[NLRS] Use of Light in VHF Contests

[Zack Widup]

I don't recall exactly why the rule was spelled out the way it was but I
know for one thing it was an attempt to discourage people from flashing
Morse code with flashlights or high-power incandescent beams and calling
that "QSO's." I don't recall how prevalent LED's were at the time. I know
there were laser diodes available in the early 70's but they were very
expensive. Other laser sources have been around for a much longer time. Even
I had a small HeNe laser in 1969. I recall it was only $50 brand new.

I'm not sure what exactly SHOULD be permissible for light sources in
contests. Obviously we still don't want people using flashlights, so the
part of the rule about at least one stage of electronic detection should
stand. LED's would be the optimum light source IMO, and there would be more
optimum frequencies for use through the atmosphere than the red part of the
spectrum.

But I'm sure someone could come up with a method of modulationg, say, a
carbon arc. This would be an intense light source but would be broadbanded.
If we eliminate coherence as a requirement, how could a rule be worded to
limit the bandwidth of the emissions? Or would it have to spell out lasers
and LED's ONLY as a light source?

These are tough questions I haven't figured out yet.

73, Zack W9SZ

On Tue, Dec 1, 2009 at 8:58 AM, David Palm <thepalmhq at gmail.com> wrote:

>
>
> Those were some very interesting comments, Jon.  One question I have: what
> is the rationale for specifying a "coherent" light source at all?  We
> certainly don't specify that our radio sources must be coherent--far from
> it.  So why should there be some difference as we get to this high end of
> the spectrum?  Does anybody know what lies behind including this specific
> term and any good reason why it should be retained?
>
> 73,.
>
> David  W9HQ
>
>
>
> On Tue, Dec 1, 2009 at 8:52 AM, <jcplatt1 at mmm.com> wrote:
>
> >
> >
> > 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
> >
> > ______________________________________________________________
> > NLRS mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/nlrs
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:NLRS at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
> ______________________________________________________________
> NLRS mailing list
> Home: http://mailman.qth.net/mailman/listinfo/nlrs
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:NLRS at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>