Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!att!emory!athena.cs.uga.edu!mcovingt
From: mcovingt@athena.cs.uga.edu (Michael A. Covington)
Newsgroups: sci.electronics
Subject: Re: Signal Propagation, Baud Rate, and Attenuation
Message-ID: <1991Jan2.071817.2071@athena.cs.uga.edu>
Date: 2 Jan 91 07:18:17 GMT
References: <17100010@inmet> <1126@soleil.UUCP> <1991Jan2.055516.14616@NCoast.ORG>
Organization: University of Georgia, Athens
Lines: 21

In article <1991Jan2.055516.14616@NCoast.ORG> richb@railnet.uucp writes:
>
>Could someone out there explain to me why a signal can physically travel
>further on a metal media at a slower baud rate ?
>

Simple. A serial signal is simply a voltage that switches from one
value to another (binary one and binary zero) very fast. The higher
the baud rate, the faster it has to be able to switch.

A long cable has both capacitance and inductance. Both of these tend
to slow down the switching, so that a sudden change in voltage at one
end is not so sudden when it gets to the other end because of the time
taken to alter the magnetic and electric field of the cable.

So a signal traveling through a long cable can't switch very fast.
Hence a lower baud rate is necessary.

(There are impedance-matched coaxial cables that don't have this
problem. I'm speaking about a typical RS-232 signal in a typical
wire cable.)