.

Typically, the closer consumers live to the signal tower, the better reception they will receive. They may also be able to use an indoor antenna versus an outdoor. The farther away a consumer lives, the opposite is true.

CEA Antenna Selector color code scheme

There is also a CEA-certified indoor antenna mark, which does not apply to this mapping system, but certifies that your indoor antenna will work in geographic areas that are appropriate for indoor antenna use.

CEA Indoor aerial certification

To determine which color code corresponds to your station, visit the antennaweb.org website and enter your street address. For more information on the different meanings associated with the different antenna selection color codes, click here.

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DTV Reception Guide (2) Digital TV Antenna Requirements