According to Kraus' "Antennas" 92nd edition, chapter 2)....

An electric charge traveling at a uniform radiation along a straight wire
does not radiate.

When the charge reaches the end of a wire and reverse direction, it
undergoes acceleration (and deceleration) and radiates.

AN electric charge moving at uniform velocity along a curved or bent wire
is 'accelerated' and radiates.

An electric charge moving back and forth in simple harmonic motion (that is,
sine wave) has periodic acceleration and radiates.

If you have two parallel wires, one carrying a positive charge and the other
carrying a negative charge, it will not radiate.

If the two wires are bent away from each other, the charges radiate.

Kraus goes into more detail on all of this. Get yourself a copy of the book
or find one at the library. If they do not have one, they can get one on
interlibrary loan.

--
Jim
N8EE

to email directly, send to my call sign at arrl dot net
"Ron" wrote in message
. com...
Can someone explain how a transmission line starts radiating as the
separation
between the center conductor and ground plane becomes greater and greater.
Assume you out start with a wire over an infinite copper ground plane that
forms
a 50 ohm Zo transmission line. Then increase the distance between the wire
and
the ground plane until the wire becomes an end fed antenna. What happens
to
cause radiation to begin?

Ron