Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!lll-winken!rogue.llnl.gov!oberman
From: oberman@rogue.llnl.gov
Newsgroups: comp.dcom.lans
Subject: Re: 50-75 ohm impedance matching
Message-ID: <1990Jul13.080836.1@rogue.llnl.gov>
Date: 13 Jul 90 15:08:36 GMT
References: <8592@uhccux.uhcc.Hawaii.Edu>
Sender: usenet@lll-winken.LLNL.GOV
Organization: Lawrence Livermore National Laboratory
Lines: 24

In article <8592@uhccux.uhcc.Hawaii.Edu>, querubin@uhccux.uhcc.Hawaii.Edu (Antonio Querubin) writes:
> 
> Don't know if anyone has run into this situation before but we have a
> requirement to setup a point-to-point link between two buildings using a
> previously installed 75-ohm video cable.  For various reasons, we can't 
> just replace the cable with a 50-ohm thin-net cable to run an ethernet
> link.  So the simplest and cheapest way to get the link is to use the
> existing cable.  Now it seems that one should be able to solve the impedance
> mismatch and associated reflection problems by using a 75-to-50 ohm impedance-
> matching transformer at each end of the video cable so that the ethernet
> transceivers on either side effectively sees a 50-ohm cable.
 
TCL, the granddaddy of Ethernet hardware companies, used to make Ethernet
eqipment already set up for 75 ohm cable. We have quite a bit of this stuff
because of a similar problem, but it's all been here for a while and my not
still be available.

					R. Kevin Oberman
					Lawrence Livermore National Laboratory
					Internet: oberman@icdc.llnl.gov
   					(415) 422-6955

Disclaimer: Don't take this too seriously. I just like to improve my typing
and probably don't really know anything useful about anything.