[Laser] Atmospheric effects on optical DX, 50 miles +

[Karel Kulhavy]

> Also, a major problem with our optical DX has been the loss of lens 'gain' 
> through dewing late at night. It always pays to keep the lens or its cover 
> glass a fraction of a degree in temperature above ambient to avoid 
> condensation. As I use a series class-A modulator on my 1-watt Luxeons, we 
> dissipate quite a bit of power as heat from the series modulating 
> transistor (type MJ15003) and the related current limiting resistor. Surely 
> there must be some way of channeling this heat energy over the lens, 
> perhaps with a small muffin fan, to reduce the tendancy to the formation of 
> dew?
> 
> In a permanent link that I had in 1991 between VK3KAU and my home QTH, a 
> distance of 43 km, the dewing of my lenses proved to be a major nuiscance. 
> Perhaps even some form of hygroscopic oil film on the lens covers might 
> help, in at least softening the surface tension to provide a uniform fluid 
> coat? Any ideas here, people?

http://ronja.twibright.com/tubular_head_130/building.php
Look for "Installing heating on front cap with lens".

This system seems to work even in very harsh conditions:
http://images.twibright.com/tns/371.html
http://images.twibright.com/tns/3e9.html

I just wonder why people are inventing wheelcart here again when they
could just take what has been developed on Ronja and published for free
download.

They could also write building spec of their hardware suitably for Ronja
(that basically means building guide with mechanics drawing in a free
software tool) and both project could move on faster.

I would be personally interested in a large aperture Fresnel optical
head because it will have to be developed at some point in the future
very probably anyway.

Cl<