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Comment by kilo_bravo_3 | Hacker News Reader

The L- and X-band radars used by the S400 are exceedingly easy to jam, and no matter what Russia says they have not figured out a way around the laws of physics that enables them to reliably target low-observable aircraft.

So yeah, if an F-15 blindly stumbles within the effective range of an S400 it will be shot down.

The fingerprint of the S400's radar are detectable from thousands of kilometers away and a nice little icon will be plopped onto the pre-mission overlays before the F-15 takes off.

You don't even have to detect the radar beam, you can detect the data link.

As for casualties, what casualties?

The only casualties a drone launching a glide bomb results in are those on the receiving end.

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I am with computerex. Your explanations are extremely simplistic and biased. S400s can toggle on and off, share data, have Pantsir systems around them, etc.

You ignore the same problems with air platforms emitting.

Your claim about detecting the data link is absurd.

RF is RF. If it is emitted it can be detected.

Even point to point microwave links can be detected off-axis.

Hundreds of watts of point-to-point means dozens of watts of sidelobes.

Dozens of watts in the middle of the desert is easy to detect.

If the AN/MLQ-40 could do it at tens of kilometers 20 years ago I bet datalinks could be detected from space today.

You are literally making statements that don't make any sense and I'd bet you can't back up anything with a primary source.

Everything he said makes sense to me, and I'm just a lowly software engineer with a single unit of RF background back at uni.

What part are you confused about?

There is no such thing as a perfectly directional antenna. Radiation profiles consist of multiple lobes which generally point towards a single direction on 3 axes, but there are always side lobes, like so: [1]. You can't hide these, therefore they can be detected and targeted.

There's a whole class of missiles that simply look for RF sources and head that way. The only way to avoid such missiles is to stop being an RF source. But if you do that, you're also unable to target the attackers or defend against those missiles. You also have to turn off your data link and lose situational awareness.

The S-400 is the best air defence currently fielded, but it is by no means magical or invulnerable.

https://www.cisco.com/c/dam/en/us/products/collateral/wirele...

All this makes the assumption that S400 is a sitting duck with no countermeasures. Which is far from reality. The entire point of a decentralized and mobile/distributed system like s400 is to make it difficult to target. It is ground based, therefore has much better detection capability than anything in the air. Its long range missiles have a greater flight envelope than any surface to air missile.

You don't think the s400 has any jamming capability and protection of its own? You don't think the system can detect when it's being targeted and locked on?

It can definitely be defeated but not without suffering heavy casualties. That's _why_ it's called anti-access/area denial technology.

Israel has already destroyed pantsirs with standoff missiles in syria.

Do you have a reliable source for any of the stuff you are claiming to be true? Because you are not making any sense.

Read up on SEAD tactics, it's pretty interesting. The nature radar propagation and reflection means that a plane will know a radar is active long before the radar can detect the plane. Planes can then fire anti radiation missiles that home in on the radar emissions source. Also, most radars are limited by the horizon. Low level flying can let planes get close without detection.

Now this doesn't mean destroying air defenses is easy. Factor in smaller SAM sites dispersed around th larger ones, as well as enemy air superiority fighter operating in the area and SEAD gets more complicated. SAM sites also sometimes turn their radars off until planes are close and ambush them. But SAM sites alone are not an impervious defense against air power.

>a plane will know a radar is active long before the radar can detect the plane.

The other bit of information that might be perhaps missing from some (other!) explanations is that this arises entirely because the ground station has to receive a radar reflection _of the original beam_ from the target. Given that power goes as 1/r^2, this means that in practice range drops off sharply for the ground-based station as 1/r^4. Meanwhile, the aircraft can just _detect_ some sort of blip-over-thermal power spectral density coming from somewhere. Given identical amplifier performance (which, with good designs, should be limited by physics) and you end up with the attacking aircraft "winning" from a back-of-the-envelope point of view.

This ignores the fact that it can be traditionally quite easy to confuse radar by "just" transmitting the "right" signals at the right time. There's a good 1960s video that explains a lot of the basic ideas here: https://www.youtube.com/watch?v=pyFqaaqqph0

Planes can then fire anti radiation missiles that home in on the radar emissions source

It’s worse than that (for the defender). Missiles can loiter and wait, if the emitter is switched off, then strike when it switches back on again.

Detected with what, AWACS? Do you know how big those radar signatures are?

Detected by Radar Warning Receivers (RWR). These are passive sensors, they're listening to the radar emissions that other planes and Radar stations are emitting. Because the radar needs to send a signal that bounces off the plane and have enough energy for those bounces to travel back to the radar, whereas th RWR only needs to detect the emissions traveling from the radar to the plane the radar will be detected by RWR from much further away. Most modern aircraft carry RWR, not just AWACS.

1. Let's stop re-explaining how radar works as an argument, everyone gets it. For those who don't - radar works like turning on a flashlight, end of story.

2. Non-SEAD RWR is generally limited to "There is light shining on me." Not where it's coming from, let alone providing targeting information.

All modern (1980s and later) RWRs can determine the bearing of emissions. Heck, even the RWR in the Mig-21 (1950s plane) could determine bearing. With bearings known, all you need is two planes to determine location by taking the intersection of the two bearings. Most RWRs can also identify the type of radar, as well as whether it is searching or locked into a target. Planes can also equip targeting pods that have even more advanced passive sensors: https://en.m.wikipedia.org/wiki/AN/ASQ-213

Passive sensors have advanced significantly.

The sensor you linked is limited to SEAD missions in most occasions.

I am going to admit to moving the bar - but at this point you have MIG-31s in the air looking for SEAD and taking down any AWACS.

You might also cite some sources for your claims...

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