This video shows some simple ways to measure the velocity factor (VF) and impedance of a known length of coax. (Please pardon the simple decimal point error in the metric conversion - see the annotations inline in the video - sorry about that!)
It uses a simple TDR technique using a cheap homemade fast-edge pulse generator, as detailed in this video:
• #88: Cheap and simple ...
which is based on the simple schmitt trigger oscillator shown in this video:
• #87: Schmitt Trigger O...
Here is a companion video that shows how to measure the length of a piece of coax, assuming that you know the VF:
• #37: Use a scope to me...
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