From owner-freebsd-hackers Thu Oct 2 17:00:58 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id RAA02792 for hackers-outgoing; Thu, 2 Oct 1997 17:00:58 -0700 (PDT) Received: from unix.tfs.net (root@unix.tfs.net [199.79.146.60]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id RAA02785 for ; Thu, 2 Oct 1997 17:00:51 -0700 (PDT) Received: from argus.tfs.net (pm3-p26.tfs.net [206.154.183.218]) by unix.tfs.net (8.8.5/8.8.5) with ESMTP id RAA07783; Thu, 2 Oct 1997 17:58:56 -0500 Received: (from jbryant@localhost) by argus.tfs.net (8.8.7/8.8.5) id TAA03036; Thu, 2 Oct 1997 19:00:41 -0500 (CDT) From: Jim Bryant Message-Id: <199710030000.TAA03036@argus.tfs.net> Subject: Re: thickwire<->thinwire In-Reply-To: from Mike Newell at "Oct 2, 97 04:36:31 pm" To: mnewell@newell.arlington.va.us (Mike Newell) Date: Thu, 2 Oct 1997 19:00:40 -0500 (CDT) Cc: freebsd-hackers@freebsd.org Reply-to: jbryant@tfs.net X-Windows: R00LZ!@# MS-Winbl0wz DR00LZ!@# X-Operating-System: FreeBSD 2.2.2-RELEASE #0: Wed Jul 9 01:01:24 CDT 1997 X-Mailer: ELM [version 2.4ME+ PL31H (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@freebsd.org X-Loop: FreeBSD.org Precedence: bulk In reply: > On Thu, 2 Oct 1997, Wilko Bulte wrote: > > wilko> Not completely. The collision detect uses a diode connection to the central > wilko> conductor on the thinwire tranceiver, and is directly connected for > wilko> thickwire (or the other way around, I forgot that detail). This is at least > wilko> the difference in the NS8392 based implementation I used when I built > wilko> a couple of tranceivers myself (years ago, when they were rare and $ were > wilko> few ;-) > > For short distances we had good success using an "N" to BNC adaptor (a few > bucks in most "real" electronics stores). Just pull the terminator off > one end of the thick, screw the adaptor on, twist on the thin, and put the > standard BNC type terminator at the end of the thin. Wouldn't recommend > it for cables near their max length, but for short ones... my memory fails me... the wire frequency is 20MHz, correct? the max length is limited by distributed capacitance [assuming a long, random, non-resonant length of transmission line], correct? applying conventional transmission line theory, could you not use longer lengths that are multiples of one wavelength of the base frequency in use? this should apply maximum in-phase signal to the downstream connection. or am i completely misunderstanding ethernet here? i would think that the only problems that would occur through the N<->BNC adaptor would be a small insertion loss [avg for a good connector around 1.05-1.1 dB], and slight increase in SWR. jim -- All opinions expressed are mine, if you | "I will not be pushed, stamped, think otherwise, then go jump into turbid | briefed, debriefed, indexed, or radioactive waters and yell WAHOO !!! | numbered!" - #1, "The Prisoner" ------------------------------------------------------------------------------ Inet: jbryant@tfs.net AX.25: kc5vdj@wv0t.#neks.ks.usa.noam grid: EM28pw voice: KC5VDJ - 6 & 2 Meters AM/FM/SSB, 70cm FM. http://www.tfs.net/~jbryant ------------------------------------------------------------------------------ HF/6M/2M: IC-706-MkII, 2M: HTX-212, 2M: HTX-202, 70cm: HTX-404, Packet: KPC-3+