Szczepan Białek wrote:
Could you tell us if the "almost double voltage" is the measured of
theoretically predicted?
Since a voltage reference point is difficult to achieve
at the ends of a dipole, we rely on the conservation of
energy principle. Since the current is zero at the ends
of a dipole, all the energy must be contained in the
electric field. With that knowledge, the voltage can
be estimated.
Such is easy to understand by taking voltage measurements
on a 1/4WL open-circuit stub. If one uses resistance wire
for the stub, one can simulate radiation loss in a dipole.
The following is a transmission line simulation of a 1/4WL
monopole designed to run on the free demo version of EZNEC
available from
www.eznec.com
http://www.w5dxp.com/stub_dip.EZ
The user defined resistivity of the wire is what causes
the 35 ohm feedpoint resistance akin to a 1/4WL monopole.
The 10 megohm load allows us to look at the voltage
across the "open" end of the stub. It is 1033 volts for
a 100 watt input. We can assume the forward voltage and
the reflected voltage at the end of the stub are equal
at 516 volts.
--
73, Cecil, IEEE, OOTC,
http://www.w5dxp.com