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Comment by w0mbat | Hacker News Reader

This is not true. 5G uses spectrum way outside the band that RADAR altimeters are supposed to be using. Boeing had years to fix their shoddy RADAR equipment, and the fix now can be as simple as fitting a high-pass filter.

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Agree, the societal benefits of 5G are far higher than the cost of retrofitting aircraft with radar altimeters that are compatible with 5G.

The fix can be as simple as doing nothing. All the antennae in question are directional and there is no evidence of interference.

That's not true. I work in aviation and we've had a number of reports of radar altimeter interference during takeoff and landing near airports with the new 5G towers. Older aircraft are particularly effected.

Can you share these reports? How does interference exhibit itself?

It seems there a disagreement on factual truth which as another commenter pointed out could be resolved by say a YouTube video showing "here's a radar altimeter malfunctioning near a 5G antennae"

Also your comment seems inconsistent with the fact that the telcos delayed deployment of 5G towers near airports due to concerns about interference during takeoff and landing. So how can there be reports of interference from 5G tower if they haven't even been deployed there (edit: are these international reports)?

(I work on radar, this all feels like lawyers lawyering and techies blogging, but not engineers engineering)

I've also heard these reports from a couple of friends who are commercial pilots. At least one of them filed an ASAP safety report, but I don't know of any way for the public to query that database.

I don't know of any commercial pilot who is going to jeopardize their job and their certificate by filming a YouTube video while landing. There is literally no incentive for them to do so - there's formal channels to report these things (like ASAP, see above).

Also, while turning on the 5G towers near airports was temporarily delayed, it was only a short delay (two weeks). Those towers have already been turned on.

The best news I can find about reports of interference is from this Bloomberg article. As a airline consumer, I’m glad the airline industry is being cautious, but as a radar engineer, I can say there is very, very low SNR to these reports of reports:

https://www.bloombergquint.com/amp/business/pilots-report-ov...

“The reports have come in the form of radioed descriptions to air-traffic controllers as well as through more formal incident-reporting channels. The FAA often gathers unconfirmed reports of aviation incidents, such as drone sightings, even if they’re difficult to verify. At least some of the reports from pilots of possible interference have occurred at locations where the C-band broadcasts don’t exist, suggesting no connection with the service, said two people briefed on the issue.”

If 5G was using spectrum way outside the band that these altimeters are supposed to be using... then we wouldn't have this issue. Those 737s aren't new, they certainly had permission to use that spectrum for years and while they may have had years to fix their equipment, it's certainly not as trivial as "add a high pass filter".

Now, I do agree that this should have been caught 5-10 years ago, when the standard was being developed. Boeing's incompetence wouldn't surprise me, which is probably why we see "FAA says problems for Boeing in 5G" as the headline, instead of "Aircraft companies warn of interference in safety, navigation equipment, ask FCC to reconsider" as the headline, 5 years ago. Although, as noted in the article, it seems that the FAA has been warning about the conflict - I'm just surprised that the FCC would go ahead with 5G if they had been flagged early enough.

So here we are, the FCC, in its negligence, assigned conflicting portions of the spectrum, Boeing, in its incompetence, didn't catch it - and now it's a big mess.

>they should have caught this 5-10 years ago

They mostly did. They've been warning about this for 3+ years now (see this report from the FCC back in September and October 2019) https://ecfsapi.fcc.gov/file/102214765103/AVSI%20RA%20Interi...

They couldn't have warned folks about more than a year or so sooner than that, because the spectrum bands for 5G hadn't even been fully decided prior to it. (The public notice of band reconfiguration only got announced back in May 2019)

Yup, they should suspend the rollout due to noncompliance by airplane manufacturers and fine said manufacturers for the delay.

The aviation hardware was compliant with the FCC rules (transmitting only within 4.2-4.4 GHz). FCC didn't specify anything about received interference, and didn't apply any of the methods used elsewhere in the world to limit leaking by 5G towers in 3.8-4.0GHz range.

> Those 737s aren't new, they certainly had permission to use that spectrum for years

This statement seems to be at odds with what many others in this thread are saying: that they were never approved to operate in this band. I don't know enough about this issue to know who is correct--do you happen to have a source for that since you are certain of it?

They never had permission to use the 5G spectrum, and in fact never did. The issue is that the filtering is so shoddy that signals more than 200MHz away from the band they are using can cause issues. The fault for that lies squarely on Boeing.

>The fault for that lies squarely on Boeing.

Why? They don't make the radar altimeters and multiple aircraft manufacturers are affected. Why is Boeing at fault for issues that (also) manifest themselves on Embraer and Airbus aircraft?

Boeing is ultimately responsible for every part that goes into their planes. They didn't manufacture the equipment, of course, but they signed off on it meeting their standards.

> Those 737s aren't new, they certainly had permission to use that spectrum

No they don’t, and never have. Hence the current shit show today.

Boeing got away with it because old users of the 5G spectrum where lower power satellite comms. Hilariously the oldest 737 model is unaffected by this issue, probably because Boeing actually let their engineers do good work back then, rather than forcing them to produce the sloppy crap they build today in the name of profit.

Well the whole point is they didn't have permission to use that spectrum. The interference the FAA is complaining about is explicitly outside of the radalt allocated spectrum.

FCC has allocated radalt's 200Mhz, with another 200Mhz guard on either side. If these devices are not properly filtering out frequencies outside of this massive 600Mhz range, those devices are faulty and should never have been certified by the FAA in the first place.

It's reasonable for the FCC to assume that spectrum users will not be affected by interference from so far outside their allocation.

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