REGISTER | LOGIN
Breaking News
Comments
Newest First | Oldest First | Threaded View
satter
User Rank
Author
Re: All well and good, except...
satter   2/4/2014 7:04:21 PM
NO RATINGS
Sorry; however I think you are missing the point.  The varied twist of the pairs reduces the metallic coupling between pairs just as you have pointed out.  The coupling I am speaking of here is the longitudinal coupling between the pairs treated as single conductors.  In the article you can see that I have shorted the two conductors of each pair and teat each pair as a single wire.  These conductors do form transmission lines and store energy -- and can get you in trouble if not addressed.

Thanks for reading the article,

 

Jim

dougp01
User Rank
Author
All well and good, except...
dougp01   8/17/2013 6:40:55 PM
NO RATINGS
This all well and good except for one thing that seems to be ignored in the article. 

An assumption seems to be made that the coupling bewtween the conductors is a constant impedance over the entire legnth of the cable.  In fact, when Bell Labs first developed the concept of paired bundles for telcom wire many years ago, the problem of coupling between pairs was addressed.  The solution they adopted on pair-wises cables was to introduce a different twist rate on each pair of wires.  The effect they were seeking was to ensure that field coupling between pairs was cancelled every few centimeters.  With 8-pair cable this can be easily verified.  With 25-pair or 50-pair is it a little more difficult but this is where twist of pair-bundles comes into play.

 

-doug

 

 



Like Us on Facebook
EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Martin Rowe

Test Tool Finds Ethernet Wiring Errors
Martin Rowe
Post a comment
When my house was renovated several years ago, I had the electrician install network outlets in numerous places, then run the LAN cables to a wiring closet. But he didn't document the ends ...

Martin Rowe

Local Electronics Store Supplies Engineers and Hobbyists
Martin Rowe
5 comments
Rochester, N.Y. — Tucked away in this western New York city known for its optics is Goldcrest Electronics, a local store that's supplied businesses and individuals with electronic ...

Martin Rowe

How to Transform a Technology University (Book Review)
Martin Rowe
1 Comment
The Presiding Genius of the Place by Alison Chisolm. WPI, Worcester, Mass., 234 pp., 2016. Engineers love to discuss, and often criticize, engineering education. They often claim ...

Max Maxfield

Aloha from EEWeb
Max Maxfield
Post a comment
Just a few minutes ago as I pen these words, I posted this blog about this month's Cartoon Punchline Competition over on EEWeb.com.