4 ms·

If our war machines crash because of spectrum allocation, there may be a problem with the military’s threat modeling.

by DaniloDias 6y ago

NavinF 6y ago
ikr, is it really that easy to mess with a radar altimeter? (hides signal generator and RF amp behind my back)
- jacquesm 6y ago
  From this comment I deduce you have been working out. You must have at least a 19" wide back then, I suspect that a good ramp generator and an amp for that kind of frequency range with sufficient power and bandwidth is going to be a rackmounted device if not multiple of those. This baby from Rohde & Schwarz https://cdn.rohde-schwarz.com/pws/application/cards/3607_4464/amplifiers-accelerator-physics_ac_3607-4464-92_01a_w1300_hX.png https://cdn.rohde-schwarz.com/pws/application/cards/3607_446... should do nicely.
  - jameshart 6y ago
    So 5G rollout is going to put one of those on every street corner?
    - jacquesm 6y ago
      Those little boxes at the bases of antennae for cell phone towers are quite full of gear. Nothing that massive but a single rack with various bits and pieces (and batteries!) is the norm. https://www.extremetech.com/wp-content/uploads/2013/06/sprintltecellsite01.jpg https://www.extremetech.com/wp-content/uploads/2013/06/sprin... Look at all those Samsung goodies.
      - DaniloDias 6y ago
        Pic is from 2013. Image appears to have a sprint watermark. Looks like a base station controller (or whatever the cdma equivalent is). I don’t see the Samsung branding. Not aware of them as a major appliance vendor for cell sites.
        jacquesm 6y ago
        Yes, so what? This is typical of what a base station looks like inside, whether or not it is current isn't really all that important, the gear gets a bit smaller every generation but it's not as though it suddenly becomes pocket size. As for you not seeing the Samsung branding, you can take my word for it or you can look up some of type numbers visible. Your lack of knowledge about what Samsung offers doesn't really matter.
        DaniloDias 6y ago
        Sorry- not attacking, just observing.
  - NavinF 6y ago
    Google says 120W for the largest 5G MIMO arrays. 50 dBm is nothing crazy for a benchtop unit.
upofadown 6y ago
Presumably the military assumes that radar altimeters can be jammed. The potential problem here is that they might be jammed when there is not an actual war in progress. It's a generic aviation thing and is not specific to any one group.
- tolien 6y ago
  In a war situation, blasting out high power RF would also be painting a huge target on your antennae for an AGM-88 HARM.
  - mhh__ 6y ago
    It's still a game of cat and mouse, because the operators either will have enough sources not to care or be clever enough to only paint a target at the last moment. Anti-radiation missiles seem fun to work on, for example the (now retired) ALARM missile will loiter at 13 km with a parachute then use a secondary rocket motor to attack a target it finds. The signal processing these things do is probably unbelievable.
    - tolien 6y ago
      Thinking about it some more, a radar altimeter is only effective to ~2000 feet so it’s probably going to be a relatively close range highly-directional beam which would make it harder for a seeker head to find but also means you’d need a truck close to the airfield perimeter, painting aircraft on final approach. WRT last minute painting, I guess the E model would help a bit with that: > the AGM-88E Advanced Antiradiation Guided Missile (AARGM), features the latest software, enhanced capabilities intended to counter enemy radar shutdown At 870k USD a pop you wouldn’t want to be lobbing a lot of them, though - as you say, it’s going to cheaper to build jammers than countermeasures to destroy them.
- mywittyname 6y ago
  I certainly hope that there's some sort of channel-hopping strategy in place to prevent accidental jamming. In fact, I would hope that "can't be accidentally jammed by a bunch of 14 year olds on their cell phones," is a lower-bounds for measuring the efficacy of the system.
mekkkkkk 6y ago
Even if interference is accounted for, it seems unnecessary to apply it knowingly, no? It might only increase the probability of failure by a tiny amount, but if applied constantly, I'd be concerned too.

If our war machines crash because of spectrum allocation, there may be a problem with the military’s threat modeling.

NavinF 6y ago

ikr, is it really that easy to mess with a radar altimeter? (hides signal generator and RF amp behind my back)

jacquesm 6y ago
From this comment I deduce you have been working out. You must have at least a 19" wide back then, I suspect that a good ramp generator and an amp for that kind of frequency range with sufficient power and bandwidth is going to be a rackmounted device if not multiple of those. This baby from Rohde & Schwarz https://cdn.rohde-schwarz.com/pws/application/cards/3607_4464/amplifiers-accelerator-physics_ac_3607-4464-92_01a_w1300_hX.png https://cdn.rohde-schwarz.com/pws/application/cards/3607_446... should do nicely.
- jameshart 6y ago
  So 5G rollout is going to put one of those on every street corner?
  - jacquesm 6y ago
    Those little boxes at the bases of antennae for cell phone towers are quite full of gear. Nothing that massive but a single rack with various bits and pieces (and batteries!) is the norm. https://www.extremetech.com/wp-content/uploads/2013/06/sprintltecellsite01.jpg https://www.extremetech.com/wp-content/uploads/2013/06/sprin... Look at all those Samsung goodies.
    - DaniloDias 6y ago
      Pic is from 2013. Image appears to have a sprint watermark. Looks like a base station controller (or whatever the cdma equivalent is). I don’t see the Samsung branding. Not aware of them as a major appliance vendor for cell sites.
      - jacquesm 6y ago
        Yes, so what? This is typical of what a base station looks like inside, whether or not it is current isn't really all that important, the gear gets a bit smaller every generation but it's not as though it suddenly becomes pocket size. As for you not seeing the Samsung branding, you can take my word for it or you can look up some of type numbers visible. Your lack of knowledge about what Samsung offers doesn't really matter.
        DaniloDias 6y ago
        Sorry- not attacking, just observing.
- NavinF 6y ago
  Google says 120W for the largest 5G MIMO arrays. 50 dBm is nothing crazy for a benchtop unit.

upofadown 6y ago

Presumably the military assumes that radar altimeters can be jammed. The potential problem here is that they might be jammed when there is not an actual war in progress. It's a generic aviation thing and is not specific to any one group.

tolien 6y ago
In a war situation, blasting out high power RF would also be painting a huge target on your antennae for an AGM-88 HARM.
- mhh__ 6y ago
  It's still a game of cat and mouse, because the operators either will have enough sources not to care or be clever enough to only paint a target at the last moment. Anti-radiation missiles seem fun to work on, for example the (now retired) ALARM missile will loiter at 13 km with a parachute then use a secondary rocket motor to attack a target it finds. The signal processing these things do is probably unbelievable.
  - tolien 6y ago
    Thinking about it some more, a radar altimeter is only effective to ~2000 feet so it’s probably going to be a relatively close range highly-directional beam which would make it harder for a seeker head to find but also means you’d need a truck close to the airfield perimeter, painting aircraft on final approach. WRT last minute painting, I guess the E model would help a bit with that: > the AGM-88E Advanced Antiradiation Guided Missile (AARGM), features the latest software, enhanced capabilities intended to counter enemy radar shutdown At 870k USD a pop you wouldn’t want to be lobbing a lot of them, though - as you say, it’s going to cheaper to build jammers than countermeasures to destroy them.
mywittyname 6y ago
I certainly hope that there's some sort of channel-hopping strategy in place to prevent accidental jamming. In fact, I would hope that "can't be accidentally jammed by a bunch of 14 year olds on their cell phones," is a lower-bounds for measuring the efficacy of the system.

mekkkkkk 6y ago

Even if interference is accounted for, it seems unnecessary to apply it knowingly, no? It might only increase the probability of failure by a tiny amount, but if applied constantly, I'd be concerned too.