Here's an interesting quote from _Transmission Lines, Antennas, and Wave
Guides_, by King, Mimno, and Wing:

"The amplitude of the current is not the same at different points along
a conductor, because electric charge is deposited all along the surface
of the conductor. Superficially it may appear that an antenna consisting
of a straight conductor that is an appreciable fraction of a wavelength
long and with a generator at its center may be looked upon simply as an
open-end transmission line with the parallel conductors bent to lie
along the same axis instead of being parallel to each other. Although
there is considerable similarity between the two cases from the point of
view of the approximate distribution of current, *they are nevertheless
fundamentally different*. The transmission line may be analyzed to a
good approximation in terms of ordinary electric-circuit theory, because
equal and opposite currents are very close together. This is not true of
the antenna and ordinary electric-circuit theory cannot be applied. *It
is fundamentally incorrect to treat a center-driven antenna as though it
were the bent-open ends of a two-wire line.*

Circuits that satisfy the condition for the near zone, either because
they are sufficiently small or because they have equal and opposite
currents everywhere so close together that the currents in widely
separated parts of the circuit exert a negligible effect on one another,
are analyzed correctly by the methods of ordinary electric-circuit
theory. All other circuits must be investigated in terms of
electromagnetism. This nearly always involves a study of the
electromagnetic field as a useful intermediate step in determining
distributions of current and charge."

The above text surrounded by asterisks is printed in italics. The quote
begins on p. 85 of the paperback 1965 Dover reprint. I highly recommend
reading Chapter II, of which the quote is a part.

Roy Lewallen, W7EL

Cecil Moore wrote:
Tdonaly wrote:

Universally recognized principles of electromagnetics are obfuscation?


Complicating a simple measurement task beyond belief is obfuscation.

You changed the geometry. But even if you hadn't, you might be able to
say the changing electrical fields are greater at the ends of a
dipole, but not the voltages, because the voltages aren't uniquely
defined.


When a dipole is bent into an open loop, the relative voltage between
the ends is uniquely defined just like the voltage across a transmission
line is uniquely defined. If I poke two wires through two holes in a
faraday cage and ask you to measure the 10 MHz voltage between them
with 10% accuracy, would you say it can't be done?

You'll give some people the impression that things are as simple as
you say they are when things are not simple
at all.


The measurement may be extremely challenging, but the *concepts* are
simple.
All you need to do is note the similarity of the transmission line
impedances
on an SWR circle to a wire antenna. If the spacing on a transmission
line is
an appreciable percentage of a wavelength, the transmission line will
radiate.
That's all a center-fed wire antenna is - a transmission line with large
spacing between the conductors and it radiates.