Cecil Moore wrote:
One thing I was originally confused about until I sat down and drew some
phasor diagrams. The phase of the *net* current doesn't change much over
the length of the mobile antenna. It's the phase of the forward current
and reflected current that is changing. But those phases are changing in
opposite directions so the sum of those two phasors results in very little
phase change in the net current.

It might be helpful to indicate your point of reference when talking
about phase, i.e. phase is changing with respect to voltage, or phase is
changing with respect to the source, phase is changing with respect to
position, etc.

Take the sentence "it's the phase of the forward and reflected current
that is changing" for example. For a traveling wave it is certainly
true that at any given point along a waveguide, the phase of the wave is
constantly changing with time. But it isn't necessarily true that at
that point, the phase of the current relative the voltage is changing
with time.

In the problem we've been discussing both points of reference are
relevant. In some case we're addressing the phase shift between voltage
and current, and in other cases we're discussing the change in phase
along the length of a conductor. I think it's helpful to be specific
about this.


For a 1/4WL vertical, the net current is approximately equal to 90 degrees
of a cosine wave, 1.0 at zero degrees and zero at 90 degrees. The magnitude
of the net current is an indication of where between zero and 90 degrees
the current is being measured. Where = arc-cos(|net current|)

That angle is the 'phase' of the current standing wave as a function of
position, not to be confused with the phase of the current with respect
to voltage. Roger?

73, Jim AC6XG