## Monday, January 03, 2022 ... //

### Precautionary insanity invades the electromagnetic spectrum

Alarmism and hurtful, ludicrously ineffective methods to fight the overhyped threats have become an omnipresent part of policymaking and a giant pain in the aßes of those of us who aren't brainwashed morons (and especially those of us who often have to pay for this craze, unlike the fearmongers who usually benefit from the destruction instead).

It's common for millions of psychopaths to talk about climate threats and demand hundreds of medieval rituals claiming to improve the weather. The Wuhan virus and the corresponding respiratory disease, while very real, have been uselessly fought against by regulations whose total cost exceeded 10 if not 20 trillion dollars and most of which have had no detectable positive impact and many of which continue even now when the epidemics is demonstrably over.

But people can invent new kinds of alarm, can't they? The conspiracy theories about 5G have been associated with "truly independent", usually right-wing, folks who don't hide their negative attitude to standard science. For example, we've heard that 5G has killed birds. These low frequencies are extremely unlikely to cause any health issues in any organisms. Low-frequency radiation isn't ionizing and from the cells' viewpoint, they are just slow waves on the ocean.

But two new groups have joined the anti-5G tin hats' movement: some pilots' organizations and the Biden administration. On New Year's Eve, the U.S. secretary of transportation Mr/Ms Buttigieg – whose main qualification for politics is being homosexual – asked AT&T and Verizon to delay the activation of their 5G services which is expected this week. To make the story short, Verizon and AT&T rejected this demand hours ago. The safety concerns are unjustified and it's also bizarre and possibly illegal to single out two companies.

The critics' concern is that some aviation equipment, especially the radar altimeters, may fail to function or may malfunction because of some interference between their signals and the 5G signal. It is rather clear how the people are divided to the two camps in this disagreement. The 5G alarmists include many pilots who know how to look at some gadgets in the aircraft, Buttigieg who is gay, Biden who is senile, and some pilots' bureaucratic organizations such as the FAA (the U.S. aviation regulator), IATA, and IFALPA that sometimes write a superficial 2.2-page critique of 5G whose only argument is some rumor about a dissatisfied pilot in Tel Aviv.

On the other hand, you have the FCC, the U.S. communication regulator, and the providers such as Verizon and AT&T whose work is all about the electromagnetic spectrum, who actually understand it, who care how effectively the real estate of the spectrum is used, and whose profits depend on doing it right.

The electromagnetic spectrum real estate

I gradually understood that the different radio (and TV) stations were transmitting at different frequencies and the frequency was effectively a "new dimension of space". So each point was actually a line (labeled by frequency) and different parts of the line were dedicated to different radio (and TV) stations. A better description is a 6D space: each point in the regular 3D space is actually a 3D space spanned by the "wave numbers" organized in the vector $$\vec k$$. The information about all the radio stations could still be encoded into a single function of time. But that function may be Fourier-transformed (and you may do so back and forth) and parts of the Fourier transform around specific frequencies are dedicated to specific stations.

Only as a teenager, I really understood the Fourier transform – and also Chapter 23 of the Feynman Lectures on Physics that explains resonance. That includes the crucial differential equation (and its solutions) that is responsible for having antennas that are sensitive to particular frequencies or frequency bands. Cutely enough, the same differential equation (and Feynman's chapter) also described the mechanical resonance of pendulums etc. (and arguably many other seemingly different situations in physics). The language of quantum mechanics later made the "doubling of the dimensions" really transparent. Indeed, at each moment of time $$t$$, photons live in a 6D space labeled by $$\vec x$$ and $$\vec k$$ but the space isn't quite classical. Instead, there are minimum cells in the 6D phase space whose 6-volume is $$(2\pi)^3$$. That just follows from the commutator $$[x_m,k_n]=i\delta_{mn}$$ that is normally known in quantum mechanics for $$\vec p = \hbar \vec k$$.

At any rate, let me assume that you understand that the electromagnetic waves are qualitatively the same thing but all the diversity of their behavior is encoded in the frequency. So the lowest frequency ones are radio waves, then you go through microwaves, infrared radiation, visible light (including colors from red to orange to yellow to green to blue to violet), ultraviolet light, X-rays, gamma rays, if I simplify it a little bit.

The pilots-vs-providers' 5G controversy is a battle taking place in the battlefront near "several GHz" (gigahertz is a billion cycles per second). Relatively to the previous, 4G, mobile data frequencies, the frequencies used for 5G are higher. Higher frequencies allow a higher bitrate. The numbers of "bits per second" (bitrate) and "cycles per second" (frequency) are actually comparable. 5G operates in Frequency Range 1 which is 3.3-4.2 GHz (Koreans love 3.5 GHz, the n78 band); and Frequency Range 2, 24-54 GHz. You may want to see a much more detailed tables of 5G New Radio bands. The critical bands assigned to 5G are 3.7-3.98 GHz.

As quoted at various pro-aviation pages such as Skybrary and a text at The Verge, the pilots are afraid of their 4.2-4.4 GHz which is used for radar altimeters. What are they? As the picture at the top indicates, they are very simple ancient tools. The aircraft sends some signal towards the ground, it is reflected, the device in the aircraft measures the delay, and when it's multiplied by the speed of light, it can calculate twice the distance from the ground (bats have done the same thing with the speed of sound for millions of years).

It should still be safe because the altimeters use 4.2-4.4 which is separated from 3.7-3.98 GHz by a gap whose width is 0.22 GHz (and my understanding is that this gap is supposed to remain empty in the U.S.). But they are afraid of the interference between the two bands, anyway. In principle, because of the uncertainty principle (the quantum character of the "phase space" that I mentioned above), it is true or possible: the frequencies are never "perfectly separated" from other frequencies, even very distant ones. The phase space isn't a sharp classical space, it is fuzzy. Whenever you change the frequency a little bit, and according to the Fourier transform, other frequencies are involved whenever you violate the "precise periodicity of the signal", the pre-existing frequency gets mixed with other (mostly nearby, but in principle, any) frequencies. So they may interfere. The question is how much. And the resonance curves show that $$\Delta f$$ away from the right frequency, and far enough from the very good resonance, the intensity of the signal drops like $$1/(\Delta f)^2$$.

Needless to say, the 5G signal doesn't have a reason to be "insanely stronger" than the altimeter signal (the 5G towers want to reach a bit further than the altimeters' range of 760 meters but not "many orders of magnitude" further), and the very big distance between the two frequency bands guarantees that the interference is low. If the 5G providers guarantee that their 5G signal is less than X orders of magnitude stronger than the altimeter signal at typical distances near the airports, and X may be calculated in a straightforward way (the width of the band or the precision of the frequencies that are used play a role in the calculation), it guarantees that the altimeters' signal beats the 5G signal according to the altimeter frequency receivers, and the interference is small enough to be harmless. Note that the altimeter is only needed when there is fog at the airport, otherwise the pilots may trust their eyes when it comes to the altitude.

There are surely better solutions. Verizon and AT&T have generously offered some weaker signals at the airports, or an agreement to delay the 5G launch near a dozen of selected airports in the U.S. Also, the 5G antennas could only be turned off (and switched to 4G) when an aircraft approaches (the aircraft uses the altimeter when the altitude is below 760 meters). At some moment, the battle for these bands has to be resolved and a more permanent solution will have to be found. I personally find the 4.2-4.4 GHz altimeter band to be extremely wide and generous relatively to the usage (and the pilots should shut up if they want to keep the band at all). Why? You know, there are nearby frequencies that will be transmitting "one gigabyte per second" or so. What about the altimeter? It really needs to transfer a few useful bytes per 0.01 second (a time shorter than the reaction time of the pilot), the altitude with some limited precision. Throughout the whole flight, the altimeter almost certainly transmits less than "one kilobyte of useful information". Surely it could be done in a better way, a way that doesn't waste the precious frequency space "real estate" so incredibly much. These radar altimeters using these huge bands so inefficiently are not just legacy devices, they are true dinosaurs. Maybe regular radios are also dinosaurs and we should switch to radios that extract some signal digitally from the nearly omnipresent 5G signal which could be ordered to carry the basic radio station in each region (although yes, it's fun to have radio in mountains even when no mobile phone signal is available).

In fact, I am nearly certain that the altimeters could be remade in such a way that they could directly work with the 5G frequencies i.e. co-exist with the useful 5G signal. The aircraft should communicate via 5G, anyway, and the delay is something that a device communicating in 5G may easily measure. To be honest, I would say that the whole aircraft-initiated analysis of the altitude seems obsolete. All allowed terror-non-attacked airports should actively measure and know the precise location and altitude of all nearby aircraft and broadcast the information to them, too. Well, in fact, you might be surprised that the complaints don't go in the opposite direction. Verizon and AT&T could complain that the damn altimeters broadcasting at "nearby frequencies" are perturbing their nice 5G signal near the airports! ;-) The main reason why they don't do it is that they realize that it's not really happening (and there are many levels of insurance in the case that some packets get killed).

While this looks like a technical question in the industry of electromagnetic waves whose "sides" are equally likely to possess the right arguments, I think that in reality, it is just another battle between common sense combined with conventional science and technology on one side; and overhyped worries and precautionary principle-based reasoning (or the absence of reasoning) on the other side. You know, the gap between the two bands is over 0.2 GHz which is some 5% of the frequencies themselves. They are hugely separated. We are supposed to believe that they are "too close", anyway.

As far as I know, not even in the 19th century, people were hysterical about the interference between frequency bands where the gap was over 5% of the frequency. When we allow this kind of alarmism to thrive without a proper quantitative analysis of the amplitudes, we guarantee that similar hysterias will also grow more extreme. Maybe microwaves shouldn't be allowed because when they're turned off, they also have a chance of producing a gamma particle? The visible light interferes with the infrared remote controls and you will not be allowed to use one in the presence of the other. TV broadcast should be banned because it sometimes emits an ultraviolet photon and causes skin cancer, and so on. ;-)

Please, stop this insanity. The radar-altimeter and 5G-range-1-restricted-to-the-US-subset are two bands that are hugely separated and if some fixes really need to be done to avoid the interference, we should only do it after we see a nontrivial number of examples when an aircraft was really affected by this interference. The interference isn't the end of the world, the airplane still has other options, and indeed, when things are really bad, it may be diverted. At least, the stopping of the 5G towers should be restricted to the airport, and to the moments when the aircraft actually seem to need it. Too much precautionary principle may really kill the economy and perhaps kill many people, too. I think that the comparison of costs and benefits may be done even by passengers: do they want to sacrifice 5G at the airports (or 5G in the whole U.S.?) just because 1% of flights need to be prolonged by a minute in average because of some need to replace the legacy altimeter procedure by a different one?

Disclaimer: I own Nokia stocks that produces the most complete 5G solutions and I don't know whether it has served Verizon and AT&T and whether it could still be affected by these U.S. aviation battles.