As stated in other responses, it is not measured with simple instruments.

Every wire has self inductance. It can be calculated using commonly
available equations.

Every pair of wires has self capacitance. It can be calculated using
commonly available equations.

So, the 300/75/50 ohm term, characteristic impedance, is the square root
of L/C

W1MCE

Dan Jacobson wrote:

Dear antenna pros, I've always taken it for grunted about the
300/75/50 ohms of TV ribbon, coax, etc. But how does one measure it?
My ohmsmeter doesn't budge. Is there some standard formula, like wrap
grandma 100 times, with the far end connected to a cheeseburger in her
mouth, the near end finally displaying the characteristic 300/75/50
whatever ohmses?