3 ms·

Right, so, the issue is NOT the BTS that is being raised, it is the phone on the plane, which are a lot closer to the antenna on the plane, which is on the ass

Right, so, the issue is NOT the BTS that is being raised, it is the phone on the plane, which are a lot closer to the antenna on the plane, which is on the ass end of the plane which is the low point during take off and landing. this is the white paper that the FAA bases their concerns on 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... that is the issue they are raising I have run the numbers and there is no way even at phone full power that it can interfere unless it was less than 2m away even then it would have to be free space, etc. the body losses, airframe, antenna back scatter all taken into account, very very unlikely unless the radar bandpass filters are from the 1960's

upofadown 5y ago
>...unless the radar bandpass filters are from the 1960's ... Were filters particularly bad in the '60s? If you claim to have run the numbers you will have to reveal your assumptions.
- zw123456 5y ago
  yes, DSP's did not exist then :) The numbers are in the doc i posted.
amirhirsch 5y ago
Thanks for sharing. I’m going to read this report now. Are you in Radar? Potentially looking for a job at a well-funded startup making very high powered phased arrays in c and x bands?
amirhirsch 5y ago
The conclusions in the report are more severe than your comments are presenting. I don't think this is a good forum to discuss it further though. There is another comment suggesting a clash of two vastly different safety cultures that really hits the nail on the head, and I think that even the hypothesized/speculative risk to aviation needs addressing, though you are also probably right that the aircraft industry wants cash from the telcos for a retrofit that they should pay for themselves and were willing to drag their feet assuming FAA would trump the FCC in this matter (they will). Frankly if they want digital pulse-compression radar altimeters that are going to operate even with adversarial interference, I built/am-building the most advanced matched filter in the world though it will cost a bit more than a sub-$1K High Pass Filter plugged in line with the antennae which is probably sufficient (though avionics safety requirements will probably find a way to make it $100K anyway)

upofadown 5y ago

>...unless the radar bandpass filters are from the 1960's ... Were filters particularly bad in the '60s? If you claim to have run the numbers you will have to reveal your assumptions.

zw123456 5y ago
yes, DSP's did not exist then :) The numbers are in the doc i posted.

amirhirsch 5y ago

Thanks for sharing. I’m going to read this report now. Are you in Radar? Potentially looking for a job at a well-funded startup making very high powered phased arrays in c and x bands?

amirhirsch 5y ago

The conclusions in the report are more severe than your comments are presenting. I don't think this is a good forum to discuss it further though. There is another comment suggesting a clash of two vastly different safety cultures that really hits the nail on the head, and I think that even the hypothesized/speculative risk to aviation needs addressing, though you are also probably right that the aircraft industry wants cash from the telcos for a retrofit that they should pay for themselves and were willing to drag their feet assuming FAA would trump the FCC in this matter (they will). Frankly if they want digital pulse-compression radar altimeters that are going to operate even with adversarial interference, I built/am-building the most advanced matched filter in the world though it will cost a bit more than a sub-$1K High Pass Filter plugged in line with the antennae which is probably sufficient (though avionics safety requirements will probably find a way to make it $100K anyway)