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FrozenGate by Avery

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Alaskan said:
What I'm presenting I want to do isn't everything I'm considering, I like the idea of being able to flash from one mountain top to another with these, when using cameras but at great distances it is difficult to put a spot on someone in the far distance, especially if infrared! What I was planning was using a plano convex cylinder lens in front of the output a few inches out to let the high divergence beam from that lens spread some before turning it into a line, then the line is swept up and down in the general direction of someone in the distance, they should see flashes at the high pulse power and repetition rate these units produce and no worry about getting the spot right on them as it will have a large lateral pattern, although weaker due to the horizontal spreading, of course, but with several of these all shooting into one 8 inch long lens like that, the powers add in the line so it should be bright anyway.

There are a lot of things I'm considering, if I can find a better lens to produce the line so it is limited to just a few degrees wide, instead of the huge 20 degree wide line I'm getting right now, I will go that direction. This is all just play for me, not engineering for a need, so what ever it ends up, is what it ends up being. Mostly, I just like tinkering and this is fun. If I could find a high power pulse single mode, I'd use that. The reason why I've moved to IR is due to not wanting to flash aircraft in the far distance, and these high peak power units are far less hazardous close in with their low average power, spread out as I have the beam, it's just a small wisp of average power.
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I thought that might be part of it, I remember your other device you built in the wooden box with the .....were those dry cell or alkaline batteries......I can't remember.

Anyway the Barker code I linked to above is used to identify the modulated signal from background noise in devices like the range finder, but it is looking for the scattered backsplash of the emitted signal. Still it could be used in initial set up and for low bandwidth modulation of a pulsed carrier in poor atmospheric situations.

You don't get ionic skip with a laser as far as I know. But you are looking to do line of sight with the transmitter and receiver aligned...correct ?

I'm not even going to talk to you about microwave as you understand that very well already, but what is the most efficient frequency from VLF to X-RAY for line of sight signal transmission ?

I can see where an IR signal could be used where interception/detection of radio is a concern, and I know I asked this or looked it up before, but what is the best frequency of light ( laser diode generated light ) for open air transmission in line of sight applications ?

I think you would be better off to purpose build/source your own driver to modulate rather than repurpose the range finder board, you are going to want to fine tune things.

Also is the very short duration pulse albeit high intensity the best way to go ?

As a digital signal with such short pulses it may be hard to detect at distance with atmospheric interference.

I'm thinking analog with a modulated carrier, but for an aligned line of sight digital IR signal atmospheric conditions could be a big factor.


Sorry that was the wrong link > http://web.archive.org/web/20130215161346/http://esc.gsfc.nasa.gov/267/271/Ground-Terminal.html

Not a new idea and not without challenges I like to read about what others have done for ideas. > https://www.extremetech.com/extreme...etwork-made-with-red-and-green-laser-pointers

No offense intended, just asking if you have read this yet? > https://en.wikipedia.org/wiki/Free-space_optical_communication
 
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I read about 1550nm being the better choice albeit more expensive for us, it's also eye safe as for diffuse reflections as it wont penetrate the cornea the way 808 and 905 easily will. ( Attention casual readers: NO LASER IS EYE SAFE )

Those rangefinders receive the pulse train back as backscatter and pick it out of the noise using the Barker code, it's great for range finding but not so much for free space data transmission.

Something I find helpful is reading about what others have done and learned as I'm sure you do, saves us a lot of legwork/time/expense, it seems that using techniques to get the signal through and accepting a lower bandwidth is a good approach, maybe analog modulation of the laser carrier rather than high brightness digital pulses, especially very short duration pulses. :beer:
 
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Yes, it's fun to experiment, and I am learning as we talk about it too, I just found that page about NASA's laser data link, very cool stuff.

---EDIT---
I don't know if you were thinking about pulse position modulation or a binary data stream, but multiple receivers in an array could help make sure the signal gets through.

http://web.archive.org/web/20130215161346/http://esc.gsfc.nasa.gov/267/271/Ground-Terminal.html




----EDIT----

Here's a guy doing it with amplitude modulation.





----EDIT----

Off topic but interesting, this guy has a good technique to create defensible space when confronted with an edged weapon, which has always been a reaction time problem. IE the 21 foot rule.

Amazing how a little knowledge changes everything.

 
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Very nice, looks like a rock crawler with all the articulation, I like the all electric approach better than the hydrostatic, with traction control electric will be more capable, more efficient, and have higher wheel speed.

Here's some others along the same lines although I like the way swincar uses the pendulum counterbalance, but every job has the perfect tool.

 
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I did enjoy seeing your link to the swincar, Tero. Being all electric has advantages, but it would have been better if they included more battery for longer outings between charges. Using a pendulum effect to keep the operator centered regardless of the terrain is not novel, but it sure seems to work well. :thanks:
 
Here's my humble cheer for Guido. You were the best pilots out there...
R.I.P Guido Gehrmann :(

 
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I'm off to bed Tero, but I can't wait to watch all these yt vids you've posted man.
I love watching these, thank you.

Good night all.
:tired:
 
That looks like a lot of fun, I know it can be dangerous too, but such great views and a natural high. :beer:
 
Great videos, Tero. I might like to try if I were only younger and didn't have back problems. I guess I am in the nostalgic phase of my life.
 
I have a piece of Icelandic calcite that I bought several years ago to replace a much larger piece I had for over 50 years. I got it for its birefringent properties as these are what make up a waveplate. I didn't know that Vikings used it to find the sun a thousand years ago.
 
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