michael brown wrote: > From: "Dennis J. Murray" > To: > Sent: Thursday, February 20, 2003 1:40 PM > Subject: Re: [PIC]: How would I build a reflectometer? > > >> I'll tell you guys - I've been following this link since it's >> inception and you REALLY have my curiosity piqued!! I've used TDRs >> quite a bit in a past life and I DEPENDED on the visual >> representation on the screen to interpret what is really on the >> line! I don't think I EVER had a clean line that didn't require >> some interpretation - was that hiccup a sharp bend? water in the >> line? an unauthorized tap? A long-forgotten splice? etc. >> >> How do you plan to accomplish this using a PIC or an oscillator >> circuit???? Or don't you? Just looking to determine overall length >> to the most significant reflection?? > > I only wanted to measure the length of installed network cabling. I'm > not really looking for wiretaps or anything that subtle. ;-) I'm > thinking that as long as the injection end is terminated to match the > characteristic impedance of the wire, there should only be one large > reflection and that would be from the far end. I'm thinking that > using the latest arriving "echo" would represent the distance to the > far end of the wire. > > michael hehe, again, I take back what I said in the last email, sent seconds ago. You are in true trying to measure the wire distance. If you build a cable loop terminator, simply a connector to make a loop between the cat-5 wires, lets say, building a 4 pairs loop, so you are multiplying by 8 the cable distance, and using any low cost thing as I suggested, a million pulses repeater, measuring the time, you could do it with less than $10 hardware. -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu