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This is just as much the FCCs fault as the FAA. They were the ones that certified the frequency usage of these altimeters, and they should have noticed that the

This is just as much the FCCs fault as the FAA. They were the ones that certified the frequency usage of these altimeters, and they should have noticed that these altimeters could experience interference from satcom frequencies over 400MHz (!!!) away. They could have stopped this decades ago, but they let it go on long enough to become a massive problem. A lot of people don't seem to grasp the magnitude of the spectrum lost to this snafu. At today's realizable spectral efficiencies, that is 2.5 TB/s of usable data throughput lost to the 400MHz guard band alone. It's also ~$130B worth of revenue that the FCC could have had if they could actually sell it.

toast0 4y ago
Sure, the receivers could experience interference from satcom frequencies in theory, but in practice satcom broadcasts are very low strength, so there was not much risk of harmful interference until the frequency was repurposed for terrestrial, high power broadcasts. You don't put hurricane windows on buildings that have no hurricane risk, and you don't put tight bandpass filters on receivers in the satellite bands. When hurricane patterns or satellite bands change, you get problems though.
- darksaints 4y ago
  Satcom downlinks might be low power, but uplinks, especially from dedicated base stations (as opposed to satellite phones) can easily run into the hundreds of watts.
shadowgovt 4y ago
The problem here was sort of ideal for falling through the cracks. The FAA is an executive administration ultimately organized under Dept. of Transportation. The FCC is an independent executive agency overseen, ultimately, by Congress. As a result, neither org has unilateral authority to tell the other to go pound sand, nor do their up-org leadership (ultimately, the President v. Congress). Their inability to find a resolution that didn't leave American pilots floundering is reflective of the inability of the Legislative and Executive branches to work together in modern federal governance, in general. Expect more issues like this in the future.

toast0 4y ago

Sure, the receivers could experience interference from satcom frequencies in theory, but in practice satcom broadcasts are very low strength, so there was not much risk of harmful interference until the frequency was repurposed for terrestrial, high power broadcasts. You don't put hurricane windows on buildings that have no hurricane risk, and you don't put tight bandpass filters on receivers in the satellite bands. When hurricane patterns or satellite bands change, you get problems though.

darksaints 4y ago
Satcom downlinks might be low power, but uplinks, especially from dedicated base stations (as opposed to satellite phones) can easily run into the hundreds of watts.

shadowgovt 4y ago

The problem here was sort of ideal for falling through the cracks. The FAA is an executive administration ultimately organized under Dept. of Transportation. The FCC is an independent executive agency overseen, ultimately, by Congress. As a result, neither org has unilateral authority to tell the other to go pound sand, nor do their up-org leadership (ultimately, the President v. Congress). Their inability to find a resolution that didn't leave American pilots floundering is reflective of the inability of the Legislative and Executive branches to work together in modern federal governance, in general. Expect more issues like this in the future.