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Thread: Laser media frequencies

  1. #11
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    ................
    Last edited by kecked; 02-03-2019 at 06:55.

  2. #12
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    Electronic destructive interference is just as complex as developing a new laser material due to the extremely high radio frequencies that drones and gps operate at. It would require complex mixing and digital signal processing in order to detect a drone signal halt the sensing antenna and then phase shift in the dsp and retransmit. Thus switching would have to be very rapid and would also have to simultaneously jam the gps signal

    The power supply would be large as well

    Also my obsession with lasers goes back 27 years.

    Quote Originally Posted by kecked View Post
    Why not try a good old mortar the fires a net at the props. BTW there are many electronic ways to force it down.
    Last edited by akmetal; 12-14-2018 at 16:50.

  3. #13
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    Quote Originally Posted by akmetal View Post
    Electronic destructive interference is just as complex as developing a new laser material due to the extremely high radio frequencies that drones and gps operate at. It would require complex mixing and digital signal processing in order to detect a drone signal halt the sensing antenna and then phase shift in the dsp and retransmit. Thus switching would have to be very rapid and would also have to simultaneously jam the gps signal

    The power supply would be large as well

    Also my obsession with lasers goes back 27 years.
    Any form of RF jamming would likely be illegal anyway. Unless you're the military, in which case you already have those capabilities.

  4. #14
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    Quote Originally Posted by Diachi View Post
    Any form of RF jamming would likely be illegal anyway. Unless you're the military, in which case you already have those capabilities.
    We are becoming more and more of a police state where everything is illegal. I can’t even keep track. The more esoteric the law the harder (or almost impossible) it is to enforce.

    If you turned on a passive jammer (only turned on when a signal came on) it would take considerable resources to trace.

    But discussing legalities does not really absolve one of deep intellectual thought on a sub forum for deep intellectual topics.

    You don’t just get to say - oh it’s illegal so I don’t have to think now lol

    I don’t even know that it truely is illegal or not, passive signal destructive interference of specific frequencies or a range of frequencies is much different that flooding the air with noise.

  5. #15
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    There has to be a branch of chemistry for crystals, “crystal chemistry” on how to make synthetic crystals?

    https://www.youtube.com/watch?v=XbBc4ByimY8

    Using the Czochralski technique new crystal types can be made in the same way silicon wafers are made
    Last edited by akmetal; 12-15-2018 at 13:41.

  6. #16
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    Quote Originally Posted by kecked View Post
    Why not try a good old mortar that fires a net at the props.
    Because a directed energy weapon can act at far greater distances, probably. But yeah, for close-in work a physical intercept is pretty lethal and a lot cheaper.

    BTW there are many electronic ways to force it down.
    Agreed. Although to be fair the military is currently investigating directed-energy weapons for anti-drone work. But yes, interfering with the flight electronics directly (difficult, but very effective if you succeed) or the RC control link / GPS signal (easier to accomplish, assuming the drone isn't flying autonomously) also works.

    Quote Originally Posted by akmetal View Post
    Electronic destructive interference is just as complex as developing a new laser material due to the extremely high radio frequencies that drones and gps operate at.
    Ah, no. Just - no. Electronic jamming has been around for 6 to 7 decades. It's a very mature technology. Developing a new laser gain medium is *far* more difficult.

    And you've got your physics backwards. It's *easier* to interfere with, overpower, or outright block the shorter wavelength radio waves. It's the long wavelength stuff that is hard to block. (This is why missile submarines use VLF and ELF radio for launch orders; short of a nearby supernova detonation you're not going to stop that signal from reaching the receiver.)

    It would require complex mixing and digital signal processing in order to detect a drone signal halt the sensing antenna and then phase shift in the dsp and retransmit.
    Ahem. Your understanding of jamming is woefully incomplete. Yes, sampling the control signal in real time, modifying the phase and/or pulse widths, and then re-broadcasting a phantom duplicate signal is *one* means of jamming. (And one that was implemented as early as the Vietnam War to combat early radar-homing anti-air missiles.) There are far more sophisticated methods available today.

    More to the point, however: if your goal is merely to stop the drone, all you need is a stupidly-powerful transmitter that splatters across the entire control band plus a directional antenna. This is something most hobbyist electronics geeks could build in their garage. (Though admittedly such a construction *would* violate several FCC regulations.)

    Also: just for the record, the DSP chip needed to accomplish the signal processing described in your example (even against commercial-grade, high-frequency, agile, spread-spectrum control schemes) can be purchased for about $200 from Digikey. (And that's for the 8-core TMS320C6678, clocked at 1.25 Ghz, which is overkill.) Like I said, the technology has advanced a great deal.

    Thus switching would have to be very rapid and would also have to simultaneously jam the gps signal
    GPS jamming is even easier (although it's equally illegal). GPS signals have no means to detect or avoid jamming. Thus, simply overpowering the signals from space with a local transmitter is a trivial task. Now, if you want to SPOOF the GPS signals so that the drone *thinks* it is on course when it really isn't, then yes, that is more involved, but even so this is essentially a programming challenge, not a technological limit. The math itself isn't that hard to calculate. (Once again, the DSP chip above is more than capable.)

    The power supply would be large as well
    Given that you are protecting something located on the ground, the size of the power supply (on the ground) seems irrelevant. The limits are all on the drone, which has to be able to fly...

    Quote Originally Posted by akmetal View Post
    If you turned on a passive jammer (only turned on when a signal came on) it would take considerable resources to trace.
    That is not a passive jammer. A passive jammer does not generate or amplify a signal. It channels and re-directs an incoming signal and often modifies the modulation by stretching or compressing the pulse train. Basically it's a fancy antenna.

    What you are describing is an active jammer with instant-on capability. (Note that as far as the FCC is concerned, both are illegal.)

    I don’t even know that it truely is illegal or not
    Everything we're discussing - passive interference of radio control signals, active interference of radio control signals or GPS signals, and the use of a directed energy weapon to disable a drone... *ALL* of these things are illegal in the USA. Yes, the military is researching the subject and developing new systems. But you and I are not the military. It is most definitely a *federal* crime!

    passive signal destructive interference of specific frequencies or a range of frequencies is much different that flooding the air with noise.
    Let's ignore for a moment that "flooding the airwaves with noise" is *already* quite illegal all by itself. The FCC has specifically ruled on the subject of passive devices that intentionally create harmful interference with incident radio signals. The actual ruling is rather lengthy and dry, but here is the relevant text: "...operation of an intentional, unintentional, or incidental radiator is subject to the condition that it may not cause harmful interference."

    Adam

    https://transition.fcc.gov/Daily_Rel...C-97-404A1.pdf
    https://www.fcc.gov/general/jammer-enforcement

  7. #17
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    ... and not to forget - EMP-"canons"

    AFAIK the police owns "handsome" portable EMP generators which can stop a car in a distance of some Kilometers by overpowering/wrecking all the internal electronics with a single directed/focussed microwave-flash ...

    Viktor
    Aufruf zum Projekt "Müll-freie Meere" - https://reprap.org/forum/list.php?426
    Call for the project "garbage-free seas" - https://reprap.org/forum/list.php?425

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    ...............
    Last edited by kecked; 02-03-2019 at 06:55.

  9. #19
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    Quote Originally Posted by buffo View Post
    Because a directed energy weapon can act at far greater distances, probably. But yeah, for close-in work a physical intercept is pretty lethal and a lot cheaper.



    Agreed. Although to be fair the military is currently investigating directed-energy weapons for anti-drone work. But yes, interfering with the flight electronics directly (difficult, but very effective if you succeed) or the RC control link / GPS signal (easier to accomplish, assuming the drone isn't flying autonomously) also works.



    Ah, no. Just - no. Electronic jamming has been around for 6 to 7 decades. It's a very mature technology. Developing a new laser gain medium is *far* more difficult.

    And you've got your physics backwards. It's *easier* to interfere with, overpower, or outright block the shorter wavelength radio waves. It's the long wavelength stuff that is hard to block. (This is why missile submarines use VLF and ELF radio for launch orders; short of a nearby supernova detonation you're not going to stop that signal from reaching the receiver.)



    Ahem. Your understanding of jamming is woefully incomplete. Yes, sampling the control signal in real time, modifying the phase and/or pulse widths, and then re-broadcasting a phantom duplicate signal is *one* means of jamming. (And one that was implemented as early as the Vietnam War to combat early radar-homing anti-air missiles.) There are far more sophisticated methods available today.

    More to the point, however: if your goal is merely to stop the drone, all you need is a stupidly-powerful transmitter that splatters across the entire control band plus a directional antenna. This is something most hobbyist electronics geeks could build in their garage. (Though admittedly such a construction *would* violate several FCC regulations.)

    Also: just for the record, the DSP chip needed to accomplish the signal processing described in your example (even against commercial-grade, high-frequency, agile, spread-spectrum control schemes) can be purchased for about $200 from Digikey. (And that's for the 8-core TMS320C6678, clocked at 1.25 Ghz, which is overkill.) Like I said, the technology has advanced a great deal.



    GPS jamming is even easier (although it's equally illegal). GPS signals have no means to detect or avoid jamming. Thus, simply overpowering the signals from space with a local transmitter is a trivial task. Now, if you want to SPOOF the GPS signals so that the drone *thinks* it is on course when it really isn't, then yes, that is more involved, but even so this is essentially a programming challenge, not a technological limit. The math itself isn't that hard to calculate. (Once again, the DSP chip above is more than capable.)



    Given that you are protecting something located on the ground, the size of the power supply (on the ground) seems irrelevant. The limits are all on the drone, which has to be able to fly...



    That is not a passive jammer. A passive jammer does not generate or amplify a signal. It channels and re-directs an incoming signal and often modifies the modulation by stretching or compressing the pulse train. Basically it's a fancy antenna.

    What you are describing is an active jammer with instant-on capability. (Note that as far as the FCC is concerned, both are illegal.)



    Everything we're discussing - passive interference of radio control signals, active interference of radio control signals or GPS signals, and the use of a directed energy weapon to disable a drone... *ALL* of these things are illegal in the USA. Yes, the military is researching the subject and developing new systems. But you and I are not the military. It is most definitely a *federal* crime!



    Let's ignore for a moment that "flooding the airwaves with noise" is *already* quite illegal all by itself. The FCC has specifically ruled on the subject of passive devices that intentionally create harmful interference with incident radio signals. The actual ruling is rather lengthy and dry, but here is the relevant text: "...operation of an intentional, unintentional, or incidental radiator is subject to the condition that it may not cause harmful interference."

    Adam

    https://transition.fcc.gov/Daily_Rel...C-97-404A1.pdf
    https://www.fcc.gov/general/jammer-enforcement

    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.

    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.

    The challenge I was having with jamming was dsp design that would take directly high frequency inputs without complex mixing. 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. 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.

    Out here in no mans land no one cares what you do so long as you are not committing sexual assault or domestic violence. I could build a particle accelerator and start producing plutonium and no one would care. Of course what do you produce the mile long linear proton accelerator out of that wont break the bank (recycled booze bottles lol).

    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. I will send you a PM.

    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.

  10. #20
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    Quote Originally Posted by VDX View Post
    ... and not to forget - EMP-"canons"

    AFAIK the police owns "handsome" portable EMP generators which can stop a car in a distance of some Kilometers by overpowering/wrecking all the internal electronics with a single directed/focussed microwave-flash ...

    Viktor
    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. EMP's are cool but a real emp requires explosives and a massive AC power supply and I don't like messing with explosives.

    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.

    These also dont work on older vehicals. I also will never understand why newer cars dont use the same systems as airplanes for fuel injection systems. My plane uses a gear driven pump off the main crank shaft and the injection lines are hydraulicly ballanced and the mixture is controlled by the pilot. There are no chips or computers. In fact the only thing electrical is the mags which are built like a brick shit house and the starter which is the biggest head ach lol.

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