Archived posting to the Leica Users Group, 2000/11/30

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Subject: Re: [Leica] Re: Bandwith
From: "Dan Post" <dpost@triad.rr.com>
Date: Thu, 30 Nov 2000 11:09:15 -0500
References: <3A24A1E7.D79B2CE7@primus.com.au> <B646FAF1.36D%imxputs@knoware.nl> <3A24A1E7.D79B2CE7@primus.com.au> <4.1.20001129071833.0182f590@xsj02.sjs.agilent.com>

Jim-
Remembering my communications days, and what I remember about Shannon's
Theory is that the amount of information is related to the number of changes
of state a carrier can make in a given time period- the frequency in other
words. That is to say, if you have a state change- from zero to one as in a
digital system per second, then you have a one Hertz signal. The higher the
frequency, the greater the potential information carrying capacity. On old
style systems, the higher the frequency, the greater the bandwidth needed.
So a television signal required a 6Mhz bandwidth because that much spectrum
was taken up by the sound and image signal.
I think this idea has carried over even into the digital age where the
information coding no longer actually depends on the ability of a line to
carry a wide spectrum of frequencies.
Dan
- ----- Original Message -----
From: "Jim Brick" <jim_brick@agilent.com>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Wednesday, November 29, 2000 10:29 AM
Subject: [Leica] Re: Bandwith


> At 09:49 AM 11/29/00 +0200, you wrote:
> >>
> >>The reference is to the term Bandwidth.  The context in which this is
used is
> >>wrong.
> >>
> >>Bandwidth has nothing to do with the length of a message. A message of 2
hour
> >>length uses no more bandwidth, than a message of one second.
> >>
> >>Bandwidth has to do only with the actual speed a message is send. If a
> message
> >>is send with  a speed of 300 baud, then the bandwidth is less than
> >>if a speed of
> >>1200 baud is used.
> >
>
> Actually, in this RF & ether age, "Bandwidth" has taken on the meaning of
> "VOLUME" which does not necessarily relate to actual moving speed, ie,
1200
> baud vs 2400 baud. Think of it like water in pipes. Pump up the pressure,
> make the water go faster, you do indeed get greater bandwidth, that is,
the
> delivered volume is greater. Also, by making the pipe fatter, or adding
> multiple pipes, yet keeping the same flow rate, the delivered volume is
> greater.
>
> ISDN is made up of two 64KB data lines. Quite often only one is used. If
> there is a backlog of data to be sent, the other line will kick in. The
> data is still being sent at 64KB/sec but there is twice as much of it
> getting through. More bandwidth.
>
> So in reality, long message use up bandwidth as they require volume.
>
> Jim
>

In reply to: Message from "A.H.SCHMIDT" <horsts@primus.com.au> ([Leica] Bandwith)
Message from imx <imxputs@knoware.nl> ([Leica] Age and style)
Message from "A.H.SCHMIDT" <horsts@primus.com.au> ([Leica] Bandwith)
Message from Jim Brick <jim_brick@agilent.com> ([Leica] Re: Bandwith)