Cecil Moore wrote:
John Popelish wrote:

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.


But I am not talking about displacement currents within the
transmission line, as exists in free space. I am talking *solely*
about the displacement currents to *earth ground*. I contend that
those are often secondary effects as proven by the coax example.
Just how much displacement current to "earth ground" is there for
a coil located halfway between here and Alpha Centauri?

Almost exactly as much as there is between a coil that is a half
wavelength from a grounded surface.

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

And completely ignoring the H-field? In the treatment of those fields,
the only variation is Z0. For EM fields, there is no "across" and no
"through". The difference between voltage and current essentially
disappears except for their Z0 ratio. The equation for current in
a transmission line is identical to the equation for voltage except
for the Z0 term. Current "drops" are commonplace in lossy transmission
lines.

For instance, what is the current at the end of 200 feet of RG-58
terminated by a 50 ohm antenna used on 446 MHz when the source
current is 2 amps?

Somewhat less then 2 amps. Loss certainly occurs along that length,
at that frequency? So what? Are you thinking that this is the
predominate mechanism that is altering the current magnitude through
your coil? It is part of the answer, but not the whole answer.

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.

Maybe in the field of physics - not in the field of RF engineering.
For any two current points, I can calculate a point in between.
Sorry, but that's a characteristic of a *continuous* single-valued
function and can be proven mathematically. I admit to being a EE/math
major. I didn't take many pure physics courses so I am missing your
point about me being able to prove anything additional. Maybe it
will dawn on me after awhile.

That is the best outcome I can hope for.

What you don't get is, that the currents that each of those traveling
waves would have generated were localized, to begin with.

I realize that is the physicist talking and it agrees with my
earlier assertion that standing wave current doesn't flow.

No current flows. Charges flow (move) the magnitude of that movement
past any point is current. I am picking nits, here, but the
distinction is important if you want to build on these simple
concepts. By the way, I am an EE, not a physicist, but I have to
think physics to do engineering.

I guess I'm so dense that I need help in proving what you think
I can prove with that information. Right now, I am apparently
missing something, maybe because of too much California Merlot.

Sounds like something I might do, this afternoon.