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The FAA has noted that in other countries there were mandates for lower power levels for 5G and that the antennas be pointed down toward the earth so that they
by mdasen 5y ago
The FAA has noted that in other countries there were mandates for lower power levels for 5G and that the antennas be pointed down toward the earth so that they interfered less.
https://www.faa.gov/5g https://www.faa.gov/5g
Lower power levels and a downward tilt on the antennas would mean less range for C-Band networks so carriers would rather not do that - especially in the US where the population is much more suburban and rural than Europe.
It's possible that C-Band won't interfere even at higher power levels and even without downward antenna tilts. However, other countries have mandated greater permanent restrictions on C-Band than the US's temporary 6-month measures.
- ajmurmann 5y agoAFAIK it's not the power level, but 5G in the US has a sightly higher spectrum range that's closer to that of the radio altimeters. Finland apparently even uses power levels that are do high that they'd be illegal in the US without any problems. Source: https://www.lightreading.com/5g/why-does-5g-only-pose-a-problem-for-us-airplanes/d/d-id/774629 https://www.lightreading.com/5g/why-does-5g-only-pose-a-prob...?
- mdasen 5y agoThe FAA doesn't cite that concern on their page, but having a 200MHz buffer in the US rather than a 380MHz buffer is a difference. As noted in the article you posted, Canada is requiring antenna down-tilting nationwide as well as exclusion zones around airports. EDIT: "an exclusion band is allowed ±10% around the band, within which the HIRF levels are very low—for radar altimeters, this spans 3.78–4.84 GHz" https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-Interference-Risk-to-Radar-Altimeters.pdf https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-In... So, in Europe, their C-Band ends at 3.8GHz and barely enters the range. In the US where we're going to 3.98GHz, we're well into that range. It looks like Korea's band ends at 3.7GHz which is outside the range (and definitely by 3.8GHz which is where band N78 ends; the US is using Band N77 which ends at 4.2GHz, but we've only licensed spectrum to 3.98GHz)
- DannyBee 5y ago200 is already crazy large. Super crazy. The original request from Boeing was only 100 These altimeters are dangerously defective if they need a 400mhz guard band. That is nuts
- indrora 5y agoyou're actually looking at the intersection of three problems: * LTE is very noisy (it has echos in its sidebands for up to 100Mhz) * low-frequency LTE is *loud* -- punch through mountains loud. * These altimiters are doing the RF equivalent of looking for a needle in a haystream While FCC Part15 says "accept any/produce as little as possible", much of this comes down to the physics of RF.
- berkut 5y agoI've read it's multiple concerns: https://www.faa.gov/5g https://www.faa.gov/5g https://www.airlines.org/5g-frequently-asked-questions/ https://www.airlines.org/5g-frequently-asked-questions/ In Europe, the power output seems to be ~2.5 time lower, there's a bigger frequency separation in Europe, the 5G towers are placed further away from approaches, and the antennas have to point downwards.
- gormandizer 5y agoC-Band in the US is rolling out in 2 phases, the first uses spectrum from 3.7 to 3.8 GHz. The second - in roughly two years - adds the remaining 3.8 to 3.98 GHz. So for the first two years the spectrum used by C-Band 5G in the US is essentially the same as in most of the rest of the world. https://www.commscope.com/blog/2021/maximizing-c-band-deployments-with-commscope/ https://www.commscope.com/blog/2021/maximizing-c-band-deploy...
- Terry_Roll 5y agoDoesnt this show that some country's dont plan ahead that much or different elements of Govt are too disconnected to work cohesively? Still, this chatter will no doubt give some loon some ideas on how to bring down a plane or mess around with the flight patterns at busy airports.
- kolanos 5y ago> Doesnt this show that some country's dont plan ahead that much or different elements of Govt are too disconnected to work cohesively? This can be a feature, not necessarily a bug. There are plenty of examples of government central planning and cohesion going very wrong.
- MomoXenosaga 5y agoRadio spectrum was decided somewhere in the 1950s and as I understand it the US military owns most of it. It's difficult to plan ahead for future technology.
- Terry_Roll 5y agoOh I dont know, I think other countries seem to be making less of a hash of it, compared to the US. And does it really matter if the US Mil own the spectrum? Thats like me saying the UK Govt owns the spectrum, they should still both be subjected to the court of law, if the laws are fit for purpose in the first place!
- kyrra 5y agoI thought that AT&t and Verizon offered to do lower power towers near airports. The story from November seems to say as much. https://www.theverge.com/2021/11/24/22801008/verizon-att-midband-5g-c-band-lower-power-six-months https://www.theverge.com/2021/11/24/22801008/verizon-att-mid...
- RNCTX 5y agoAll cell phone towers seem to be aimed toward the ground. I've flown a GA aircraft all around the lower 48, and only get a cell phone signal briefly when flying directly over a cell tower.
- Fatnino 5y agoNaturally. Why would a cell carrier want to expend energy beaming signal into space? That said, you do get the occasional misaligned antenna or weird bounce off terrain that gets you signal midflight for a minute.
- jcalvinowens 5y agoIt's really regional. I get 5 bars pretty much anywhere below 5000ft in the bay area.
- _moof 5y agoYep, I get signal up to about 3000' AGL where I am.
- supernova87a 5y agoWell, given that the possible range to a cell tower is about 35 km / 20 mi (max, an absolute limitation of how the GSM/timing is done), it's very plausible that even if cell broadcast antennas are generally pointed down + flat with the horizon, you're gonna get some signal from some antenna in the distance.