4 ms·
There's a 200 MHz guard band between, and (on top of that!) another 200 MHz unused. The altimeters aren't even close to the 5G spectrum. The gap between C-band
by 37ef_ced3 5y ago
There's a 200 MHz guard band between, and (on top of that!) another 200 MHz unused. The altimeters aren't even close to the 5G spectrum. The gap between C-band 5G and the aircraft frequencies is ENORMOUS, wider than anywhere in the world.
- _djo_ 5y agoIt’s not that simple. Radar altimeters use very low power levels and are extremely sensitive to both adjacent channel and out of band interference. Until now this has not been an issue because systems operating in the 3.8-4GHz range have had low power levels. When you’re pumping that much RF energy out, 200MHz separation isn’t nearly enough. Especially as many aircraft have been flying for decades and frequency filtering standards for radar altimeters against this level of interference weren’t a design requirement in the past. The RTCA did a comprehensive study on this and found substantial interference of radar altimeters from 5G networks at the intended power levels would result. Given that RAs are the only mechanism by which an aircraft can reliably know its height above the ground on take off and landing, this is a crucial safety issue. https://www.rtca.org/wp-content/uploads/2020/10/SC-239-5G-Interference-Assessment-Report_274-20-PMC-2073_accepted_changes.pdf https://www.rtca.org/wp-content/uploads/2020/10/SC-239-5G-In... Again, there’s a reason that every single country other than the US that’s approved 5G spectrum has avoided this issue by insisting on lower power levels, frequencies further apart, larger frequency gaps, and buffer zones around airports.