[sdiy] Information Content of Signals

[John L Marshall]

I believe that very few amateur radio operators use Baudot since maybe 1977.
Most hams use computer based terminals with ASCII encoding.

Domestic teletype, for example KSR33, used ASCII encoding.

International teletype, used Baudot, as well as the wire services, AP, UPI,
CP.

Reminds me of the well establish news editing technique call "rip and read".
Rip the paper from the teletype at 15 seconds to the top of the hour then
edit the news while reading. The down side is getting halfway through a news
item only to find the "shift out" for numbers did not "shift in" for the
remaining test leaving the remainder of the test garbled. Pause....

Take care,
John, WA7BSR
------------------------------------------------------------------
Pacific Northwest Synthesizer Meeting
August 9, 2003
www.sound-photo.com
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----- Original Message ----- 
From: "Neil Johnson" <nej22 at hermes.cam.ac.uk>
To: "Tim Ressel" <madhun2001 at yahoo.com>
Cc: "Grant Richter" <grichter at asapnet.net>; "Magnus Danielson"
<cfmd at swipnet.se>; <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, May 17, 2003 5:42 AM
Subject: Re: [sdiy] Information Content of Signals


>
> Easy one...
>
> Tim Ressel wrote:
> > I want to know how they can get 53kbps on a phone line with 3khz
> > bandwidth. Oh I know they use this funky phase-constellation thingie.
>
> Remember that "baud" != "bits per second".  The proper definition goes
> something like "symbols per second".
>
> "bits per second" is a special case of baud, where each symbol represents
> only two states (1 or 0).  If we give each symbol 4 states, then we can
> encode two bits per symbol.  As DSP gets better, we can decode many more
> states per symbol.
>
> Take your phone line, and lets say we have an upper limit of 3,000 symbols
> per second.  Now leys say we have 16 states per symbol, which we can
> encode 4 bits per symbol.  Now the bit rate is 16 x 3,000 = 48kb/s.
>
> Interesting side note: "baud" is named after the French telecomms man
> Baudot, who developed an ecoding scheme using 5 bits per letter, and a
> special little typewriter for sending messages.  There are plenty of
> references on the web about Emile Baudot.  Indeed, baudot code is still
> used by radio hams, and was used for punched-tape.
>
> Neil
>
> --
> Neil Johnson :: Computer Laboratory :: University of Cambridge ::
> http://www.njohnson.co.uk          http://www.cl.cam.ac.uk/~nej22
> ----  IEE Cambridge Branch: http://www.iee-cambridge.org.uk  ----
>