Hi again, The cable impedance measurement was in a different video (linked below) but it can use the same HC14 TDR as in the first video. The concept is to just put a pot on the end of the cable and adjust it until the reflection goes away. Simple!
https://www.youtube.com/watch?v=Il_eju4D_TM --Jim Stone Hi Bob, Take a look at this nice simple little one chip "TDR" and lesson on how to use it to measure cable length and cable impedance. It uses a single AC14 (can use a DIP so no SMD needed) and gives a nice crisp 2 or 3 ns rise. The AC family is nice fast logic and has been used in many Time-Nuts application like cheap zero-cross detectors using the AC04. https://www.youtube.com/watch?v=9cP6w2odGUc Regards --Jim Stone Bob Albert wrote: Well I got my adapter boards from China and managed to build my first SMT project, a square wave generator for TDR use. And it works! The IC seems to run hot so I used my IR temperature measurement device and it checks out at about 37C, acceptable. I can now drive a square wave at about 3 kHz into 50 Ohms. The rise time isn't very short but I must have not used the best part for the generator. Still, I can do some TDR experimenting as long as the line isn't too short. Thanks to all for the ideas and encouragement. I didn't use a microscope, mostly just a magnifier. My tiniest soldering iron is a bit large but it did the job. Bob _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
