> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > Sent: Saturday, March 01, 2008 2:25 AM > To: time-nuts@febo.com > Subject: Re: [time-nuts] GPS-Attached Equipment Lightning Protection > > > Yes, this is the case, but it's easy to induce a couple 100 > Volts into the center conductor through the exposed elements > of the antenna. > ... > > bye, > Said >
This is due to a property known as "transfer impedance". Transfer impedance is the ratio of voltage induced (diffferentially) on the center conductor of a coax cable versus the current flowing through the braid (externally). Transfer impedance is solely driven by shield/braid and termination (connector) quality and has nothing to do with the characteristic impedance of the cable. The effects of poor transfer impedance are similar to poor shielding and usually related. Signals get in the cable from the outside. The remedies against that are the same: better shield and better connectors. It is seldom, if ever, specified when you buy a piece of cable. Cables with solid outer conductor, such as semi-rigid cable, have much better (lower) transfer impedance than woven braid cable for instance. Didier KO4BB No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.21.2/1305 - Release Date: 2/29/2008 6:32 PM _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
