[Laser] Lasers vs LEDs & ARRL contests
James Whitfield
n5gui at cox.net
Tue Jul 22 11:59:50 EDT 2008
Jon and the group:
I am late making comments to your questions because I was away from home on
business. When I returned, there were many ( many many ) comments, each of
which I wanted to consider before forming my response. It has also been
difficult to read the comments at a rate that was faster than they seem to
be continuing to come in.
I could start by trying to recount the events of a few years ago when I
tried to ask of the ARRL what technical standards are applied to "coherent
radiation" so that it would be possible to determine what was allowed and
what was permitted. The short version is that I contacted my local rep,
then after waiting a month or two for response, I contacted HQ ( which
seemed to be more concerned that I not be annoyed with the local rep than
with a straight answer ) which eventually lead to the claim that no one was
still around from the days when the rule was created ( or that much cared
since there was no "real radio" activity there ).
And I don't want you to think that I am just bashing ARRL as being
non-responsive. It just depends on whether you have an inquiry that fits
into the current agenda. This I know after I asked the simple question how
a test session coordinated by cell phone, as described in a news article,
met the "public announcement" rule for testing sessions. The test session
was for a space tourist. Boy! Did I ever get fast response on that. Seems
the article was a little shy on the details and the integrity of the testing
team should not be challenged. I still don't think I got a straight answer,
but I didn't see any point in pushing the issue as it would be bad in so
many ways for the entire amateur radio community. It could be that I made a
lasting impression, if however small. A few months later the rules were
changed so that test sessions could be held without public notice. Not a
good change, but in my opinion better than the old rule that had no
standards by which to measure compliance.
Now that you know a little about my perspective, here is my response to your
questions:
Question #1 ...does [ARRL General VHF Contest > rule 1.12] include or
exclude...
The rule of itself does not indicate how to distinguish what is and what is
not (other than the specific example of laser) coherent radiation. To my
knowledge the ARRL has not seen fit to clarify the rule with any technical
standards by which determine what is and what is not coherent. Nor has ARRL
perceived the necessity to empower any person or entity to judge the issue.
In that, I have to say that to me the rule includes lasers, and it implies
that non-lasers may be excluded without indicating any way to determine
which, if any, non-lasers are included and which are excluded.
As a practical matter, that leaves lasers, and only lasers, for the entire
"band" from 300GHz and up! Back in the time before current memory that may
have been the original intent. I can but presume that "ordinary" radio
methods were not expected to be able to reach those frequencies. So
considering the cost and types of lasers available, I take it as a simple,
and at the time effective, method to stifle, or at least not encourage,
communication investigations in the region by ARRL membership. I know that
I certainly was discouraged from working on anything that would operate in
that range in an ARRL VHF contest. It was so successful in fact that I have
never operated in any ARRL contest (unless you count Field Day as a contest,
which I don't).
Time passes and technology takes some interesting paths. Solid state lasers
become cheap enough for laser pointers to become a nusance in the classroom.
At the same time it becomes possible for "real" radio experimenters to
nibble up to the 300 GHz boundary, even up to 400. To make things worse,
atmospherics conspire so that LEDs have proven to be more effective, dare I
say safer and less expensive, for experimentation and communication. No big
deal for those of us that deliberately avoid ARRL VHF contests, but that
leaves some who might want to use non-laser on the 300GHz band. Note that I
did not say it is a problem only for LED users. Rule 1.12 doesn't provide
guidance on the "coherent-ness" of Gunn oscillators either. Until the rule
is fixed, the use of any non-laser is subject to challenge.
Question #2 ...what should the rule say ?
The first thing that I think needs to be done is to break up the "band".
There are important differences between 300GHz and 300 THz. The contest
rules should not ignore the difference. To start it is a 1000 time
difference in wavelength. Common optics, say 2 inches in diameter, are
equivalent to structures more than 50 meters for the low end of this "band".
There is also a natural "window" of transparency in the atmosphere for
"light" that is not true for much of the spectrum from 300 to 300,000 GHz.
Separate "light" from the other spectrum, then give each rules appropriate.
You could then fall back on the "laser only" mentality, but that would be
wrong. Open up the options so that the best technology can be pursued. Why
rule out incandescent bulbs before you give them a chance to complete with
lasers and LEDs. Most of the light receivers cannot distinguish between the
light sources. And it is not like any of them are going to start a rash of
RFI complaints. Lasers on the other hand, have safety concerns. So much so
that on my demonstrations I have nothing more than LEDs and laser pointers -
and the pointers have restricted use. If the rules encourage the use of
lasers, it increases the likelyhood that an experiementer will be branded as
a terrorist trying to down an airliner, or that a real threat will result in
experiementation being banned.
As far as I am concerned, if cave man waving a burning branch will out
perform a 21st century gadget, then he deserves the credit.
Which brings me to another topic: modulation methods. The classic
modulation of a laser was to stick a fan in the beam. I think that is
marvelous, but if there are going to be rules about what light sources can
be used, then there should be rules about modulation methods. I happen to
like pulse modulation, and light is an opportunity to use pulse without
causing interference. Encourage ingenuity. Let the hairball ideas get
tested. The bad ones will go away. Somebody might actually learn something
about why the good ones work.
One last comment about two kids with flashlights: It has been said that
such activity should not be allowed. Why not? If there were fifty new HAMs
coming out of test sessions each years, each telling the story that they got
interesting in communications and eventually radio, simply because a kid
there was this buddy across the street, and they decided to send messages
from their rooms at night. If that were to happen, shouldn't the ARRL try
to encourage kids with flashlights?
Shouldn't we all be trying to encourage kids to learn and grow?
Best wishes to all of you.
James
n5gui
----- Original Message -----
From: <W0ZQ at aol.com>
To: <laser at mailman.qth.net>
Sent: Friday, July 18, 2008 6:59 PM
Subject: [Laser] Lasers vs LEDs & ARRL contests
> Hello to all Laser/light enthusiast.
>
> As some of you may know, I am the ARRL's Dakota Division VHF/UHF Contest
> Committee (VUAC) representative. I am seeking your comments. One of the
items
> that has been under discussion by your VUAC is the ARRL General VHF
Contest
> rule 1.12 that states "1.12. Above 300 GHz, contacts are permitted for
contest
> credit only between licensed amateurs using coherent radiation on
> transmission (for example, laser) and employing at least one stage of
electronic
> detection on receive." This rule requires that the contact be made by
licensed
> amateurs and that the detection requires at least one stage of
electronics, that
> much seems fairly clear despite whether you agree or disagree with that
part
> of the rule. What is less clear is the requirement that the source use
> "coherent radiation" and "(for example, laser)". How coherent is coherent
?
>
> What I would like your comments on is this.
>
> 1. Given this rule as it is now, does it include or exclude the use of
> narrow band LEDs like the Luxor. I am no optics expert but it seems to
me that
> some of these newer power LEDs are very close in coherence to really poor
> lasers. Does the current rule have enough latitude to include narrow
band LED
> emitters ?
>
> 2. IF we could rewrite the rule, what should the rule say ? Do we want
to
> be much more specific and tighten the rule so it states "Laser only", or
do
> we want to open the rule up to specifically allow the use of newer
> technologies like power LEDs ? In either case what should the rule say
?
>
> It seems that on the one hand we don't want to allow a blinking white
light
> bulb, but if not that where is the line ?
>
> Again, your comments and perspective are most welcomed.
>
> 73, Jon
> W0ZQ
> Dakota VUAC Rep
>
>
>
>
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