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

Wed Jan 19 09:53:05 UTC 2022

Jay, one thing you’re missing is that a maximum of 2 (and almost always 1) radar altimeter will be in use per airfield, as one aircraft will be landing at a time. 

2 at SFO in good weather. (Where it doesn’t matter if they work). 

Apparently some old gear has trouble with even a 500MHz guard band, which I also find astonishingly bad for any time, but a lot of aviation tech is truly from another century. 

They also have main lobes approx 80* wide so they still function when the plane is in 40* of bank.

Ms. Lady Benjamin PD Cannon of Glencoe, ASCE
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> On Jan 18, 2022, at 2:25 PM, Jay Hennigan <jay at west.net> wrote:
> 
> On 1/18/22 12:29, Michael Thomas wrote:
>> I really don't know anything about it. It seems really late to be having this fight now, right?
> 
> From a technical standpoint it seems to me to be a non-issue. There's a 220 MHz guard band. 5G signals top out at 3980 MHz and radar altimeters operate between 4200 and 4400 MHz.
> 
> If a signal 220 MHz away is going to interfere, then radar altimeters on other aircraft operating in the same band would clearly be a far greater threat, and those radar altimeter signals will be rather numerous near airports. In other words, if non-correlated signals 220 MHz away are going to interfere, then signals within the same band are going to be a far greater source of interference.
> 
> Radar receivers are typically some form of direct conversion with rather good selectivity, synchronized to the frequency of the transmitted pulse. In addition, radar altimeter antennas are pointed at the ground, perpendicular to the horizon. Cell site antennas by design are aimed more or less toward the horizon, not pointed straight up at the sky.
> 
> There's also an existing FCC mobile allocation from 4400 to 4500 MHz directly adjacent to the aeronautical radar band on the high side with no guard band, yet no complaints about that.
> 
> IMNSHO, the concern that 5G cellular signals will cause airplanes to fall out of the sky has about this >< much more credence than the concern that 5G signals cause coronavirus.
> 
> It shouldn't be that hard to instrument an aircraft with test equipment, buzz a few operating cell towers, and come up with hard data.
> 
> -- 
> Jay Hennigan - jay at west.net
> Network Engineering - CCIE #7880
> 503 897-8550 - WB6RDV