[Laser] Re: Laser Digest, Vol 11, Issue 5

[Karel Kulhavy]

> [1] The light emitting effect from diodes was discovered in 1906, by some of
> the early experimenters of crystal detectors.  It was noted that when a 
> current flowed through carborundum (Silicon Carbide), a faint bluish-yellow

Will it work if I try it with a current source and silicon carbide
sandpaper? Will the grains glow blue? :)

> One possible reason for the effect may have been to rule out things such
> as large incandescent light bulbs, which would seem to give an unfair
> advantage to people using them.  Additionally, there were things such as

I think they give fair advantage.

You could use a welding apparatus for an arc and a large fresnel lens
and some kind of optomechanical modulator and I think your balls would
pop out, not from the light, but from the achievable distance ;-)

> solar based signalling systems dating many decades (centuries?) into the
> past.  Such systems, while being interesting, have little relation to "radio".

And they worked exceptionally well. They were being in routine use for
ranges like 20kms by army.

I just don't see why the fact that something has been usefully used
before disqualifies it in eye of ARRL for contensts.

> I briefly played with an optical system back in the 1970s using a fluorescent 
> tube (although I never made any contacts).  The fluorescent tube was a
> good souce back then for producing a lot of light (40 Watts or more)
> with a somewhat reasonable frequency response (100 Hz or more, primarily
> limited by the response of the existing phosphors that were commercially
> available, but that could probably be improved with higher speed 

I have read somewhere that the red phosphor is very fast. How far up do
you think it would be possible to go with a fluorescent?

You could just take a pack of florescents, light them up with some
not-so-strange circuit and impose FM modulated signal in hundreds of
kilohertz. You would get a radio, LEGALLY!, covering the whole
neighbouring area!

The users would just use something like Ronja RX with a positioner. If
they wanted to change station, instead of MHz there would be GPS
coordinates.  And it would be like changing satellites with a dish
system.

You could also modulate it digitally with manchester or whatever and
get a whole packet of DRM (digital radio mondiale).

"Yes, we are doing amateur radio. Radio mondiale. Digital radio
mondiale. And we do it on optics because we don't want to pay fees for
HAM registration. Tune in, here is our playlist ;-) "

Cl<