From mountain top to mountain top if you had good
equipment but the aiming would be tricky. Every once
in a while I'll notice something mentioned in qst,
they're always trying to set new distance records.
You'd most likely use a.m.

--- Brent Harding <[log in to unmask]> wrote:
> Why would one want to modulate voice over light? How
> far away could such a
> signal be transmitted compared to infrared TV
> remotes?
>
> ----- Original Message -----
> From: "Martin McCormick" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Monday, April 05, 2004 2:14 PM
> Subject: Re: voice modulated light?
>
>
> >         That is somewhat of a broad question.
> Most light sources
> > except for incandescent bulbs can be modulated.
> Even incandescent
> > bulbs can be modulated, but they can't change
> brightness fast enough
> > to produce much audio.
> >
> >         Most of the schemes I know anything about
> for sending audio
> > over light involve using a fluorescent tube or
> even a LED since those
> > light sources are much faster at responding to
> changes in electric
> > current than are incandescent lamps.
> >
> >         The LED or fluorescent lamp is run at some
> frequency which is
> > way too high to hear.  That carrier is then
> frequency-modulated.  A
> > receiver need only have a photo detector capable
> of decoding the
> > carrier.  The rest of the receiver could be any FM
> radio once the
> > photo cell receives the carrier.
> >
> >         It is even possible to modulate an
> infrared LED with
> > a fast-enough stream of digital data to cary audio
> and even voice.
> > That is how the photo detector works in your CD
> player to begin the
> > process of turning a flashing stream of light in
> to music.
> >
> > Martin McCormick
> >
> > Jim Stevenson writes:
> > >From light bulbs to lasers to ir devices,
> > >what equipment can modulate them with voice?
> > >
> > >a.m or f.m?
> > >
> > >Thanks much again as always.
> > >
> > >73
> > >wb6 yoy
> > >
> > >(650) 604-5720
> > >
> >


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