Question

what is the basic principal behind the antennas how they are actuly convert electric signals to emf waves???????

Answer 1

An electric current in a wire creates a circular magnetic field around the wire, its direction depending on that of the current.

Answer 2

Antenna is basically a transducer.it converts em waves to VI waves and vise versa.The basic principle behind antenna is electromagnetic induction.the electromagnetic waves in air or some medium induces a voltage across the terminals of antenna according to faradays' law.for VI wave to em wave conversion there wil be some circuitry to convert into high freq.then only they propagate in air /freespace.