Digital Television Troubleshooting Guide

We have already covered a good deal of information on Digital TV reception.

Still, there may be a few points worth considering when it comes to troubleshooting problems that may arise in the process.

1. Antenna Repositioning and Pointing

A significant improvement in the received signal level and quality can often be achieved by simply repositioning the outside digital television antenna, either by using a longer pole or by moving the mounting point to a different location on the roof.

If you are using an already existing antenna - originally used for the reception of analog TV, this may need to be realigned to pick up the new DTV services as detailed further on in this article.

2. Replacement TV Antennas

Because of the channel re-allocation associated with the digital television transition process, some DTV signals may be out of group from the existing analog channels. If this is the case, than you have to use a different group antenna. As indicated in our DTV antenna guide, your best bet when getting a new antenna is to ensure you get a CEA certified TV antenna.

Sometimes, a higher gain antenna may be necessary. In DTV overlap areas where the same digital television broadcast channel is used on two different transmitters, it may be necessary to use a highly directional antenna.

This should then be pointed towards the required broadcast station to minimize RF interference from the intruding broadcast station. In this case, the use of a TV antenna rotator such as the Channel Master 9521A Remote control antenna rotor may be necessary to help position the antenna for optimum reception when viewing DTV programming from different broadcast stations.

3. Cables and Connections: Do not fall to the 'low loss' trap

Use of high-quality UL-rated dual or quad-screened RG-6 coaxial cable—such as the quad-shield RG-6 UL-approved 75-ohm coaxial cable by MP—for the digital television antenna downlead, complemented by good quality RF connections between equipment within the house, is essential for best DTV reception results.

Do not use inferior quality cable with poor screening, and do not fall to the 'low loss' trap. Unfortunately, the terms 'low loss' and 'ultra low loss' are often abused by some cable retailers to help sales as non-technical users tend to associate 'low loss' with premium quality. But a poor quality cable can still be 'low loss' and correctly sold as such.

Do not take us wrong. Use of 'low loss' and 'ultra low loss' designated cables is extremely important irrespective of whether we are dealing with analog or digital television. Low loss cables are designed to minimize the loss when handling signals of minute power such as those picked by a TV antenna.

However, low loss alone is not enough when dealing with digital television. It may be enough for analog TV where interference is more tolerable—showing mainly in the form of 'snow' and intermittent white lines in the picture. But with digital TV, interference would often lead to a freezing picture, an artifact much less tolerable by the viewer.

It is here that proper shielding comes in; shielding is as important as the thickness of the inner conductor. These cable attributes are both defined by the cable type. Instead, the term 'low-loss' does not in itself refer to some cable standard and therefore it can be abused. The inner conductor thickness is mainly responsible for the signal loss, or attenuation while the quality of the shielding determines the cable's ability to protect the signal from interference.

What differentiates poor from good quality cable is the amount of copper. Copper is the most expensive raw material used by the cable industry and as such, it is here that some manufactures try to make their savings. A well built-cable would have an inner conductor of the correct thickness (e.g. inner core diameter of an RG-6 is 1.0mm) and an outer copper shield that gives 100% cover to the dielectric and inner signal conductor underneath. In cables using twin-shield made of copper wire and foil, the copper braid on the outside would often cover some 60% t0 95% of the metal foil shield underneath. All one would has to do to determine cable quality is to inspect the way the shield looks after carefully removing the outer cable jacket—the more cover it gives the better. The use of both foil and braid shielding helps provide a more effective shielding against both high and low frequency interference. Note that a way to save on copper in twin-shield cables is to use copper braid shield and an aluminum foil underneath. This is equally effective but when used outside, copper braid on copper foil cables lasts longer.

Note: When working with coaxial cables, you have to use the appropriate connectors, crimp tools and coaxial cable cutters. If you are in the process of a whole-house installation, it may be better to go for a 250-feet or even better a 500-feet wiring kit such as the Cables To Go 29836 RG6 Quad Shield Coaxial Cable Installation Kit - which apart from the 500ft of RG6/U quad-shield in-wall coaxial cable, also includes a cable-cutting shear, a dual blade coaxial cable stripper, coax hex crimping tool, F-type connector removal tool and a pack of Hex Crimp F-Type connectors.

Antenna downleads should run as much as possible direct from the DTV antenna to the tuner; minimize the number of splices—these increase signal loss. Also, avoid sharp bends in the cable as these can impair performance.

Finally, all outdoor antenna installations - including cables and connections, should be regularly checked for deterioration due to the elements, and for corrosion at connection points.

4. Use of amplification

In case of insufficient signal strength, it may be necessary to use amplification in the form of a masthead amplifier, either as a separate add-on unit, or integrated as part of an active DTV antenna. We have already touched upon the subject of amplification in our digital television antenna guide.

Keep in mind however the limited extent to which reception can be improved in this way - in particular because amplification increases not only the DTV signal level but also noise and interference signals. In other words, the use of amplification is recommended only as long as you can receive a good quality DTV signal. Good quality does not imply a strong signal level, but one that is free from noise and interference.

This means that amplification is there to amplify a weak signal but not to restore poor quality reception. This 'signal quality - signal level' issue is an extremely important aspect in the reception of digital television.

A Word of Advice: TV Antenna Return Policy and Technical Support

Always ensure you get a good return policy when purchasing TV antennas and any related gear. This applies irrespective of whether you buy on-line or direct from a brick and mortar store. Equally important is good technical support from your DTV antenna supplier.

Similarly, this applies for any related RF amplification gear; you may well find that once you install a masthead amplifier, the resultant amplified RF signal is either still too weak or too strong - overloading your DTV decoder. In either case, you will have to replace it with a suitable alternative.

The real problem with digital television reception - and the main reason why many fail when it comes to installing a proper TV antenna - that that TV reception is highly dependent on local conditions; therefore, what may apply under normal conditions, need not necessarily apply in your case.