[Laser] Field Day laser activity

[TWOSIG at aol.com]

"Any other FD  laser activities to report out there?

  - Kerry N6IZW -"

What I did was not much, but I took my Ramsey units to field day and 
demonstrated them, with my latest modifications, to some of the Hams and wives.  The 
units are mounted in 2 inch diameter plastic pipe.  The mod was to expand the 
beam by adding a 20mmX100mm lens.

Earlier this year I had used them at the Engineering Expo sponsored by the 
Society of Women in Engineering student chapter at Wichita State University.  
The Expo is targeted to middle school students.  My demonstration was on the 
stage in an auditorium where the kids sat at two tables and talked to each other 
over the light beam.  There was an obvious problem keeping the laser dot on 
the receiver, even when only 30 feet away.  I was also concerned about the small 
dot hitting one of the kids in the eye.  The power level should have been 
safe, but...  Anyway I decided to expand the beam, and I got adequate indoor 
performance with a single lens.  Before I decided on that lens, I tried a much 
shorter focal length that expanded the beam to about three feet across the 
indirectly lighted stage.  The "dot" was still clearly visible on the wall behind 
the receiver, but the stock Ramsey circuit was detecting the audio only 
intermittantly.  I now have a range of more than 100 feet indoors, probably more at 
night, which will be fine for demonstrations.  If I remove the lens, the range 
goes back to 1/4 mile.

I will try to post some pictures.  I hope build a better demonstrator for 
next year.

James
N5GUI