The concepts of "forward" and "reflected" power are sometimes (but not
often) useful, but have to be carefully confined to a very specific set
of conditions and applications. When you start thinking of them as real
packets of power bouncing around inside and outside a cable, you can
easily be led into a number of traps which you can get out of only by
distorting reality and ultimately reaching conclusions which are more
and more wrong.

I strongly suggest forgetting completely about "forward" and "reverse"
power. If you must deal with directional waves, look at forward and
reverse voltage and current waves. Superimpose them as necessary, and
when you're done, calculate power from the result. Trying to separate
moving packets of average power will eventually force you into reaching
wrong conclusions, or at least to serious confusion.

The whole issue of power loss is extremely simple, and it provides a
good example of how trying to invent these moving packets of average
power can lead to unnecessary complication and confusion.

Roy Lewallen, W7EL

Jim Kelley wrote:


Roy Lewallen wrote:

Only you could take such a simple concept as power loss in a two port
device and muddle it with bouncing waves of average power.

I didn't explicitly give the loss in dB because I thought that you
would be able to do it yourself. You seem to be able to, but for some
reason regard it as some kind of major operation. I don't know how you
do it, but here's how I do.

From my previous posting, the power into the line is 50 watts and the
power out is 25 watts.


I think the source of part of the confusion here is that some people
apparently interpret the 'forward power' reading on their meter to mean
the power into their transmission line.

The confusion I think stems from the contention that any 'reflected
power' (unfortunate nomenclature IMO) is first sourced and then after
reflection returned back into the source, or to a circulator load as the
case may be. The latter case is certainly correct. The former is
phenomenologically problematic.

73, Jim AC6XG