On Jun 25, 9:00*am, Cecil Moore wrote:
On Jun 25, 2:13*am, lu6etj wrote:

In a TL, instead, total destructive interference in one point would
mean energy stop flowing from that point forwards (is it OK say
"forwards"?) and reverse its flow direction doubling his value, is it
OK?.

In our ham transmission line systems, the goal is to accomplish total
destructive interference toward the source, i.e. zero reflected energy
incident upon the source. So let's talk about destructive interference
toward the source and constructive interference toward the load.

You name it "redistribution" too, not reflection.

By definition, reflection is something that happens to a single wave.
By definition, superposition involves two or more waves. The
redistribution that I am talking about can include both reflection and
superposition if both are present. Depending upon the system
configuration, both may be present, both may be absent, or one exist
without the other.

Well, my
question was how we can set (devise) an experiment to get such
behaviour in a TL?

I've presented it before and it is a simple Z0-match involving a 1/4WL
matching section.

50w-----50 ohm------+------1/4WL 300 ohm------1800 ohm load

On the source side, rho at '+' is 0.7143

Using a TDR, we can verify that there is indeed a reflection from the
50/300 ohm impedance discontinuity. What happens to that reflection
during steady-state?

What happens to Vfor1(rho) = 50v(0.7143) = 35.7v?

Using superposition, when you add Vrev2(tau) to Vfor1(rho) you get
zero.
With zero voltage comes 0 energy transfer.

For further learning, do not just examine steady state, but also
examine
how it gets to steady state. Using a lattice diagram, examine what
happens as the first reflection and then each re-reflection arrives at
'+'. Determine how Vrev2(tau) slowly builds to equal Vrev1 and cancels
it, using the simple addition of superposition. While this process is
occurring, there is a Vrev1 which decreases after each round trip in
the second line section.

This is all done with simple addition. No need for products and square
roots.

For further marks, decide whether you should think of Vrev2 as an
infinite sum of reverse waves or is it okay to think of it as one sum
that slowly accumulates.
Which is it really?

Same question for Vfor2.

What happens to Pfor1(rho^2) = 50w(0.51) = 25.5w?

Once you have computed total Vrev1 using simple superposition, it is
easy to compute that the "reverse power", Prev1, is 0.

Do you really need rho^2 to understand what goes on in a transmission
line?

....Keith