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A comment on Any way to find a lost Kindle inside a house?. Parent comment

Re:Any way to find a lost Kindle inside a house? by dr_orpheus on Thursday January 02, 2020 @03:35PM (#21939507)
That's pretty clever. Also if you are interested (not 100% applicable because it's not something most people can do at home) there is a practice for finding breaks/partial breaks in cables using time domain reflectometry (TDM) [0]. You send a pulse in to one end of the cable and measure how long it takes for some reflected energy at the break to return. It's pretty cool stuff and you only need access to one side of a cable. I have used this in my job for finding discontinuities in large RF cables.

If you do have some electrics equipment at home (o-scope, sig-gen) you can make do it yourself [1]

[0] https://en.wikipedia.org/wiki/Time-domain_reflectometer

[1] https://www.allaboutcircuits.com/projects/build-your-own-tim...

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Re:Any way to find a lost Kindle inside a house? by b06tmm on Thursday January 02, 2020 @07:53PM (#21941811)
We did this in the Navy to check circular wave guides to the ECM antennas in the leading edge of our bombers wings. We had to do this once every 6 months (I think) with a sweep generator to see if the cables needed to be replaced. Also, installing these were a complete PITA! Nothing was a straight run to where it needed to go, so you had to bend them as gently as possible as you fed the new line into the wing. Then you had to test it again.

These were very expensive and I've seen more than a few screwup's while installing them.

A coworker's cat-5 tester also has a TDR function that shows you where an issue is on the line.

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Re:Any way to find a lost Kindle inside a house? by tech2 on Sunday January 05, 2020 @03:47AM (#21960357)
Many _many_ years ago we used to have to do that on occasion in our office to find where the break in the coax network was. That brought some amusing memories back for me, thanks :)
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Re:Any way to find a lost Kindle inside a house? by daemoncoder on Friday January 03, 2020 @02:06AM (#21943905)
I got the capacitance idea from having worked with TDR in the late 80's. As students we used them to tune FM antenna combiners, but I never quite got the hang of it at the time.
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