Date: Fri, 04 Aug 2000 16:04:31 -0400 From: "Louis A. Mamakos" <louie@TransSys.COM> To: "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net> Cc: freebsd-questions@FreeBSD.ORG (questions FBSD) Subject: Re: Router "ep2" issue Message-ID: <200008042004.QAA85387@whizzo.transsys.com> In-Reply-To: Your message of "Fri, 04 Aug 2000 11:40:18 PDT." <200008041840.LAA80077@gndrsh.dnsmgr.net> References: <200008041840.LAA80077@gndrsh.dnsmgr.net>
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[Note trimmed To: and Cc: to freebsd-questions] > > > The spec does call for medium grounding for 10Base5 and allows for it > > (but does not require it) for 10Base2, but that's about it. > > Anyone running Coax of any real length is a fool not to have it > properly gounded. Without the ground it is one big antenna, and > in a lightning storm the EMP wave can induce 100's to 1000's of > volts on a long piece of ungrounded coax, especially something > as large as 10Base5. I observed this first-hand years ago when 10Base-5 ("Thick" ethernet to you, buddy!) was run between two building, and underground at that. A lightning strike nearby caused the premature death of a bunch of thick ethernet transceivers, most convieniently located in the ceiling above various offices. There was also a considerable DC offset in the ground between the buildings, on the order of a couple of volts! I don't know if anyone ever measured the current when the cable was connected to the bulding ground in each building. I think this is why you're only supposed to ground the ethernet shield conductor in exactly one place. louie To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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