[Laser] 5 mW lasers & LEDs

[steve kavanagh]

I've been trying to work out a scheme for fast contest QSOs and have followed the route of using a wide transmit beamwidth which can be immediately seen even if only roughly pointed, so the aiming problem comes down to pointing the receiver at a visible light.  That's still not trivial, but the red dot rifle scope used in http://www.qsl.net/ve3sma/LEDTransceiver.pdf works pretty well.  But this rig, with 15 degree transmit beamwidth, is no good for real dx....I've done a bit over 4 km so far and there's margin for a few more km with a similar rig at the other end.  More work is needed on operating procedures before it becomes easy.  Haven't had much luck in persuading the locals to build their own gear, though!
 
As far as small LEDs go, I have been happy with the Cree C503B series devices (the 15 degree red ones).
 
A few more links to get you up to date:
 
http://reast.asn.au/optical.php
http://groups.yahoo.com/neo/groups/UKNanowaves/info
http://www.earf.co.uk/nanotrx.htm
 
73,
Steve VE3SMA



On Friday, November 1, 2013 12:23:24 PM, Steve J. Noll <sjnoll at ix.netcom.com> wrote:
  
Hi Steve,

You're absolutely right! Guess I read that too fast.
Thanks for the link. Looks like a lot of good work has been done since I got out of it.
Still figuring out what I want to do. Would at least like to get some locals interested in using this during contests.

73,
Steve WA6EJO



On 11/1/2013 5:32 AM, steve kavanagh wrote:
> Steve
>  
> The way I read the ARRL contest rules, the 5 mW limit only applies to lasers:
>  
> " Laser usage is restricted to ANSI Z136 Class I, II, IIa, and IIIa (i.e.; output
> power is less than 5 mW)."
>  
> So if you go with LEDs, you are ok up to 1.5 kW, I think !  As you may be aware, most of the long distance stuff nowadays is being done with power LEDs with focusing lenses  - KA7OEI's website is an excellent example:
>  
> http://modulatedlight.org/optical_comms/optical_index.html
>  
> I recall reading some of your articles way back.....glad to see you are back at it again !
>  
> 73,
> Steve VE3SMA