On Wed, 29 Jun 2005 13:56:53 -0700, Frank Gilliland
wrote:

Well, let's put it this way: the radio and antenna don't connect to
the dielectric of a coax.
*****

No it does not directly.

I know this concept is not easy to see but at the begining of the
coax, one can then consider the energy that travels down the coax as a
TEM wave. It is inside the dielectric where the E and H fields of the
traveling wave can be measured and found.

In transmission lines it is by far easier to think of E and H fields
within the the transmission line. Once that concept is mastered then
the rest is rather easy.

When the wave reaches the end, you have the final induced currents.
You can take a dipole and look at it as if the legs were an extension
of the transmission line. This can better be seen if you consider a
dipole and it is fed with open twin lead. The leads of the dipole then
are an extention of the twin lead except they are now at 90 degrees to
the transmission line.

Current is high when the magnetic field is high. This is so because
the induced current is controlled by the density of the magnetic
field. The E field is high when magnetic field is low. The E field
does not require current but voltage. On a center fed dipole the
impedance is low and the corresponding currents are high. The E field
off teh antenna is also low. As you progress a quarter wave from the
feed point in either direction the H field increases and the E field
decreases. With increasing H field the RF currents induced in the
antenna are high. Thus Ohm's law hald true. Z = I^2*R. Where R is the
radiation resistance of the antenna. The ends of a center fed dipole
are high impedance.

james