I note new radio altimeters make mention that they are resistant to 5G interference.
Sent from my iPhone > On Dec 12, 2021, at 2:17 PM, Chuck McCown via AF <[email protected]> wrote: > > > But it was probably not developed in 1955. > > From: Bill Prince > Sent: Sunday, December 12, 2021 1:57 PM > To: [email protected] > Subject: Re: [AFMUG] C band 5G vs Radar Altimeters > > Yet somehow the range-finding in my Mazda can figure out the distance to the > car in front of me and adjust accordingly without a flat surface or using > much bandwidth. > > > > bp > <part15sbs{at}gmail{dot}com> > On 12/12/2021 12:22 PM, Chuck McCown via AF wrote: >> From a white paper: >> >> Radar Altitude resolution is defined as where Bandwidth refers to the >> amount of linear frequency modulation in Hertz and c is the speed of light >> in meters per second. Specifications for Commercial Transport Altitude >> Accuracy found in industry document DO‐155 within 1.5 feet at or below 75ft >> of altitude and within 3 feet at or below 150 ft of altitude. These accuracy >> levels were determined from requirements for safety and smooth reliable >> performance for every landing under all visibility conditions. >> >> The above calculation then reveals that to resolve 3ft of altitude range >> requires 164 MHz of modulation bandwidth. In order to reach 1.5 ft >> resolution would have required 328 MHz of operating bandwidth, but that is >> not available within the legal band. To reach 1.5 ft resolution requires >> “sub‐resolution” of the data by signal processing means. But this >> sub‐resolution is only possible with exceptionally high signal to noise >> ratios and over the flat surface of the runway at low altitudes. >> >> The total bandwidth is: 164MHz Resolution + 10MHz Multiple Altimeter Offset >> +15 MHz Frequency temperature stability results in a total 189MHz with the >> remaining 11 MHz of bandwidth reserved for 5.5 MHz wide “guard bands” at >> the band edges to assure that the minor sidebands created by the altimeter >> do not intrude on adjacent band users and similarly to avoid adjacent band >> users that might otherwise interfere with normal altimeter operations. >> >> From: Chuck McCown via AF >> Sent: Sunday, December 12, 2021 1:05 PM >> To: Mike Hammett ; AnimalFarm Microwave Users Group >> Cc: Chuck McCown >> Subject: Re: [AFMUG] C band 5G vs Radar Altimeters >> >> Start with every single airliner worldwide and probably every single >> military aircraft. This is a global system, global frequency allocation and >> brand new planes come with radar altimeters. >> >> From: Mike Hammett >> Sent: Sunday, December 12, 2021 12:19 PM >> To: AnimalFarm Microwave Users Group >> Cc: Chuck McCown >> Subject: Re: [AFMUG] C band 5G vs Radar Altimeters >> >> There can't be THAT many old planes in the air that have this automated >> landing system. >> >> Buy new receivers or install some filters. >> >> 5 MHz away? Okay. >> 10 MHz? Maybe. >> 200? Bugger off. >> >> >> >> They're not making new spectrum, so everyone (even incumbents) needs to move >> with the times. >> >> >> Just like the 30 MHz T1 microwave links out there. Put something else in the >> air more efficient. >> >> >> >> ----- >> Mike Hammett >> Intelligent Computing Solutions >> >> Midwest Internet Exchange >> >> The Brothers WISP >> >> >> >> >> From: "Chuck McCown via AF" mailto:[email protected] >> To: "AnimalFarm Microwave Users Group" mailto:[email protected] >> Cc: "Chuck McCown" mailto:[email protected] >> Sent: Sunday, December 12, 2021 1:06:03 PM >> Subject: Re: [AFMUG] C band 5G vs Radar Altimeters >> >> Lots of old planes in the world. Lots of old front end filters too. And >> the system chirps the band to get a more sure return so it needs the >> bandwidth. It was designed to be robust, not to be spectrum efficient. >> Probably came out of WW2. >> >> Sent from my iPhone >> >> On Dec 12, 2021, at 11:45 AM, Mike Hammett mailto:[email protected] wrote: >> >> >> If radio altimeters have 200 MHz (which seems excessive), it seems equally >> excessive to be complaining about noise from 200 MHz away. >> >> >> >> ----- >> Mike Hammett >> Intelligent Computing Solutions >> >> Midwest Internet Exchange >> >> The Brothers WISP >> >> >> >> >> From: "Tim Hardy" mailto:[email protected] >> To: "AnimalFarm Microwave Users Group" mailto:[email protected] >> Sent: Sunday, December 12, 2021 9:50:44 AM >> Subject: Re: [AFMUG] C band 5G vs Radar Altimeters >> >> Deja Vu all over again. Very similar to the OBE / adjacent channel concerns >> voiced in the 6 GHz unlicensed proceeding. The FCC’s total lack of >> understanding of receiver filtering in even current devices is astounding >> and its fairly clear that money / politics beats physics everyday. >> >> On Dec 11, 2021, at 3:59 PM, Chuck McCown via AF <[email protected]> wrote: >> >> I understand the issue now: >> https://youtu.be/942KXXmMJdY >> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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