Hello David,

     Yes, the "steam-gauge" altimeter that relies on the pressure altitude is very
much still in use and is in fact required instrumentation for instrument flight, along
with a requirement for biennial re-certification and calibration. 

         With the advent of GPS, terrain avoidance displays are employed in an effort
to reduce the incidents of CFIT (Controlled Flight into Terrain) but a number of
aircraft still use the radar altimeter systems.  I have experience with the radar altimeter
in the approach segment of flight and personally I always found that instrument
useless during the approach.... unless the approach inside the outer marker was
"corn-field flat".


                                                  73, Kermit W9XA



On Thursday, December 10, 2020, 8:27:10 AM CST, david davidsiddall-law. com <david@davidsiddall-law.com> wrote:


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.



On Dec 9, 2020, at 3:11 PM, Michael Ritz <w7vo@comcast.net> wrote:

 

I don't understand the issue. The FCC is supposed to be vacating others off those frequencies, meaning they have to go somewhere else. Is this a situation where the particular propagation of 3.5 GHz signals will affect wideband receivers used in the radar altimeters? 

 

I guess I don't know how they work.....

 

73;

Mike

W7VO

 

 

On 12/09/2020 1:25 PM Kristen McIntyre <kristen@alum.mit.edu> wrote:

 

 

Above our allocation, but it might be relevant to the ultimate disposition of that band.

 

 

                                    -Kristen (K6WX)

"Your eyes ... it's a day's work just looking into them" 
                                       Laurie Anderson

(--... ...--  -.. .  -.- -.... .-- -..-)


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