RadioBanter - View Single Post - Current across the antenna loading coil

April 11th 06, 01:08 PM posted to rec.radio.amateur.antenna

wrote:
I take it you are saying you think current can flow two directions at
the same instant of time in a conductor, can be "lost" from a single
conductor through radiation and resistance without a shunting
impedance, conservation of charge isn't important, and Maxwell's
equations are wrong.

EM energy is certainly flowing in two directions because it is
a standing wave antenna. The forward current phasor is proportional
to the forward H-field. The reflected current phasor is proportional
to the reflected H-field. The two H-fields are superposed. That is
the same thing as adding the two current phasors.

Quoting Balanis: "Standing wave antennas, such as the dipole,
can be analyzed as traveling wave antennas with waves propagating in
opposite directions (forward and backward) and represented by
traveling wave antenna currents I(f) and I(b)."

W8JI says an antenna cannot be analyzed in that way. Who are we
to believe? Balanis or W8JI?

Balanis gives us permission to analyze two currents flowing in opposite
directions at the same time. After all, the superposition principle
allows us to do that. I'm sure Dr. Balanis would like to hear your
argument to the contrary.

Kraus agrees with Balanis and disagrees with you. "A sinusoidal
current distribution may be regarded as the standing wave produced
by two uniform (unattenuated) traveling waves of equal amplitude
moving in opposite directions along the antenna."

W8JI says it cannot be regarded in such terms. Who are we to
believe? Kraus or W8JI?

... can be "lost" from a single
conductor through radiation and resistance without a shunting
impedance, conservation of charge isn't important, and Maxwell's
equations are wrong.

All we are saying is that the currents drops the same percentage
amount as does the voltage. Voltage and current share the same
identical attenuation factor. The E-field and H-field drop by the
same percentage. If your model absolutely requires a shunt
impedance, it can be found in the distributed LCLCLCLCLC model
of a transmission line.

Conservation of charge and conservation of energy are inviolate.

Maxwell's equations, as opposed to the flawed lumped-circuit model,
are correct. The distributed network model is a lot more like
Maxwell's equations than is the lumped-circuit model.
--
73, Cecil http://www.qsl.net/w5dxp