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Homemade 6 GHz pulse compression radar

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Re: Homemade 6 GHz pulse compression radar

#81

Post by instagib »

auspiv wrote: post #15

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…

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

Re: Homemade 6 GHz pulse compression radar

#82

Post by rangestransform »

gertrunde wrote: post #6
throwup238 wrote: post #2

This is great. It’s the last piece I needed for my suburban missile guidance system! This will be the last year the Joneses survive the annual block party. Can you do phased array radars next? I need the extra precision. There’s a few neighbors who don’t clean up after their dogs…

There is this: https://www.crowdsupply.com/krakenrf/krakensdr (Although they had to take the radar elements out of the firmware/software, most likely due to ITAR - ref link: https://forum.krakenrf.com/t/where-has-the-passive-radar-cod... )

if they really wanted to, they could make this a first amendment case, no?

Re: Homemade 6 GHz pulse compression radar

#83

Post by beeeeerp »

KeplerBoy wrote: post #67
beeeeerp wrote: post #47

Earlier quoted context omitted.

Cutting-edge AESA radar like on the F-35 is incredible. It actually looks like a black and white photograph. I think your guess on antennas is roughly correct based on what we know about modern AESA.

Isn't that Synthetic Aperture Radar though? You can get similar results (black and white aerial pictures) by strapping a pretty basic siso radar system on a drone.

I’m honestly not sure what the difference is. I kind of understand SISO, MIMO, and beam steering concepts, but just the basics from nerding out on my Starlink dish.

This is what I’m talking about: https://www.twz.com/f-35-will-get-new-radar-under-massive-up...

Specifically this image: https://www.twz.com/uploads/2023/01/03/20065813381381024.jpg

I don’t know how targeting works, but with this level of resolution, I think basic image algorithms can start to come into play. It blows my mind.

Re: Homemade 6 GHz pulse compression radar

#84

Post by Animats »

gertrunde wrote: post #6
throwup238 wrote: post #2

This is great. It’s the last piece I needed for my suburban missile guidance system! This will be the last year the Joneses survive the annual block party. Can you do phased array radars next? I need the extra precision. There’s a few neighbors who don’t clean up after their dogs…

There is this: https://www.crowdsupply.com/krakenrf/krakensdr (Although they had to take the radar elements out of the firmware/software, most likely due to ITAR - ref link: https://forum.krakenrf.com/t/where-has-the-passive-radar-cod... )

Wow. I haven't looked at the ITAR list in decades. There are lots of electronics items on there now that have useful civilian applications and can be built at low cost. You can build such things, but can't ship them cross-border to or from an ITAR country.

I'm amazed at what people are building as hobbyist RF gear. I wonder what test equipment they have. The test equipment for GHz RF is very expensive. If you build it and it's not working, you may need test gear.

(I tried to build a LIDAR in 1990s. It didn't work, and I didn't have access to gear that would let me see what was happening up there.)

Re: Homemade 6 GHz pulse compression radar

#85

Post by numpad0 »

wbl wrote: post #74
CamperBob2 wrote: post #59

Earlier quoted context omitted.

Interesting article. I wonder if any progress on the ITAR issue has been made since 2022? If Brad Parkinson can't steer ITAR in the direction of common sense, nobody can. (For those who don't know, he was the principal architect of the original Navstar GPS system.)

I would prefer we not have homemade cruise missiles all over the place. The people who need them can make them after all.

Sure, it's getting increasingly easier to just buy China made for ITAR-protected products. Night vision cameras, thermals, drones. They're fine, way more user friendly, often cheaper too.

Re: Homemade 6 GHz pulse compression radar

#86

Post by mNovak »

maestroia wrote: post #37
throwway120385 wrote: post #35

Earlier quoted context omitted.

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.

Re: Homemade 6 GHz pulse compression radar

#87

Post by mNovak »

throwup238 wrote: post #2

This is great. It’s the last piece I needed for my suburban missile guidance system! This will be the last year the Joneses survive the annual block party. Can you do phased array radars next? I need the extra precision. There’s a few neighbors who don’t clean up after their dogs…

Well if we follow the historic development arc, frequency-scanning waveguide arrays would come next. Nicely, very minimal modification required, and you can start cranking up the antenna gain. Mostly just a physical fabrication challenge, which is hobby-approachable.

https://www.radartutorial.eu/06.antennas/Phased%20Array%20An...

Re: Homemade 6 GHz pulse compression radar

#88

Post by AnarchismIsCool »

kijiki wrote: post #72
auspiv wrote: post #15

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…

>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 expecte…

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.

Re: Homemade 6 GHz pulse compression radar

#89

Post by willvarfar »

AnarchismIsCool wrote: post #88
kijiki wrote: post #72

Earlier quoted context omitted.

>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 expecte…

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 :)

Re: Homemade 6 GHz pulse compression radar

#90

Post by azalemeth »

Dylan16807 wrote: post #75
SheldonSteves wrote: post #69

Earlier quoted context omitted.

There is but it's sun burn type risks, not nuclear reactor type. A few unlucky people have been literally cooked to death by military radar. It's as awful as it sounds.

> It's as awful as it sounds. Well to me it sounds like you'd get heat stroke and pass out before anything reaches particularly painful temperatures, because it's heating you pretty evenly and not via contact, but maybe that's not the right way to think about it? At higher frequencies I would guess it gets closer to normal burning?

This isn't really correct I'm afraid. The cause of SAR is predominantly dielectric losses and the loss tangent is a strong function of tissue type -- CSF, fat and bone are really quite different in terms of epsilon r and sigma, and one has to solve Maxwell with a human voxel model to work out SAR effectively which computationally is a pain.

Once tissue heating has occurred what happens next is well described by the bioheat equation, which is basically the thermal diffusion equation with a massive percussion term. The blood supply is very different to different tissue types and the depth at which peak heating occurs is a very strong function of wavelength.

For frequencies, the combination of these effects means that your eyes are most at risk -- water like and terrible blood supply. This gives rise to the first piece of advice I was given when a graduate student playing with electron paramagnetic resonance -- never look down a waveguide and treat them like a loaded gun!

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