[Laser] New Cloud bounce system being built Optical detectors

[Tim Toast]

Paul,
Yes it is always a compromise. I have that FOV formula here somewhere, i'll try to find it and post it later. 
or someone else might have one more handy. Mine isn't the real formula but a simplified geometric version.
You can take the focal length of the lens and detector size then come up with a FOV in degrees. Or a 
desired FOV and get the required detector size or lens focal length etc.
 
 
 

----- Original Message -----
> From: Paul A. Cianciolo <paulc at snet.net>
> To: 'Tim Toast' <toasty256 at yahoo.com>; 'Free Space LASER Communications' <laser at mailman.qth.net>
> Cc: 
> Sent: Sunday, July 17, 2011 1:23 PM
> Subject: RE: [Laser] New Cloud bounce system being built Optical detectors
> 
>T im,
> 
> This is my philosophy on illuminating clouds  for CB.
> Its always a compromise.
> 
> With LED's, let's say 40 degrees wide or so I would think that by the 
> time
> the beam hits the clouds the beam is very weak.
> But you have the advantage on the receiver side of not having to aim
> critically, and also covering such a large area of the clouds the
> probability of energy being directed toward the RX is averaged.
> The signal on my last attempt exhibited scintillation you mentioned.  The RX
> lens was 6" diameter with a focal length of  8" and a detector size 
> of  5mm
> sq.
> I know there is a way to figure FOV from those numbers but I cannot remember
> it now.
> 
> Aiming was not critical, although I was able to "find" the hiding 
> spots my
> friend was moving the beam to.
> Cloudbounce Hide and go Seek.
> 
> So these diodes I just received are +/-   5 degrees to the -3 db point much
> tighter and the field intensity at the clouds should many times what I had
> with the last array.
> 
> 
> With a laser the dot size on the clouds is so small that  say a 1 degree FOV
> RX would be seeing mostly noise.
> If one figures 1mR divergence at about .06 degrees, hell of a power density
> but scintillation, aiming problems etc.
> 
> No I never did find a ham or other enthusiast to experiment with around
> here.
> Wish I could.
> 
> Thanks Tim
> 
> 
> 
> Paul A. Cianciolo
> W1VLF
> http://www.rescueelectronics.com/
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