1. The problem statement, all variables and given/known data We measured the time between a signal source, and it's reflection coming back through our probe after going through an open-ended coaxial cable. My teacher told us this: the cable has a polyethylene insulator between central wire and the grounding web, which has a dielectric constant of 2.3, which slows the speed of the signal in the wire. Find the length of the wire. You may need to use the web to look up cable properties. 2. Relevant equations The resistor that 'cancelled' the reflected signal was 51 ohms, so I'm assuming that is the characteristic resistance of the cable. I found that RG-9/U cables have this characteristic resistance. I have also found that in a transmission line, signal velocity is the reciprocal of the square root of the capacitance-inductance product, where inductance and capacitance are typically expressed as per-unit length. v = 1/ sqrt(LC) But I can't find the characteristic L or C of this wire anywhere. 3. The attempt at a solution I'm not sure. Is this analog to waves in classical mechanics? What does the dielectric constant have to do with the speed of the signal if it's surrounding the wire that the signal has to travel through? I'm not really sure how I am supposed to do this, and that is literally all the information provided to us. This is for a lab writeup. The delay in the reflected signal I measured as just about 300 nanoseconds.