using sig generator and scope as TDR for troubleshooting ethernet

Question

I had some problems with a new run of cat5e. I have already established it's definitely a damaged cable using a cheap network continuity tester and double checking my wiring and crimps.

I saw on YouTube there are people using a signal gen and scope as a DIY TDR. However I don't have a signal generator and my scope is a cheap tenma(farnell brand) scope with a 40MHZ bandwidth I believe.

Is it possible for me to build an oscillator that's within the bandwidth of my scope and use it as a tdr to locate where the fault is? This is just for fun really.

Answer 1

It's unlikely that you'll have much success with TDR, which stands for "time-domain reflectometry", with such limited equipment. In order to get usable resolution, TDR requires very fast signal edges (nanosecond rise/fall times) and wide-bandwidth analysis equipment.

But if you understand the theory, there's an equivalent frequency-domain analysis that you can do with more modest equipment. You'll still need a signal generator, though — preferably one with very accurate frequency settings. I would suggest getting one of those DDS signal generator modules that are available at modest cost all over the Web.