While this thread interests me, I feel it is wandering a bit OFF-TOPIC
for old computers. I have had some experience with optics and telescope-
making as well as analog and digital circuits.
From: Garry <[EMAIL PROTECTED]>
> Yes, line of sight. Hmmm . . .
> <dream mode>
> A real challenge would be inventing some way
> of "broadcasting" such a light-spectrum signal.
I would suggest "beamcasting" as more efficient and secure. Laser diodes
and sensors are now fairly cheap - even available in surplus 1X CD-ROMs.
Lasers are monochromatic, so you only need thin, simple lenses (or
mirrors). I would guess 3 or 4 inches (75 to 100 mm in diameter) would
do nicely. The idea is to spread the beam so that most of it passes
around raindrops, etc.
With luck, you may be able to find appropriate lenses in surplus stores at
a good price. Small lenses (like elements from a microscope, or eyepiece)
could be useful in spreading the beam to the width of the big lens as if it
came from the focal point of the big lens, so that the beam out is parallel.
They should be solidly mounted - with means to make fine adjustments. Given
a parallel beam, the width of the lens, in the visual part of the spectrum,
I would suggest using a beaded slide projection screen behind the receiver
to align them.
Long lens hoods would also be a good idea, to keep out rain, etc., but
removable for cleaning.
Note: It is not a good idea to look into the beam - especially after dark,
when your pupils are wide open.
> I suppose with a little thought (or a lot) one
> could devise a roughly circular array of emitters
> and receptors . . . although finding a way to
> multiplex that would require more engineering
> skill than I have . . . alternatively, each channel
> could simply be assigned its own frequency.
> </dream mode>
For multiple connections, unless you are broadcasting to the whole
neighborhood, you would need separate transmitter/receiver pairs.
Unless you modulate the diode output (complicated) or use multiple colors
and filters, you can't use different frequencies. One frequency of light =
one pure spectral color.
> But, for what this design was intended, it's
> brilliant: it takes the IrDA support circuitry
> that's already on most newer mother boards
> and routes it through a modified version of
> that kind of hardware, taking advantage of
> existing network drivers! Sweet.
~~ Garry
As for the electrical connection to your computer, the COM port or a network
card should do nicely, too.
----- Original Message -----
"Bob George" <[EMAIL PROTECTED]> wrote:
>>
>> Neat, but line-of-sight only. I suppose you could put up towers on the
>> rooftops...
Boyd Ramsay
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