[Laser] Chris VK3AML and Mike VK7MJ RE: Coherent Source - back on my soap box

[Chuck Hast]

On Mon, Nov 9, 2009 at 08:18, Chris L <vocalion1928 at hotmail.com> wrote:
>
> Hello again Jim - it has been four years since our last.
>
> I would point out that:
>

I rarely post but I lurk. I think that the common point here, coherence does
not work over FSO paths nearly as well as non-coherent energy through the
atmosphere has been well proved, now how to we go about getting the people
at ARRL to change the rule? Does each one of us need to send a letter,
holler at our local ARRL people, but it needs to be changed.

I too am in favor of a change of the list name to something more in common
with what we are all trying to do. I would say FSOcomms or something like
that indicating we are experimenting with Free Space Optical communications,
thereby dropping the facade of LASER, yes laser experimentation will continue
but FSO is all inclusive and I have several books on the book shelf about
FSO with FSO in the title. Seems that should indicate where things are.

With regards to lasers over long atmospheric paths, the only thing I have
seen really work is systems with several lasers placed around a common
receiver, with spacing from laser to laser on the order to 30cm or more, so
in effect what you are doing is sending out 4 laser beams allowing that there
are 4 of them transmitting you are getting the energy from at least 1 or more
of them arriving at the RX end. So in the end you achieve the same thing as
a 30cm lens with a large LED behind it,  Now, the real question from my
vantage point is how fast can I modulate each device? I am more interested
in speed vs distance, so I may have to take the 4 lasers in order to be able
to turn the on and off fast enough to get the data speed, but if a LED will work
I prefer to go there as I can make do with a single lens rather than 4 of them.

I believe that the modulation demodulation methods should be such that the
infamous flashlight "links" are ruled out. Anyone can do much better than that
and someone who tries to do such a thing should be filtered out.

Just my 0.02 (whatever coin of the realm you want here) worth.

-- 
Chuck Hast  -- KP4DJT --
To paraphrase my flight instructor;
"the only dumb question is the one you DID NOT ask resulting in my going
out and having to identify your bits and pieces in the midst of torn
and twisted metal."