Sometimes, it's useful to think about problems such as this in terms of
analogous systems that behave in similar ways.

For example, imagine a gasoline-powered engine driving a water pump though a
friction belt and pulley. The pump is attempting to pump water into a short
plugged pipe (shorted transmission line). After the first couple of seconds
the reflected water from the plugged end creates a back pressure on the
pump, a situation in which the pump is then not capable of delivering
additional water to that which is stored in the pipe. Now, a number of
things can occur, short of mechanical failure of some part of the system:

1) the belt between the motor and pump can start to slip, dissipating the
energy generated by the motor as heat lost to friction in the belt and
pulley

2) the motor can slow or cease to function, incapable of working against the
increased torque (impedance) created by the belt that has been constrained
by the pump that can't pump water into the plugged pipe.

In case 1), the power is being generated by the motor, but it is not being
delivered to the load. It is being dissipated (converted to heat) `in
between.
In case 2), the power simply cannot be created. The motor can't work against
such a load. The power is not being dissipated anywhere -- it's simply not
being generated. As Cecil has suggested, in this case, the engine stops,
which stops using gasoline, which reduces the demand on the Middle East oil
supply, which lowers prices, which .....

Case 2) is not one in which reflections "cancel" the energy being generated,
although it can be thought of that way. Energy can't be "canceled" ( a
fundamental law). If a generator isn't delivering energy to a load, it's
because the energy either doesn't exist (isn't being generated), or it's
being rerouted, stored, or being converted to another form.

Although this analogy could be complicated by making it a pumping system
that generates sinusoidal water pressure waves with wavelength-related pipe
lengths, it doesn't need to be for it to work.

Al WA4GKQ


"Cecil Moore" wrote in message
...
Henry Kolesnik wrote:
What if the source doesn't or can't dissipate?

Heh, heh, you're on your own for that discussion. I personally
believe it is possible for reflected energy to wind up decreasing
the power consumption from the DC source that is supplying the finals,
which winds up decreasing the load on the 60 Hz power grid, which
decreases the oil required from the Middle East, which tends to
decrease the possibility of world war, which bodes well for the human
race, but that is another thread for another time.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----