[Laser] Optical comms at 100 + miles in Australia

[aflowers at frontiernet.net]

Chris,

I just wanted to address your comments about the "viability" of
laser-based communication in light of your experiments with LEDs.  I'm
sure you are aware of this, but I just wanted to bring it up for those
who may not be aware.

Many amateur radio operators use the laser because it falls under
"coherent transmission".   This has been one of the requirements of the
ARRL when it comes to counting them for contests and awards when
contacts are made above 300 GHz.  I think this rule went into effect
back in the early 80's, along with the requirement that one have at
least one stage of electronic detection--ie, no "eyeball" QSOs.  I
think their intention was to keep people form sending morse code with
car headlights between mountain tops, etc, as a way of manufacturing
"easy contacts".

Of course, we all know that there are varying degrees of "coherenence",
and a laser diode really isn't all that coherent when compared to a gas
laser, but it "coherent" in comparision to an LED. (Correct me if I'm
wrong on this.  I haven't been keeping up with LED technology, but I
thought that the spectral distribution of an LED is much larger).  Much
of the bias toward lasers (no pun indended) results more or less from
the ARRL's requirement of "coherence", whatever that means.

Personally, I wouldn't mind seeing LEDs allowed into the field for ARRL
sponsered events, especially when they stay within the spirit of
things.  All of the things you've talked about are very good reasons--
like you say, they are much less regulated, at least here in the states
and certainly less than here in the State of NY (the land of
laserphobia)!  Also, I think it allows for more people to play without
breaking the bank, and it certainly would encourage experimentation
from the electronic novices to experts.

I'll get off my soapbox and back to building things.  You've certainly
given me some ideas :-)

Andy
K0SM/2

Quoting Chris L <vocalion1928 at hotmail.com>:

> Mike and I are seriously beginning to wonder whether laser
> communication
> through the atmosphere is worthy of pursuit - it certainly would be
> if we
> lived in a vacuum.