[NLRS] Light wave communications

[Dr. Gerald N. Johnson]

Allowing LEDs by calling them monochromatic is kind of a cop out because 
the spectrum of the LED is a great deal wider than a laser, but a lot 
narrower than the spectrum from a hot tungsten filament. Its probably 
possible to achieve as narrow a spectrum from an incandescent source and 
a filter as from a LED. On the other hand the LED power spectrum is more 
likely to fill the receiver filter improving the signal to noise ratio 
as received. And the energy efficiency of the LED is better than a hot 
tungsten filament unless IR and warmth is a desirable side product. In 
times past, a LED didn't meet ARRL criteria for "monoghromatic" or 
"coherent."

73, Jerry, K0CQ

On 3/16/2013 11:57 AM, w0zq at aol.com wrote:
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> On this subject, but relating to contesting with light, there is a rule regarding what type of lasers can be used.   In the ARRL general rules for contests above 50 MHz, rule 1.12 says "Above 300 GHz, contacts are permitted for contest credit only between licensed amateurs using mono-chromatic signal sources (for example, laser and LED) and employing at least one stage of electronic detection on receive.  Laser usage is restricted to ANSI Z136 Class I, II, IIa, and IIIa (i.e.; output power is less than 5 mW)."
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> Of course lots of fun can be had outside of contesting too.
>
> 73, Jon
> W0ZQ
>
>
> -----Original Message-----
> From: David Palm<thepalmhq at gmail.com>
> To: nlrs<nlrs at mailman.qth.net>
> Sent: Sat, Mar 16, 2013 11:15 am
> Subject: Re: [NLRS] Light wave communications
>
> Hey Doug and the group,That was a great posting, Doug.  Lots of interesting information there.  Ihave also done a bunch of reading in the last couple of years on lightcommunications.  I've also looked into the use of laser diodes forillumination during nighttime coyote hunting, using a digital cameraconnected to a rifle scope to see the beam, since the camera can "see"infrared (and can be used for aiming a comm link too.)One thing that has spooked me a little is the possibility to literally "putyour eye out, kid".  These more powerful lasers can do serious eye damageand it would be easy to sweep your eye or even accidentally catch apowerful reflection, especially from a laser that's not in the visiblespectrum.  So just a word of caution on that.  But I do hope that hams cando more and more with this technology, because it's now so readilyavailable and makes homebrewing equipment very simple and inexpensive.73,David  W9HQ
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