Jim Kelley wrote:
Correction. The Z matching device functions to increase the energy
flow toward the load and decreases the energy flow toward the source.
Interference is just the mathematical description of the resulting
spacial distribution.

The decrease to zero in reflected energy flow toward the source
is known as "total destructive interference" in the noun version
of the word as used by Hecht. The increase in energy flow
toward the load is known as constructive interference. One need
not refer to superposition as the cause of interference since
the interference *event* implies superposition of two (or more)
coherent waves as the *cause* of the interference *process*.

I am using "interference" as a noun synonymous
with an "interference process" event, not as in "interference
rings". The Z0-matching event cannot occur without an interference
process (event). "Total destructive interference" as defined
by Hecht is *necessary and sufficient* for a Z0-match to occur,
i.e. if total destructive interference exists toward the source,
a Z0-match has been achieved.

From Websters: "interference - n. the *process* in which
two coherent EM waves combine to reinforce or cancel each
other." The reinforcing or canceling can be partial or total.
Thus, I am using Hecht's noun definition of "interference"
which "yields a resultant irradiance that deviates from the
sum of the component irradiances". Reinforcement or cancellation
is the *result* of that *process*. Superposition is the *cause*
of that *process*.

The *result* of the interference *process* is sometimes wave
cancellation if the appropriate conditions exist. That's
what happens at a Z0-match.

The interference pattern of an antenna is the *result*
of the interference *process*. Hecht says interference
"corresponds" to the "interaction" of two or more
coherent EM waves "yielding a result ...". He clearly
considers interference to be in the cause and effect
chain of events, as do I.
--
73, Cecil http://www.w5dxp.com