Re: [PSUBS-MAILIST] home-built strobe location beacon

[Jon Wallace <jonw@psubs.org>]

Hi Frank,

Cannibalizing a reflector of some kind would work as you suggest, but 
the problem is that it would also produce a narrow lobe of light 
direction rather than being omni-directional.  For surface location you 
want the strobe or other light to be as omni-directional as possible 
since you can't ever know how the sub will be configured (directionally) 
when it surfaces.  Most LED's suffer from the same problem in that they 
usually have a narrow angle of illumination.  This is perfect for 
directed light like a flashlight, but even hi-intensity LED's lose 
effectiveness at extreme angles of viewing.  You can see this especially 
well on emergency vehicles that use LED light bars or window flashers.  
If the emergency vehicle is directly behind you the effect is great and 
you can't miss them coming.  But walk to the side of the vehicle a few 
feet and they lose their effect.  However, your point is well taken.  
The strobe kit I purchased is intended to be installed in the headlights 
and taillights of emergency vehicles, which of course have nice 
reflectors that intensify the light.

A Fresnel lens or magnifying lens would go a long way to distributing 
the light and making it appear brighter by directing it within some 
confined angle.  Some of the aviation beacon lenses are designed like 
that, but I couldn't find any specs on material thickness.  And because 
they are all sort of egg shaped, it wasn't clear to me how much external 
pressure they would take.  I'd have to buy a few and field test them.

I could also try frosting the pipe a bit to see if that helps.  Even by 
themselves they are quite bright.  Perhaps someone going to the 2010 
convention will offer to install the strobe so we can check out the 
effectiveness on the water in daylight and dusk conditions.

Jon


shellydalg@aol.com wrote:
> I wonder if cannibalizing a large flashlight for it's reflecting 
> parabolic disk would help focus the light into a more contained beam 
> shape.
>
> The bench demonstration of their LED array in the shop looked good. I 
> think the array had 25 bulbs in it.
> Much less heat generated with LED's.
> Frank D.




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