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Having Fun With Through-the-Air Optical Communications Kerry Banke N6IZW kbanke@qualcomm

Having Fun With Through-the-Air Optical Communications Kerry Banke N6IZW kbanke@qualcomm.com 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 -

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Having Fun With Through-the-Air Optical Communications Kerry Banke N6IZW kbanke@qualcomm

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  1. Having Fun With Through-the-Air Optical Communications Kerry Banke N6IZW kbanke@qualcomm.com Updated 06/08/05

  2. Basics of Common Amateur Equipment Audio communicators Wideband Laser Pointer link Non- line-of-sight communication Field Day Laser QSO

  3. 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

  4. 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).

  5. 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

  6. 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

  7. W9FQN

  8. 35 KHz audio optical communicator schematic

  9. Reasonably flat frequency response to 500 MHz and Useable to 1300 MHz

  10. Cloud Bounce Dust/pollution/moisture scatter NLOS Communication Paths

  11. 4” optics Both Tx & Rx Maximum distanced tested so far is 15 miles

  12. 3 mile NLOS signal Displayed using Spectrum Lab Free softeware

  13. NLOS Reception equipment

  14. 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

  15. Simple Photo darlington photo detector for use with the soundcard in in a PC.

  16. Laser

  17. Rifle scope Positioner LED Tx Rx

  18. 35 KHz audio communicator Front View Scope Laser Rx unit LED Tx unit

  19. LED Transmitter Early LED Tx unit capable Of 4 miles with 35 KHz communicator

  20. Pin photodiode with preamp 35 KHz audio communicator

  21. Fresnel Lens cut from plastic reading Sheet lens

  22. Micrometer Az/El adjustment Moves scope & Laser only

  23. 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

  24. LED/Reflector Test Fixture Round reflector with LED in center which is modulated at 35 KHZ. Used to align Tx & Rx optics

  25. One end of 15 mile Field Day laser contact

  26. Laser pointer seen from 15 miles away

  27. Sun Relflected off mirror from Palomar Mt.

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