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

Jay Hennigan jay at west.net
Tue Jan 18 22:21:11 UTC 2022

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

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