Transcript Wb_Laser - EarthSignals.com

Having Fun With
Through-the-Air Optical Communications
Kerry Banke N6IZW
[email protected]
Updated 06/08/05
Basics of Common Amateur Equipment
Audio communicators
Wideband Laser Pointer link
Non- line-of-sight communication
Field Day Laser QSO
Modulated Light Sources
HeNe Lasers Chopped Using FAN for MCW
Can be 10% AM Modulated
Bragg Cell AM Modulator
Laser Diodes & LEDs Pulse On/Off
Linear AM
Red and I/R Wavelengths
Class 2A Visible Lasers (400 to 700 nm)
Lasers emitting visible light not intended for viewing, and under
normal operating conditions would not produce a
injury to the eye if viewed directly for less than 1000 seconds.(i.e.
bar code scanners)
Class 3a
Lasers that normally would not cause injury to the eye if viewed
momentarily but would present a hazard if
viewed using collecting optics (fibre optics loupe or telescope).
Transmit Beamwidth
Laser - Typically 1-2 milliRadian (.057-.114 deg)
Spot Size > 100 Feet at 13 Miles
LED (with optics) - 1.4 degrees
Spot Size >1000 feet at 13 Miles
Photo Detectors
Photo Transistors Sensitive but slow & Noisey
PIN Diodes - Fast But Lower Output
Low Noise
LEDs - High efficiency LEDS look similar
to Pin Diode in Sensitivity
Relative Speed & Noise Unknown
Microphone
Audio
Amplifier
Fresnel Lens
35 KHz
VCO
Power
FET
LED
Transmitted Red Light
Laser
Pointer
145 MHz
Oscillator
35 KHz
Amplifier
PIN Diode
Photo Detector
2M FM
Receiver
145.035
Mixer
Optical Communicator Block Diagram
Received Red Light
W9FQN
35 KHz audio optical communicator schematic
TV
Camera
CH3
RF Modulator
Laser
Pointer
Amp
0 dB
Video
RF
Mirror
MIC.
RF
Amp
Pin Photodiode
Television
on Ch 3
-45VDC
Bias
Reasonably flat frequency response to 500 MHz and
Useable to 1300 MHz
Basic TV Video/Audio modulated RF
Laser pointer link
- N6IZW - 05-16-05
Cloud Bounce
Dust/pollution/moisture
scatter
NLOS Communication Paths
Tx
Laptop
with PSK31
260 Hz
Audio
Laser
Driver
Interface
910 nm
Laser
Diode &
Lens
IR Tx Beam
4” optics
Both Tx & Rx
Rx
Laptop
with PSK31
260 Hz
Audio
Rx Lens
Pin diode
Preamp
Maximum distanced tested so far is 15 miles
NLOS communicator setup using PSK31
IR RX Beam
3 mile NLOS signal
Displayed using
Spectrum Lab
Free softeware
NLOS Reception equipment
Basic K3PGP type optical receiver used for NLOS
Experiments. So sensitive you can hear the light from
stars scintillating which sounds like wind rushing
over a microphone
Simple Photo darlington photo detector for use with
the soundcard in in a PC.
Laser
Rifle scope
Positioner
LED Tx
Rx
35 KHz audio communicator
Front View
Scope
Laser
Rx unit
LED Tx unit
LED Transmitter
Early LED Tx unit capable
Of 4 miles with 35 KHz
communicator
Pin photodiode with preamp
35 KHz audio
communicator
Fresnel Lens cut from plastic reading
Sheet lens
Micrometer Az/El adjustment
Moves scope & Laser only
Where to Find More Information
A Construction Article for the 35 KHz optical
communicator Published
in June-Aug Issues of 73 Magazine by
Chuck WB6IGP Who is a Member of
The San Diego Microwave Group and Writes
the “Above & Beyond” Column for 73 Mag.
Good Laser Web Site and Laser Email Reflector:
http://www.qsl.net/wb9ajz/laser/laser.htm
LED/Reflector Test Fixture
Round reflector with LED in center
which is modulated at 35 KHZ.
Used to align Tx & Rx optics
One end of 15 mile Field Day laser contact
Laser pointer seen from 15 miles away
Sun Relflected off mirror from Palomar Mt.