[Laser] 100+ miles optical DX in Aust

[Chris L]

So much to comment on...

Firstly, to Karel. The raising of far-field transmitted flux by increasing 
transmitting aperture (beam spreading) is actually a safe way of operating.

Let us say that a dilated eye has a pupil area of 1 cm square...

Let us say that I'm radiating flux from a Luxeon through a fresnel 40 cm by 
40 cm = 1600 square cm...

They eye can therefore intercept only one sixteen hundredth of the radiated 
flux.

Let us say that we're transmitting a laser beam of 1 cm square cross 
section, perhaps less...

The eye can intercept ALL of the laser beam's flux.

Though the ARRL probably didn't intend their 'coherent light only' 
contesting rules to promote situations inimical to eye safety, it is an 
unfortunate concomitant. The thought of unspread laser beams being squirted 
indiscriminately horizontally through the atmosphere, frankly, gives me the 
heebie-jeebies - I value my eye safety!

In Australia's case, the Wireless Institute of Australia is the governing 
amateur body. A 30 km duplex Luxeon contact between Mike VK7MJ and Rex 
Moncur VK7MO covering (I think) two grid squares was claimed as a 474 THz 
contact by Rex in contest lists published by the WIA in ''Amateur Radio'' 
magazine several times over the last two and a half years (contact was in 
October 2002 on my gear and Mike's). The contest claim has remained 
unchallenged so I guess our WIA's requirements are a bit more flexible. Rex 
is a proment 'JT' sub-noise level digital mode afficionado and the former 
head of the Australian (Government) Antarctic Research Division, so his 
status in the art may have had something to do with the lack of a challenge 
to the contesting claim, though as I've said it's not a direct concern of 
mine...

I'm operating this email through a free mail service so I'd better cut this 
short and send the rest in a second posting.

All the best,

Chris Long (Melbourne, Australia)