Nu este vorba de pierderi in antene, ci de ce le provocate de radiatia liniilor de alimentare, care, fiind asezate in apropierea diferitelor obstacole sau corpuri mai mult sau mai putin bune conducatoare de electricitate, toata energia radiata este pierduta- in general utilizam linii de alimentare cu doua conductoare paralele (panglica) sau concentrice (cablu coaxial).
Liniile concentrice, respectiv cablurile coaxiale, nu radiaza aproape deloc, deoarece camasa metalica exterioara fiind legata la masa serveste drept blindaj pentru conductorul central.
În liniile cu conductoare paralele (panglica) situatia este diferita. Atita timp cit curentii care circula in cele doua conductoare sint egali si in opozitie de faza, nu vom avea radiatii ale liniei. Daca insa curentii nu sint exact in opozitie in punctele vecine ale celor doua conductoare, linia de alimentare radiaza. Asemenea situatii pot fi provocate de o disimetrie intre cele doua conductoare, de exemplu (fig. 290), daca linia face o cotitura brusca in unghi drept, conductorul exterior se gaseste decalat fata de cel interioR si apare disimetria.
La liniile de alimentare panglica, trebuie evitat orice cot si ca cele doua conductoare sa aiba pozitii diferite fata de corpurile inconjuratoare. Astfel, cind linia de alimentare trece pe linga un zid, este bine sa fie asezate paralel cu zidul, astfel ca ambele conductoare sa aiba aceeasi distanta fata de zid.
La liniile de alimentare panglica de 300 Ω impedanta, distanta dintre conductoare este mentinuta constanta de materialul izolant in care sint inglobate.
În general, cu cit vom avea disimetrii mai mari la liniile de alimentare, pierderile prin radiatii parazite vor creste.
This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Cookie settingsACCEPT
Privacy & Cookies Policy
Privacy Overview
This website uses cookies to improve your experience while you navigate through the website. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may have an effect on your browsing experience.
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.
Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.