having fun with through-the-air optical communications kerry banke n6izw kbanke@qualcomm
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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 - - PowerPoint PPT PresentationTRANSCRIPT
Having Fun With Through-the-Air Optical Communications
Kerry Banke [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 MCWCan be 10% AM ModulatedBragg Cell AM Modulator
Laser Diodes & LEDs -Pulse On/Off Linear AMRed 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 degreesSpot 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 SensitivityRelative Speed & Noise Unknown
~~
800 HzOscillator
LEDor Laser
555Timer
Photo Detector
AudioAmp
Speaker
TelegraphKey
Photo Detector
AudioAmp
Speaker
LEDor Laser
AudioAmp
Microphone
Bias
~~
Basic 800 Hz MCW Link
Basic AM Voice Link
35 KHzVCO
PowerFET LED
Fresnel LensMicrophone
Audio Amplifier
Laser Pointer
PIN DiodePhoto Detector
35 KHz Amplifier
Mixer
145 MHzOscillator
Transmitted Red Light
Received Red Light
2M FMReceiver
145.035
Optical Communicator Block Diagram
W9FQN
35 KHz audio optical communicator schematic
TVCamera
CH3 RF Modulator
Video RF
LaserPointerAmp
0 dB
Mirror
Pin Photodiode
-45VDCBias
RF Amp
Television on Ch 3
MIC.
Basic TV Video/Audio modulated RF Laser pointer link - N6IZW - 05-16-05
Reasonably flat frequency response to 500 MHz and Useable to 1300 MHz
NLOS Communication Paths
Cloud Bounce
Dust/pollution/moisturescatter
TxLaptopwith PSK31
LaserDriverInterface
260 HzAudio 910 nm
LaserDiode & Lens
IR Tx Beam
IR RX BeamRx LensPin diodePreamp
RxLaptopwith PSK31
260 HzAudio
NLOS communicator setup using PSK31
4” opticsBoth Tx & Rx
Maximum distanced tested so far is 15 miles
3 mile NLOS signalDisplayed using Spectrum LabFree softeware
NLOS Reception equipment
Basic K3PGP type optical receiver used for NLOSExperiments. 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
LED Tx
Rx
Rifle scope
Positioner
Front View
LED Tx unit
Laser
Rx unit
Scope
35 KHz audio communicator
LED Transmitter Early LED Tx unit capableOf 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 adjustmentMoves scope & Laser only
Where to Find More Information
A Construction Article for the 35 KHz optical communicator Publishedin June-Aug Issues of 73 Magazine byChuck WB6IGP Who is a Member of The San Diego Microwave Group and Writesthe “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 centerwhich 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.
