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Boeing's altimeters should have always operated within the frequency bands allocated to them and been resistant to interference from other bands. These altimete

by tssva 5y ago

Boeing's altimeters should have always operated within the frequency bands allocated to them and been resistant to interference from other bands. These altimeters are operating outside the specification they should have met when deployed. This is an utter failure on the part of aircraft manufacturers, airlines and the FAA. They are all screaming loudly to try to shift the public perception to this being an issue created by the FCC and telecom companies.

NovemberWhiskey 5y ago
>Boeing's altimeters should have always operated within the frequency bands allocated to them and been resistant to interference from other bands. These altimeters are operating outside the specification they should have met when deployed. What is your basis for this extraordinary claim?
- jaywalk 5y ago
  What's extraordinary about the claim? The guard band between 5G and radio altimeters is ~200MHz, which is massive. If your filtering can't handle signals over 200MHz away from what you're looking at, then it's garbage filtering.
  - anfilt 5y ago
    200 Mhz may be massive for communications (especially digital encoded signals), not necessarily for radar when you sensor is receiving weak reflected signals that very likely can have a frequency shift on reflection. So radar receivers need to receive on a wider frequency band than a receiver for communications. Depending on the strength of 5G transmitters the higher order harmonics could be above the noise floor.
    - NovemberWhiskey 5y ago
      Especially for FMCW applications using homodyne transceiver architectures; like you see in most civilian radar altimeters.
- avianlyric 5y ago
  This is not an extraordinary claim, it’s how all basic radio spectrum allocation works. How else are you supposed to make sure that equipment made today won’t interfere with equipment made tomorrow if people don’t stick within their frequency allocations? The claim above is basically the equivalent of “car should have always operated on the roads that are allocated for them, and should never have been driving through empty fields”. If you’re driving your car through a field you don’t own, you don’t get to complain when someone builds a house there.
  - NovemberWhiskey 5y ago
    Do you know how a typical radar altimeter works? Do you know what the source of the specifications for radar altimeters for airborne applications is?
    - avianlyric 5y ago
      What has that got to do with spectrum allocation? All radio equipment is meant to be specified to operate only within its allocated spectrum, and to handle RF noise and interference from anything outside it’s spectrum. How a radalt works is irrelevant, the allocation determines the operating parameters. If your equipment can’t operate within those parameters then it’s faulty, simple as that. Nobody would try to defend a building whose foundation crept over outside of the plot of land belonging to it. If you’re house can’t standup without putting parts of itself into your neighbours garden, then your house is faulty, not you’re neighbours home when they decide to repurpose their garden.
- MobiusHorizons 5y ago
  How is it extraordinary? Equipment is typically required by law to operate only within its specified frequency bands. 5G spectrum was never allocated to aircraft radar altimeters. I agree that quoted suggestion lacks nuance in the history that brought us to this state, but from a technical perspective it does not seem extraordinary. More that it simply advocates a very expensive and uncooperative way to solve a problem of the commons.
  - NovemberWhiskey 5y ago
    Equipment is required to emit only within its allocated frequency bands. No-one is suggesting that the radar altimeters are emitting outside of their allocation; but there's no law that says that devices have to be immune to interference from other transmissions outside their allocated bands.
    - fennecfoxen 5y ago
      There’s definitely laws that say certain equipment had to “accept” interference from lawful transmissions. You’ll find a label to that effect on every piece of 802.11 and Bluetooth gear in the US, for starters. “Immunity” is largely your own problem though.
      - NovemberWhiskey 5y ago
        >There’s definitely laws that say certain equipment had to “accept” interference from lawful transmissions. You’ll find a label to that effect on every piece of 802.11 and Bluetooth gear in the US, for starters. That's specifically for unlicensed Part 15 devices ref. https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-15#p-15.19(a)(3) https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A... ... the point of that wording is that unlicensed devices have no rights vs. licensed emissions.

by tssva 5y ago

NovemberWhiskey 5y ago

>Boeing's altimeters should have always operated within the frequency bands allocated to them and been resistant to interference from other bands. These altimeters are operating outside the specification they should have met when deployed. What is your basis for this extraordinary claim?

jaywalk 5y ago
What's extraordinary about the claim? The guard band between 5G and radio altimeters is ~200MHz, which is massive. If your filtering can't handle signals over 200MHz away from what you're looking at, then it's garbage filtering.
- anfilt 5y ago
  200 Mhz may be massive for communications (especially digital encoded signals), not necessarily for radar when you sensor is receiving weak reflected signals that very likely can have a frequency shift on reflection. So radar receivers need to receive on a wider frequency band than a receiver for communications. Depending on the strength of 5G transmitters the higher order harmonics could be above the noise floor.
  - NovemberWhiskey 5y ago
    Especially for FMCW applications using homodyne transceiver architectures; like you see in most civilian radar altimeters.
avianlyric 5y ago
This is not an extraordinary claim, it’s how all basic radio spectrum allocation works. How else are you supposed to make sure that equipment made today won’t interfere with equipment made tomorrow if people don’t stick within their frequency allocations? The claim above is basically the equivalent of “car should have always operated on the roads that are allocated for them, and should never have been driving through empty fields”. If you’re driving your car through a field you don’t own, you don’t get to complain when someone builds a house there.
- NovemberWhiskey 5y ago
  Do you know how a typical radar altimeter works? Do you know what the source of the specifications for radar altimeters for airborne applications is?
  - avianlyric 5y ago
    What has that got to do with spectrum allocation? All radio equipment is meant to be specified to operate only within its allocated spectrum, and to handle RF noise and interference from anything outside it’s spectrum. How a radalt works is irrelevant, the allocation determines the operating parameters. If your equipment can’t operate within those parameters then it’s faulty, simple as that. Nobody would try to defend a building whose foundation crept over outside of the plot of land belonging to it. If you’re house can’t standup without putting parts of itself into your neighbours garden, then your house is faulty, not you’re neighbours home when they decide to repurpose their garden.
MobiusHorizons 5y ago
How is it extraordinary? Equipment is typically required by law to operate only within its specified frequency bands. 5G spectrum was never allocated to aircraft radar altimeters. I agree that quoted suggestion lacks nuance in the history that brought us to this state, but from a technical perspective it does not seem extraordinary. More that it simply advocates a very expensive and uncooperative way to solve a problem of the commons.
- NovemberWhiskey 5y ago
  Equipment is required to emit only within its allocated frequency bands. No-one is suggesting that the radar altimeters are emitting outside of their allocation; but there's no law that says that devices have to be immune to interference from other transmissions outside their allocated bands.
  - fennecfoxen 5y ago
    There’s definitely laws that say certain equipment had to “accept” interference from lawful transmissions. You’ll find a label to that effect on every piece of 802.11 and Bluetooth gear in the US, for starters. “Immunity” is largely your own problem though.
    - NovemberWhiskey 5y ago
      >There’s definitely laws that say certain equipment had to “accept” interference from lawful transmissions. You’ll find a label to that effect on every piece of 802.11 and Bluetooth gear in the US, for starters. That's specifically for unlicensed Part 15 devices ref. https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-15#p-15.19(a)(3) https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A... ... the point of that wording is that unlicensed devices have no rights vs. licensed emissions.