Q.Write a note on Antennas.

An antenna is a device that radiates electromagnetic waves into space when transmitting and captures them when receiving. Antennas are essential to television, satellite and radio broadcasting and to cellular telephony, and they come in many shapes and sizes chosen to suit the job. Five types are studied in the Karnataka 2nd PUC Electronics course.

• Helical antenna — a conducting wire wound as a helix (coil), usually mounted above a flat conducting ground plane. It is widely used at earth base-stations in satellite communication.
• Yagi antenna — an array of parallel straight elements on a boom: one driven element plus parasitic elements (a reflector and directors) that shape a strong directional beam, so it is often just called a 'beam'. The name honours the researchers Yagi and Uda, who studied how parasitic elements affect directivity.
• Loop antenna — a coil of wire on a former, with an air or powdered-iron core. Its gain is low, but it picks up little noise and responds mainly to the magnetic component of the wave, which makes it useful for direction-finding and for compact receivers. …