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Celicni stub sa antenama.

Sve je vise celicnih stibova sa antenama u gradu.
Antena je naprava koja sluzi za slanje i prijem radiotalasa.
Otpremne antena pretvara jednodimenzionalni talas iz prenosne strukture u trodimenzionalni prostorni talas, usmeravajuci pri tome energiju u zeljenom smeru. Prijemna antena prima elektromagnetsku energiju zavisno o jacini polja koje dolazi do antene.
Pasivne antene su napravljene od reciprocnih elemenata i mogu se koristiti i kao prijemne i kao otpremne. Aktivne antene sadrze elektronicke elemente koje im omogucuju da menjaju dijagram zracenja, smer snopa, itd.
Linearne antene su najcesce zicane, zanemarivog preseka pa ih posmatramo kao jednodimenzionalne. Koriste se u nizem frekvenciskom podrucju. Povrsinske antene zrace svojom povrsinom, gledamo ih kao dvodimenzionalne i koriste se u mikrotalasnom frekvencijskom podrucju.
Uskopojasne antene su rezonantne, s malom sirinom frekvencijskog podrucja koje pokrivaju. Sirokopojasne antene pokrivaju siroko frekvencisko podrucje te su zato najcesce prijemne.

Sve je vise rasprava na losem uticaju antena na prirodu i zdravlje coveka.



Steel pole with antennas.

There are more and more steel poles with antennas in the city.
An antenna is a device used to send and receive radio waves.
The transmitting antenna converts a one-dimensional wave from a transmission structure into a three-dimensional spatial wave, directing energy in the desired direction. The receiving antenna receives electromagnetic energy depending on the field strength coming to the antenna.
Passive antennas are made of reciprocal elements and can be used as both receiving and transmitting. Active antennas contain electronic elements that allow them to change the radiation pattern, beam direction, etc.
Linear antennas are most often wire, of negligible cross-section, so we consider them as one-dimensional. They are used in the lower frequency range. Surface antennas radiate their surface, we observe them as two-dimensional and are used in the microwave frequency range.
Narrowband antennas are resonant, with a small width of the frequency range they cover. Broadband antennas cover a wide frequency range and are therefore most often receiving.

There is a growing debate about the bad impact of antennas on nature and human health.

Fis2, ikeharel, jhm, ChrisJ, mcmtanyel has marked this note useful

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Additional Photos by Pavle Randjelovic (pajaran) Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 12908 W: 2908 N: 26324] (108832)
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