art wrote:
I am aware that the impedance of a particular
atmosphere is 377 ohms but that is certainly not a ratio.

From: http://whatis.techtarget.com/definit...845268,00.html

Mathematically, the Zo of free space is equal to the square root of the
ratio of the permeability of free space (µo) in henrys per meter (H/m)
to the permittivity of free space (o) in farads per meter (F/m):

Zo = (µo/o)1/2

= [(1.257 x 10-6 H/m)/(8.85 x 10-12 F/m)]1/2

= 377 ohms (approximately)

The exact value of the Zo of free space is 120 pi ohms, where pi is the
ratio of the circumference of a circle to its diameter.
--
73, Cecil, w5dxp.com