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Comment by auspiv | Hacker News Reader

Incredible work. Crazy that this could be done by a single person. Stick it on a rotating pedestal and you've got a planar radar detector. Add some tilt and then it's not much different than aircraft/weather radar I suppose.

The cost (in $LOCAL_CURRENCY, or $570 according to another comment) isn't great but I can only imagine how many hours this took.

Given a proper budget, the sky is the limit.

Anyone know how .mil aircraft would interpret being tracked by a 6 GHz radar build by a civilian(yes I am aware that his estimated max distance is 1200m, assume he increased that by a factor of 10 with larger antennas or something)?

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> Anyone know how .mil aircraft would interpret being tracked by a 6 GHz radar build by a civilian(yes I am aware that his estimated max distance is 1200m, assume he increased that by a factor of 10 with larger antennas or something)?

Regulations for signal strength are ERP, so a more directional antenna could make it no longer legal to use the 6GHz band.

I doubt anyone intentionally tracking military aircraft is gonna be too worried by ISM radio band regulations.

(They're either the kind of idiot who aims laser pointers at police helicopters, or they're doing it with intent to get in much more serious trouble than just ignoring radio regulations...)

There are different ways

First and foremost, aircraft radars have receivers, which will also receive the transmitted pulse from the other radar. In fact, that is how radar jamming works - you deluge the other radar with power on the same band / wavelength, and it will fill the display with clutter.

With that said, radars have a bunch of characteristics that makes it somewhat easy to identify. Frequency, PRF (pulse-repetition frequency), waveform, etc.

The bands at which radars operates are regulated, and various agencies - military and otherwise - will pick up radar transmissions. These tiny DIY projects aren't a huge "threat" in that sense, but if you're active anywhere near a radar installation, and especially military ones, it could land you in hot water, real fast.

I'm not sure about Finland, but where I live, civilians for example are not allowed to fingerprint or build fingerprint databases of military radars. In fact, the military is the only ones allowed to do so.

The power-scaling makes these things go from DIY to non-DIY real quick.

Would be cool to see this guy build a phased-array (radar)

Source: Worked with radars

>Anyone know how .mil aircraft would interpret being tracked by a 6 GHz radar build by a civilian(yes I am aware that his estimated max distance is 1200m, assume he increased that by a factor of 10 with larger antennas or something)?

No specific knowledge, of course, but I'd imagine it wouldn't trigger a serious threat warning. Military TWRs are highly tuned systems dedicated to the threat environment they're expected to operate in.

Depends on the system, any pulsed emission of sufficient strength should start triggering things as you can't know for sure what bands and systems are going to be used against you. I believe they usually have 'unknown' IDs for stuff that isn't in the threat database.

There is a story of a police speed camera catching a fast jet going around. The snopes debunking has some interesting technical details of why this is really unlikely https://www.snopes.com/fact-check/police-radar-missile/

But of course people have built nuclear reactors at home, so they could probably assemble a sufficiently powerful radar too.

Edit: didn't mean that people need to power homemade radars using homemade nuclear reactors! I'm sure that's not necessary :)

They get something similar to “radar warning” / “radar lock” notifications or verbal warnings.

Wouldn't the FAA or FCC in the US have some jurisdiction over such a setup?

The "6 GHz" band is an unlicensed frequency for very-low power (VLP) devices in the US.

Specific bands are: "U–NII–5 (5.925–6.425 MHz) and U–NII–7 (6.525–6.875 MHz)".

VLP is defined as those devices which "operate at up to −5 dBm/MHz power spectral density (PSD) and 14 dBm EIRP".

https://www.federalregister.gov/documents/2024/01/08/2023-28....

14dBm EIRP is extremely low power for a radar however. Off the bat the author is using 1W (30dBm) PA, and you could readily get another 20dB from a moderate sized antenna (e.g. repurpose a scrap DirecTV dish).

Unless you're next to a base, it's the FCC that will come knocking long before the military.

In fact you can get WiFi routers that use 6Ghz as the third band after 2.4Ghz and 5Ghz.

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