Re: [ARSCLIST] long range file storage

[Don Cox <doncox@xxxxxxxxxxxxxx>]

On 13/08/05, Mwcpc6@xxxxxxx wrote:
> In a message dated 8/12/2005 8:43:32 PM Eastern Standard Time,
> stevenc@xxxxxxxxxxxxxx writes:
>
> Given that we can use 56K (bits, not bytes) modems...could this be
> recorded on a shellac disc, given the inherent signal-to-noise ratio?
> It could probably be done on vinyl...but are there any lifespan
> considerations for vinyl discs?
> ***************
>
> In the 1920s Video signals were recorded on shellac discs using a
> modulated tone similar to the way the cassette tape data recorders for
> early PCs worked. I don't see why a modem signal that can pass through
> a voice telephone line couldn't be recorded on any audio medium,
> though it might have to have better speed regulation than most analog
> machines do.

Modern methods of modulation, using a combination of amplitude and phase
with error correction, can carry several bits in one cycle of the
carrier. Basically, it is a matter of having various distinguishable
shapes for the wave, and mapping each to a number.

http://www.physics.udel.edu/wwwusers/watson/student_projects/scen167/thosguys/qam.html

You could probably store 3 minutes of CD quality (16/44.1) sound on a 3 minute 78.
Maybe even 24-bit sound.

Regards
--
Don Cox
doncox@xxxxxxxxxxxxxx