nanog mailing list archives
Re: What do you think about this airline vs 5G brouhaha?
From: Brandon Martin <lists.nanog () monmotha net>
Date: Tue, 18 Jan 2022 18:51:29 -0500
On 01/18/2022 16:57, Mel Beckman wrote:
Bo, it’s the radar altimeter, not the barometric altimeter. This is a radar distance measurement device for determine the precise height above the ground, critical for low-visibility approaches. Where frequency interference is concerned, under FCC rules the existing users have priority, and are entitled to interference-free operation.
Hmm, I'm seeing that "radar altimeter" and "radio altimeter" can indeed refer to the same class of instrument, so perhaps there's confusion (perhaps including by myself).
Nonetheless, while indeed existing users are granted some reprieve from interference by new users of other services, this is mostly in the planning stage of things and not the actual operations. The time to get this addressed would have been back when this portion of the band was re-allocated to wireless systems (from space-to-ground satellite systems) several years ago.
Further, it seems that good engineering practice was not used in the design of these vulnerable systems and that they are subject to interference from broad-spectrum "jammers" (i.e. signals that, in terms of modulation and timing, don't necessarily correspond to what they're expecting to receive) transmitting well outside their allocated band (by separation comparable to the entire band in which they operate) let alone outside the expected, tuned frequency of signal reception. All of these are typically very high on the list of consideration when designing an RF receiver and seem to have been either ignored entirely or at least discounted in the design of these instruments from what I'm hearing.
That is, I have yet to see any source (even from the aviation industry) claiming that there is in-band interference issues from the new wireless systems or that these radio altimeter systems somehow need such extreme receiver sensitivity that a several hundred-MHz guard band between services (with an existing service in between, albeit one with the transmitter usually in the other direction) is not sufficient to ensure proper receiver isolation from unwanted signals.
-- Brandon Martin
Current thread:
- Re: What do you think about this airline vs 5G brouhaha?, (continued)
- Re: What do you think about this airline vs 5G brouhaha? sronan (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Mel Beckman (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Mel Beckman (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Lady Benjamin Cannon of Glencoe, ASCE (Jan 19)
- Re: What do you think about this airline vs 5G brouhaha? Mike Hammett (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Shane Ronan (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Brandon Martin (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? sronan (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Nick Hilliard (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Mel Beckman (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Brandon Martin (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Jay Hennigan (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Brandon Martin (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Michael Loftis (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Brandon Martin (Jan 18)
- Re: What do you think about this airline vs 5G brouhaha? Bryan Fields (Jan 19)
- Re: What do you think about this airline vs 5G brouhaha? Jay Hennigan (Jan 19)
- Re: What do you think about this airline vs 5G brouhaha? Bryan Fields (Jan 20)
- Re: What do you think about this airline vs 5G brouhaha? Scott McGrath (Jan 19)
- Re: What do you think about this airline vs 5G brouhaha? Brandon Martin (Jan 18)