[TenTec] Slightly OT: SSB vs AM

[Mark Erbaugh]

Ron,

The thing that has changed is the capability of today's PC. I suspect that
with appropriate software, a PC with a soundcard could to the same thing and
the expensive tape recorders.

I would suspect that you wouldn't recover all the information.
Unfortunately, with nature there's no free lunch (which is what prompted my
question on AM vs. SSB bandwidth and information). However, with a normal HF
SSB circuit we lose information all the time, yet we are able to understand
conversation and even recognize voices and emotions. The issue is how much
information can you lose and still have an acceptable performance.

73,
Mark

----- Original Message -----
From: "RON ZOND" <K3MIY at csonline.net>
To: <tentec at contesting.com>
Sent: Wednesday, April 23, 2003 8:14 AM
Subject: RE: [TenTec] Slightly OT: SSB vs AM


> Guys
>
> What you ae discussing is called time compressd speech. It has been around
> since the early fifties. There are tape recorders on the market
(expensive)
> which incorporate this feature.
> There are also IC chips designed to do the same thing. If you compress the
> speech by a factor of
> five, you decrease the bandwith by a factor of five. When you slow the
> speech down to normal,
> you do not recover all of original information. i did research with this
> thirty years ago.
>
> Ron
> K3MIY
>
>
> -----Original Message-----
> From: tentec-bounces at contesting.com
> [mailto:tentec-bounces at contesting.com]On Behalf Of Mark Erbaugh
> Sent: Tuesday, April 22, 2003 9:11 PM
> To: tentec at contesting.com
> Subject: Re: [TenTec] Slightly OT: SSB vs AM
>
>
> Carl,
>
> Yes, with that scheme we would change bandwidth for increased time. Kind
of
> like how we can send a picture in SSTV, but it takes many seconds.
However,
> I was proposing first doubling the speed (but using some sort of magic to
> keep the pitch constant) before slowing it down.  So a 5 second message
> would first be sped up to 2.5 seconds, but holding the pitch constant. The
> 2.5 second message would then be played at half speed, getting back to the
> original 5 seconds.
>
> Mark
>
> ----- Original Message -----
> From: "Carl Moreschi" <n4py at earthlink.net>
> To: <tentec at contesting.com>
> Sent: Tuesday, April 22, 2003 19:04 PM
> Subject: Re: [TenTec] Slightly OT: SSB vs AM
>
>
> > Assuming you recorded your voice message on a tape recorder and played
it
> > back at half the speed,  it would take twice the time to send the
message.
> > So we would be using half the bandwidth but twice the time.  So the
bands
> > would in effect be just as crowded.  You could get twice as many
stations
> on
> > a particular band but everybody would need to talk twice as long.  You
> would
> > not gain anything and you definitly could not talk in "real" time.
> >
> > Carl Moreschi N4PY
> > Franklinton, NC
> > ----- Original Message -----
> > From: "Mark Erbaugh" <mark at microenh.com>
> > To: <tentec at contesting.com>
> > Sent: Tuesday, April 22, 2003 8:45 PM
> > Subject: Re: [TenTec] Slightly OT: SSB vs AM
> >
> >
> > > How do the circuits they use on TV to keep the audio pitch the same
when
> > > they speed up the tape work? I know they do that so that can shorten
the
> > > program and squeeze in more commercials. I remember watching a show
once
> > and
> > > after a commercial break, they didn't reengage the circuit and
everybody
> > was
> > > Alvin the chipmunk.
> > >
> > > At any rate, suppose you played the audio twice as fast, but used a
> > similar
> > > circuit to restore the original pitch. Then you took that processed
> audio
> > > and played it at half speed, this time with no pitch correction.
> Wouldn't
> > > that compress each frequency to half it's original value?
> > >
> > >
> > > 73,
> > > Mark
> > >
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