>>but I would expect that there should be good bandpass filtering at its input.
That, I think, is the point... you would _expect_ the altimeter to have good bandpass filtering but it may well not have any - after all before 5G came along the altimeters were not expecting any sort of signal remotely close to their nominal operating frequency, other than thier own.
It does seem odd, to me, that the FAA has waited so long to make their concerns known but the 5G pushers are also slightly off in their "think of the children" response and their apparent "Ah.. it will be OK... don't worry about it; if there is an accident related to 5G then our lawyers are paid more than yours and, anyway, if the FAA has approved the bandwidth use then it is their problem not ours" approach.
As someone else said above, it all seems a little fishy - at least it does to this particular greybeard.
Biting the hand that feeds IT
