Hackers Measure Cable Lengths with Time Domain Reflectometers

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Dont Ask Meimnoexpert:

Looks pretty simple!!

Originally posted on Hackaday:

[android] has built up a fast edge pulse generator for time domain reflectometry (TDR). TDR is a neat technique which lets you measure cable lengths using electrical signals and can also be used to locate faults within the cable.

TDR works by sending a pulse down the cable. When the pulse reaches the end of the unterminated cable it is reflected back to the source. By monitoring the delay between the original pulse and its reflection you can determine the length of the cable. We’ve seen projects that use TDR before, and it’s often used in telecoms industry to locate faults in long cable runs.

You can try TDR in your lab using only a scope to observe the delay and a function generator to create the pulse. However, the technique works a lot better with pulses that have very fast rise times. So [android] built a fast edge…

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It’s All Good

This post has been a long time coming!!  I’m tired and busy right now, so I need to make it brief. I’ve spent too much time thinking my life is ‘small’……..many mechanisms of modern life can contribute to that type of mindset. There’s been a lot of dialogue about that very thing lately; ‘Everyone’s life is great and mine isn’t……..just look at Facebook and you’ll see!”  Poppycock, I say.

I have a great life. I have two amazing kids. I have a (fairly) loving wife. I have a good job and a good home in a good neighborhood. I have a smart brain and a good education. I help others who have a hard time helping themselves.

I can exert very little control over what mean people do to nice people who own a pizzeria in Indiana. I can do very little to impact human trafficking in Cambodia. I doubt that I can do a lot this week to effect polar ice caps or radiation leakage somewhere. Nope I don’t own anything that floats.  But, I can do something and I do do MANY things to help the world while living a full life. No, my life isn’t amazing. It isn’t filled with supermodels and high performance motorcycles (and whatever other stupid material thing that wont come to mind right now!) But I have good people and good co-workers and good neighbors and good fellow church-members in my life…..and that’s good. My life is good and I want to keep giving GOOD back to the world. I’m OK….I’m really, really OK…..and that’s great. Heck, that’s a long way from a ‘small life’!

Remember all the good in your life. Entropy resides all around us. Drink in today’s good stuff….because it won’t last forever!

It is what you make it!


I’m weird. I’m not particularly ashamed of it. I like esoteric things.

I work for a state agency…..and some months ago, I found a gigantic stack of old forms (from the 1970’s!!) near the big office shredder and I thought they were cool. Apparently, they’re the documentation concerning call-ins that people would make to complain about various public health issues. Here’s one (pretty much verbatim) from April 1977:

“Mrs. ‘B’ from Myrtle Springs, Texas calls in stating she has a shallow well for water supply. She complains that her next door neighbor has a mobile home and runs sewage out on the ground, less than 100 feet from her well. Couple both work in Dallas.

Action taken: Wrote letter — check June 20 — Called Mrs. ‘B’ Aug 8 — she said nothing has been done. Inspected this place with Mrs. ‘L’s’ son, 3-21-78 [nearly a year later!!!] Septic tank and field lines have been installed and apparently are working properly.”
—————— It appears to’ve been closed on 3/22/1978