I'm studying the trasmission of signals though coaxial cable; I'm using a coaxial cable (of course!), an oscilloscope, a generator an some different endings. This is the scheme:

I was told that if I use a very long cable that has impedence \$Z_0= 50 \Omega\$ and put, at the end of it, a **resistor of \$47\Omega \$**, the signal will be reflected.

I have obtained this:

If I have correctly understood, the height of the step pointed by the green arrow is the half of the V given by the generator.

I can't understand why the step pointed by the red arrow is shorter than the one that is on the other side. And I can't understand what's the physical meaning of the step pointed by the red arrow.
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Then, I have terminated the cable with a **short circuit** and I have obtained this:

Could you explain me what's up at the points indicated by the two arrows and the yellow and red points?
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Then, I have terminated the cable with a **resistor of 100 ohm** and I have obtained this:

Could you explain me, why the step pointed by the green arrow is higher than the step pointed by the red arrow?

 

Good question.
I think that you are seeing the effect of multiple reflections. Try increasing the pulse width of your signal and see if that shows more reflections with decreasing amplitudes.

 

Good question.
I think that you are seeing the effect of multiple reflections. Try increasing the pulse width of your signal and see if that shows more reflections with decreasing amplitudes.

Thanks for your answer but I can't repeat the experience because now I haven't the instrumentation... Can you help me to have some ideas about these horrible results? What should I have obtained?

Many thanks