Re: Radio waves...

[David Bowman <dbowman@tiger.gtc.georgetown.ky.us>]

> Those data rates don't seem to present a problem; Shannon says the  
> limiting bit rate is B*log_2(1+S/N)
> Taking a bandwidth B=3000 and a S/N level of 56 db (S/N=10^5.6=398107) 
>
> gives 3000*Log_2(398108) = 55808 bits/sec.
>  
> A good S/N ratio will get you there!

I'm quite surprised that a telephone line could have a S/N remotely as high
56 db.  This seems to be a dynamic range of better than 18 bits.  This seems
to be at least CD quality sound here.  When I use the phone there often seems
to be significant background noise and have a hard time believing that there
can be a S/N anywhere near that high.  I also didn't know that the telephone
channel bandwidth was as high as 3000 Hz.  The voices I hear over the phone
usually seem to sound more distorted than I would expect from a 3000 Hz
bandwidth.

> For much more than you care to know about modems go to:
>
> http://www.paranoia.com/~filipg/HTML/LINK/PORTS/F_MODEMS_DOC.html
>
> Bob Sciamanda           sciamanda@edinboro.edu
> Dept of Physics
> Edinboro Univ of PA     http://www.edinboro.edu/~sciamanda/home.html

Thanks Bob for the pointer.  I'll look it up.

David Bowman
dbowman@gtc.georgetown.ky.us