Directional HDTV Antenna

The LPDA (log periodic dipole array) or Grand directional antenna has several dipoles arranged in a step and criss-cross fed from the front. The name comes from the geometric growth, which is bursting logarithmic.The LPDA antenna on the scene in the 1960s as a practice with the directional antenna gain and a very large (theoretically unlimited) range of frequencies. Like the Yagi-Uda array, it used linear elements. In the upper HF range and above, the elements may be tubes or aluminum rods
By experimenting with various models of IPRA antenna, it was determined that the antennas greater extent boom can give much more gain. For example, 13 elements of the frequency of 145 MHz to the distribution of its components on the length of 7 m boom were able to win just over 16 дБ. This large gain can also be received at the use of satellite dishes or antennas multidipole "channel of the wave", organized in some levels, but thus their design and a power circuit is much more complex. Therefore, for the reception of high gain (about 40 times on capacity) recently radio fans more likely to LPDA antenna more elements.
The great power gain of the LPDA antenna with a wide range of items is reached due to significant reduction in bandwidth of the antenna, but at the same time means that the size of the antenna are very critical

In LPDA antennas with more elements, items are generally made from drivers with a minimum (in terms of sustainability of a design) in diameter. The diameter of more elements of the antenna was less able to win. The head of thin due to a small area has a small capacity, but at the same time greater inductance and, consequently, a great attitude L / C. Therefore, these elements we will compare to a narrow resonance oscillatory contour.
The element having the diameter of a larger conductor, therefore has a low attitude L / C, and therefore has less strongly influenced the properties of resonance, as in this case is equivalent to the gain reduction the antenna. To reduce losses due to the effect of the superficial surface of fine drivers must have good conductivity.
If the diameter of an element is equal to 3 mm (diameter is most appropriate for a series 2) the component can be executed from copper tubing or aluminum small diameter, if the drivers of the surface must be silver is used (for example, if the spokes of bicycles as elements of the antenna used). For the reduction of losses, it is desirable that the thickness of a silver coverage was greater to the extent possible. At coverage of the elements of the money disappears the need for additional protection of a surface element of the influence of weather conditions while the surface of aluminum or copper should focus on the elements of a protective varnish. To this end, the colorless varnish with good insulation properties and a small dielectric constant is used.

Read also: Guidelines to Satelite Tv Antenna