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5G versus commercial aircraft Radio Altimeters in the US, wtf?

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It looks as if US airlines and manufacturers are warning of a serious threat to flights when 5G is turned off in the US. Are they just scaremongering? Even the FAA seem to warning of possible interference problems with the Boeing 787.

Tell me somebody thought this through. :o

--- Quote ---5G phones: How serious is the threat to US flights?

Ten leading US airlines are warning that the imminent rollout of 5G services could be disastrous.
They say the new technology could cause thousands of flights to be delayed, and risks leaving large parts of the US aircraft fleet grounded indefinitely.

--- End quote ---

I suppose it makes a change from the other conspiracy theories!

The issue seems to be that the radio altimeters were made with the assumption that the band below 4.2GHz would be relatively clear.  Turns out it isn't any more.  But you should never make that assumption in a design so critical.

The solution is probably to fit a notch filter to the antenna input.  Such a solution, being aviation in nature, probably requires about as much paperwork as a 737 weighs.  But it would be a solution.     It's not uncommon to have parts retrofitted to aircraft well after they are manufactured, provided they're properly designed and approved.   I imagine it gets more difficult the further away from production an aircraft is... an old DC-10 / MD-10 might be a lot harder to retrofit, yet Fed-Ex still use them for freight.

Given it's an acknowledged issue, why are the airlines in this position?  It would have been known about for at least half a decade, but dither and confusion has led to a standoff between airlines and mobile carriers?

Yes, it seems to be an adjacent frequency issue with small guard band (narrower than other countries?). It beggars belief that they haven't actually done some testing, let alone foreseen and implemented some mitigating measures. It sounds like more than old buses - Curious that the FAA and 787 are mentioned.

No idea how true this but I just heard on the news that 5G in the US is transmitted at a higher power than the UK and Europe and that is the concern. I would have thought that any power level would interfere at low altitude so it is most likely the US has gone with a different frequency, cannot think why as it would be better for travellers to have universal frequency bands, hardly likely that you would get trans atlantic interference as can happen between Europe and UK on the coast.   

Just watching the story on the BBC news broadcast, apparently negotiations between the phone providers and airlines are happening 'at the highest levels of government'.


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