Suggestions for the TDR:
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get a known length of 50 ohm coax
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and another known length of 50 ohm coax
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and a known length of 75 ohm cable TV coax
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and a 50 ohm load
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and a 75 ohm load
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and a short
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use the TDR to determine the pulse length of each coax and calculate the scope trace to coax length ratio
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put the 50 ohm cables end to end with the far end terminated and find the middle connector
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put a 50 ohm coax, a 75 ohm coax, and the other 50 ohm coax together and see the fine mess that creates
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repeat all experiments with all possible combinations of 50 ohm, 75 ohm, open, and short circuit terminations
put a length of unterminated coax in the TDR and cut it close to the end while watching the TDR trace
Not pulling your leg: in the days of way back when they would hang a length of coax in a vertical borehole for a nuclear bomb test and measure the speed of the shockwave by filming a TDR as the RG213 turned into RG174