Half-power beam of terrestrial TV antenna

The angle of the beam (for the actual polarization) is determined by the two points on the antenna's characteristics where signal level decreases by 3 dB in comparison with its maximum value.
In the case of terrestrial antennas, lower half-power beam means better directivity, i.e. capability of rejecting reflected signals. In analog TV these signals are superimposed on the main image as "ghosts" - displaced images on the right of primary video information.

Half power beam is inversely correlated with the length of an antenna.
It is not always sensible to use antennas with narrow half-power beam. Sometimes one wants to use single antenna for receiving signals from transmitters situated in different locations - a shorter antenna with a wider angle will be more suitable then.

In the mountains, where usually there is no visibility of the transmitter, there should also be used antennas with wider beam. This solution gives a chance to receive any signal at all, and the reflections are a necessary evil.

Requirements for input signals in multiswitch systems

In the case of large multiswitch installation there have to be used many amplification stages, which increases the noise figure of such system. It directly translates into increase of BER. BER values above 10^-4 (in the outlet) will prevent the user from receiving satellite broadcasts (the receiver will not be able to restore the original signal). To ensure reliable and high quality decoding, the BER values should be at least about 10^-8 (in LNB outputs). Signals with low BER are ensured by use of appropriate dishes, e.g. 110 cm. It is very wise to use large dishes - the whole multiswich system needs only one set of dishes, being a small part of the total costs, but deciding on the quality of the input (and output) signals.

Telecommunication in Israel

Telecommunications is one of the most important industries in this small country. Population of Israel: 7.7 million. Its technological level can be measured by the percentage of homes using broadband access to the Internet - ca. 70%, securing the fourth position in the world - after South Korea, Hong Kong and Iceland.

Mobile telephony is also included in the top rankings - already in 2006 there were more mobile phones than the number of inhabitants (7%). 97% of the residents can potentially use cable TV (52% of households subscribe it).

Israel belongs to the small group of countries having own satellites. The first satellite has been successfully launched on the orbit in 1996, and together with the second one - AMOS-2, is mainly used for direct TV transmissions.

Other satellites, Gurwin-II TechSAT and EROS, are used for communication, cartography, and other research purposes. Great potential of high-tech industries in Israel has attracted international corporations - IBM, Motorola, Cisco, or Deutsche Telekom were opened just in this country.
Among the companies listed on the NASDAQ stock market, Israeli firms are the second most numerous group, after Americans. They include Alvarion, Gilat Satellite Networks, Radware, RAD Data, Tadiran, Teledata, Telrad, VocalTec, Verint.

Photo report: http://www.dipolnet.com/telecommunications_in_israel_bib856.htm

Leonardo da Vinci

While performing some routine conservation works in the Czartorysky Museum in Cracow, a group of experts of the Historical Artifact and Relic Preservation Organization have discovered some images that were hidden in one of the paintings by Leonardo da Vinci. As it is a well-known fact, this genius invented the bicycle, helicopter, and even submarine. Now, it turns out that the "antennology" has finally found its forefather too, and its history is much longer than previously believed. A commission composed of art historians has decided to restore the picture back to its familiar motif so that it could look like before the conservation work. If that hadn't been done, the cost of renaming the painting from "Lady with an Ermine" to "Lady with an Antenna" in all art books and art guides would have outgrown the budget of the Ministry of Culture and National Heritage. However, we've managed to take this unique photo. :-)))

Winter

Tips for TV-Sat installations

Development of television and telecommunications techniques promotes quick spreading of modern antenna installations just like in the past the common use of electric devices extorted careful designing of electric installations.

Some advice for all who would like to do such installation:

1.Place and way of mounting the antennas

Most of damages in antenna installations are the result of collapse of improperly fixed mast or breaking badly laid cable lines. Nowadays, the most popular solution is clamping the antenna mast to a chimney. Masts can also be fixed with wall brackets. Satellite dishes are usually fastened on separate masts. Antenna cable should enter a building already on the roof.
A WLAN antenna has to be mounted the way guarantying mutual visibility with the counterpart (usually of the Internet provider).

2. Kind of installation (pass-through, star-shaped, mixed)

Currently the pass-through installations are not preferred, especially in larger systems. Star installations are more universal and more resistant to interferences induced by connected receivers. They are used both for distributing terrestrial and satellite programs (multiswitch installations).

3. The Method of laying cables
In new office blocks and even apartment buildings cable trays become more and more popular solution for placing electrical, computer, telecommunications and RF installations.

There should be planned main vertical conduit from the basement to the attic, with possibility of leading branches on every floor. Such layout will allow to implement modern installations, change location of main devices etc. It is not recommended to lay unprotected cables just under the plaster. Each cable has limited life and can also be accidentally damaged (e.g. when drilling holes in the wall). The exchange would be extremely difficult.

If the installation is to be laid traditionally, conduit tubes should be applied.

More informations: http://www.dipolnet.com/some_tips_and_hints_dodatek.htm