Interesting, I thought that altimeters were purely mechanical devices. The auction is in progress, but the Commission has broad discretion to delay or condition licensing if it determines that this is a safety-of-life issue.
$2.6 billion dollars already has been bid after just the first 5 rounds for the 3.700-3.980 GHz spectrum. The auction can be followed here:
https://auctiondata.fcc.gov/public/projects/auction107.
73, Dave K3ZJ
From: arrl-odv <arrl-odv-bounces@reflector.arrl.org> on behalf of Kermit Carlson via arrl-odv <arrl-odv@reflector.arrl.org>
Reply-To: Kermit Carlson <w9xa@yahoo.com>
Date: Thursday, December 10, 2020 at 9:06 AM
To: Michael Ritz <w7vo@comcast.net>, Kristen McIntyre <kristen@alum.mit.edu>
Cc: "arrl-odv@reflector.arrl.org" <arrl-odv@reflector.arrl.org>
Subject: [arrl-odv:31463] Re: Aviation Groups Seek Halt to FCC Spectrum Auction | Aviation Pros
Hello Mike and Kristen,
I was cleaning out the garage this weekend, and did put two radar altimeters
into the electronic waste stream. These were Bendix-King units that are basically
range detecting 3.5-3.6 GHz CW units that use a processed swept doppler method to display the altitude on a panel mounted gauge. I seem to remember that they were simple non-locked
cavity oscillators, they had impatt diodes oscillators with a diode mixer front end.
This model is currently in use and similar newer systems are improved but the requirement for selectivity had not been demanding because it operates in a portion of
the spectrum designated for radiolocation......
73, Kermit W9XA
On Wednesday, December 9, 2020, 9:37:20 PM CST, Kristen McIntyre <kristen@alum.mit.edu> wrote:
My guess is that if there are cellular carriers in or
near the frequency range used by radar altimeters, they could easily interfere when flying over the towers. Probably S-band at 3.2 GHz. Those are strong signals and there might be enough energy to cause de-sensing. Radar altimeters are most
common on helicopters which fly pretty low and need AGL altitude accuracy to avoid terrain.