[Laser] Getting Started

[James Whitfield]

Welcome Jim. And to your friend Brian.

Since you are getting started, I suggest that you build your receiver system
and get it working.  There are lots of existing light sources for you to
test and align it, such as street lights, florescent lights in office
buildings, strobe lights on towers, even AC powered incandecent bulbs will
have frequency components that are useful.

When I started I got the inspiration from a four and a half inch lens from a
brokent florescent lamp / magnifier, which I stuck onto the end of a powered
chocolate drink mix container with masking tape.  I then put together the
transmitter using a laser pointer by replacing the batteries with a fixture
made with masking tape and the barrel of a ball point pen to hold wires.
The circuit was a current limiter switched on and off by a 555 circuit I had
used on a club code practice oscillator project.  At that point I had the
optics of a receiver and simple, but effective MCW transmitter.  What I
didn't have was a receiver circuit.  The project lost a lot of momentum
while I tinkered with ways to bias a CdS photo resister so it would drive an
audio amplifier.  Crude, but it worked.  There are certainly much better
ways.

You might want to consider building a transmitter using LEDs before you step
up to working with lasers.  The availability of LED flashlights, some of
which seem to have reasonable optical mountings, should make practical
communications systems much easier than even a few years ago.

Have you considered what mode you would like to work?  You spoke of cloud
bounce, but are you thinking voice, MCW, PSK, or perhaps another digital
mode?  Just for fun you might try bouncing signals off a water tower,
building, or billboard.

If you have not found a source for fresnel lenses yet, you might check an
office supply store.  The clerk probably won't know what a fresnel lens is,
but they may stock "sheet magnifier".  ( I have some that are 8.25" X 11".
If you would like to have the brand name, UPC code, price, and the name of
the store chain where I bought them, please contact me off list.)

I hope that you have fun.  Please tell us how you are proceeding with the
project.  You might even consider demonstrating to your local clubs.

Best Wishes

James
 n5gui