[Laser] Chris VK3AML and Mike VK7MJ RE: Coherent Source - back on my soap box
Chris L
vocalion1928 at hotmail.com
Mon Nov 9 08:18:12 EST 2009
Hello again Jim - it has been four years since our last.
I would point out that:
(1) Chris VK3AML first made the points about the advantages of
non-coherent light for atmospheric optical comms,
and demonstrated those advantages by setting a
world DX record (168 km) on 19 Feb 2005, which Clint has now
extended by a refinement of the Fresnel/Luxeon technic
that we pioneered in Australia. We recall that several people
on the "laser reflector" (and that blog name SHOULD be
changed in view of our findings as regards the undesirability
of coherent atmospheric light ops) simply shouted
Chris VK3AML down into a withdrawal from the blog,
and we withdrew from further blog involvement as a result.
Instead, we joined with Clint and jointly presented a scientific paper
on our findings at the SPIE's Photonics West confrence in San Jose
last year - refer:
http://www.modulatedlight.org/Dollars_vesus_Decibels_colour.pdf
How many more years must we present one scientific
paper after another, to finally have our fellow
hams accept the basic truth that laser communication
at visual frequencies via the atmosphere is a flawed
concept?
(2) Coherent light sources simply CAN NOT provide
atmospheric optical comms at VISUAL optical frequencies.
The coherent beam is gone virtually as soon as it leaves the source.
The beam can not stay coherent in the presence of
atmospheric turbulence: coherent atmospheric optical
communication AT VISUAL WAVELENGTHS is no more than
a myth made in ignorance of the basic physics involved.
The usage of laser sources is contra-indicated by simple
atmospheric physics at visual optical frequencies, and
spatial coherence CAN NOT be maintained through any
significant atmospheric path length. Spatial coherence
may be a partial prospect at middle or far infra-red
wavelengths, but coherence is actually a great disadvantage
in terms of extra noise sources via cancellation & addition.
(3) The "KA7OEI" site is in fact jointly run by Mike VK7MJ,
Clint KA7OEI and Chris VK3AML in terms of textual input.
(4) The ARRL "coherence" rules, in the context of atmospheric physics,
are a technological and academic nonsense. Yes, they should
be changed. No, this does not suggest a return to "flashlights".
And if the rules of the ARRL are not changed, we in Australia
will ignore them. If the ARRL maintains an ignorant stance,
then the organisation will be publicly held to ridicule.
(5) LEDs are NOT coherent sources. They do not provide any
spatial coherence of emitted wave fronts. Monochromaticity
is an unrelated concept. Diode lasers are only weakly
coherent in terms of spatial wavefront alignment. Gas lasers
are somewhat more coherent. You cannot "draw a line" for the
rule because no absolute limit of coherence is specified - another
ARRL nonsense. And there can be no coherent received beam
in any case!
(6) Amateur radio is supposed to include - presumably - a fun
approach towards IMPROVING communication technology.
What greater proof of that improvement can Clint, Mike and
Chris provide, other than to simply smash all DX records set
so far, year after year? The proof is in our results,and the theory is provided
by Korotkova et al on scientific papers linked to our site. If
certain types of non-coherent light communication, in
conjuction of beam expansion by Fresnels to provide
turbulence cell aperture averaging, are a better means of
communication than the use of laser, what idiocy could
possibly deny that improvement?
I say change the ARRL rule, or leave the organisation behind.
(7) In terms of eye safety, the Luxeon/Fresnel technic that
we've pioneered is inherently far safer than using unexpanded
laser beams, where the whole power of the laser beam is
capable of passing through the diameter of the pupil of the
human eye. By expanding the transmitted beam to the area
of a Fresnel collimator, for example using a Fresnel of aperture
50cm by 50cm, the flux is spread over a beam cross-section of
at least 2500 square centimetres. If a dilated human eye
pupil can intercept a maximum of 1 sq cm beam area, then in
our case the eye can only ontercept 1/2500th = 0.0004 of the
total beam flux.
(8) For pity's sake, can't "laser reflector" be dropped as a blog
title while we're at it? The title itself draws all sorts of fundamental
assumptions about the desirability of a flawed technic.
Let it be "atmospheric optical comms reflector", and let's not
start with an incorrect assumption - that of "laser superiority" - one that all
too many of us have proven in theory and practice to be
a central falsehood.
Since being chased off the "reflector" by fatuous criticism
in 2005 we have made no further comment - let this be our
"one statement in every four years".
We've no wish to be aggravating or argumentative, Jim, but
resolution of this is overdue, and those of us who've done
the spadework deserve a little more credit.
Frankly, we think this "contesting" stuff begs ridicule on ham
radio as a whole.
Hoping for resolution,
Chris Long, VK3AML.
Dr M J Groth, VK7MJ.
===========================================
> From: n5gui at cox.net
> To: laser at mailman.qth.net
> Date: Sun, 8 Nov 2009 22:29:20 -0600
> Subject: Re: [Laser] Coherent Source - back on my soap box
>
> I appreciate the comments made on this topic.
>
> I was particularly touched by WA2GFP. Anyone that can refer to me as one of
> the "youngsters" deserves special recognition. That he was able to clarify
> the situation and events leading up to the writing of rule 1.12 makes his
> comments significant.
>
> Tim Toast showed considerable gumption to suggest an interpretation of what
> the rule means, though I have a hard time following a bandwidth
> interpretation as it does not address the fundamental issue of what is and
> is not a coherent source. I suppose that an "official" interpretation would
> serve better than the current situation. Better still would be a codicil
> written and posted so that the interpretation is clear. The practical
> advantage of a codicil is that when the interpretation changes again, only
> it needs to be rewritten and posted. I much prefer an honest discussion
> about a re-write of the actual rule.
>
> In the comments of KA7OEI are both technological advances and what I will
> call socal issues for lack of a better term. The technology has changed
> since rule 1.12 was included. The most relevant to this discussion is ready
> availability of powerful LEDs coupled with the understanding that coherence
> serves to the detriment of terrestrial communication. The work of KA7OEI
> is well documented on the referenced websites. As this is the case, there
> is not much value in repeating it here.
>
> Which brings me to "social issues". In particular, there is information
> that I did not previously know which disturbs me. To explain, I need to set
> a little background.
>
> As have others, W9SZ pointed out that contest rules only apply to contests.
> Respectfully, I disagree. The impact of contest rules reaches out to the
> larger community. Suppose for the moment that there is an organization that
> represents a large segment of the amateur radio hobby, and as such sponsors
> activities and contests. Further, it has enough "pull" that its general
> rules are the blueprint for many contests, including those that it does not
> specifically sponsor. Now suppose one of those general HF rules, formed
> many years ago, prohibits the use of DSBSC. There may have been valid
> reasons at the time to do that, perhaps the organization wanted to promote
> SSB as being more frequency efficient. To complicate matters, there were
> consessions for the AM old timers as a legacy mode, but DSBSC was tried and
> labeled as unfair since it used all the spectrum of AM but did not have the
> power "wasted" in the carrier. On the other hand it was technologically
> simple to produce, costing far less than an SSB system. The AM camp
> considers it a nusance since it is as hard to receive on their equipment as
> is SSB. The SSB camp are equally annoyed since it is cheap, uses the
> bandwidth of AM, and has more power available in each sideband than AM, if
> only 3 dB less than SSB for the same emitted power. The issue gets really
> angry during contests. The SSB camp dominates any contest that is willing
> to mix AM and SSB, so segregation occurs "naturally".
>
> Now, the "rule" only applies to contests. But suppose the amateur radio
> community is in transition from a large fraction of the HAMs building CW and
> AM transmitters to mostly purchaced transceivers. In all this, a
> manufacture of transceivers has to decide what features to include in the
> next model. AM might be included, but DSBSC probably not. SSB, a strong
> candidate. Is that because the contest rules said to the transceiver
> manufacturer cannot include DSBSC? Of course not. However, contest rules
> are written for a variety of reasons. Sometimes it is to promote a
> particular mode. In any case, their influence extends out into the
> community. From there into the equipment that becomes available, either
> commercially or the building projects in the popular literature.
>
> Do I think ARRL VHF rule 1.12 had stifled the development of a commercially
> available equipment for light communication? No. But there was an article
> I came across about modulated light using a gas discharge source followed by
> filters to get a "monochromatic" source. Since it was not coherent, it
> could not have been used in a contest. It was a long way from flashligh and
> eyeball, but I doubt it would have met the standards of the day.
>
> That brings me to the "pieces of paper" that KA7OEI received from the ARRL
> and the very disturbing social issues. I respect KA7OEI and believe he
> fully deserves recognition for his work. However, it is my opinion that
> Rule 1.12 specifically excludes the equipment he uses. What I find most
> disturbing is that the officials at ARRL seem to not have the necessary
> ethical qualifications to read or follow their own rules.
>
> I find no more compelling argument that KA7OEI equipment violates the
> coherent source section of rule 1.12 than his own words on his website. He
> is very clear that it uses non-coherent light and that non-coherent light
> has communicaton advantages over coherent ( laser ) light.
>
> Rule 1.12 clearly states the requirement for the use of coherent radiation.
> It is not ambiguous. It allow no exceptions. This I understand. I can
> read it for myself.
>
> What I don't understand is how the ARRL could issue a certificate in the 10
> gig and up contest to someone using the equipment. It could be that the
> contest folks have never looked at, or cannot understand, the material in
> the KA7OEI website. That would place them in the "light" of not being able
> to determine a violation of rule 1.12.
>
> KA7OEI would seem to disagree with such an assessment. He asserts that the
> ARRL does know the relavent facts and has chosen to "interpret" the rule as
> no longer requiring coherent radiation.
>
> I confess, it certainly appears that he has proof to support his assertion.
> The first consequence of that is that we are back in the flashlight days, if
> not the reception by eyeball. All that has been done is to ignore the
> coherent provisions. They did not modify or expand the rule. They simply
> ignore whatever portion of they find expedient at any given time.
>
> That makes the ARRL contest officials as morally and ethically bankrupt as
> the worst of the politicians I have ever heard of. Rules exist. For
> whatever reasons they happen to have been created, once set in place, they
> should be followed. If the rule has a problem, then fix it. Recend it.
> Modify it. Correct it. If absolutely necessary, empower someone to provide
> exceptions.
>
> Some of you may think that it is an acceptable practice. If we were talking
> about our governmental legal system, it would be called selective
> enforcement. It certainly exists. There is even a governance philosophy of
> making all things illegal, then by selective enforcement, only the
> undesireables are prosecuted. It works very well for the "IN". Of course,
> who is "IN" can change...
>
> I do not know what the ARRL may use as a canon of ethics. For me, I would
> much rather think that they are uniformed or monumentally stupid. That
> would be better than deliberate abandonment of ethical conduct.
>
>
> James
> n5gui
>
>
>
>
>
>
>
> ______________________________________________________________
> Laser mailing list
> Home: http://mailman.qth.net/mailman/listinfo/laser
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Laser at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
_________________________________________________________________
Download new and classic emoticon packs at Emoticon World Brought to you exclusively by Windows Live
http://windowslive.ninemsn.com.au/emoticon.aspx?
More information about the Laser
mailing list