Video: terminations, reflections and transmission lines - Page 1
Forum section: electronics / beginners

author: w2aew
author_rank: Super Contributor
timestamp: April 29, 2014, 03:18:55 am
content: This video gives a brief overview of when and why you'd use terminations, and the basics of reflections, signal propagation and transmission line properties. Bonus at the end... ...how to measure the length of a transmission line with a scope and signal generator.

author: BravoV
author_rank: Super Contributor
timestamp: April 29, 2014, 03:42:22 am
content: Thanks Alan, great video !About termination, I can see you're using the Tektronix feed through terminator like the right photo below.My question is, compared to using a cheap bnc T connector + extra 50 Ohm terminator, at what condition the difference using these two will become obvious ?VS

author: w2aew
author_rank: Super Contributor
timestamp: April 29, 2014, 03:56:23 am
content: Quote from: BravoV on April 29, 2014, 03:42:22 amI would susect that the performance of the through termination vs. the Tee as shown will be virtually the same up for frequencies up a few hundred MHz, provided the male end if the Tee is connected directly to the scope input.

author: BravoV
author_rank: Super Contributor
timestamp: April 29, 2014, 04:03:08 am
content: Quote from: w2aew on April 29, 2014, 03:56:23 amThanks, so as a ballpark performance as long theTee is connected directly at the scope's bnc input, its "safe" to say that we will not see any significant difference say signal < 300 MHz ? Picked the number 300 MHz just from the thin air, cmmiw.

author: w2aew
author_rank: Super Contributor
timestamp: April 29, 2014, 04:24:43 am
content: Quote from: BravoV on April 29, 2014, 04:03:08 amI'd think so - there will be some difference, but not too significant I think (just gut feel, I haven't tested it yet...).

author: BravoV
author_rank: Super Contributor
timestamp: April 29, 2014, 04:28:34 am
content: Since you have all the supporting tools there, I think this will be a good material for upcoming "short" video as well, just a suggestion.Again, many thanks.

author: w2aew
author_rank: Super Contributor
timestamp: April 29, 2014, 12:23:24 pm
content: Quote from: BravoV on April 29, 2014, 04:28:34 amNo video on this (yet?), but a quick sweep shows that neither of these solutions is as good as a internal 50ohm termination in the scope. In cases where you don't have an internal termination, both of these solutions are nearly equivalent. Some change in amplitude vs. frequency starts to become evident at about 150-200MHz, but no more than 2-3dB variation. At 300, the through termination is moderately better than the Tee+end_termination.

author: BravoV
author_rank: Super Contributor
timestamp: April 29, 2014, 03:45:04 pm
content: Alan, again, just a suggestion, please do a short video comparing between the internal scope's termination, a feed through, tee + terminator and a ghetto style terminator with a soldered big through hole resistor at a unused bnc socket without the end cap (no shielding), I guess these should be interesting to watch.

author: w2aew
author_rank: Super Contributor
timestamp: April 30, 2014, 12:34:16 am
content: Quote from: BravoV on April 29, 2014, 03:45:04 pmI'll add it to the list. To do this "right", I'll have to use a scope with more BW than the 2467 used in this video...

author: BravoV
author_rank: Super Contributor
timestamp: April 30, 2014, 01:00:13 am
content: Quote from: w2aew on April 30, 2014, 12:34:16 amThank you Sir, and with your experience, knowledge, skill and the "good enough" resources you have there, like the multi-GHz scopes and multi-GHz func/sig generators, I guess this can be easily done in the "right" way.A tiny foot note, hopefully at the end you can make the conclusion on what is "good enough" for this termination matter, especially targeting for the hobbyists crowd.Great, eagerly waiting to watch it at your channel.

author: robrenz
author_rank: Super Contributor
timestamp: April 30, 2014, 02:56:21 am
content: Most excellent video AlanAs usual you have greatly raised my level of understanding.