Why the wavelength of an antenna has to be 1/2 of the FC ?

Hi everyone,

I have a question regarding antenna can you guy help me.

If I want to transmit a signal at a frequency fc this mean it has a wavelength of c/fc, however i don't understand why the antenna's wavelength have to be 1/2 of the fc. can you guy explain this concept.

thanks

It has to do with boundary conditions. At the end of the dipole the current has to be zero. A half cycle shape of current magnitude will fit with the maximum at the center.

Hi flatulent,

I still don't understand, can you please elaborate on this concept. How do you know at the end of the dipole, the current is zero. Also, where does you see the half cycle shape.

thanks

Current has to come from somewhere and go to somewhere. At the end of the wire there is no place for it to go. One way to look at this is the energy in the current radiates which makes the current smaller.

Hello,

From my understanding. A wave repeats itself after every half cycle, hence the desired properties of the antenna can be achieved by half LAmda. E field is equivlent to current and H field equivalent to Voltage.