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Open-Source Passive Radar Taken Down For Regulatory Reasons – Hackaday

Open-source technology brings a world that laws and regulations are not quite prepared for. As a result, every now and then, open projects need to work around governmental regulations. In today’s news, KrakenRF team has stumbled into an arms-trafficing legal roadblock for their KrakenSDR-based passive radar code, and is currently figuring it out. There’s no indication that there’s been any legal action from the USA government – the team’s being proactive, as fas as we’re told.
KrakenSDR hardware, to simplify it a lot, is five RTL-SDRs on one PCB – with plenty of work put in to do it the right way. It gets you much further than a few dongles – there’s shielded case, suitable connectors, reliable power distribution, a proper USB hub, and importantly, receiver synchronization hardware. Naturally, there’s nice things you can build with such a hefty package – one of them is passive radar, which was a prominent selling point on both KrakenSDR’s pre-launch page back in 2021, and on their crowdfunding page just a week ago. How does that work?
There’s RF emissions floating around you in the air, unless you’re at sea or in the desert. Whether it’s airplane transponders, cell towers, or a crappy switch-mode PSU, the radiowaves emitted interact with objects all around you. If you have multiple receivers with directional antennas, you can catch waves being reflected from some object, compare the wave reflected wave to the wave received from the initial source, and determine the object’s properties like location and speed. If you’d like to know more, IEEE Spectrum has covered this topic just a week ago, and the previously-deleted KrakenSDR wiki page has more details for you to learn from.
Through exposure in IEEE Spectrum, the KrakenSDR work has received plenty of attention and comments. And this is where the International Traffic in Arms Regulations (ITAR) laws come in. We’re not lawyers, but it does look like passive radar is on the list. Today, the code repository and the documentation pages are scrubbed clean while the team is talking to legal experts.
Dealing with this is intimidating, and we wish them luck in clearing this with legal. In the bad old days, certain encryption algorithms were famously in scope, which appeared absolutely ridiculous to us at the time. The laws did eventually change to better reflect reality, but the wheels of justice turn slowly.
Of course! Why not? Especially if used to detect something some imbeciles want us to believe doesn’t exist that’s illegal (whether device(s) and/or act(s) using device(s)) and/or not to be classified per Executive Orders covering national classified information:
Executive Order 10290 (September 24, 1951; Harry S. Truman)
Executive Order 10501 (November 5, 1953; Dwight D. Eisenhower)
Executive Order 11652 (March 8, 1972; Richard Nixon)
Executive Order 12065 (June 28, 1978; Jimmy Carter)
Executive Order 12356 (April 2, 1982; Ronald Reagan)
Executive Order 12958 (April 17, 1995; Bill Clinton)
Executive Order 13292 (March 21, 2003; George W. Bush)
Executive Order 13526 (December 29, 2009; Barack Obama)
OK, hope that wasn’t a tangent and is unrelated. Still… ITAR, what? I bet some want people to believe passive radar doesn’t exist so they can justify more signals to traffic with.
I’m not sure that train of thought has a caboose but the idea of ITAR is not to give away capabilities we have, lest they be used against us. Usually there’s a specification so that companies can’t sell things above a frequency, or power level, or accuracy, or something. Since everybody knows that passive/bistatic/multistatic radar is possible, there’s probably a restriction against the particular algorithm that pulls targets out of that stream of bits.
Hmm. You mean like leaving hundreds of billions of dollars worth of US weapons and defense equipment in the hands of ISIS??
More like allowing some young and rebellious maximalists to track and happily publish online stuff that they are better not to track and publish… Because otherwise they’ll make some russian and chinese dipshits happy. And let me assume that nobody wants it here.
However, I think that such a technology should be allowed, at least for scientific reasons.
Any and all listening technology should be allowed. Any detectors, any instrumentation, any sensors including high-precision machining measurements, and even any and all kinds of machining itself.
Science or application, only bureaucrats make these differences. After WW2, a lot of decommissioned radar sets were recruited for scientific research. SOSUS array data are handy for marine biologists. The devices do not care. They just do their job.
Everything is dual-use. Every weapon can be a tool and every tool can become a weapon. Doesn’t matter if it is a radar or a hammer. Or a knife.
Math is speech.
Physics is speech.
Code is speech.
Math should be free for all, whether it is cryptography or signal processing. We can make it so. The bureaucrats have only their respective countries and geopolitical blocs. We keep forgetting the West is less than a half of everything. Each treaty has a range of countries that did not sign. This can be leveraged.
This idea that something is allowed is ridiculous on it’s face. The government works for us, they are not our parents, they are our employees. If Math posses a threat then it does and strategies need to change. We’re a nuclear power with multiple dead man switch’s what the hell threat could we possibly face that would require the limitation of technology? The entire TS/SCI system is dumb. It just creates containers that adversaries can target and always fail. We should have scrapped that archaic myopic strategy decades ago and moved to true information operations and flat communications within the dod. If China could track EVERYTHING we were doing in real time but information and intelligence flowed in real time through Gmail do you know what would happen? Nothing but us operations would be slightly faster, and china would be overwhelmed in processing and acting in the info. Add to that competent information ops that bled false info in with the real and we’d be ten fold better then we are now banning math. GSM exploitation, a 15 year old trick based on math and an openly published standard that EVERYONE knows we do is still classified as top secret!!!!???.
As someone who has had to deal with ITAR on a couple of occasions, I agree that it seems, at face value, to be excessive regulation, perhaps even violating free speech. The reality is, it does not prevent the use of even selling of the technology to other US entities. In fact it doesn’t really prevent anything.
It’s more of a CYA list. You don’t have to check ITAR, however if the government finds out your exporting something covered, you better be prepared for federal pound-me-in-ihe-ass-prison.
Seriously though, they are smart to take this step, but I doubt the government would care if they hadn’t. There is nothing in their product that couldn’t be relatively easily replicated using public domain information. Of course proving that if/when the government comes after you wouldn’t be fun, so CYA.
Useful idiots is the generous take, but it would be trivial for a motivated foreign power to set this up themselves without this open source project. So without that defense the only remaining reason would be for domestic control.
No. That’s not what he means. Its so “greedy bastards” don’t sell our best technology to our enemies, “true believers” don’t steal our best technology for our enemies, and “useful idiots” don’t give it away to our enemies.
Which category do tou fall into?
The one that disagrees with enemies.. and before you got in some high horse I fought, bled and lost friends in Iraq to genuinely see that country stabilized and free then watched the soldiers and police I trained and helped, three years of my life, friends lives thrown away because our ‘alies’ were no longer our allies. Is iran our enemy? Cause the admin that abandoned our ‘alies’ didn’t think so and sent them pallets of cash.. technology matters and should be made readily available at all times. Miss use it, and charge the person for the misuse. I can do a shot ton of damage with a computer, should computers be banned? Your take is naive and sad .
Good thing we did no such tjing
“Good thing we did no such thing”
What thing are you referring to?
@Teh stig – It’s so sad to see the brain dead red propaganda even here on a technical site like HaD. Shame on you. Go look for real information on the broken and outdated stuff that was left behind.
Good thing we didn’t leave ISIS hundreds of billions worth of hardware… We didn’t leave them anything. Iraqi troops retreated and left a bunch of vehicles behind that they’ve been using. Anywho, I’m guessing you don’t know the difference between ISIS and the Taliban… As far as the Taliban goes, we did leave dozens of unarmored land vehicles and more than a few helicopters behind… But we trashed ’em all. The only way those choppers will ever get airborne again is if they throw one off a cliff.
Could you try and at least thinly veil your political moaning with something that has to do with the article, the ongoing discussion here, or even like just any technology related subject in general?
I think ITAR gives away a bunch of capabilities we have by listing them in such a way to prohibit them.
concur. To me there is a lack of continuity in the drawing of ITAR lines. When I worked at a major supplier of space-based imaging satellites back in the early 2000’s I was appalled that our government would permit Google to openly publish space imagery of nearly any place in the world; talk about access to technology that can be used against us. People will still figure out how to access passive radar. Attacking KrakenSDR seems a little harsh. In my opinion, KrakenSDR’s passive radar is a toy for exploring and energizing young people in the field of electronics and Ham Radio. Let them play and learn.
Yikes, I’d definitely be getting a visit from the Space Force for trying this out.
Well that sucks. I bought one and now I can’t use it.
Who would ever know?
You can still use it for radio direction-finding of an active transmitter. Only the passive radar code was taken down. But there are still recent forks floating around the Internet, among other resources that they either forgot about or can’t take down.
That’s true. I think I might have a git pull somewhere.
then make it available on i2p if you can
-> https://geti2p.net/en/ (torrent tracker http://tracker2.postman.i2p/)
or maybe on the/a i2p git(lab) service/server
I2P: http://git.idk.i2p
Visible: https://i2pgit.org
Alternate Addresses
.b32.i2p : 7qeve4v2chmjdqlwpa3vl7aojf3nodbku7vepnjwrsxljzqipz6a.b32.i2p
.onion : 47ggr2fa3vnwfyhvgskzdmr3i32eijwymxohtxsls45dulmriwxszjad.onion
I hope you realize that you asking the guy to commit an illegal act. If the code is covered by ITAR or by the Wassenaar agreements, the moment the government catches wind of this he is going to be in a lot of legal trouble so that you can have fun …
@jan ciger:
You do relaize not everyone lives in the US, right?
also this is clearly a case of trying to put back the genie in the bottle… there’s plenty of university around the world that have toyed around passive radar, including some see through the wall applications…
ITAR is a real PITA. I sold something on ebay and someone overseas bid and won. I for some reason decided to double check itar and low and behold it was on it. I told him what was up and he got angry so I messaged ebay. They zapped it instantly and returned my fees and his money. Even ebay fears ITAR.
Can’t stop the signal, Mal.
Yep, there’s forks floating around, and *I think* you can also just revert deletion commits from the official repo? otherwise, yeah, earlier forks will help.
Of course you can still use it! All you have to do is find a copy of the software. The authors took their original repo down, but there are still forks of the original package floating around Github.
The only possible restriction (and that hasn’t been ordered by any government official yet) is that the software not be exported. But even if someone decides ITAR is in full force, there’s no restriction on running it. Just don’t carry it over a border.
You can also get in ITAR trouble for handling it to a foreign national within US borders. It’s still considered exporting.
The original work and the original library it is based on “pyAPRiL” are not even of USA origin, they are by a Hungarian developer who’s at a Hungarian university in Budapest.
Which implies that the US considers it “business as usual” in applying its laws to the product of foreign nationals. Has nobody in the US ever heard of that piece of prevert deviant propaganda generally called the US Declaration of Independence, where applying one nation’s laws to the citizens of another without their consent, is generally frowned upon? Or a little war, 1812-1815, fought because one nation did precisely that, to the citizens of another nation.
You can use it. Are you in the US? You wouldn’t even be violating arms export treaties in that case. Even if you aren’t… who cares. It’s an rx only device
Lol it looks like you’re saying you need a prescription for it.
This is way too far for proactive work, no one is going to care about such a weak-specced device (no offense) under arms regulations. This is basically commodity hardware anyway. Just makes me think of yak-shaving.
Maybe a certain country invading superpower can use it.
Nah. US Army has those things for at least 40 years.
So true.. but we invade for sacred, holy “our democracy” dontcha know
ITAR is not something you want to mess with. Ask Boeing or ITT. These are the exceptions. The government likes to make examples of the little guys first.
It is not yak-shaving. That something is commodity hardware doesn’t mean you can’t cause a lot of damage with it. See the news about Russia buying washing machines to scavenge chips for their tanks and missiles out of or how PS3s were ITAR restricted because they were used as a cheap supercomputer to process data from US airforce drones for a while.
Nobody has mentioned it but passive radar is one of the technologies that is capable of defeating the stealth capabilities of modern fighter jets. Stealth often works by simply reflecting the incoming radar signal away from the radar receiver, so it can’t “hear” the echo.
However, if you are using “environmental” signals *not* aligned with your receiver direction, then some are likely to get reflected towards your antenna. That’s how the Czech Vera system works.
This SDR dongle device certainly does not have the same capabilities as that military radar system but it also doesn’t costs many millions and is easily transportable. Having free code that is working and capable of detecting aircraft using low cost, off the shelf hardware without emitting any detectable signal (unlike a conventional radar) could give someone a pretty significant R&D boost – or maybe even a military capability they don’t have yet.
There are some rather good reasons why ITAR and Wassenaar agreements exist, even though they bring insane bureaucracy and trouble to “mere mortals” – e.g. I had Digikey refuse to sell me some PIC microcontrollers unless I filled several pages of ITAR-related forms (and Mouser having no issues selling me that even without), former colleague who has acquired some surplus hardware and was looking for documentation got some rather scary interactions with the military secret service because it turned out that this gadget was also used by the French Exocet anti-ship missile.
Trust me, this isn’t one you want to be pooh-poohing out of ignorance …
Seeing someone on a website dedicated to hardware hacking actually believing the crap about scavanging chips from washing machines for military use makes me sad. As if they could not buy plenty of much more powerful chips directly from their neighbour and somewhat ally China. Even though a modern washing machine has plenty of computing power so has any cheap smartphone which would be way cheaper and also readily available.
The washing machine chip scavenging sounds fairly possible to me. Particularly if it was as a source for replacing chips in an existing design. Micros for washing machines will handle a lot of io. Cell phone systems are highly integrated, but for handling very different tasks.
With the chip shortage from covid pandemic issues still not really abated and now made worse by Russia’s invasion causing even more supply disruptions I’d not be at all surprised to find what they need they can’t get except as recycling from a device with them in. Lots of chips are damn nearly impossible to get at the moment, even for the big consumers.
And if you are banging through your stockpile of rockets, their warheads and tankrounds at such a rate, not to mention loosing the launching vehicles as well… You will need a huge quantity of all sorts of silicon chips they don’t make for themselves. And it need not be the really ‘smart’ general purpose compute ones you are short on – Maybe its a specific I2C or SPI device, a sensor or multiplexer etc – and non-direct substitutions are not a good idea or easy to deal with their use on the front line, it makes supply chains more complex, failures more likely etc.
Probably because they read about it here.
You guys think the Russians are idiots?
I’m not an engineering I have a lifetime of experience a and the idea that a super power capable of manned space flight uses reclaimed, used consumer grade chips on their tanks ( of all things) is…..fuck!
What are you stopped? Or just so caught up in politics you can’t smell bullshit anymore.
Hey if anybody can produce a list of chips used by both the ap
pliance and tank manufacturers, I’d love to see it.
That was first to come to mind when talking about passive radar – Tamara and Vera projects. Fun fact, these SDR contraptions is not that by far.
Tamara and Vera has 2 main very important components these things don’t have – Software and very special type of receiving antenna. What is so special about their antenna (besides it is the most secretive part of both projects) – it is wide band, yet their LNAs on the input are VERY low noise.
And the software? The positioning and tracking algorithms are not that specia. What is very special is signatures of targets. If you want to track something like stealth fighter jet, you first need to know it’s RF signature and getting that is VERY HARD.
At least the USA is not claiming that Intel CPUs are military grade as they can be used as such and therefore restricted – claiming that this thing is some secret military whatever is BS. But US departments of whatever can still do that doh.
You don’t look for the signature of a jet. This is passive: you map your local signal.
If, for example, you are using a noisy power supply as source, you monitor that. Get a good sample, then crack open your DSP books at the section on “correlation” to detect reflections (cat on roof, tree leaves in the wind, jets).
I suspect the limiting factor is range. Detecting weak signals is HARD and passive radars don’t have a big source signal to help.
Wouldn’t you want to pattern changes in local signals as targets to discriminate?
I know life got strange, with more than smearing, after I published my target material discriminator work (and very vaguely since more a trade journal) in American Laboratory October 2008 edition.
That’s what led me to focus more on recovering from the “Health Attacks” and hard core (ideally hard stop) advocacy work to remind the officials and public what’s not classified and readily available info not only clear enough in patents.
Thanks to the CBS News 60 Minutes, “The Minds of Men,” et.al. teams really documenting the history of some of the work and when news wasn’t so fake where the last efforts by Dr. Jose Delgado demonstrated clearly his intent on, and already, being able to completely wireless body and mind control without implants or contrasting agents. Plus demonstrating the LIDA and other mind reading devices.
Target electrophysiological signals discriminating must be something else… especially ideally only using background emissions and subtracting those out.
I agree that ITAR should be respected and I agree that low-cost projects can be tremendously effective, but this project is one step above an example out of a textbook. Whether they implement passive radar in software, gateware, or hardware makes no difference from where I’m sitting; the biggest limiting cost for passive radar isn’t the brains, it’s the hardware. Not the frontend or the DSP, but the antennas. It’s easy to make an inaccurate radar, making a useful one requires design for circumstances.
Who? What nation would get a boost from passive radar? What nation on earth doesn’t have an rf engineer? This isn’t Rickey science, it’s been known and done for 30 years! All forms of classification and this argument is made by those who simply don’t understand the math and science behind it. This is why the us government STILL considers GSM exploitation TS! GSM was exploited by the chaos computing club in the early 2000’s, and there work was replicatable from them on to anyone who cod afford the hardware and read. Hell in 2006 Al-Qaeda was already swapping sims all the time to try to avoid it..in 2006 THEY NEW AND ITS 2022 AND ITS STILL CLASSIFIED AS TOP SECRET!? You have no argument, just ignorance and the government most certainly agrees with you but who believes in the government being good anymore?
Passive radar can’t guide missiles – illumination is sort of a pointer, “smash this”. So, I guess, stealth airplanes would tease anti-air observers having passive radars, but they would still be untargetable. Not so much “stealthy” any more, but still “slippery”.
Another passive and very underestimated method is infrasound. With dense enough mesh of sensors we can hear disturbances flying through the air. With subsonic disturbances we do not know about them much in advance, but we can hear when they passed, and triangulate, giving advanced warning. Then the adversary either flies high and gets exposed to radars, or flies low and is well-heard.
Kind of like atmospheric variant of SOSUS.
Can be also handy for civilian weather research/monitoring, maybe otherwise undetectable clear-air turbulences can be heard.
Using more like an array of SODAR sensors or like the InfraSonics Network?
Talking about itar, Chinese company started manufacturing and selling ~$300 _25hz_ 256×192 microbolometers. Look up INFIRAY T2S+. STS Telecom “Infiray T2S+ Thermal Camera Review”:

The plane at the end o.O
From my reading of the munitions list, it’s explicit about passive radar equipment that has greater than 125 kHz & a center frequency lower than 2 GHz.
KrakenSDR notes that the SDR has a maximum supported frequency of 1.766 GHz, and a bandwidth of 2.56 MHz, so it seems to fit solidly in that description, unfortunately. In spite of not having an active transmitter, which I would have thought would be the reason it for the exclusion of a radar from the list.
If this was an American product, it would depend on the pixel size, frame rate and resolution to determine whether the company is allowed to export it outside US.
There are American companies that started development of thermal sensors in the EU to get around this commercial restriction.
The American government is shooting in their own foot with this ITAR legislation. The countries that want the technology will always find a way and it hurts American export.
Exactly. Even a cheap cellphone will be perfectly acceptable for most drones at the battlefield. And US is by far not the major producer of cellphones… The horse has left the barn decades ago.
“The American government is shooting in their own foot with this ITAR legislation. The countries that want the technology will always find a way and it hurts American export.”
Export American nukes to Iran. Help America with it’s export problem.
We sold WMD to Iraq, then invaded them because they had WMD and the whole Kuwait thing started to mess with our oil supplies. So I would not be so nonchalant on the US Govt actually selling a nuke to Iran.
Specifically $48 million sold to Iraq for “protection of the head of state”, on top of the $1.5 billion in dual-use (items that have both civilian and military uses).
Unironically yes give Iran nukes
It’s super annoying that even those of us living in the US have been stuck with gimped thermal tech until now because of ITAR. I wish I had this thing instead of a flir camera.
FLIR is very handy.
Are FLIR ITAR restricted ?
80 × 60 @ 7.8 fps (FLIR) ~€206 including VAT (AMAZONdotDE: FLIR ONE)
160 × 120 @ 7.8 fps (FLIR) ~€540 including VAT (FLIRdotEU: FLIR ONE Pro)
256×192 @ 25 fps (InfiRay) ~€330 including VAT (AMAZONdotDE: InfiRay P2 Pro)
Yes they are. Take a look at the refresh rates. All US manufactured thermal cameras for export have a refresh of less than 9hz. This is a legal limitation, not technical.
This is an attempt to stuff a genie back in to the bottle.
The attorneys can legislate whatever they want. Unless they get cooperation from the public, it’s just words in a book. My guess is that most people who were going to do this will actually be emboldened by this stupidity. Congratulations. They’ve just created a new underground movement.
This is a replay of the open source encryption harassment debacle. The only shame of all this is that the fools who persecute people for practicing technology never seem to get punished. This is a corrosive thing to do to a society that tries to encourage people to get in to STEM subjects. They are literally prosecuting people for harmless technical endeavors.
This is the act of a dying civilization.
True. And about as effective as church banning Heliocentrism in 16th century.
Even Kimmy who has been sanctioned to hell and back has ICBMs now.
You can buy anything for a little extra.
It is dying, and as you say the acts of a dying civ get quite capricious and ugly. But these things take centuries to die, so buckle up
code is speech
Too bad rights are completely made-up
Many the hill commenters die upon.
Watch out Lady Adafruit, they’re coming for you next.
The comments here seem a bit lean on links. Is there secret censorship going on? I am concerned. Of course HaD may feel there is legal liability for linking, but if there’s censorship going on, it should be in the daylight (“this post was removed because $reason”) not secret…
No censorship, just that nobody posted anything. If links is what you want, here’s a HackerNews page with plenty.
Thanks, that’s reassuring to know.
Trying to keep this tech out of the hands of foreign governments is silly, because they’ve had better stuff for decades. Think about other actors like drug cartels and loonies hiding in caves.
I guess I’ll just leave this here https://github.com/yuvadm/krakensdr_pr
I worked for Lockheed Martin and heard Second-hand a decade ago this exact idea was tested and worked… Worked too well as something was found that was not on radar and when the program made calls trying to figure out what it was the program was summarily canceled and details buried. Take it for what it’s worth but its conceivable something that took a defense Contractor to do a decade ago is now in the realm of knowledgeable hackers
lol creepy. I wonder how many of those the kraken folks picked up. I bet they turned it on, saw 300 glow-in-the-dark birds, then decided nope nope nope let’s delete everything before somebody from the X-Files shows up at our door and melts us. Now I kinda want one
That would be a cool story if only it didn’t take me 5 minutes to google academic papers from 2012 describing a passive radar made with multiple USRPs by knowledgeable hackers. Not to mention that the project described here didn’t pop out yesterday, it’s been developed in public for years.
A friend once told me:
1. Make a project that uses 1000 Volts, and wierd things happen.
2. Make a project that uses 10000 Volts, and really wierd things happen.
3. Make a project that uses over 1,000,000 Volta, and the Government kicks your door down, confenscates all your stuff, and puts you in jail.
That happend to my friend.
Details? What project? Marx generator? Pulsed power in general? Million volts, that sounds sexy!
There’s an “I hate the antichrist” meme in here somewhere. Also: https://www.amazon.com/Voltage-Generator-Ignition-Transformer-Cigarette/dp/B07KCHNSDJ
What did your friend do? Drop those deets my man
This is a pretty nice little high voltage module. Sadly, far less than the promised megavolt. Given that it will spark over about 20mm between sharp-ish tips, my guesstimate is about 20 kV. (Do not try to get much more, the output cap will flash through.) The spark can be pretty LOUD.
These modules are popular in various kinds of tasers and stun guns. Small and easily concealed. Also handy for ignition of gas/vapors. For lighting up discharge lamps. And all sorts of low-power high(ish)-voltage shenanigans.
I assume that with some kind of feedback control and ballast resistors and so on it could feed lower-power laser tubes. For a while. The modules aren’t built for full-power operation at prolonged times and WILL overheat and typically have no protection. The output voltage and/or current can be easily regulated with input voltage and/or current.
Could also be a fun cheap HV feed for a Marx generator, if you want more. 100 kV should be easy.
When did this happen? (date & time)
Where was the door that was kicked down? (City / State / Country)
Where is the friend now? (still in custody? released? deceased?)
Details matter.
The US Govt doesn’t want anyone to be able to track the UFOs they say don’t exist.
this site needs upvotes
100% This has been the best thread ever!
change name to astronomical radar and go on 😉
I spent the last hour reading at https://www.ecfr.gov/current/title-22/chapter-I/subchapter-M/part-121. Man, o man, there is a *lot* of interesting stuff on that list. Among them are foot-and-mouth disease virus, certain types of specialized eye-protection (sunglasses), a huge list of chemicals and explosives, and lots of radar with specialized characteristics. I think the one in question here is Category IX, “chapter?” C, “paragraph?” xxvii. (No, I don’t know proper names for the sub-headings) Anyway, the list specifically mentions “radar” that makes passive use of commercial TV and radio broadcasts.
The list was obviously made with the help of experts in a number of fields. Also, one might be able to learn what neat-o characteristics of certain kinds of radar are useful for nefarious purposes. The list is very detailed about prohibiting radar if very specific characteristics are “too good”.
It’s fun to get drunk or high and try to figure out how this or that parameter could be achieved or exceeded with home shop class tools and budget. The electronics especially, and the mechanical measurements and machining.
Excellent calibration task for figuring out the proper individual value of the Ballmer Peak. Which is best observed on coding but also works, possibly with task-dependent optimum differences, for general engineering.
Double fun when you were born on the then-“wrong” side of the Iron Curtain.
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