[Laser] Laser Communications in the Sacramento, Ca. area.

[Kerry Banke]

Chuck, WB6IGP and I built up a couple of Laser pointer communicators a few
years back & Chuck published a three part article in 73 Magazine on those
units.  If someone is willing to put a number of pictures up on a web site
somewhere, I can provide the article as well as a number of photos of the
parts & pieces.   Basically the transmitter unit uses the VCO from a 4046
type PLL chip to provide a 35 KHz square wave which is modulated by audio
from an electret microphone and  op-amp for about 5 KHz deviation.  The VCO
drives a FET which supplies a 4 volt square wave to the laser pointer.  The
laser pointer may be used with or with out additional optics (beam
expander).   The receiver consists of a Fresnel reading lens cut &  mounted
inside a 4" PVC pipe housing with a PIN photo detector  at the focal point.
 The diode feeds a high gain  35 KHz preamp which was salvaged from an old
TV remote control and modified for a linear output.  The amplified receive
signal is then mixed with a 144 MHz oscillator to upconvert to 144.035 MHz
so we can use a basic 2 meter FM handytalki for the final receiver.  For
data and SSTV we connect the sound input & output from a laptop computer to
the receiver and mic audio on the optical communicator and use share ware
programs available off the web.   Probably the most critical item for
success is building a stable and accurate pointing setup.  We use 24X rifle
scopes (4X will do) and have added  fine micrometer adjustments which move
the laser & scope together.   It's very important to check out the
alignment of the laser, scope and receiver each time the unit is setup to
avoid wasted time and frustration when  making the contact.  With this type
of approach, the main time spent  in establishing contact is initially
locating each other visually on the hill tops using high power  spot
lights.  After that it's a piece of cake. 

 - Kerry N6IZW -
 

At 11:05 AM 5/13/02 -0400, you wrote:
>Please share with the group your interface and modulation
>techniques..........
>
>mcsdottom
>
>60 miles NE of Detroit..
>
>Macintosh for productivity;
>Linux for reliability;
>Palm OS for portability;
>Windows for solitaire.
>
>