Owen Duffy wrote:
On Sun, 19 Mar 2006 04:57:54 GMT, Cecil Moore
wrote:

Please see http://www.qsl.net/w5dxp/current.htm

I refer to the diagram in the section entitled "What EZNEC Says About
Current Distribution Using Inductive Loading Stubs"

You use the diagram to assert that there is "not a lot of difference
between inductive loading stubs and loading coils" by comparing the
current distribution with another case.

You show graphically the current on each side of the stub. You do not
show the current in each wire of the stub or the sum of the currents
in the stub.

EZNEC calculates the currents in each wire of the stub? Aren't those
currents a relevant detail that you have omitted from the diagram.

I don't quite follow the theory on the web page, but what does it
predict should happen if there were no antenna at all, and the inductor
were connected to a simple series RC circuit instead of the whip?

I've taken the EZNEC model available there and modified it by replacing
the whip with a wire to ground from the top of the coil
(http://eznec.com/misc/test316_modified.EZ). I added a lumped impedance
in that wire to represent the impedance of the vertical wire I
deleted(*). The feedpoint impedance is the same as for the original
model, and the currents at the top and bottom of the inductor are almost
exactly the same as for the original model. Can the traveling wave
analysis be used to explain the inductor currents in this model? Is
traveling wave analysis necessary to explain them?

(*) The impedance inserted in the new wire isn't equal to the impedance
of the top wire driven against ground. The reason is that the new wire
to ground does radiate some, does have significant impedance itself, and
does interact with the inductor. The modified system, however, is quite
obviously very different in radiating properties from the original, and
isn't too different from a lumped RC load.

Roy Lewallen, W7EL