What do you think about this airline vs 5G brouhaha?

Masataka Ohta mohta at necom830.hpcl.titech.ac.jp
Thu Jan 20 00:34:13 UTC 2022

Tom Beecher wrote:

> It's also relevant that the spectrum surrounding the 4.2-4.4 range has not
> been an empty desert. It has been used for satellite downlink since the 60s
> I think?
> Yes, there are surely tons of differences in RF characteristics between the
> two.

The important difference is in power. Downlink signal from satellites
is, at the ground, attenuated a lot. Moreover, downlink signal comes
from above an aircraft, though some are scattered by the ground to
the aircraft.

> But let's be honest. Analysis would have been done decades ago on the
> impact of spurious emissions from sat downlinks on RAs, so there should be
> at least a baseline to work from.

Possible saturation of radar altimeter by 5G signal is caused
by signal power having nothing to do with spurious emission.

> Either way this should not be a discussion now. This clearly was discussed
> early in FCC filings, questions were asked, data was presented, and all
> these parties signed off.

True. FCC even doubled guard band.

						Masataka Ohta

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