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Cell Towers Can Double as Cheap Radar Systems for Ports and Harbors (2014)

(spectrum.ieee.org)
137 points transpute | 6 comments | 29 Jun 25 21:48 UTC | HN request time: 0.813s | source | bottom
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transpute ◴[29 Jun 25 23:52 UTC] No.44417727[source]▶
More coverage of RF sensing, including laptops/phones with radios+NPU to sense their human:

2025, "Espargos: ESP32-based WiFi sensing array", 30 comments, https://news.ycombinator.com/item?id=43079023

2024, "How Wi-Fi sensing became usable to track people's movements", https://www.technologyreview.com/2024/02/27/1088154/wifi-sen...

2023, "What Is mmWave Radar?: Everything You Need to Know About FMCW", 30 comments, https://news.ycombinator.com/item?id=35312351

2022, "mmWave radar, you won't see it coming", 180 comments, https://news.ycombinator.com/item?id=30172647

2021, "The next big Wi-Fi standard is for sensing, not communication", 200 comments, https://news.ycombinator.com/item?id=29901587

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Animats ◴[30 Jun 25 03:37 UTC] No.44419092[source]▶
Right. The longer range versions of multistatic radar are used to detect stealth aircraft.[1][2] All that careful stealth geometry to minimize direct reflections doesn't help much when the emitters and receivers are in different locations.

[1] https://www.presstv.ir/Detail/2024/11/18/737423/guardians-of...

[2] https://www.yiminzhang.com/pdf/radar13_passive.pdf

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1. Grayskull ◴[30 Jun 25 09:10 UTC] No.44421093[source]▶
Well, you don't even need a radar. Tamara sensor could detect B-2, when it had it's onboard radar on.

https://en.wikipedia.org/wiki/Tamara_passive_sensor

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2. rcxdude ◴[30 Jun 25 12:20 UTC] No.44422369[source]▶
stealth does in general go out the window when you turn on your radar. It's much like dressing in black and then running around with a flashlight at night. (and yes, there are equivalents to the various forms of night vision here, with associated tradeoffs)
replies(1): >>44423144 #
3. ta20240528 ◴[30 Jun 25 13:10 UTC] No.44422853[source]▶
It turns out for the Iran drama, that radar's like the Tamara have to survive the F-35s first, then the F-15s…

Which they don't.

Then the B-2s fly in in unopposed.

The key to the B-2s is dropping the F-35s. Which seems to be hard.

4. chipsa ◴[30 Jun 25 13:28 UTC] No.44423050[source]▶
Doubt: the APQ-181 radar on the B-2 is a Ku band radar, about 15 GHz. Tamara is about 1 GHz. This is entirely incompatible frequency ranges.

Also, the APQ-181 is a LPI radar, which means it’s specifically designed to avoid correlation of signals such that you can track by the signals emitted. There are presumably some downsides to working in LPI, but the upside is that the signal is designed to be indistinguishable from an increased noise floor.

5. engineer_22 ◴[30 Jun 25 13:39 UTC] No.44423144[source]▶
Nah, there is much secret about radar
6. wat10000 ◴[30 Jun 25 15:20 UTC] No.44424415[source]▶
I'm pretty sure that "don't operate your radar in enemy airspace" is right below "don't email your flight plan to the enemy" on the list of tips for stealth pilots who want to survive a mission.