[Laser] mechanical rotating shutter

[TWOSIG at aol.com]

Art, KY1K, included some information about "Radio Mobile software" as a  
predictor of radio paths.  I am not familiar what that software and will  try to 
research it a little.  What radio software I have had contact with  compensates 
for the effect that has radio waves seeing over the optical  horizon.  
Generally the software calculates a "line of sight path"   (for radio) using a 
larger radius for the Earth.  I think the values was  125 % of the real value.  For 
software that does that, and as I said, I do  not know if the software 
suggested by Art does or not, then its value for  predicting LOS paths is limited.
 
I have used Delorme Topo 4.0, which has feature that will make a side plot  
of the elevation of a route.  By defining a route as a direct line from one  
observation point to the next, it will give you a elevation profile of the  
path.  It has no correction for the curvature of the Earth.  However,  if you move 
the cursor along the plot, it will display the ground path distance  from the 
origin of the profile and the elevation at the cursor location.  I  wrote an 
Excel spreadsheet to create a graph of a table that I would transcribe  from 
the elevation profile.  Once I had enough points that my graph looked  like the 
elevation profile, I found it simple to calculate the true 3D profile  of sea 
level path from the origin's latitude and longitude that of the  destination. 
 Then it was a simple matter to add the sea level hump (a  parabola, or at 
least real close to one for paths under 500 miles) to the  elevation profile.  
Then a simple straight line on the corrected graph  showed the interference 
points.  The big drawback was time to transcribe  the points on the profile.  I 
tried to contact  the software company  to find out if there was any way to 
access the table of values that was used for  creating the profile.  No progress 
there.
 
 
An additional comment about On Target:  They have a one day event that  does 
not involve camping.  Hiking up to a mountain peak in the morning with  the 
equipment, operating for about five hours, then hike down before dark.   It 
would be a big jump in their activity to operate at night.  I am sure  that there 
would be interest in laser communications, but if it requires night  
operations, it may need to be a separate event rather than an extension of their  
current program.
 
 
James
N5GUI