On Tue, 18 Nov 2003 23:32:11 -0600, Cecil Moore
wrote:
|Wes Stewart wrote:
|
| Jim Kelley wrote:
|
| |Cecil Moore wrote:
| | Shirley, you jest. Reference pages 17-20 in _T-Lines & Networks_ by Johnson.
|
|Now change the context from a DC example to an RF example:
|
| | Consider a T-line with an SWR of 5.8284:1 and a constant 100W Z0-matched
| | source. The forward power will be 100W, 150W, 175W, 187.5W, 193.75W,
| | 196.875W, 198.4375W, ..., 200W. After steady-state is reached, the
| | reflected power is a constant 100W (sans modulation and noise).
| |
| |Interesting reference. Wish I had it.
|
| I have it and it doesn't say anything of the sort.
|
|I didn't quote anything it says, Wes, I just gave it as a reference. Then I
|suggested a different example to be considered. When the SWR is 5.8284:1,
|the reflected power is 1/2 of the forward power making mental calculations
|easy. The RF example was out of my head, not out of the reference.
Well then, I'm citing Einstein's Theory of Relatively, but I'm going
to use another example.
How about a DC voltage source and a switch connected to a Zo
transmission line terminated in R = 3*Zo. Sound familiar? (For those
without the text, it's Johnson's example)
Johnson says in part, "The first reflected wave will in turn be
reflected when it reaches the sending end. The terminating impedance
is *zero* (emphasis added) at the end....."
It's quite a leap from a DC situation with zero source impedance to a
RF situation with a matched source.
|