christofire wrote:

I hardly dare to say it but, actually that's incorrect for the radiation
field (which is what I wrote about). The radiation resistance of an antenna
accounts for its ability to radiate power into the surrounding space and,
like all other resistances, the peak of current co-insides with the peak of
applied voltage - so one doesn't occur '1/2-period later' at all. What's
described in the passage above is the situation in respect of the temporary
storage of energy in the 'reactive near fields' corresponding to a reactive
component of the terminal impedance, not the radiation resistance. I would
expect the latter to be of greater importance to those interested in
communication.

I wouldn't disagree with the statement that stored energy is concentrated in
the regions near the 'maximum charge regions' but if you plot the equipotent
lines around a dipole and equate the amount of energy stored to the electric
field strength it illustrates that the spatial distribution of energy in the
electric field is similar to that in the magnetic field ... as one might
expect.

Chris

That's a good explanation. It might help some people to visualize the
process by comparing it to a series RLC circuit, which its feedpoint
impedance resembles over a moderate bandwidth. In both an RLC circuit
and an antenna, the current and voltage aren't in phase, but they're not
exactly in quadrature (90 degrees out of phase) either. This means that
during each cycle, some of the energy entering the RLC circuit or
antenna is stored and some is consumed. In the RLC circuit, the stored
energy is stored in fields in the capacitor and inductor; in the
antenna, it's stored in fields near the antenna -- the near field. And
the consumed power is dissipated in the resistor in the RLC circuit; in
the antenna, it's radiated. The antenna's equivalent to the RLC circuit
resistance is, of course, the radiation resistance, which "consumes" --
radiates -- some of the applied energy each cycle.

Roy Lewallen, W7EL