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Friday, April 15, 2011

Erecting an Antenna

Erecting a TV Antenna

If you have been told that you may not erect a small outdoor TV antenna, that is probably wrong. The Telecommunications Act of 1996 has a provision that preempts (overrules) nearly all local restrictions such as deed restrictions, home-owners association rules, renters contracts, and so on. For more details see FCC Fact Sheet.

Late news: Note that now is not a good time to buy a Yagi antenna. Present Yagi antennas are optimized for channel 69. But in the U.S. 51 is now the highest channel, and a new generation of Yagi antennas cut for channel 51 will be the most desirable. For the next few years Yagi buyers must pay close attention to the frequency specs.

Many people live in areas where TV signals are strong. Even if these people know nothing about selecting or installing an antenna, they will probably succeed anyway. This website is written mainly for people in areas where reception is nontrivial to very difficult. A trip to the website www.antennaweb.org will tell you quickly into which group you fall. If your must-have stations are in the yellow or olive-green range then there is not much reason to study anything. (But if your present antenna is disappointing then read on.)

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http://www.hdtvprimer.com/ISSUES/erecting_antenna.html

Common TV Antenna Types

Shown above is the radiation diagram for a 9-element Yagi antenna that the author once used to receive channel 12. To interpret this diagram, imagine that the antenna is at the origin. The length of a line from the origin to any point on the surface is proportional to the gain in that direction.

HDTV Antennas

An antenna made for analog TV will work fine for DTV. There is nothing different about an antenna for DTV or HDTV. Unscrupulous people have labeled their antennas “HDTV Antennas” as a marketing ploy. The honest antenna makers have had to re-label their products likewise to avoid losing sales.

Some terms

Gain – a measure of how much signal the antenna will collect.

Beam width – how directional an antenna is.

Bandwidth – how the gain varies with frequency. A narrowband antenna will receive some channels well, but other channels poorly.

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http://www.hdtvprimer.com/ANTENNAS/types.html