Jeff wrote:

So if what you are saying is correct then terminating a piece of coax
with a 50 ohm resistor will not cause a perfect match and the load will
not be 50 ohms due to the shunt impedance to earth of the coax braid.

I think not.

Maybe you can draw a diagram and show yourself where the current flows.
The earth connection on the shield outside is in parallel with the
earth connection on the shield inside. You can't have any current flow
on the outside because any current flowing on the shield inside balances
with the current flowing in the center conductor. The resistor requires
the two currents are equal with none left to travel down the shield
outside.


Indeed, as you state there is no current flow on the outer of the coax;
the same situation exists for a perfectly balanced dipole attached
directly to the coax, as far as the coax is concerned the situation is
no different, all it sees is a perfectly matched load, just like the
resistor, all of the power is dissipated in the antenna and none flows
anywhere else including the coax outer.

Jeff

That current flows on the outside of the shield is observable and
measurable.

How much flows is totally dependant on how long the shield is and
whether or not it is grounded somewhere along the way.


--
Jim Pennino