Dr. Slick wrote:



Do you know of anyone who has mathematically derived the 73 Ohms
of a dipole in free space?


Antennas, John Kraus, McGraw Hill 1950, Chapter 5-6, pages 143 to 146
gives a complete derivation for a 1/2 wavelength Antenna.

You need some Calculus and infinite series to understand the derivation.

Deacon Dave, W1MCE