Keith Dysart wrote:
On Dec 30, 9:51 am, Cecil Moore wrote:
Roger wrote:
Roy Lewallen wrote:
Yes, that is correct. The impedance of the source (a perfect voltage
source) is zero, so the reflection coefficient seen by the reverse
traveling wave is -1.
The logic of this assumption eludes me. In fact, it seems completely
illogical and counter to the concept of how voltage and current waves
are observed to move on a transmission line.

The reflection coefficient for a short is -1, is it not?

One way of viewing a short is that it is a perfect
voltage source (i.e. 0 output impedance) set to 0
volts.

Good point. The power disappears here, but energy transfer is evident
(we have current). We both have power and do not have power.

At the source, when the reflect wave returns and re-reflects, we have 2v
from the reflected wave matched with 1v from the source. We have both
1v and 2v.

OK.

Setting it to some other voltage (or function describing
the voltage) does not alter its output impedance. It
there fore creates the same reflection of the travelling
wave, regardless of the voltage function it is generating.

A real world voltage source has an output impedance. Use
this impedance to compute the reflection coefficient.
The reflection will be the same regardless of the
voltage function being generated by the source.

...Keith

Thanks for pointing out the short circuit voltage view. I had not
thought of that.

What would you think of using a perfect current source for these thought
experiments? My suggested perfect current source would supply only as
much current as could be absorbed by the load, so no power would be used
by the source, and current would be limited by the load.

73, Roger, W7WKB