Second harmonic of 4.2GHz is 8.4GHz, third is 12.6GHz so unlikely to be an issue.
I would tend to go with the FCC, Ofcom etc rather than the aviation authorities and it will be the FCC who approved the use of these frequencies in the US.
Major U.S. airlines warn 5G could ground some planes !
- Thread starter tracertong
- Start date
Isn't it fm with some bandwidth taken above and below central frequency - as ian suggests.
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... I suppose you don't know in advance which runway your plane will land at to select those furthest from 5g masts
e:
https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-Interference-Risk-to-Radar-Altimeters.pdf
5G user equipment (mobile phones) that may be operating onboard aircraft were also found to exceed the safe interference limits for Usage Categories 2 and 3.
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I don't see any mention of FM above
I'll use round figures rather than the actual frequencies because it's easier to calculate. If the highest frequency you're allowed to transmit on is 100,000.000KHz and you're using a signal that's 50kHz wide, 25kHz each side of centre frequency, then you don't transmit above 9,999.975kHz. That's how things work, you don't put your carrier outside of your frequency allocation.
I still think it's garbage but safety has to be the priority and the headline grabbing perception here is that planes are going to fall out of the sky. If the airlines think that the filtering on their radar isn't up to it then surely it's the responsibility of the equipment manufacturers to improve it.
Last time I flew I downloaded a playlist whist the plane was on the tarmac over 5G. Like living in the future, 200mbps personal internet on a magic slate, sitting in a giant metal bird machine
Deleted User 298457
Deleted User 298457
I'm fairly sure I'll trust these three chaps over a radio enthusiast:
Jean-Luc Robin - Radionavigation Expert at Airbus and SC-239 Co-Chair
Seth Frick - Radar Systems Engineer at Honeywell and SC-239 Co-Chair
Dr. Sai Kalyanaraman Technical Fellow at Collins Aerospace and SC-239 Secretary
And forcing the hand of airlines/manufacturers to fix a critical safety issue by deploying 5G anyway and pushing the issue sounds incredibly.... well, yeah...
Why would you trust them - they don't appear to be very well published and only sit on one side of the arguement?
Deleted User 298457
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Lol what?? What's the other side of the argument?
Doesn't radar work using doppler effect? So whatever frequency it broadcasts on it'll also need to be listening for a response on a larger range. I've no idea how big that range would be though?
Soldato
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First, 5G gives everyone Covid, and now it’s grounding planes!
Scandalous.
We must scrap it!
Its ok theres no coverage here, enough people must have refused to take their vaccines
Soldato
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Didn't the FCC outline 4.2 to 4.4GHz for aviation use (radio altimeters)?
https://www.ntia.doc.gov/files/ntia/publications/compendium/4200.00-4400.00_01MAR14.pdf
And i'm sure i read somewhere that the FAA puts/requires a plus/minus 10% exclusion around the band due to HIRF. If that's the case, then it puts the lower end into the FCC's designated C-band (3.7 to 4.2GHz).
Still, i don't understand why this wasn't dealt with prior to giving the go ahead and i would have thought others that use that band (sat downlinks, weather radars etc) would be complaining as well
I don't see any mention of FM above
Radio altimeters use a mixture of pulsed, FM and CW and i suspect that is what @jpaul was getting at.
Seriously?
Soldato
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no phones on planes is nothing to do with interference - it's phones drawing extra power to boost signal and causing a fire hazard.
I think, it depends on what you are trying to achieve with the Radar (for example measuring speed). But yes some of them do rely on the doppler effect.
Deleted User 298457
Deleted User 298457
Yes, what is the credible argument 'on the other side'? That 5G makes no difference and it's all make belief?
Soldato
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No. Just no.
Jeez.Yes, what is the credible argument 'on the other side'? That 5G makes no difference and it's all make belief?
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Good posts
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Still, i don't understand why this wasn't dealt with prior to giving the go ahead and i would have thought others that use that band (sat downlinks, weather radars etc) would be complaining as well
WX radar is much higher power (75km/40nm+ range) so the received pulses are also higher power and therefore above the O/P power of the 5G masts at the range that a plane would be from them. Sat Downlinks AE's are generally placed on the top of the aircraft and that shields them somewhat for almost all stages of flying just due to the height the aircraft are flown at. Neither systems are considered safety critical during a landing phase so I can see why there's little issue with them so far.
Rad Alt's on the other-hand are uniquely at risk due to their low power TX/RX (only 2km/1nm range) which puts the power levels of returned pulses much closer to the levels output by 5G masts, after propagation due to distance, plus they're downward facing as well so they aren't shielded by the airframe and finally they are considered to be safety critical during the landing phase.
Yeap, however with the Radar Altimeter it's just a time based calculation rather than Doppler Shift which gives the distance. Generally a "sync pulse" within the TX section starts a timer when a pulse is sent out and the processing section stops the timer when a return is detected by the RX aerial, then it's just basic maths - Speed of light X time taken - divided by 2.