On Fri, 25 Jan 2008 05:32:33 GMT
Owen Duffy wrote:

Roy Lewallen wrote in news:13pirk5h1cpt4f5
@corp.supernews.com:

Owen Duffy wrote:
Roger Sparks wrote in
:

... The reader can
also see that more power is present on the transmission line than is
delivered to the load.

The notion that "power is present" is a different one.

Owen

It's reasonable, though. Looking at demo 4 with the TLVis1 program, you
can see that there's power all along the line except at specific nodal
points (where I or V is always zero), yet there's no power at all being
delivered to the load.

Roy, my though was that on anything but a lossless line with VSWR=1,
instantaneous power (being the rate of flow of energy) varies with time
and location, so to make the statement that "power is present" and to
quantitatively compare it with the power at a point (being the end of the
line where the load is attached) seems to not be so reasonable.

If the statement is about average power in both cases, then it is
reasonable, obvious even, that power decreases with distance from the
source.

Perhaps "power is present" is an avoidance of the somewhat tautological
form "power flows to the load".

Owen

Nothing mysterious was hinted with the words "power is present".

As I finished writing the post, I wanted to call attention to the assumption that the reflected power is true power and adds to the amount of energy "stored" on the transmission line. But "stored" is a word that implies static conditions, and static conditions are not found on a transmission line. So I substituted "present" for "stored.

73, Roger, W7WKB