Question

a)      At very large frequency (VLF) ranges, it is practically not possible to transmit horizontally polarized waves. Give reasons.                                                                                                                          

b)     Give the significance of radiation resistance of an antenna. Calculate the radiation resistance of a wire dipole antenna in free space.     

  

Answer 1

a) At very high frequency horizontally polarized wave is highly attenuated as compared to vertically polarized wave. At higher frequency horizontally polarized wave can be cancelled by earth image antenna radiation, that's why it is practically not possible to transmit at higher frequency. Though both horizontally and vertically polarized wave are transmitted at higher frequency, but due to higher attention it is not preferred.

b) Radiation resistance is the resistance of an antenna which is the equivalent resistance which dissipates same amount of power as antenna radiates when input current is applied. Means radiation resistance is used to radiate power which is required to transmit signal.