You want a great reflection from the end? Just leave the end open or shorted! A good termination impedance match doesn't return much signal. A short or open gives you a great spike (different directions, of course). ----- Original Message ----- From: "michael brown" To: Sent: Thursday, February 20, 2003 3:30 PM Subject: Re: [PIC]: How would I build a reflectometer? > 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 > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu