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>if its the altimeters on the planes that are actually defective/not within spec. Is there any evidence this is the case? This sort of thing is a lot like prop
by upofadown 4y ago
>if its the altimeters on the planes that are actually defective/not within spec.
Is there any evidence this is the case? This sort of thing is a lot like property zoning. If a steel mill starts up next door to your residential property in what used to be a park then there is nothing stopping you from adding more sound proofing to your walls to make it so you can sleep. But should you have to do this and can you do this at all? In this case the neighbouring band was originally used for satellite downlinks. So barely detectable signals with large dishes required. Radar altimeters in aircraft actually used to cause interference to the satellite downlinks when the aircraft flew over.
The fact is that you need to have sufficient physical separation between services in adjacent bands. In this case, you can't expect things to work if an aircraft flies directly over a 4 GHz 5G transmitter at a low altitude. This aspect of adjacent band interference is an important part of spectrum management. You can't just wave the issue away...
- crote 4y agoAltimeters are allowed to use the 4.2GHz - 4.4GHz band. They are getting interference from signals at 3.98GHz and below. This means they need over twice the spectrum that was allocated to them. It's more like the family who is first to move into a neighborhood under construction, complaining that their kids can no longer play in the empty lots because houses are being built there. And it's not even the empty lot next to them, but one lot over.
- chmorgan 4y agoThis! The altimeters with issues are not operating to their design specs. No one noticed until 5g apparently but imo it’s on the altimeters, and not 5g, if they aren’t properly rejecting out of band noise/energy.
- ominous_prime 4y agoUnfortunately these altimeters are part of a very large critical infrastructure, which can't be ignored. Just saying they shouldn't be working that way doesn't negate the fact that they are working that way. Part of engineering is taking the real world into account, even if the real world is inconvenient for you.
- stevenhubertron 4y agoSo your suggestion is we ground all flights for 6-12 months while they retrofit new altimeters so you can have your phone battery die faster?
- uncomputation 4y agoYes, that’s exactly what OP proposed. /s
- upofadown 4y ago>The altimeters with issues are not operating to their design specs. Then what is the required passband attenuation at 220 MHz away from the centre frequency as per the spec? What altimeters are not meeting this spec? I find it weird that people are claiming that the altimeters are defective here. That would be a big deal if true.
- upofadown 4y agoFilters are not magic. They have tradeoffs. If you make a filter with a really sharp cutoff you end up with a really large filter with a lot of loss. So then you have trouble receiving really weak signals, say, reflections from the ground. One way you might overcome this is to really ramp up the transmitted power but that can cause radar receiver problems and can cause interference with services in adjacent bands, say, 5G. This sort of thing is why allocating TV frequencies is and was complicated. That is because someone might live right next door to a TV transmitter and they might be trying to watch a weak signal on an adjacent channel. You usually have to allocate some dead channels for the area to prevent receivers from being overloaded. So in that case would it be fair to say that receiver was using channels it had no right to when set to the weaker signal? After all, the transmitter was there before the receiver was... Note that other countries have managed to deal with this routine and common issue with respect to the introduction of 4 GHz 5G. There is something weird going on in the USA...