IR Receiver/Demodulator

Um, after you "vaporize the water content", what are you proposing to reflect the light off of? ;-)

ISTR that in the mid 70's not long after cheap LEDs came available someone published a way to do moderate range communications on a light beam using amateur astronomical telescopes in the 3-10" range that would work in daylight. Transmitter at placed prime focus of a 3" refractor and the reciever at the prime focus of a 10" Newtonian reflector.

Closed tube scopes with diffraction limited optics and the larger aperture at the receiver. Next time I see one of the group I knew who did it I will ask if they can recall the details.

I think it was written up in Sky & Telescope. Electronics wasn't much more fancy than a faster version of Dalek voice AM modulation on a carrier wave (over) driving a LED and a matched detector at the focus of a large scope. Good enough to cover one hill to the next if a bit crackly in the days before mobile phones.

ISTR pretty basic amateur electronics and 70's era red LEDs - may even have been published in Everyday Practical Electronics in the UK. Filtering was nothing more fancy than Wratten 25 red.

Pretty sure it was in the visible red too as they needed to manually focus the beam onto the sensor to get enough signal.

Regards, Martin Brown

The moon? That's what ham radio folks do with EME transmission :-)

I guess that works for half the day. The 1/r^2 is rather extreme, though.

reflect

though.

Yep. Hams use very sensitive receivers and very high gain antennas 35 dB= and up.=20 Though getting much past 44 dBi is rather difficult IIRC.

reflect

up.

I guess for an optical link, Palomar would have a gain right up there. ;-)