Tom,
Please listen to the podcast available here
Long story short: the aviation industry is hyping the possibility of dead bodies all over the place if the cellular carriers (which have paid big bucks to put 5G equipment in "C Band") don't stop and change their plans and go someplace else.
Here's the point that I'm confused about: according to the podcast, the cellular authorizations go up to 3.98 GHz, and the aircraft altimeters that we're hearing all these dire warnings about are assigned to a range which starts at 4.2 GHz. I'm old-school, admittedly, but having 220 MHz of "guard" space between those two services seems adequate to me.
Ergo, why the fuss?
- Are the avionics salesmen trying to create a firestorm of fear that motivates airlines to buy brand new radar altimeters? * Do the old altimeters have substandard design? * Is the cellular industry choosing to ignore known risks? * Is it all a ploy by the cellular carriers to grab more spectrum for cheaper prices?
I'm just waiting for the other shoe to drop, because there's something unsaid in this debate.
Replies intended for publication should be sent to snipped-for-privacy@remove-this.telecom-digest.org <mailto: snipped-for-privacy@remove-this.telecom-digest.org?Subject="[telecom]">.
Bill Horne Moderator, The Telecom Digest
The problem is that the FAA standards for altimeters required them to exclude signals from "more than 10%" away. That's 420 MHz of allowable sloop in the receiver. They made that standard in 1983 and never updated it. Many altimeters are better than that, but some apparently aren't, or aren't much better, so they can pick up signals from 3.8-3.98 GHz.
So both sides are at least partly to blame. The FAA allowed crap altimeters to stay around too long, simply because there was no immediate need to do better. And the FCC discounted their concerns, because the actual risk is pretty small. Also, the FCC allowed the mobile base stations to operate at higher power levels than European ones can, and if they actually do run full power