[Laser] Ramsey Laser Comm Demo

[TWOSIG at aol.com]

For the second year I have used my Ramsey Laser Comm units for a  
demonstration to middle school kids and younger at a local Engineering  EXPO.  I seem to 
get a lot of interest from the parents as well as the  kids.
 
We set up along the side of a gymnasium floor.  One improvement that I  did 
this year was to put a 50 X 300 mm lens in front of each laser transmitter  to 
broaden the beam.  The jiggle of the tables did not cause loss of signal  like 
I had problems with the small dot of the laser pointer last year.  A  shorter 
focal length lens will expand the beam faster and be easier to aim, but  will 
weaken the signal too much to cross a gym floor with typical lighting.  The 
automatic gain system of the transmit units do cause the system to  seem very 
noisy, but a simple instruction to the kids to talk in a normal tone  and 
volume level about 8 to 20 inches from the microphone seemed to work out  OK.
 
I had a volunteer helper at each of the units to help the kids sit down  
behind the units and put headphones on.  I gave a short talk on pulse width  
modulation before directing the kids to the transmitter/receiver units.  If  they 
had a friend to talk to at the other end, it seemed to spark more  interest.
 
I used an external battery pack of 8 AA cells at each end to power  both the 
transmitter and receiver.  They were not fresh batteries and ran  the display 
for 4 hours on Saturday and for two hours on Tuesday night with no  sign of 
weakness.