[Laser] Lasers vs LEDs & ARRL contests

[GeoffK]

Geoff WA2GFP,  having done Lasercomms intermittently over the last 25+ 
years, responds:

> rule 1.12  that states "1.12. Above 300 GHz, contacts are permitted for 
> contest
> credit only:
a) >   between licensed amateurs using
GFP: these are rules for use during an Amateur Radio contest, so the 
contacts should be between licensed hams (you want to be in this contest, 
you gotta be part of the group, otherwise we have no way to keep Joe Ham's 
unlicensed family, friends, dog, etc. from showing up in the log)

b) > coherent radiation on transmission (for example,  laser)
GFP: how many of you were active in the later 70s/early '80s, when lasers 
were expensive and some folks used ligth bulbs in VHF contests? >> this led 
[ no pun!] to the requirement for 'coherence', which is one practical way to 
eliminate bulbs, and, IMHO, LEDs etc. which are not particularly spectrally 
clean. I'm not an Optical Physicist, but LEDs are not coherent (nor are some 
types of lasers below certain thresholds!) Certainly, any source of 
broad-sprctrum radiation, like white light, can not coherent with known 
technology. We no longer use broad-spectrum HF, like spark, etc. becasuw it 
is no State-of-the-Art (SOTA); we should not be going against the trend of 
technology by allowing  broad-spectrum emissions even above 300 GHz., where 
there are usable narrow-spectrum (one present definition of 'soherent') 
available.

and
c) >employing at least one stage of electronic detection on  receive."
GFP: eliminates the reception by eyeball of lightbulbs, etc.

>.  How coherent is coherent  ?
GFP: How spectrally-clean are modern HF, VHF,UHF transmitters? Why do we 
have transmitters with IMD of 30-35 dm, when commercial  transmitters with 
IMD3 at -50 db. or better are quite possible? In the latter situation, it is 
a question of how much the manufacturer wants to spend to meet a 
coherence-IMD spec (and most hams will not pay for -50db at 100 watts, or, 
as better put, using sufficient feedback to achieve -50db. would make the 
output power 20W and that is not going to sell! Since there are few 
commercial ham lasercomm products, and none that I know of that have serious 
performance, this is not manufacturer drive.
    So, what level of coherence does ARRL want to legislate into the contest 
rules?
    How do they want to have this level tested such that a contester can 
show compliance (and, since every contest brings at least one complaint abut 
splatter, IMD or other transmitted 'garbage', why do they NOT do that for 
any other band????)