[NLRS] Use of Light in VHF Contests

[jcplatt1 at mmm.com]

I am taking my VUAC hat off for a discussion.   Before I dive in, I would
like to point out that I am not a physicist, nor do I play one on TV.

Coherence is not a yes/no parameter, it is not an attribute - there are
degrees of coherence.   There are also different kinds of coherence (or,
different ways to measure coherence).  To have a contest rule that simply
states "using coherent radiation" is not enough information.  Remember that
this rule was most likely created some time ago when Lasers were novel and
solid state light emitting devices was emerging technology.   The current
rule also does not state that one has to use a laser, it says ""using
coherent radiation, e.g. Laser", so it points to a laser as one example of
coherent radiation.

In my brief review of the current state of the art in light emitting
technology, in attempting to understand (?) and to identify degrees of
coherence with different types devices, it becomes a specmanship game -
that is, how do you define the measurement of coherence, and then give
that, where is the line as to "this is coherent, but this is not".

Compounding this discussion is the real world.  Darn that real world.
There are three points.   First point is that highly coherence light, like
a laser, is actually not a very good choice for long distance
communications through the atmosphere.  Some of the better laser DX records
actually place a diffuser in front of the laser to decrease its coherence.
Second, lasers carry safety issues.  As amateur radio op's, we know that
the way to make longer haul contacts is with more power - aiming a high
power laser carries all sorts of negative issues !    Third, low cost, high
efficient, high power, monochromatic LED light sources have become
available and are now one of the top technologies of choice for long haul
Light communications (and they are much safer to use than a laser).

So we circle back to the question.  What should rule 1.12 say ?   I have
heard general agreement that the part of the rule that requires at least
one stage of electronic detection is good - that should stay.   But what
about the part of the rule regarding the signal source - should the rule be
stiffened to say "only laser", should it be modified with a statement as to
how coherence is measured and what the spec is (ex: 1 cm, or 1 mm), should
the rule be tailored towards a requirement for being monochromatic and
allowing the use of both laser and LEDs ?   Or, should it say something
else.

One thing that I am sure of.  There is a lot of interesting work going on
with Light communications.  I think it would benefit both that work & its
technology, as well as contesting in general, if the rule would be
inclusive and would encourage continued development rather than be divisive
and stifling.

Please keep your thought and ideas coming.  What are your thoughts as to
what rule 1.12 should say ?

73, Jon
W0ZQ