Reflection on Resistive loads
 

Bob Agnew wrote:
So how does a 1/2WL piece of transmission line driving a
50 ohm load wind up with the voltage and current in phase
no matter what the SWR?

If the characteristic impedance of the transmission line is 50 ohms, then
there are no reflections; furthermore the current and voltage are in phase
at every point along the line, There are no standing waves in this case.

But I didn't say Z0 equals 50 ohms. What if Z0 equals 75 ohms?
300 ohms? 450 ohms? 600 ohms? Assuming lossless lines, those
Z0's will all result in 50 ohms looking into them when they
are 1/2WL long. Thus the voltage and current will be in phase
for 1/2WL no matter what the characteristic impedance and no
matter what the SWR.
--
73, Cecil http://www.qsl.net/w5dxp

Reflection on Resistive loads
 

Bob Agnew wrote:
When the reflection coefficient rho is +/- 1 the VSWR is infinite. When rho
= 0 the VSWR is 1:1. A VSWR of 1:1 corresponds to the unit circle at the
center of the Smith Chart.

And when SWR = 1:1, that circle has a radius of zero, i.e.
it is a point at the center of the Smith Chart.

But it seems to me that no matter what the Z0, whether purely
resistive or containing some reactance as does ordinary transmission
line, on a line with reflections, there will be a point where the
ratio of net voltage to net current has the current leading the
voltage and a short distance away, the current is lagging the voltage.
In between those two points, it seems to me that there must exist a
point where the voltage and the current are in phase. How could the
net (virtual) reactance go from capacitive to inductive without having
the voltage and current in phase at a point in between?
--
73, Cecil http://www.qsl.net/w5dxp

Reflection on Resistive loads
 

On Mon, 31 Jul 2006 19:35:45 -0500, "H. Adam Stevens, NQ5H"
wrote:

That I knew in Jr High.

Finally understood it when I studied E&M in college.

You're miles ahead of me then. I'm tackling phonon dispersion right
now. I know it, I should understand it (especially after weeks in the
library), but there's always something in the corner of my mind on all
sorts of these subjects that asks:
"What the #%!@ ?"
or as we said in tech school to conform to comm systems lingo:
"What the #%!@ ? - Over."

73's
Richard Clark, KB7QHC

Reflection on Resistive loads
 

Bob Agnew wrote:
Hi Bob, I have never taught at the University level myself, this is an
"Amateur" newsgroup. If you look at the Smith Chart, 1/2WL reflects

OK __ I won't post here anymore. I once was an Amateur when I was 14.
I thought that I wanted to get back into the hobby now that I am retired.

Hi Bob, I'm sorry if you read something into my "amateur" statement
that I did not mean. I for one would welcome you to post on anything,
anytime you wish. I would also like to welcome you back into the
hobby, if that what you would like to do. I became a Ham when I was
about 14. Am an EE, but never worked in the RF end of things. When I
post on the antenna group, I am an Amateur.
73 Gary N4AST