[Laser] Coherent Source - back on my soap box

[James Whitfield]

Jon, W0ZQ, hit on a sore point in his message of October 29, 2009; subject: 
"Re: [Laser] SVHFS Conference Call For Papers"


>
> ...  For example, the contest rules say the use of a coherent source "eg 
> laser"...
>

I presume that he refers to ARRL general VHF contest rule 1.12.


Before I get onto my soap box about this issue, I need to make a blanket 
apology to the VHF community.  I went overboard in my comments on the 
previous subject.  I was at fault for being too quick to take offense and 
far too quick to presume that insult was intended.  More importantly, I was 
at fault for expressing my feelings about the matter in this forum.  I all 
respects, I am sorry.




Now for the matter of ARRL VHF contest rule number 1.12.  It reads:

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.

As I have stated before, I do not understand, within the context of this 
rule, what is meant by "coherent radiation".  The rest of the rule is in my 
opinion reasonable and fairly easy to use to decide what is, and what is 
not, allowed.  If both parties to the contact are not licensed amateurs, the 
contact is not allowed for contest credit.  This seems to acknowledge that 
the FCC does not require a license to operate within the "band", but does 
below.

The receiver used must have at least one electronic stage of detection. 
That would prohibit the use of your eyes to see blinking lights directly, 
but supposedly would allow using an LED in a wave guide which blinks on and 
off when the desired signal is present.

The transmitter has only the "coherent radiation" requirement.  It does not 
have requirements that it be modulated, or if it is, how.  There is an 
indirect suggestion that "laser" meets the requirement.  "Light 
Amplification by Stimulated Emission of Radiation" is a mouthful, but it 
does not contain, nor does it imply coherent.  The physics of what we know 
today as laser ( not the historical LASER, or originally patented Optical 
MASER ) may or may not have a fundamental relationship to coherent.

It does not matter.  From what I understand, the finest laser available 
today, much less when this rule was crafted, has a phase noise of more than 
250 MHz.  Does that make it "coherent"?  Is there any way for an "amateur" 
to know?

The point that I am trying to make ( and for those of you who have heard 
this before, I am sorry ) is that Rule 1.12 does not include any provisions 
for the determination of what is, and is not, "coherent radiation".  It is 
not possible for anyone to fairly apply the rule.  Even if one could measure 
"coherent", the rule does not suggest what is "coherent enough."

I have already told the story about trying to find out what the rule means. 
First I was ignored.  After a lot of persistence, I got a response:  pretty 
much nobody is still around that knows or even cares why the rule was 
written that way  --- we don't know or care what it means  --- you are a 
nusance, go away.

It was within the context of my experience trying to make some sense out of 
Rule 1.12, that I asked the question of K4IDC in the previous subject 
exchange about SVHFS policy toward "All above 275 GHz".  I was also very 
careful to not use the word "laser" in any of that communication.

His response, and perhaps I should have expected it, what there was no 
policy and that he was confident that a paper with "laser" in the subject 
would be welcomed.  There followed some other messages suggesting laser work 
would have transferable value.  One even included tropospheric ducting.  I 
don't mean to insult anyone, but how is possible to get optical 
communication ( my terminology, not specifically limited to laser ) and 
tropospheric ducting?  And that to me was just the most rediculous 
suggestion of blending.

I find it very hard to believe that the VHF community has any genuine 
welcome for optical communication when their "invitation" for laser would 
specifically exclude my interest, whether that was the intention or not.  It 
is not really the VHFers problem.  I am just a cantankerous old curmudgeon 
likely to call them a bunch of pig-headed fools for not discussing changes 
to a contest rule after four decades and nobody uses anyway.

James
 n5gui