[Laser] Tutorial.

[n9jim]

Happy New Year All!

2 stations with <3mW and no lenses, a PIN diode RX can easily do >1 mile 
  on MCW (modulated CW).

2 stations with <5mW, 90mm lenses can easily do >20 miles on MCW.

As bandwidth increases, (MCW is <100Hz) the power required will 
increase.  I have not run anything >130KHz.  At 130KHZ, (using FM audio 
subcarrier) LED's (like TV remotes) work in daylight over 100ft with no 
lenses. My experiments with higher BW have been limited to "down the 
hall" which is about 60 ft round trip.

Jim
N9JIM/6




Zack Widup wrote:


> 
> P.S.  This whole thread started when the list was asked for advice about a
> 15-watt laser.  Being pragmatic, I'm curious why someone would need such
> power for a laser comm system.  I've had fairly reliable QSO's over 5 mile
> distances with 3 mW and a very crude system with a receiver which I'd
> liken to a "crystal set" for HF reception.  Nowhere near the quality of
> some equipment I've seen on peoples' websites.  I have a couple 10-15 mW
> HeNe lasers and a 100 mW IR laser diode I've yet to play around with.  I
> figure with a decent system, collimated beam and Fresnel lens or reflector
> receiver, I could be in the 25-50 mile category on a clear day.
> 
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