What do you think about this airline vs 5G brouhaha?

Nick Hilliard nick at foobar.org
Tue Jan 18 22:18:39 UTC 2022

Mel Beckman wrote on 18/01/2022 21:25:
> /The collective tech industry needs to admit that it made a huge blunder 
> when it urged the FCC’s clueless Ajit Pai to “blow off” the clearly 
> demonstrated FAA spectrum conflict. Sorry, passengers, but if you look 
> out your window, you’ll see that aviation owns this spectrum and is 
> entitled to interference-free operation. Replacing all radar altimeters 
> isn’t going to happen in time for 5G anyway — it took more than ten 
> years just to deploy anti-collision technology. So do what you should 
> have done from the beginning: follow the FCC rules of non-interference 
> to existing users, who have clear priority in this case.”/

The original fixed satellite comms (space-to-earth) allocation was 
3700-4200MHz, which was split into two parts in 2020: a mobile wireless 
spectrum allocation on 3700MHz to 4000MHz (for 5G) with 4000-4200MHz 
remaining allocated to satellite comms. The 4200-4400MHz range is 
allocated to aeronautical navigation and is used for radio altimeters.

So by rights, aviation doesn't now and never did own this spectrum. 
That said, spectrum bleed on radio transmitters is something that 
happens, and I've no doubt that there are plenty of broken altimeter 
receiver antennas out there which will pick up signals outside their 
formal allocation of 4200-4400MHz.  Regularly tested band pass filters 
should deal with most of this.

Even if technically the aeronautical sector doesn't own this spectrum, 
the consequences of transmitter or receiver bleed from nearby 
allocations could be serious for the same reason that if someone walks 
out on a pedestrian crossing without checking and gets mown down by a 
drunk driver, they're not going to be jubilantly talking at their 
funeral about how at least they were acting within their rights.


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