Date: Thu, 2 Oct 1997 19:00:40 -0500 (CDT) From: Jim Bryant <jbryant@unix.tfs.net> To: mnewell@newell.arlington.va.us (Mike Newell) Cc: freebsd-hackers@freebsd.org Subject: Re: thickwire<->thinwire Message-ID: <199710030000.TAA03036@argus.tfs.net> In-Reply-To: <Pine.BSF.3.96.971002163416.3472H-100000@bigpuppy.newell.arlington.va.us> from Mike Newell at "Oct 2, 97 04:36:31 pm"
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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+
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