One of my favorite vloggers is w2aew. A recent posting has got me thinking TDR…. supersized. I was planning on playing around with a compass/barometic pressure sensor with the Raspberry Pi but that may wait.. (or perhaps I should pick up a cheapo model A). I don’t use a lot of coax these days but a TDR for CAT5 might be handy. If you watch this video I imagine you can fill in the blanks and see how I believe with an A2D converter and a stable parts (read: frequency) you could have yourself a real nice basic TDR.

5 EA 74AC14 ‘s are $3 and some change right now on eBay. I had some eBay bucks ready to expire so I ended up getting mine for “free”.

I tried the circuit out with a 74LS14 which is obviously turtle powered compared to the ‘AC14.. I could still determine the approximate length of my CAT5 even with the circuit on a breadboard. If you make an attempt the value’s used in the video will not work. If you need a little help ( ) If you’re going the same route don’t forget CAT5e’s impedance is roughly 100ohms so make the necessary changes in your parallel resistors.

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