Chart a sine wave, then adapting it to draw a conclusion
I have simulated this lab experiment for you. 
 I've not done this since 1974 in the Microwave 401 lab. (but I have used a similar method using a return loss bridge to tune a dipole)

You can pull the slider or tick the left/right end for a fixed increment then record the data for Vpp and Wavelength mm and ns and plot it.  You can then compute s11.  

With the end of the transmission line shorted, you should be able to locate the lengths for the 1/4 wave inverse impedance ( open circuit = 0 current)  and half-wave short circuit looking at the input voltage after the 300 Ohms.

You can change the impedance of the delay line as well as the fixed resistor. I just made them both 300 Ohms.