In a separate thread started by Susan called “Will your flip phone work tomorrow?”, where the topic was the effect of the staggered end of support of telecoms for 3G cell phones and other wireless equipment to be replaced with 4G ones, beginning with AT&T earlier this week, the discussion moved to 5G and then to the problems this new system will bring in a potentially major way by interfering with two things critical to the functioning of today’s advanced industrial world, and of a good many places that are less so: the safety of flight and the proper functioning of GPS and of the similar satellite positioning and timing systems of other nations and the EU, known collectively as GNSS, or Global Navigation Satellite Systems.
I wrote there to give my unfavorably view of 5G on the ground of those being extremely serious problems, and examples of the phenomenon of progressive encroachment by various money-driven interests on the radio spectrum that belongs to everyone and to no one. This spectrum has frequency bands apportioned for various uses, by law first and then by the auctioning of the bands within each band by government bodies to companies that intend to use them with legitimate and possible beneficial purposes.
However, as the topic of Susan’s thread was not about 5G, I made the description of the problem rather sketchy for brevity’s sake. Now I intend to remedy this to some extent here.
There are two radio frequency bands that are in play here: the C Band and the L Band.
(1) C-Band 5G vs. Aviation:
The use of the C band for 5G transmissions in the USA has run into stiff opposition from the aviation companies and from the FAA, among other entities public and private, because of the potential to interfere with aircraft radio altimeters and other equipment needed to ensure the safety of flight. The altimeters in particular are important because they determine the distance of the airplane to the ground, most important when landing, especially in conditions of reduced visibility. There are other kinds of altimeters that do not depend on radio, such as laser ones, but radio altimeters can “see” through clouds and fog and laser ones can’t:
https://www.gpsworld.com/us-agencies-tangle-on-possible-c-band-interference/
(By the way, there is a typo in the article: it is “5G” not “4G” — it used to be 4G in a previous life of this company.)
Of course, the US government could force airlines and private airplane owners to use radio altimeters that work at a different frequency. The problem then is that the USA, being the recipient of flights from and to all over the world, would have some trouble making the whole word move to using a different standard frequency for their airplane altimeters and retrofit all of them accordingly.
(2) L-Band G5 vs.GPS:
In the USA, there has been a very long fight, still going, between, on one side, the owner of a hedge-fund and head of a wireless nation-wide company he has tried, in various way, for a number of years, and under two different names divided by a bankruptcy, to get permission from the FCC to set up and operate. And, on the other side, the DoD, NASA, other agencies, GPS/GNSS equipment manufacturers. And companies that provide GPS/GNSS services, such as precise positioning of farm equipment so the furrows come nicely straight and parallel and turn in the right places, but also for keeping the power grid working harmoniously, without starting nation-wide cascading blackouts, and countless other practical, important and vital uses that this type of satellite system has, even in our daily life:
https://en.wikipedia.org/wiki/Ligado_Networks
The problem with this company, in particular, is that instead of C-Band 5G, it has managed to get from the FCC a portion of the L band used by GPS/GNSS for a 5G country-wide system. As it happens, the L band is also the part of the radio frequency spectrum where the signals of GPS/GNSS happen to be transmitted. There is no direct overlap of Ligado’s 5G signals and those of GPS, but that is not the problem. The problem is that, while telephone signals are, supposedly, nice sine waves with some nice modulation on top, the real signals are not quite like that, because they are inevitably suffering from some distortion, even if this is small enough not to be a problem for their intended use: one can still understand what the other party is saying.
But there is distortion enough to create spurious signals, harmonics of the intended ones, above the band of 5G and right on the middle of the GPS/GNSS band. Now, while this distortion is tiny, so the power spilling over with these harmonics is also tiny, the GPS signals coming from more than 20,000 km high above and spread over almost half the world from each satellite, are much tinier still, and get swamped.
Or such has been the contention of the government agencies, the military most prominently, GPS equipment manufacturers, the professional associations and academies of scientists and engineers (myself included) that, among other things, use those signals to do things that require knowing the position of vehicles and other objects, moving or fixed on the ground, very precisely, as well as very precisely synchronizing clocks, for example so as not to have nation-wide cascading blackouts because of collapsing power grids. And there is legislation to end this threat to GPS for good being pushed in Congress.
So Ligado and its part of the spectrum are on rather shaky ground:
But who knows how this is going to end.
But I would not spend money to buy in a hurry anything with “5G” on it.
Ex-Windows user (Win. 98, XP, 7); since mid-2017 using also macOS. Presently on Monterey 12.15 & sometimes running also Linux (Mint).
MacBook Pro circa mid-2015, 15" display, with 16GB 1600 GHz DDR3 RAM, 1 TB SSD, a Haswell architecture Intel CPU with 4 Cores and 8 Threads model i7-4870HQ @ 2.50GHz.
Intel Iris Pro GPU with Built-in Bus, VRAM 1.5 GB, Display 2880 x 1800 Retina, 24-Bit color.
macOS Monterey; browsers: Waterfox "Current", Vivaldi and (now and then) Chrome; security apps. Intego AV
