I think they mean fancy IFF (Identify Friend or Foe) emitters. If you think about it, it sounds like a pain of a problem, the plane must be as stealthy as possible, but somehow, during those moments, communicate in a non-spoofable way that it's a friendly. No idea how they do this. Is there any interesting textbook on electronic warfare, I wonder?
I don't know either, but thought about it a lot at one point.
First, you only respond to correctly encrypted/signed requests. Everything else you ignore.
So, second, once you have your valid request, you respond to it, also in an encrypted fashion. IIRC F-35 can use their radars, with their bean-forming abilities, for stealthy comms, sending a very narrow beam of radio signals to the recipient.
And if this is fantasy, I suppose by the time you receive an IFF query, you know you're about to be shot at. So you might as well respond, sacrificing stealth. Hence why you want to really be sure you're really asked by your side, rather than receiving a spoof request.
Airlines just broadcast a ton of public information about themselves, so they don't really need an IFF system. They put their hands up and say "don't shoot, I'm a civilian!".
> by the time you receive an IFF query, you know you're about to be shot at
I don’t think that’s the most common case for an IFF query. AWACS oversight aircraft likely issue more IFF queries than fighter intercepts do. You still want to respond to a friendly AWACS inquiry, even though that aircraft is 100nm away and no direct/immediate threat to you.
An AWACS aircraft within 100 nanometers of you would indeed represent a direct and immediate threat. :)
TIL that nm isn’t actually accepted as an abbreviation for nautical miles. (It’s used so commonly in aviation that I assumed it was correct and it took me 3 or 4 searches to accept that this thing I knew was correct actually wasn’t. Thanks [seriously]!)
> Is there any interesting textbook on electronic warfare, I wonder?
I know that there are unclassified textbooks on this very topic, but I've long forgotten their names.
> If you think about it, it sounds like a pain of a problem, the plane must be as stealthy as possible, but somehow, during those moments, communicate in a non-spoofable way that it's a friendly. No idea how they do this.
Well, part of this problem is pretty trivial to solve: if you're coming back from a mission and are well in friendly airspace, you don't need to be stealthy at all, so you turn on your radio transmitters.
It's my understanding that when you're on a mission where you need to be as hard to spot as possible, you turn off all unnecessary transmitters and rely on Command telling Air Traffic Control and other interested parties where you're operating so as to reduce the chance that you collide with another aircraft and/or get shot down by friendlies.
DSSS is magic. Truly. It's like you can create an ~infinite number of "new frequencies" to send on, each being orthogonal to any other, then chose them cryptographically as needed. With enough care it's possible to make it difficult for the adversary to even detect the presence of a signal. And the tech used by the likes of F-35 with MADL and low-probability-of-intercept radars may be even fancier than that.
That being said in the Red Sea incident they likely were not stealthy at all. For one F-18 has a rather big cross section, it's a 4th generation jet. For another the Houthis are not known to operate any sensible air defense (I may be wrong here, someone please correct me if I'm wrong).
Any serious hardware Ansar Allah operates is provided by Iran, and Iran is not capable of shooting down IAF aircraft flying over their own territory. Ansar Allah did not shoot down an F-18.
AESA radars send radar impulses on different frequencies that appear to the observer to be random (and thus hard to figure out and jam).
They could use something similar for communication. Send the first byte on a frequency, the second byte on another one, etc.... The frequencies could be calculated to be un-distinguishable from the background radio radiation. Of course, both the sender and the receiver have to agree on this mechanism.
The really clever counterpart is how to transmit through your own spread-spectrum jamming. Quiet slots in the jamming must be manipulated in the same way as the active broadcast. For example, this allows communication to a ground convoy that is jamming all frequencies to prevent wireless remote-control IED detonation.
