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Use laser to send morse code?

versd0ra

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I'm thinking about using a laser to send morsecode a few kilometers as an experiment...

However, my experiance with lasers is mostly by pointing at the projector screen in powerpoint presentations.

So some questions.
What power is needed if it should be just possible to see when the laser is turned on and off, at ~5km (3 miles) away at night. (Would be perfect if you couldn't see it on a sunny day, but it should not be any problem at night)

And of cource without ANY risk of damaging your eyes. (IR filter, any more that should be done?)

I guess i'll be fine with some 1mw one? But I have never used lasers over these distances, so I really don't know.

And how many times can you turn a laser on and off before it breaks? (typically).

Or maybe some LED setup would be more suitable?
All input to this project is appreciated!
 

Pi R Squared

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If I were going to do this I would probably use an IR laser to avoid attracting attention. If you want it to easily be visible at night I would think 200mW 520nm/532nm green should work or certainly 1W or more 445nm/450nm blue will work.

Alan
 

Sigurthr

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Divergence (and thus spot size at target) and alignment precision become incredible obstacles in long distance laser operation. A simple laser module of any type can be TTL (on/off) modulated by hand for CW (morse code) very easily by interrupting power to the driver. The problem is the optics needed to get a low enough divergence. You need to consider what type of detection you are planning on using at the target site to determine what power level is needed.
 

busman2

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I have tried this over a distance of 3-4km and believe me at that distance a 200mW 532nm is still very bright. The divergence over that distance spread the beam/dot to about 8 feet across but it was very bright still and not advisable to bee looking directly at the source! I am guessing you could easily see a 50mW green over that distance. Also remember if you can see it from that far so can everyone else so test it out in a non populated area.
 

Pi R Squared

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Bright at even three times that distance:


busman2 is clearly correct, I don't know what I was thinking. I think it would be too visible, use the minimum power required.

Alan
 

RYDorDIE278

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Thats a very creative way to read morse code! quite interested in your results, I guess a big question is how will the observer be viewing the signals,
Are they looking in the sky at the beam?
Looking directly towards the pointer?:)tsk: Hope Not)
Looking at an object the pointer will be pointed at ? etc.

Good Luck !
 

PainTrane117

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Like everyone else has already stated, divergence becomes a problem at long range. BUT if you need to, you can shine the laser through a magnifying glass to help focus the beam a little better. I have done this and it works quite well, I was able to decrease the divergence by quite a good amount at a far distance! You may need to experiment with different magnifying glasses and place the glass about 6 to 12 inches from the laser. Try it out ;)
 

upaa27

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The wl nano with the bluetooth app can do morse code
 

steve001

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I'm thinking about using a laser to send morsecode a few kilometers as an experiment...

However, my experiance with lasers is mostly by pointing at the projector screen in powerpoint presentations.

So some questions.
What power is needed if it should be just possible to see when the laser is turned on and off, at ~5km (3 miles) away at night. (Would be perfect if you couldn't see it on a sunny day, but it should not be any problem at night)

And of cource without ANY risk of damaging your eyes. (IR filter, any more that should be done?)

I guess i'll be fine with some 1mw one? But I have never used lasers over these distances, so I really don't know.

And how many times can you turn a laser on and off before it breaks? (typically).

Or maybe some LED setup would be more suitable?
All input to this project is appreciated!
Multimode posted a link. Within that link is this one you should take a look at. It used a 5mw red pointer. Laser Contact
 

PainTrane117

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I know this isn't really my thread or my question, (I say this because I have never used a laser at those distances) but I did read almost everything in the link from multimode. Very interesting and helpful, indeed.
But there is one thing I must say: I recommend a GREEN laser over a red one.
Green light has been proven to be more easily visible and seen by the naked human eye.
There is a reason that the U.S. military uses red flashlights when conducting night ops.
They choose red because the enemy cannot see it as easily as normal white light or green light.
Just food for thought.
 
Last edited:

Sigurthr

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There is a reason that the U.S. military uses red flashlights when conducting night ops.
They choose red because the enemy cannot see it as easily as normal white light or green light.
Just food for thought.
That's not actually why they use Red. If the enemy was watching with NV it doesn't matter what wavelength in visible they use, it would light up like a flare because the PMT doesn't care which visible wavelength is used.

The reason they use red light is because red light doesn't reset our eyes' dark adaptation by bleaching the rod photoreceptors.
 

The Lightning Stalker

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Can you fill out your location and tell us your
general area? I believe what you are proposing
is illegal in a few places.
 




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