Definition of Antenna


Definition of Antenna

 

THIS IS TO THE POINT DEFINITION OF AN ANTENNA WHICH IS AGAIN A VERY FAVOURITE QUESTION OF THE EXAMINERS IN PART 2 OF RTR(A) EXAM

 

ANTENNA

  • ANTENNA IS A DEVICE WHICH CONVERTS AC INTO EM WAVES AND VICE- VERSA
  • ITS FUNCTION IS TO RADIATE EM ENERGY INTO SPACE IN THE FORM OF EM WAVES OR TO RECEIVE EM WAVES FROM SPACE
  • IT IS IN THE BEGINNING OR END OF ANY RADIO EQUIPMENT DEPENDING ON WHETHER THE EQUIPMENT IS A TRANSMITTER OR RECEIVER RESPECTIVELY
  • IDEALLY THE LENGTH OF THE ANTENNA SHOULD BE EQUAL TO THE WAVE LENGTH OF THE WAVE WE WANT TO PRODUCE, HOWEVER, HALF WAVE LENGTH ANTENNA ALSO WORKS
  • HALF WAVE LENGTH ANTENNA IS CALLED A DIPOLE ANTENNA
  • TYPES OF ANTENNA
    • GENERIC
      • WHIP ANTENNA USED FOR VHF AND ABOVE
      • WIRE ANTENNA USED FOR HF
      • FERRITE ROD ANTENNA
    • SPECIAL PURPOSE ANTENNA
      • LOOP ANTENNA  FOR ADF
      • SENSE ANTENNA FOR REMOVING AMBIGUITY
      • PARABOLIC ANTENNA          THEY ARE HIGHLY DIRECTIONAL
      • LOG PERIODIC ANTENNA     MULTIPLE BAND MULTI ELEMENT, CATERING FOR WIDE RANGE OF Fx. LENGTH OF THE ELEMENT IS LOG                                                                                  FUNCTION OF WAVE LENGTH
    • ANTENNA TUNING UNIT
      • IT IS A DEVICE WHICH CHANGES THE PHYSICAL LENGTH OF THE ANTENNA ELECTRONICALLY
    • POLARISATION
    • ORIENTATION OF THE ANTENNA IN RELATION TO THE SURFACE OF EARTH DECIDES THE POLARISATION OF THE WAVE PRODUCED. IF ANTENNA IS VERTICAL THEN THE ELECTRICAL COMPONENT OF THE WAVE IS IN VERTICAL PLANE AND THE SIGNAL IS CALLED VERTICALLY POLARISED

 

 

 

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