On Wed, 16 Jul 2003 18:20:22 -0700, Roy Lewallen
wrote:

An antenna can reasonably be viewed as a transducer. It converts the
electrical energy entering it into electromagnetic energy -- fields. As
is the case for any transducer, the stuff coming out is different than
the stuff going in. Think in terms of an audio speaker, which converts
electrical energy into sound waves, and you'll be on the right track.

Roy:


Great analogy!

The characteristic acoustic impedance of air (standard temp &
pressure) is about 413 Rayleighs (or Pascal-Seconds/cubic meter).

Do we worry about matching 8 ohms of electrical speaker impedance to
413 Rayleighs? C.f. Paul Klipsch and the Horn speaker.

I wonder if much of the antenna radiation resitance/Tline
impedance/reflection/intrisnic impedance of free space confusion stems
from use of the same words to describe things that may be modeled
mathmetically identically, but have different physical modalities?

In heat sink calculations, for example, we use "thermal resistance"
and an Ohm's law model but few would confuse ohms of resistance with
degrees C/watt.


Jack K8ZOA