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Thread: Laser media frequencies

  1. #21
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    Quote Originally Posted by kecked View Post
    Shotgun works well. My real question is what are YOU trying to hide and from WHOM. You could always fly a second drone into the first. Train a faulken use a bright spot light to blind the camera. Use a laser to destroy the camera
    Discharging a shot gun near airports, neighborhoods, city limits, etc is SUPER illegal and because of the noise and relativly short distance (camera on drone can capture you) its super easy to get busted. Range of a shot gun is extremely paltry and you could end up hurting someone else with the shot.

    We live in a police state so anyone acting like a free person has something to fear from our nanny police state. Our police state is so massive that it is rare when the people can stand up against it (remember FAA, FCC, DEA beurocrats are not elected officials - they create laws and "regulations" that congress rarely votes on, they do it from some back office like little dictators or monarchs). Once in a blue moon someone will go through the personal pain and sacrafice (remember there is no pain or sacrafice for the bearucrat writing police) to bring the regulation to the supreme court but its rare and the beaurcrat has little to fear.

    There are things in the work with Trump administration to make these people MUCH easier to fire and to SUE - such as if the FAA creates some onerous policy for me to use my own property I can sue that guy personally and attach his entire net worth, take his kids 529 plan etc. I hope this becomes law because you will see alot of policy recalled and alot of firings.

    For instance the FAA has made it virtually cost prohibitive for any serious recreational piloting through forced annual inspections by a "qualified person" (and of course getting that qualified persons status requires writing LARGE checks to the FAA designated persons), forced medicals, outrageously expensive examination fees and on and on. All so I can fly my own personal property.

    Anyways I digress, I dont really want to get on here to talk about law because until we get enough congressmen in and a stronger president that will start disolving woodrow willsons little fiefdom then there is not much to do on the average citizens end. But I will tell you I wont table my academic endevors because of a bearucrat, especially in a state where its extremely difficult for the feds to operate.

    https://www.youtube.com/watch?v=ZwmUH5AGydQ

  2. #22
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    Could a proton beam be used to pump a crystal laser instead of diodes or flash lamps?

  3. #23
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    Quote Originally Posted by akmetal View Post
    Could a proton beam be used to pump a crystal laser instead of diodes or flash lamps?
    Why, do you happen to have a linear accelerator lying around doing nothing?

  4. #24
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    Quote Originally Posted by akmetal View Post
    In the case of passive jamming my thoughts were towards protecting aircraft with occupants (where its impossible or impractical to install a laser) and the power supply is somewhat limited on small aircraft so a targeted jam with destructive interference is far preferable to flood the air with noise since power is restricted and you want as big a bubble as possible around your plane. I have had numerous friends almost have drone strikes in the last couple of years.
    OK - A mobile airborne anti-drone system is quite a bit more complex that the ground-based station I was discussing. For one, you now have a much higher intercept velocity because of the movement of the plane (which is likely to be much faster than the drone). Also, you don't want to interfere with any of the plane's on-board systems, so denying GPS information to the drone is likely not an option, and even interrupting the control signal (depending on the band) might also interfere with navigational beacons. (VOR operates on an even multiple of the 6 meter ham band, which can be used for RC, for example.) In this case I can see the merits of actually trying to interrupt or spoof the control signal. However, this is also an edge-case scenario (protecting a light aircraft), and the method you're discussing is patently illegal.

    Just because drones are suppose to stay below tree top level does not mean that they do. And I have seen numerous drones operating near airports with no communication. Its just a matter of time before there is an incident.
    Incidents have already happened. Most have involved light private aircraft, but there has been at least one incident in Canada where a passenger airliner was involved in a drone strike.

    The good news is that in all cases the damage was not nearly enough to bring down the planes. Even a 4-passenger prop plane that took a hit dead-on the leading edge of the wing was still able to fly normally and land. (That strike was from a DJi Phantom, and most of the damage was likely due to the heavy battery it carries.) While I agree that drones are a growing problem, I don't think there's any need for a jamming system at airports. And I definitely would not suggest building one yourself. The penalties for doing so are going to be severe. (Like I mentioned above, these are federal crimes.)

    The challenge I was having with jamming was dsp design that would take directly high frequency inputs without complex mixing.
    OK, I'll pretend I didn't just read that! Seriously though, if we're having a theoretical discussion that's one thing. But if you're actually trying to build this, then we need to stop talking. What you're proposing is all kinds of illegal, and I don't want to be involved in any way, shape, or form. While you may believe that living in a scarcely populated area will keep you safe, I can tell you that all it takes is one concerned individual to contact the FCC about "strange interference" to get Uncle Sam looking into things. Then too, Ham radio operators are everywhere, and they notice things that are out of place.

    If you or a pilot friend are worried about a drone strike, spend a few hundred bucks on sheet metal to reinforce the leading edge of the wing of the plane. That's much easier than building a jammer. It's also cheaper and is more likely to yield a positive outcome in the unlikely event of a strike. Plus it doesn't have the potential to land you in federal prison...

    Actually, since you live in a remote area, maybe your best option is to reach out to the done enthusiasts in your area and discuss the problem with them. I seriously doubt that any of them are intent on causing harm. Some signage at the local airstrip warning of the danger might be another good idea to consider.

    Ideally a fully analog circuit is the best but I have not figured out how to phase shift in full analog AND allow for antenna switching so that the 2 antenna were not competing against each other.
    Um... Phase-shifting is pretty trivial. How hard have you worked on this? And preventing the outgoing signal from blocking the incoming one is a simple matter of antenna design and placement. Do you have any formal training in radio?

    I would love to talk to you further about this and learn how they build these new DSP circuits that allow for direct input of say 1-6 ghz radio frequency.
    The DSP chip I mentioned above has a development environment for Windows and for Linux. With an evaluation board (about $300) you should be able to make it dance the jitterbug if you wanted. Alas, I'm not a code monkey.

    To be honest, I'm actually feeling rather uncomfortable right now with the way this thread is progressing. Let me say this again, very clearly: Unless you are a government contractor working for the military on an approved project that explicitly gives you permission, then it is a federal crime to build a device that radiates radio waves that interfere with authorized radio communications. One could argue that developing the code for the DSP chip (even absent having the RF antenna and I/O connected) might be a crime in itself. I know *I* wouldn't want to touch it...

    Out here in no mans land no one cares what you do so long as you are not committing sexual assault or domestic violence.
    That may be true for your local Sheriff's office, but the Feds have other ideas.

    I could build a particle accelerator and start producing plutonium and no one would care.
    Now this *does* land in my wheelhouse. I'm a former Navy Nuc (submariner), and I was an ELT to boot. I realize your statement was meant as hyperbole, but honestly you couldn't have picked a worse example. So I'm going to indulge myself for a moment:

    First, you don't use a particle accelerator to make plutonium, you use an operating fission reactor. (You need to add a neutron to an atom of Uranium-238 to make Uranium-239, which then goes through two inverse-beta decay cycles to become Plutonium-239. Kinda hard to accelerate a neutron with a particle accelerator, given that neutrons have no charge!) And second, long before you ever obtained any fissile material to fuel your reactor you'd be overrun by federal agents. Seriously - fissionable material is just about the most closely monitored commodity on the planet...

    Anyways it would be cool to get to know you and learn more about advance circuits, I have the basics down as well as the advanced math (partial differentials, etc) but dont have any real design work.
    There are several electrical engineers here who are very good at circuit design. Likewise, the fourier tranformation math is not something I'm really good at, but we've got plenty of programmers here with experience. It's just that I think very few people are going to help you with this once they realize the end goal is to building something that is highly illegal. We already struggle with people going against the CDRH rules for lasers. How likely do you think people will be to go against the FCC? (Or worse, the FAA, if your jammer accidentally interferes with other aviation radio systems...)

    It would be cool to get to know steve too but I feel like he is really upset. I feel like I have found my people.
    In fairness to Steve, we have had a lot of problems with trolls lately. They take the form of new folks who appear to be very interested in lasers but clearly haven't done any research on the subject at all. OK, that's fine, not everyone is adept at using Google, and we're here to share knowledge, right? But when senior members offer advice to these new folks and then see that advice rejected immediately, well, that tends to upset people. A related issue is when a new member claims to be an "expert" at something laser-related, only to make a gross conceptual error just a few posts further down. Steve has been on the receiving end of more than a few of these sorts of people lately, and it's made him a bit more cynical. I can't honestly blame him though, as I've had similar thoughts myself. But we still do our best to give every new member the benefit of the doubt.

    Quote Originally Posted by akmetal View Post
    You could install your circitry in a farday cage and be fine, of course the entire engine compartment would have to be protected as the emp could travel through any exiting wires.
    And this is why it's difficult to harden a drone against an EMP. So long as you plan to have RF remote control of it (or even have it fly autonomously using GPS for navigation), you'll have to have an antenna sticking through the Faraday cage, and that is a potential entry point. (That's why military flight hardware includes an inertial navigation system that is isolated from the outside; if they lose remote control *and* GPS, they can continue the mission using dead reckoning.)

    Re: EMP

    I dont know what the police use but if its not a coil wound explosive device then its effectiveness is marginal and even a basic faraday cage would stop it.
    My understanding is that most of the police units are basically magnetrons. And yeah, a Faraday cage would defeat it. It's just that the typical driver who will run from the cops isn't likely to think about hardening the car's ignition control module first.

    I also will never understand why newer cars dont use the same systems as airplanes for fuel injection systems.
    In an aviation environment, reliability wins over efficiency. Also remember that fuel economy for private aircraft is unregulated. Not so for cars. (CAFE)

    Quote Originally Posted by akmetal View Post
    Discharging a shot gun near airports, neighborhoods, city limits, etc is SUPER illegal
    It's interesting that you agree with the law here, but you don't appear to agree with the law preventing the construction or use of a jammer. Typically when people in a society are allowed to choose which laws they follow (and which ones they don't), the end result is not pretty.

    And I think that's where I'll stop, as we're drifting well away from the original topic.

    Adam

  5. #25
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    Older (I do MEAN OLDER) editions of the CRC Laser Handbook from Abebooks will provide you wavelength tables and a reference to a journal article to go to a university science library and look up. They will rarely provide you with accurate estimates of laser power.

    CO2 Systems lase in a band 9.6 microns to somewhat past 10.6 microns depending on gas mixture and additives. While the majority of the power is at 10.6 there are other bands. Often you just need a grating tuning addition to the Co2 cavity.

    Koechner's textbooks on Solid State Lasers usually have that wavelength table for crystalline hosts.

    And Marvin J. Weber has two books that are relevant tables for gas lasers and solid state lasers. You will again have to pull the scientific journal referenced in the table if Google is not your friend.

    When you get into non-standard laser wavelengths, you will find its easier to bend your experiment to the wavelength or buy a tunable laser (Plug here for Altos Photonics, Spectra Physics, or Coherent Tunable OPO based Systems) rather then spend tens of thousands on constructing non standard lasers from an age where everyone was trying to find new wavelengths but often did not own accurate means of measuring the performance of the laser they discovered.

    The hows and whys of what lases when and where and how to design it as a system are are best learned from Silfvast's text "Laser Fundamentals", and Koechner's Solid State Lasers book and you want the second edition or later, the first can be a little sparse.

    Amon Yariv's book on Laser Quantum Mechanics or A.E. Siegman's Text "Lasers" are good at the graduate level.

    Answering your other questions would take me too much time, so I suggest you start reading up on why Population Inversion occurs and where in a given host.

    Steve

  6. #26
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    Quote Originally Posted by NobleGas View Post
    Why, do you happen to have a linear accelerator lying around doing nothing?
    Unfortunatly no, I have the real estate to run one through the woods but what would I make it out of that would be cheap enough? I dont have enough booze bottles to melt down into glass pipe lol. Wood? Maybe, its an insulator and I dont see why it could not hold a vacuum, with small glass sections where the magnets would be housed ....

    Never the less that is not practical to run a laser but would be highly useful for other things like converting elements.

  7. #27
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  8. #28
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    Quote Originally Posted by akmetal View Post
    Okay? Is there some reason for sharing this or...?

  9. #29
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    Quote Originally Posted by Diachi View Post
    Okay? Is there some reason for sharing this or...?
    Yea, FLIR now builds laser rod crystals, a whole assortment. I thought it was a great reference.

  10. #30
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    Quote Originally Posted by akmetal View Post
    Yea, FLIR now builds laser rod crystals, a whole assortment. I thought it was a great reference.
    Now builds? They acquired Scientific Materials Corp. in 2005, which itself was incorporated in 1989.

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