Cecil Moore wrote:
John Popelish wrote:

To the center conductor, carrying the standing wave, the shield is the
outside world. If there is no shield, the outside world is the
outside world, as far as displacement current goes. Do you imagine
this current changes in some way other than magnitude and wave
velocity when you wrap a shield around a wire carrying a standing wave?


No, that is your point, not mine. My point is that displacement
current to real ground is non-existent outside of a coax shield
(unless common mode current exists)

With you, so far..

and that it is usually a
secondary effect if the coax shield doesn't exist.

And then we part ways.

The primary
reason for the variation in standing wave current along the line
is the phasor sum of the forward and reflected wave phasors that
are rotating in opposite directions. Do you understand phasor
addition? 1 at zero + 1 at 180 deg = zero at a standing wave
node? Displacement current to real ground doesn't cause that.

I am making the point that if the displacement currents were
insignificant, outside a coax, then the speed of light for waves out
there would be infinite. And they are not, therefore those
displacement currents cannot be assumed to be insignificant.

I am explaining distributed network theory to you.


:-) How? By denying the existence of the individual H-fields
in forward and reflected EM waves? Now, that's really funny.

Exactly the opposite. I am explaining the distributed effect of the E
field along the wave.

http://www.qsl.net/w5dxp/travstnd.GIF


And I have agreed with that. Why do you keep bringing it up?


Because that's the whole point of this discussion. If you
agree with that, there is no reason to continue. I just
don't care about instantaneous current, Brownian motion, or
the exact location and velocity of every electron carrier.
There's too much uncertainty involved.

You are avoiding the very facts that would allow you to make an air
tight argument for your beliefs about "the whole point of the
discussion". You somehow picture current as a continuous thing from
one end of a conductor to the other, when it carries a traveling
energy wave. This is a misconception.

You appear to accept that current is a localized kind of thing (parts
of the conductor carry current, but those parts are separated by
nodes) when two traveling waves going in opposite directions
superpose, but have no concept that explains how this happens, only a
mathematical function that quantifies it.

What you don't get is, that the currents that each of those traveling
waves would have generated were localized, to begin with. Local
current cycles and voltage cycles are the water the energy waves ride
on over arbitrarily long distances along conductors and transmission
lines.

I know you don't care about this factoid, but understanding it would
allow you to think about "the entire reason for this discussion" much
more clearly.