In message <[email protected]>, dated Mon, 24 Apr 2006, Robert A. Macy <[email protected]> writes >symmetrical == >the signal is plus phase in one conductor and zero phase in the other >with reference to infinite ground. > >examples: > twisted pair > twisted pair in shield > 300 ohm TV lines > >unbalanced == >the signal is completely in one conductor [well, tries to be completely >in one conductor] and is referenced to the other conductor, thus with >respect to ground one conductor is supposed to have 0 signal and the >other has it all. > >examples: > 50 ohm coax > 75 ohm coax > unknown coax for 600 ohm audio
Balance is nothing to do with voltages. It's about impedances. Yes, it came as a bit of surprise to me, too, but that was a long time ago. And '600 ohm audio' was a balanced connection system, not coaxial. 600 ohm coax would be a very strange thing. The formula is Z = 138*log(D/d) where D and d are the outer and inner conductor diameters. So D = 22275d, and if d = 0.1 mm, D = 2.2275 metres. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
