question about dipoles and why 50 ohms?

can anyone answer me

hello everyone,
I have doubts in basics of antennas
1)why do we take dipole that too half wave dipole antenna as the reference antenna?
2)what is the reason for taking the characteristic impedance as 50Ω?

Re: can anyone answer me

Hi,

Reference antenna means a standard one. ie: It should perform well in all direction. But practically no antenna will do that. In the case of dipole, it is covering more area than that of other antennas. So we can say that as a reference.

Regards

Added after 17 minutes:

Hi,

I forgot to answer for your II question...........

Transmission line's characteristic impedance (Z0) increases as the conductor spacing increases. If the conductors are moved away from each other, the distributed capacitance will decrease and the distributed inductance will increase . Less parallel capacitance and more series inductance results in a smaller current drawn by the line for any given amount of applied voltage, which by definition is a greater impedance. Conversely, bringing the two conductors closer together increases the parallel capacitance and decreases the series inductance. Both changes result in a larger current drawn for a given applied voltage, equating to a lesser impedance.

This is the technical reason for taking generally 50 ohms.