"W5DXP" napisal w wiadomosci
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On Friday, July 27, 2012 12:50:32 PM UTC-5, Szczepan Bialek wrote:
Are the voltages doubled at the ends?

The voltage doubling at the ends of a dipole is simple to understand. A
dipole is a standing wave antenna. When the forward wave from the feedpoint
encounters the open-circuit at the end of the dipole wire, a reflection
takes place where the reflected voltage is in phase with the forward
voltage and the reflected current is 180 degrees out of phase with the
forward current.

Exactly like with the sound waves.

At the end of the dipole, |Vfor|=|Vref| and |Ifor|=|Iref|. So the total
voltage and total current at the ends of a dipole a

Vtot = Vfor + Vref = 2*Vfor = 2*Vref

Itot = Ifor - Iref = 0

And of course, no current is going to flow into the open-circuit at the end
of the dipole so the total energy in the magnetic field at that point is
zero.

You assume that there no field electron emission. Why?

All of the energy in the EM waves migrates to the electric field and that's
why we get a standing wave voltage maximum at the ends of a 1/2WL dipole.

Nobody know what the EM waves are. Write about electrons.

However, under certain corona conditions, when the impedance at the end of
the dipole conductor is much less than infinite, electrons actually migrate
from the antenna into the conductive air, e.g. salty fog on the coast. But
this is undesirable non-coherent behavior unless you are building a Tesla
coil.

They migrate if the voltage is:
"Field emission was explained by quantum tunneling of electrons in the late
1920s. This was one of the triumphs of the nascent quantum mechanics. The
theory of field emission from bulk metals was proposed by Ralph H. Fowler
and Lothar Wolfgang Nordheim.[1] A family of approximate equations,
"Fowler-Nordheim equations", is named after them."

I once saw a mobile antenna emitting a red corona glow in the fog on HWY 1
near Monterrey, CA. A traffic cop stopped him for having a "red light" that
could be seen by oncoming traffic.

Each your antennas are the electron emitter:
"How would the ideal field emitter look like? It should be very long and
very thin, made of conductive material with high mechanical strength, be
robust, and cheap and easy to process". From:
http://ipn2.epfl.ch/CHBU/NTfieldemission1.htm

The voltage doubling is only theoretical. In reality the voltage is rising
to the level necessary for effective field emissions.
If no proper voltage no radiation.
S*