[Laser] mechanical rotating shutter

[KY1K]

I have a couple of comments.................

1)	Yes, of course we should assist and encourage them. But, setting up a 
laser, aiming it, determining when LOS is established etc. is more than 
some of us can do. I'm not sure it's appropriate to have junior ops attempt 
this without alot of training. Perhaps a single laser link in the chain 
might work with a senior group of scouts who are a little older and up for 
the task. I don't think that a 2 tone electronic decoder will have any 
appeal to this group, they are traditionally reading and decoding Morse 
with their eyes and brains.

2)	Daylight lasercom is possible with photodiodes and proper electronics. 
The currently known and recognized method of doing this is to use a 
wideband system for narrowband reception...basically dumbing down the 
receiver sensitivity. K3PGP's daylight operation of his front end is an 
example of this.

There is a better way, although it is untested by us amateur lasercom fans. 
Burr-Brown has an ap note called something like 'cancelling ambient light 
something something'. It stops short of promising full daylight operation, 
but it does achieve operation with high ambient light WITHOUT a major loss 
in sensitivity. In the paper, formulas are given and the concept is 
explained, it also covers how to make the circuit cancel higher light 
levels by changing a resistor value with only slight sensitivity degradation.

3)	The North American distance record for laser (and probably the world 
record) currently stands at 172 miles. If the Scouts have done 176 miles, 
I'd sure be curious as to their paths. Are the longer paths documented or, 
who can we ask about this?

The longest LOS path I know of on the East Coast is the Mount Washington 
(NH) to Mount Marcey (NY) path. The Mount Washington Observatory claims 
this path is open about 10 days per year, most often in the dead of Winter 
after major snowstorms have passed.

I know atmospheric conditions are much better out west (dryer air), but 
knowing which sites have LONG LOS paths would seem to be the first step in 
setting a new distance record for laser.

Enjoy.

Art