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Looking to buy a laser for survival purposes

hakzaw1

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good info rage..+rep when sys allows
 

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Oka! It sounds like we're narrowing it down. Is it pretty agreeable that a 520 direct diode is one of the more stable and durable lasers? Durable enough to say, drop it on the ground? Or throw my backpack on the ground with it inside? To be in 100 degree direct sunlight for a few hours?

Now the question is, what power should I go with? It's hard to specify but obviously I WANT someone to see it. The point was made earlier that on a cloudless day even something like a 5W (I think it was 5W, can't remember who said it) won't be visible. I find that hard to believe given that within half a mile people in muiltple directions have been able to see a 50mW. Granted, that wasn't a COMPLETE cloudless night, and maybe that makes all the difference. But then again, the only reason I'm saying cloudless is to prepare for worst case scenario. Say we have SOME clouds, is 500mW enough? 250? 1W? It would take forever to go through every type of meterological scenario, darkness setting, angel the beam is in relation to a rescure helo, beam strength, etc... So maybe lets just try to give averages, most plausible scenarios, etc... I'm not to worried at what direction the helo is flying in relation to the beam because if such a scenario happens I'm not going to be just shinning in the exact same position, at the exact same angel, the whole time. Does any of that make sense? This is a difficult discussion to have over the internet that's for sure.

The difficulty in answering your question is figuring out just what you are looking for. As an example I am not sure what someone would do after seeing the beam from say a 7w Sanwu shining straight up in the sky. Even if you used the standard SOS signal it might not get the response you wanted. Not to mention the Sanwu has something like a 60 second duty cycle. There are probably lasers with better duty cycles and similar or better visibility but still seeing a beam in the sky is not viewed as a call for help. On the other hand if you had a radio/phone/what ever the beam might be helpful in the last part of the rescue.
It's not just the sight of the beam. It's seeing the beam in conjunction with the fact that there will likely be emergency crews looking for me and that they will likely know a general 20sq/mi region to look. If you know all that and see a strong beam at night signaling SOS that's about as much of a dead giveaway as you can have.
 
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paul1598419

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There are no laser diodes that can survive a hard knock to them. Even solid state lasers like 523nm ones use a diode to pump the crystal, so there is no free lunch here. If you are going to be tossing your backpack around it would be best to wrap your laser in something that might soften the blow. If you want to signal SOS with the beam, you will need to build a custom 520nm laser. The NDG7475 is a multi-mode laser diode that is capable of 1400 mW of optical power, but they aren't cheap. And the visibility of a vertical beam will depend largely on what particulates are in the atmosphere.
 
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SNIP

So maybe lets just try to give averages, most plausible scenarios, etc... I'm not to worried at what direction the helo is flying in relation to the beam because if such a scenario happens I'm not going to be just shinning in the exact same position, at the exact same angel, the whole time. Does any of that make sense? This is a difficult discussion to have over the internet that's for sure.



It's not just the sight of the beam. It's seeing the beam in conjunction with the fact that there will likely be emergency crews looking for me and that they will likely know a general 20sq/mi region to look. If you know all that and see a strong beam at night signaling SOS that's about as much of a dead giveaway as you can have.

First thing to consider is the duty cycle. If your laser has a 60 second duty cycle that means you can shine for 60 seconds and then it is off for 60 seconds. That assumes the best case option where you did not drop it and batteries are good and the temperature is ideal.


Some lasers do have much better duty cycles, but even then they have limits. So you will not have a beam shining up in the sky 100% of the time. Combined with the fact that the helos will not be looking in the right direction 100% of the time there are real limits.


On the other hand something like an EPIRB will broadcast your lat/long for days, or even weeks so the helos can pinpoint where you are located. Once they get close something like a hand held VHF radio can be used to help guide them in. If fact if you can get to the top of a hill in many 20 square miles area you could contact the helo first; not to mention there are plenty of places where cell coverage would also be an option.


Not trying to deter you from getting a laser. There are lots of problems that can be solved with a high power laser; but I don't think this is one of them.
 

Benm

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The difficulty in answering your question is figuring out just what you are looking for. As an example I am not sure what someone would do after seeing the beam from say a 7w Sanwu shining straight up in the sky. Even if you used the standard SOS signal it might not get the response you wanted.
That would depend indeed, but -any- response is better in such conditions. They may send a rescue team or a police squad to arrest you for lasering that aircraft, but both mean you'll be extracted from your stranded location alive, and the legalities of it all could be sorted out later.

Flashing a visible SOS pattern would be great, but a commonly accepted method of getting attention from aircraft when in need of rescue is to use a mirror to reflect the sunlight as best as possible towards the aircraft. You're not likely to be able to convey and SOS in that as it's difficult enough to hit the aircraft with the reflection, and this only works during daytime on non-overcast days either.

There is not need to get a crazy high power laser for this either, something like a 100 mW red (and certainly cyan) laser would stand out very brightly from an otherwise dark area.

I'd actually consider that such a laser would be superior to things like building 3 signal fires and setting those off when an aircraft (or ship if on a coast) could potentially see you. Not that they'd ignore the signal fire, but a laser beam of a pretty specific colour pointing around you is just more noticeable.

If you ever get in this situation i'm sure you'll be very happy seeing the aircraft bounce it wings to acknowledge seeing you, even it was some commercial jetliner that would still relay your position as best as they can to search and rescue services.
 

hakzaw1

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Looking to me like Jetlasers Yamataka has the most of your requirememts (except a low price) waiting now on reply from Gray at JL if his team can help by building some w/o the stun and W / single mode green diode laser= 200 to 400 mW would seem to me to be enough. It is very ruggedly made- its water proof- one level higher than water resistant -- would still treat as just resistant- I E NOT for SCUBA. my guesstimate for price would still be the most expensive laser of its kind-- if you want cheap..I wonder what value you place on your life.. I would expect bright LED and green laser (w/o stun)to be>$250.... both have many modes-- including, of course, SOS and disorientation strobe--able to cause some to vomit w/o control. uck!!
PM me asap.. as Gray needs a firm number before getting these altered. I am willing to host a USA GB.. others should just contact Gray w/ your request/orders. while spendy.. some Xmas/DB gifts are wanted to be expensive..
Not a toy...
carry on..
 




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