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FrozenGate by Avery

New build!! 1w 520nm with 0.13 mrad

At km distances the atmosphere messes with the beam a lot. I was trying a long distance data link and settled on leds. I tried a 20x beam expander thinking I’d get an increadable 0.01mrad. Yea no/. The noise on the beam was horrible. LEDs where better. That was not my work. NASA did the study. However for really long distance like the moon they did use lasers. I gave up.
 





kecked said:
At km distances the atmosphere messes with the beam a lot. I was trying a long distance data link and settled on leds. I tried a 20x beam expander thinking I’d get an increadable 0.01mrad. Yea no/. The noise on the beam was horrible. LEDs where better. That was not my work. NASA did the study. However for really long distance like the moon they did use lasers. I gave up.
Click to expand...
I think to create a laser with 0.1mrad divergence, I need a single mode diode with g2 lens, I can achieve <1mrad ,then use 10x beam to dow to 0,1 mrad
yes ,agree with you ,At a few kilometers, the beam will be very messy, but I think there will be some energy gathered in the area, and they still satisfy the theory we have proposed.

And i think a laser beam that can reach the moon will have less than 0.001mrad
 
Oh for sure. NASA uses large telescopes to produce the tight beams. They still have km size return beams. That’s ok because the data sites are on property large enough to contain the beam from prying eyes. They want it for neo sats and between sats. Talk of Mars earth too. Now the beams the size of the earth. My ambition was just 2km. Nothing special and just for fun. Hard to find that kind of open distance where I live. Had thought about trying ship to shore over Lake Erie. That should be easy. Never the less I lost interest.
 
kecked said:
Oh for sure. NASA uses large telescopes to produce the tight beams. They still have km size return beams. That’s ok because the data sites are on property large enough to contain the beam from prying eyes. They want it for neo sats and between sats. Talk of Mars earth too. Now the beams the size of the earth. My ambition was just 2km. Nothing special and just for fun. Hard to find that kind of open distance where I live. Had thought about trying ship to shore over Lake Erie. That should be easy. Never the less I lost interest.
Click to expand...

Yes, I think with the limit of a handheld pointer, we can completely create 0.1 mrad divergent, but 0.01, i think noway !!!
when I was a boy, I had heard about US laser weapons, they could burn an airplane for 8 seconds, but US militarry couldn't grow because of distance limitations and energy, I haven't seen them put into equipment military,I not sure about the above information, I read on some of the translated newspapers in my country
haha :LOL: :LOL:
 
kecked said:
At km distances the atmosphere messes with the beam a lot. I was trying a long distance data link and settled on leds. I tried a 20x beam expander thinking I’d get an increadable 0.01mrad. Yea no/. The noise on the beam was horrible. LEDs where better. That was not my work. NASA did the study. However for really long distance like the moon they did use lasers. I gave up.
Click to expand...
You quit to soon. This experiment was done by a hobbyist 18 years ago as I recall using a red laser. I'm including a photo of one red laser used seen from a distance of 22 miles away across the English Channel.
france.jpg
 
trinh hong phuoc said:
Yes, I think with the limit of a handheld pointer, we can completely create 0.1 mrad divergent, but 0.01, i think noway !!!
when I was a boy, I had heard about US laser weapons, they could burn an airplane for 8 seconds, but US militarry couldn't grow because of distance limitations and energy, I haven't seen them put into equipment military,I not sure about the above information, I read on some of the translated newspapers in my country
haha :LOL: :LOL:
Click to expand...
Divergences as low as 0.01 mrd and less are doable. What you can do is use more than one plano-concave lens cemented together to greatly expand the beam to keep the working length of the beam expander manageable. Conversely, shoot the laser beam through a refractory telescope's eyepiece. Keep in mind that the collimating plano-convex lens will require a diameter greater than the beam so as not to truncate the beam. 10% wider is probably good enough.
 
awesome work Trinh! thanks for sharing your build. I have had a pair of 6x sitting here for over a year... i'll get to them someday :P
 
I tried an 8” telescope. Put 7w. Blue into it. The beam was visible but the modulation was so noisy from the atm9spere it didn’t work.
 
what divergence,and how far you try???

testing with blue is a not good idea,i think, because 450nm has a very large diffraction, thinking about long distance lasers, red dominates, but I can't find a red enough strong diode
 
kecked said:
I tried an 8” telescope. Put 7w. Blue into it. The beam was visible but the modulation was so noisy from the atm9spere it didn’t work.
Click to expand...
Considering that the sky is blue that should have given you a clue why not to use a blue wavelength.

trinh hong phuoc said:
what divergence,and how far you try???

testing with blue is a not good idea,i think, because 450nm has a very large diffraction, thinking about long distance lasers, red dominates, but I can't find a red enough strong diode
Click to expand...
Really? Click link in post 21.
 
Nice!!! i love NDG7475. I lost one NDG7475 a long time ago. But I re bought it again. :D
Now it's wearing a G3 lens 1.6Amp set pen build 10440 2use. Nice divergence and bright
 
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