[0:07]Hi. A couple of years ago, we did a video where I constructed a high-powered microwave generator. And then we tested it against various materials to see what the effect of the microwave radiation would be. We then followed up with a couple of additional videos where we showed how to detect that microwave radiation, and then how to protect yourself, your person from the effects of the microwaves. If you're interested in that topic, you might want to take a look back at those videos because I think they're pretty interesting. Today, I've gone ahead and I've reconstructed another microwave transmitter generator, more powerful than the first one and for a completely different purpose. Now Alex and I follow global events pretty closely, and specifically, we've been following the war in Ukraine. Now we each have our own opinions about the issues on either side of that conflict, but that's not the topic for this video. We're going to be looking at the technology of the fight. Now for the most part, both sides have fought this battle with conventional or legacy weapons, artillery, infantry, aircraft. But all along, there has been a role for UAVs, unmanned aerial vehicles, drones. You take them out and you outfit them with visible, infrared, multispectral cameras, chemical sensors. Then you loft them up above the battlefield to take a look at what the other guys are doing, where they are. And one of the advantages of this is the operator, the person controlling it, is not located with the vehicle, they're at a safe distance, so it protects them. All along, there has been a slow improvement in the performance of these drones, the motors, the batteries, the hardware, the algorithms. And much more recently, there's been a utilization of these UAVs to directly deliver weapons onto the heads of the enemy. But the real evolution has occurred because of the explosion in the development of commercial and consumer level drones from manufacturers all around the world. This has substantially increased the availability of these devices as well as substantially decreased the cost. And that enters a new component to the equation, quantity. You see, even though these units are much less capable than their military counterparts, nevertheless, if you took, say, a hundred of them and launched them up above a battlefield, you can hide your valuable drone, your purpose-built drone, in the crowd. In addition to that, even though these things are relatively weak and fragile, if you have a hundred of them, like a swarm of mosquitoes, and most of them don't make it, if one or two of them get through, and they're carrying malaria or yellow fever, you're screwed. Now, one of the limitations of these systems is the very thing that makes it safe for the operator to run them. It has to be run remotely, and it depends on radio frequency communications between the drone and the operator. And so they're vulnerable to jamming. So, I went to my other son, who is a radio expert, and I said, how would you do this? And he said, actually, it's relatively easy. What you need to do is get a hold of a spectrum analyzer. This is sort of like a, uh, radio frequency, uh, version of an oscilloscope that can measure radio frequency energies of the radio frequency, uh, emissions that are surrounding the, the unit. And it can measure the frequency, it can measure the power. And if you get an advanced unit, it's actually able to send that data in real time over to what's called an SDR or software-defined radio, basically a computer-controlled transmitter. That can then look at the peaks and generate a large amplitude signal at those frequencies to overwhelm or wash out the communications between the drone and the controller. And you would then send that signal through to an amplifier to boost it up to give it enough power to do what it needs to do. Now, knowing Paul, it would work. The problem is an advanced spectrum analyzer will set you back about $10,000. And then with the radio controlled transmitter and the amplifier, you're talking about tens of thousands of dollars of investment for a single location, a single node. And so what I decided to do is to approach this a little bit differently. You see, there's an old adage in war that it isn't the guy with the longest spear or the most powerful gun that wins the war. It's the guy with the deepest pocketbook. If I had a $1 weapon that you could reliably stop with a $1,000 defense system, I'm probably still going to win because you're going to run out of money first or you're going to lose support for your endeavor from your population. And so I'm approaching this from a garage mechanic point of view. How simple, how cheap could we build something that is effective? So I started a search. I started looking around the warehouse here in the shop for different components. I got an old power strip from our computer system. I picked up a switch from Home Depot, a little power pack from Harbor Freight.
[5:58]And even a little light bulb from an old broken power supply. And while I was doing this, I had a flashback to the old movie ET. And it's an interesting scene because this extraterrestrial, a little extraterrestrial was trying to reach his people to rescue him, he was stranded on earth. And so he starts wandering around and scrunching around through a little suburban home, picking up what looks like junk, an old radio player and a, a piece of aluminum foil and a coat hanger and things that we would consider to be trash. But unlike the human beings, which have a limited understanding of the technology, his greater understanding of the technology allowed him to see in this junk, capabilities that could be repurposed for his application. And hopefully, I don't ruin the story for you, but he was rescued. So, I was having a ball while I was picking up all of this stuff. And probably the only thing here that's really pretty expensive is the mount. This is a telescope mount that I, uh, removed our telescope from and placed the transmitter on, simply because it makes it easier for us to do the video and produce the, the content here. But the demand for accuracy and precision with this system is quite low. You could easily mount this on a simple tripod and just control it by hand. Now, one of the things that you'll see on here is this plastic heavy-walled container around all of the electrical components. And that is going to induce me to put on my Karen hat. This is not a toy. This is quite dangerous. As you can tell, we're doing this inside. One and a half kilowatts of microwave radiation spread out into the open environment outside of this building is potentially dangerous. It's also illegal. So we're doing this inside of a completely steel-sided building, well grounded, that acts like a Faraday cage to trap the radiation inside. So effectively, I've built a really big microwave oven that Alex and I are standing in right now. Now, before you think, oh, wow, they're taking another, you know, hit for the team, it's not as much of a concern as you might think because the internal volume from, uh, in this warehouse is about 100,000 times greater than a typical microwave oven. And so, as a result, the intensity is quite low, and we measured that. We picked up one of these little detectors, you can get them online or on Amazon. It costs about $25 and they're used to examine microwave ovens commercially or at home to see if they have any kind of leakage. And after measuring this, you can detect radiation where I'm standing or where Alex is, but it's quite low. It's it's not very high. Now, the other thing about this box, this is clear so you can see the internal components, but it is an insulator. Inside of this box are some electronic components and one of them is a transformer that's changes line voltage to about 2,500 volts and when this thing is energized at a couple of amps, this is very dangerous. If you were to touch the wrong part in here when this is energized, you could literally blow the tip of your finger off. And if you're lucky, it'll hurt like hell because there's also a good chance this will instantly kill you. So, this is not a toy, this is not to be played around with, you got to be careful when you're dealing with this. So, Karen hat off. Now, the internal components here were obtained from a microwave oven, and this cost me less than a penny. I went to the local dump and I picked up three old microwave ovens. Despite the scratches and the dents and one of them had a little bit of a odor to it, nevertheless, they all worked. And so I picked out the most powerful and then I repurposed all of the components and put them in here, rebuilt them in this housing. And you don't need plans or a schematic for that because the oven itself is the schematic. You just take your time when you're taking things apart, so you know how to reassemble them. Now, the heart of what's going on in here is accomplished, the main function by what's called a cavity magnetron tube. Now, if you go on YouTube and you do research on these tubes, you'll find there's lots of different videos that explain the history, the, the development, the purpose, the way they operate. You can get a lot of details about them, and I'm not going to spend 10 or 15 minutes reviewing that in this video, but I'll give you just a real quick oversight. Inside the cavity magnetron is a small wire filament that becomes red hot. And when it does so, it evaporates off or boils off thermal electrons, negatively charged particles. Under the high voltage that's created, those electrons accelerate away from the filament. And whenever a charged particle is accelerated, it produces electromagnetic radiation. On either side of that tube are two permanent magnets that create a magnetic field between them. So as the electrons rocket away from the filament, the magnetic field causes them to begin to spiral and form a circular pathway. And because they're constantly changing direction, they're being accelerated, and as a result, produce a continuous flow of microwave radiation. This is sometimes called cyclotron radiation, or in the largest accelerators around the world, synchrotron radiation. It's actually a useful feature that can be used for research, but it also limits the capabilities of those accelerators. Because as they try to push those particles to higher and higher velocities, they're producing more and more electromagnetic radiation that is taking away energy from the particles. So they constantly have to feed electric power into the grid. So, it's a limitation, for us, it's the purpose. Now, the microwaves that come out of here are being directed this way. In a typical oven, you want them to distribute evenly through the oven to heat your food and not have any hot spots. But we want the energy not to be localized right in front of the magnetron, we want it to be way down range. Microwaves are kind of interesting. If you have radio waves, like AM radio waves, microwaves, light, they are all exactly the same thing, they're electromagnetic radiation. Nothing more, nothing less. The only difference between them is the wavelength. For example, in in AM radio, the wavelengths can be so long that it can be a kilometer between the different peaks or the individual peaks. Light on the other hand, has a wavelength that's 1/2,000th of a millimeter, enormously shorter. And microwaves lie in between, in the centimeter range. Now, my background in lasers and optics makes an intuitive understanding of the propagation and the directionality of low frequency radio waves difficult to get my head around. I always think of it as kind of strange, almost a little bit like magic. Microwaves are a little bit easier to sort of visualize. They can be absorbed, they can refract through a material, at an edge they can diffract, and as we're using this reflector to do, they can be reflected. The only requirement for this reflection is that the material that's used has to be electrically conductive. If it's electrically conductive, it will be microwave reflective. So, to try to get the energy as far down range as possible, we're using what's called a horn antenna. And these come in a variety of different shapes and sizes. You can get them that they look like a radar dish or a solar cooker, round or hemispherical. They can also look like the bell nozzle in a rocket engine, sort of curving, and they can be rectilinear like this. They don't even have to be symmetrical, they can be narrow in one direction, fat in another direction, depending on how you want the energy to propagate. In our case, it's symmetrical. Now, one of the interesting limitations of these systems is that they not only direct the energy, but they also act as a coupling interface to get the energy out of the magnetron and into free space. If they have a very broad angle like this, they will couple very efficiently, very little of the energy gets reflected back into the tube to create more heating and less less output, but the energy will be dispersed very, very quickly, and so you don't get much range. If they're very narrow, you get great directionality but low coupling efficiency. Turns out there's a sweet spot at around 15 to 18° half-angle, or 30 to 36° included angle, that gives you really good coupling and really good directionality. This is 30° in full angle. Now, the other component is length, how long do you make it? For a given angle, the longer or the shorter will have no effect on coupling, but it will on directionality, the longer you make it, the more directional it is. The only downside to that is it becomes bulkier and heavier. When we tested the system originally with its small brother, it worked, but the the distance or the range was more limited, so we went bigger. And you can go as big as you want, but ultimately, it's going to become too bulky and difficult to move. We used aluminum, and I'd highly recommend that. It's electrically conductive, so it reflects, but it's also easy to machine, inexpensive and lightweight. To fabricate this, all we did was cut some triangular pieces out of aluminum sheet, then we cut the top off or truncated it so that we could weld this down to a plate that allows us to couple it to the cavity magnetron. Then we lined up the corners and just put some welds in here along here to get everything to be stable and strong. Now, if you're not a welder or you don't have the equipment to weld, another alternative would be to simply get some of this L-shaped aluminum extrusion, drill some holes in it, you can place this along the edges like this and just rivet it down, it'll work just as well. Finally, microwaves are invisible. So, to know where you're pointing, I added a laser pointer as a guide. Now, I scrounged this from one of our early DJ, uh, entertainment lasers, uh, when we were building these things, that was actually the beginning of this channel about a decade ago. This is a nice one. It's 1 watt, green, and produces a nice green beam that you can see over there is very bright and visible inside of a lit warehouse. It's also visible outdoors in daylight, and at night you can actually see the beam as it's traversing across the atmosphere. It's it's kind of pretty. Now, mounting this thing, it has to obviously get the beam past the antenna. And I could have put this on a large arm to get it cantilevered out here to get past there. But that makes this a little vulnerable, maybe a little shaky. And it also introduces some parallax issues because you're not coming from the same source. So, simple solution. I mounted this directly on the plastic box, aligned it carefully, and then turned it on and saw where it was hitting the antenna. Then I simply drilled a 1 centimeter hole in here allows it to get through. An interesting thing about electromagnetic radiation is that once the aperture or an opening that you're trying to get the radiation through, equals the wavelength of the light that you're using. In this case, 12.5 centimeter radiation. You begin to get attenuation of the light through that hole or the radiation through that hole. When you get down to about 10% of the wavelength, it's negligible. Very, very little of the electromagnetic radiation, the microwaves in here can get back out at us through this hole. It's another reason why the intermittent welds are perfectly acceptable from the microwaves point of view, it is leak free and perfectly tight.
[21:21]So, the question, does it work?
[21:29]All right, this is all set. I'm going to go ahead and grab a drone here.
[21:44]I need to put it on the ground first, but it will probably work, right? Okay, like that.
[22:07]And now it's off, right? You get to see it. Yeah.
[22:18]Now, there's an interesting thing about this that I was pretty surprised about. If these things aren't damaged with the fall, watch what happens here.
[22:30]See, it's still working. You can go ahead and land that.
[22:40]The interesting thing is that this thing will shut them down, but it doesn't fry them, it doesn't destroy them. So theoretically, if somebody was flying a drone with something on it or whatever, and you take it out, it's now yours. And the fact is, it's kind of fascinating because the controller has no means to indicate to this to turn itself off. You have to directly hit a switch. So there's no way that just flooding this room with microwave radiation, would have accomplished that simply because you would have just lost control, and this thing would have sort of flown off to the side, hit the box where it's friends or its big brother is, and it would just sit there and buzz and and were and buzz it'd be on but uncontrolled. That's not what happens. This thing shuts them down. Now, I think what's happening is that inside of here is a PCB with a bunch of electronic components and microcontrollers in it. There are also wires to the motors, wires to the battery, and all of those wires act as antenna. And they can pick up the microwave radiation and convert it to voltage spikes, which are sending signals in there that it doesn't understand, it can't figure them out, it confuses it and the whole thing just shuts down. The reason I think that's important is because number one, that's why this will work on drones that are communicating on a frequency that isn't the same as this frequency of 2.5 MHz, GHz. Let me show you.
[24:34]Oh, that's quick.
[24:38]It works. All right, let's try something a little bit different.
[25:01]It's a little bit tougher to fly, isn't it? Yes.
[25:27]Okay, turn on the microwave in 3, 2, 1, It works.
[25:42]It took a little bit longer but it's still, yeah. Well, the reason is that that is actually operating at a different frequency. That's set 1.6 or 1.3 GHz. So, that means that this thing should be usable for a variety of different drone frequencies. You can't run it at something other than 2.5 and get away with it, it will still knock them out of the water, which is kind of a neat feature. Because not only do you destroy them, but you don't have to be selective, you don't need the spectrum analyzer and have to do a lot of very fine tuning, you just basically send them voltage spikes and it turns them off, which is kind of cool. Now, I was really pleased with this. We were experimenting with this, this cost almost nothing, it was super easy to build, and it is clearly very effective. It will also work at a much longer distance than we're demonstrating it, although I'm not going to, uh, tell you how I know that. Now, when we finished this, we went to dinner, uh, a couple of weeks ago with Chris. You might remember him as the co-host to the video that we did a couple months ago on the laser-based drone killer. And we explained what we're doing and how it worked, and he was disappointingly unimpressed. He was like, yeah, that sounds kind of interesting, it's pretty good, but I think the future is not going to find many drones vulnerable to this kind of approach. And we were both kind of looking at each other, and he said, have you ever heard of fiber drones or fiber optic drones? And neither of us had. And my first thought was, oh, he's talking about these hybrid optoelectronic circuits that include lasers and detectors along with the microprocessors, that are used in some high-end electronics and computer equipment because of the very high communication speeds available by harvesting light as well as electromagnetic, uh, signals through the wires. And he said, no, no, it's nothing that complicated. I'm talking about literally fiber optic coupled drones.
[28:25]You see, in large data centers and server farms where they have huge numbers of computers that have to interconnect at terabyte per second kind of communication rates, they've moved to optical interconnects. And so there's been a rapid development and improvement in these small little transceivers that can be placed on either end of a fiber optic hair-thin fiber, and can communicate at very, very high data rates. They're also very lightweight, and because they're made in large quantities, they're very inexpensive. And so what these clever drone operators have discovered they could do is they entered into the drone itself and they can remove the radio frequency transmitter receivers and replace it with this optical transceiver. The optical transceiver is then coupled to a fiber that is held in a small cylinder, about the size of a can of Coke, that hangs below the drone. And then out of the end of the cylinder is a small pigtail, a little polyethylene tubing that acts as a guide. The other end of the transceiver is in the controller's hands. And so when the drone takes off and begins to fly away, it's literally paying out this fiber behind it. It's leaving the fiber behind across the buildings, over the trees, around rocks and any kinds of debris, and will continue to communicate with the drone at very, very high data rates, far better than the radio frequency. It's completely immune to electromagnetic interference, and by going into the drone to install the transceiver, there's an opportunity to wrap a lot of the components in aluminum tape or aluminum foil that can protect it from this general purpose type of electromagnetic interference. Also, that spool that hangs below the drone can contain up to 30 kilometers of hair-thin fiber. So they can operate at substantially longer range from the controller than you can with the radio frequency systems. The cost of these things is about the same as the cost of the drone. It's about $1,000, and obviously, it's a one-use application, but depending on what you're doing and how much you need that drone to get there, it may be worth the additional cost, but it's not prohibitive. As soon as we heard this, both Alex and I started brainstorming, we're like, okay, how can you get rid of this thing? Do you launch other drones to try to chop the fibers and do all this kind of stuff? We're coming up with a bunch of ideas, and actually Chris had a really good idea. Uh, it's good enough that I'm not going to share it with you here. But personally, I think the best, the most efficacious way to use lasers to remove large numbers of small targets like drones. Most of them just seem to follow the mantra of more power. If it turns out that the method that I've come up with is effective, you're going to see that method for the first time when we redo the laser video. So, we'll see what happens. But I want to thank you very much for watching. This was kind of interesting. Cost me all of about 40 bucks, and it is effective. And if you like what we're doing here, please subscribe. If you have a suggestion or question, put it in the comments below the video because I read them all and I try to address as many questions as I can. And if you like the kind of stuff we're doing here, help to support the channel, the best way to do it is through Patreon. And we're going to be also providing some additional content on Patreon as a thank you to the people that have contributed and helped to support the channel. So, stay safe, but have fun, and we'll see you soon.
