On Tuesday 21 November 2006 09:33, Mel wrote: >Alan wrote: >> Controller<=====Longest Part of cable===>Drive2<===Short >> bit===>Drive1 > >If I remember my cable theory correctly, all cables should be terminated >in their characteristic impedance at both ends. If not, then reflections >occur. > >The higher the frequency, the greater effect they have on reliable use >of the cable. As you said, cable length is also a factor. > >Isn't this what "Time Domain Reflectromitry(SP?)" is based on? The spelling will do, its reflectrometry, and the answer is yes. The problem is that to do it on cables as short as the 18 inchers used for ide connections, it takes some very expensive versions of it since one must be able to see, and detect an anomoly thats only 1/8" wide. There are fast samplers, and there are damn fast samplers. For longer stuff, I've used just a schotkey ttl gate as the signal, and a 100mhz scope to read it. There I can see with an accuracy of maybe 10 feet over 500 with that simple a lashup. With the real thing, I can see the individual connectors and insulators in a length of 3.125" transmission line but I can only see burnouts with my simple lashup because its not fast enough by a factor of 100 or so. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Yahoo.com and AOL/TW attorneys please note, additions to the above message by Gene Heskett are: Copyright 2006 by Maurice Eugene Heskett, all rights reserved.
