Gene Fuller wrote:
Cecil Moore wrote:
. . .
The two traveling waves have to be analyzed separately and then
superposed to obtain valid results. If you analyze net current without
superposition, you are doing the same thing as superposing powers, which
is a known no-no.

Both those sentences are false.

In a linear system like an antenna or transmission line, superposition
applies. This means, among other things, that we can separately analyze
the system's response to various components, and the sum of the results
we get are the response to the sum of the excitation components. For
example, we can split a current into two -- or more -- components, such
as a forward traveling current wave and a reverse traveling current
wave, with the actual current (or what Cecil calls "net" or "standing
wave" current) at any point being the sum of the two. We can find the
voltage across an inductor, for example, which results from the forward
traveling current. Then we find the voltage across the inductor
resulting from the reverse traveling current. Superposition tells us
that the sum of those two voltages is what results from a current which
is equal to the sum of the forward and reverse traveling current waves.

We must get exactly the same result, in this example the voltage across
the inductor, if we find it by adding the separate voltages due
individually to the two current components, or if we find it directly as
a result of the total current. We don't have to separate the current
into two components then superpose the results as Cecil claims -- we get
exactly the same result either way because superposition holds. This has
nothing to do with attempted superposition of powers or other properties
which don't fit into the boundaries of linear quantities.

We're not restricted to splitting the current into a single forward and
reverse wave, either. We can split it into many separate traveling
waves, as well as any number of other combinations. As long as all the
components add up to the actual total current, we'll get exactly the
same result when we separately sum the responses to each individual
component that we do when we simply look at the response to the total
current.

If Cecil's analysis shows, or his theory requires, that the result be
different when adding the responses to traveling current waves than it
is by calculating the response directly from the total current, then the
analysis or theory is wrong. Superposition requires that the two results
be identical.

Roy Lewallen, W7EL