| The initial pitch pre Ajit's decision was a private auction by the CBA. Ie, the corps behind these sats would themselves auction and keep the $81B. Supposedly this would be "better" for the taxpayer, but I always thought that was bogus. In the US the taxpayer has rights already to this spectrum, we don't have to buy it back from these folks. Anyways, thankfully that all fell apart, public auction generated $81B (a staggering sum showing the potential value of this spectrum for this use). Folks clearing spectrum still getting a massive windfall. Technically, a 400Mhz guard band is ridiculous. That's guard in initial roll-out. If planes have issues with stuff 400Mhz away that is ridiculous. Also ridiculous would be that they can't figure out their height using other means. Airports should report baro pressure for standard baro altimeters. They should look into GPS and RNAV style navigation used internationally - all this is common overseas. Idea that planes can't figure out there height seems bogus. My understanding is even later in roll-out there will be 20Mhz guard band around the airplane frequencies - do these airplane systems have no clue about filtering? This is plenty in most applications. This smells political or interagency related. This auction and use has been years and years in the making, and last minute we get this stuff. |
I don’t think that word means what you think it means.
Baro altimeters don’t tell you your height above the ground (or other obstruction). A digital terrain model is only as good as your navigation source, and GPS has well known failure modes.
> do these airplane systems have no clue about filtering?
Do you have no clue how much it costs to retrofit a filter on a commercial airplane?
It’s not that adding a filter is technically challenging. It’s that it wasn’t previously a requirement, and leaving it out saved weight (and every gram adds up when you’re building an airplane). If you added every ‘nice to have’, the airplane couldn’t lift its own weight.
Now that radar altimeters exist without high Q filters, retrofitting them costs money. You’ll need to have the filter approved by the manufacturer (because you are normally required to follow their installation guidance) and the FAA. Neither of them are going to help you for free.