On Tue, 16 May 2006 05:54:59 GMT, Cecil Moore
wrote:

Roy Lewallen wrote:
It looks like Cecil is trying to use "phase" as a function of position,

Referenced to the source current, the phase of the forward traveling
wave current *IS* directly proportional to position along the dipole.
Any competent engineer knows that. So is the phase of the rearward
traveling wave current. That is obvious from the equations for those
two currents. Those are simply facts of physics that you probably
should try to comprehend instead of dismissing them.

Inet = Io*cos(X)*cos(wt) = Ifor*cos(-X+wt) + Iref*cos(X-wt)

Inet is the standing wave current. X is the distance in degrees from
the feedpoint. If the source current is 1.0 amps at 0 degrees, e.g.
from EZNEC, at t=0 Inet = Io*cos(X) = Ifor*cos(-X) + Iref*cos(X)

As I pointed out some time ago, the envelope of a standing wave isn't in
general sinusoidally shaped.

Balanis says: "If the diameter of each wire is very small (d lamda)
the ideal standing wave pattern of the current along the arms of
the dipole is sinusoidal with a null at the end."

Kraus says: "It is generally assumed that the current distribution
of an infinitesimally thin antenna is sinusoidal,..."

d lamda for an 80m dipole made out of #18 wire. I'm sorry to hear
that you disagree with both Balanis and Kraus.

Could you explain how to build one of those antennas that has infinite
impedance at its ends?

73
Gary K4FMX

Gary Schafer wrote:
Could you explain how to build one of those antennas that has infinite
impedance at its ends?

An open circuit is close enough to infinite to satisfy
almost anyone. In virtually every technical textbook,
ideal conditions are assumed until one understands the
concepts involved. Then the real world conditions are
introduced. That's all I am doing - presenting the
concepts involved in an ideal dipole as described by
Kraus and Balanis. Do secondary real world conditions
exist in reality. Of course they do and nobody is
saying that they don't. The difference between infinity
and ten megohms is often negligible for analysis purposes.
--
73, Cecil http://www.qsl.net/w5dxp