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Comment by fierycatnet | Hacker News Reader

I just kinda skimmed through it, so it detects drones in sky? Am I understanding this correctly? That might have some defense application considering what's going on in Eastern Europe right now.

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It detects drones which send out RF signals at the same frequency band. Most drones used in Ukraine are tethered with thin optical wire exactly because one of the first anti-drone measures was to simply jam them at the frequencies the operators used.

There are some more advanced anti-drone measures at work: Like blasting them with directed high-energy microwaves to destroy the circuits.

Frequency hopping is not THAT difficult.

Brute force wide band jamming would be easy too and would make hopping ineffective. Unless drones use self tuning antennas to overcome losses, they can't hop too far away from the antenna resonance frequency, which makes jammers job easier.

Jamming broadband is a lot more energy expense than frequency hopping. Orders of magnitude.

But the jammer can be plugged in to the grid or a diesel generator. Being on the ground without flight requirements grants access to such resources.

But such a jammer is expensive and a magnet for HARMs that only need that RF signature as guidance.

Which is a completely unrelated to what we were talking about.

How is SEAD unrelated to drone warfare? Unless you believe anti radiation missiles/drones can't target jammers.

The topic was energy expense of wideband vs narrowband jamming.

Both can be used for targeting.

Yes. That makes it fat, expensive and vulnerable target. There are videos of them being blown up regularly.

Which is a completely unrelated to what we were talking about.

How come? It plainly negates the "easy" part. It's not easy at all, you need to scale your signal path to the magnitude of power. I.e. the expensive part.

I mean, drones trailing fiber optic cables are widely documented https://en.wikipedia.org/wiki/Fiber_optic_drone

So I’m pretty sure avoiding jamming by a military adversary is not trivial, even with frequency hopping and suchlike.

FPV drones in the Russian war are generally pretty dumb devices, there's usually no frequency hopping involved to begin with. They have a lot more in common with baby monitors than with modern military comms.

Lol, even baseline DJI drone chipsets from a decade ago do frequency hopping. Many baby monitors probably do too.

You can literally see the analog video links in countless thousands of published recordings. Nobody really does the hopping with analog video.

From early in the war, sure.

True, but they can't use directional antennas nor lots of power, and once they're far enough from the transmitter inverse square law does the rest. Ground stations always have an advantage because of higher gain antennas and more power available.

So what? It's not the airborne platform with limited energy and an explosive payload that needs to do the jamming, it's the ground-based targets.

However, as pointed out elsewhere in the thread a lot of these jamming arguments are academic because drones are either tethered with a fiberoptic cable and/or navigating autonomously.

Most drones aren't optical because optical drones sacrifice payload and distance, they're only used when broad spectrum jamming is expected. Jamming of that type is expensive and heavy enough that infantry probably won't be jamming, or light vehicles, or a lot of infrastructure.

Most light vehicles are jamming, and infantry at least have detection capability, which is why fibre is now the standard for close range.

> That might have some defense application considering what's going on in Eastern Europe right now.

This is a bog-standard phased-array RDF calibrated for WiFi freqs; that stuff is already in every single defense show.

Also, that's why there's jamming everywhere (to blind that kind of things) and why many UAVs are now tethered to optical fibers instead of being RF-controlled.

Yeah I think it is at every defense show, but that doesn't mean it makes it to the front lines. Defense show = super expensive. This is cheap.

> Defense show = super expensive

Really depends; there you can see both Lockmart exhibiting multi-billions project, and 150m after some Serbian company selling jet engines for UAVs for a couple hundreds.

Homing in on sources of electromagnetic transmissions has been a thing since at least the BV246 in 1943.

The first phased array systems date back to 1905.

We have had some time to productionize this.

Hell, the "PA" in "PATRIOT missile" stands for "Phased Array".

I'm not saying it's new technology. The patriot missile costs $4m each. None of the drones Ukraine is using have this tech.

The new thing is that it's available for purchase for a reasonable price.

Why would they put phased arrays on UAVs? They are typically using beam-forming antennas + cheap gimbals for the same purpose.

Phased arrays are nice when you want to scan a large angular surface very fast; when it comes down to optimizing RF radiation toward your ground station, a gimbal is cheaper, simpler, and works fine.

While it doesn't produce an image, not having 2D data, KrakenSDR has some cool direction finding too.

Very much so.

I had a friend who'd just gotten out of EE school as a non-traditional student who was working for a company that was making radars for tracking drones maybe five years before the 2022 Russian invasion.

That was an active system, similar in concept to the radars used in air defense system just scaled down and faster acting.

The one in this article is a passive system that sees the transmitter on the drone. The comm link is the obvious weak spot on the drone as it can be detected and jammed, it is fairly inevitable that lethal attack drones that work anonymously will be widespread as a result.

> that sees the transmitter on the drone. The comm link is the obvious weak spot on the drone

Isn't most drones run by fiber optic nowadays around the front-lines though? Can't really jam those, but maybe still detect it somehow?

According to CivDiv's channel about 70% of the drones used are still RC FPV drones. They are cheaper longer range and have a slightly simpler supply chain. Fiber optic cable prices have exploded because of the war.

If you count recon and droppers that can use distance to avoid jamming, sure. One-way applications are increasingly fibre.

Can you back this up with any authoritative sources?

glad to see someone giving a source. a lot of people here heard of fiber optic drones and decided that now 100% of drones in Ukraine are using those

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