To try and verify your theory, I set up a signal generator at 100 and 400 MHz, -20 dBm into 50 Ohms. I drove a six foot section of RG-58 with bnc connections, and terminated in a shielded 50 Ohm dummy load. I repeated the same measurement using one of my twisted shielded pairs. I measured "leakage" current by placing a current probe around first the coax and then the TSP, sliding the probe up and down the cable looking for maxima. I did not see a significant difference at 100 MHz, but at 400 MHz there was 20 dB more leakage on the TSP than from the coax. Is it a good assumption that anything I measure with the current probe is essentially lost in transmission?
---------- >From: Cortland Richmond <72146....@compuserve.com> >To: Ken Javor <ken.ja...@emccompliance.com>, ieee pstc list <emc-p...@ieee.org> >Subject: Re: Stumped >Date: Tue, Oct 15, 2002, 12:59 PM > > Now that I've re-read the message, I see where you are coming from. > > I thought you were looking at common-mode loss of the cable (as a whole, > shield included) *above ground*; you are looking at the center conductor > common mode with respect to the overshield, almost as a coaxial cable > itself. Yes, that seems a reasonable impedance for that configuration. > > Loss is from the conductor and from the dielectric. You have a relatively > large, low-loss conductor -- but due to its high capacitance, I'd expect > dielectric loss to predominate in the setup you are using. > > A question about the braid; you said it appears to be Kapton coated. Could > it be that braid conductors are not making intimate contact with each > other? In that case, radiation loss could still be a large part of what you > saw. > > > > Cortland > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
