The Grand 5G TV Frequency Reshuffle

From now until July, TV broadcasters in the U. S. are in the final phases of a grand reshuffle of broadcast frequencies that has been going on for several years.  Unless you happen to watch TV the old-fashioned way—by getting a signal from a rooftop or indoor VHF/UHF antenna directly from the terrestrial broadcast transmitter—you probably haven't even noticed.  But this is the tail end of a process that began back in 2012, when the U. S. Federal Communications Commission (FCC) auctioned off a slather of frequencies in the 600-700 MHz range to be used as a part of the new 5G mobile-phone plan.

You may not think of the radio spectrum this way (if at all), but it is a limited natural resource, like fresh water or land.  As humanity has learned how to exploit it in increasingly effective ways, the value of various parts of it has fluctuated, mostly upward, but not always.  For the first seventy years or so of the FCC's existence, the agency treated the spectrum like the federal government treated federal land:  if you qualified, you could just get some of it for free, and then it was yours to use or sell just like any other private property. 

This wasn't always the best or the fairest way to do things.  Back in the 1920s, when it wasn't clear that radio would amount to much more than some hobbyists annoying their neighbors with loud spark-gap transmitters, it seemed like a reasonable approach.  But by the 1950s, when radio and then television frequencies were valued on the private market in the millions of dollars, politicians began to pull strings and the whole thing got very complicated.  For example, how much of a coincidence was it that the application for a new TV station that then-Senator Lyndon B. Johnson wanted to build in Austin in the early 1950s was the only application filed in that city?  None at all, because everybody else knew that LBJ was so connected in Washington that filing a competing application would be a waste of time.  So LBJ's family became the proud owners of  the first TV station in Austin in 1952, and the next TV station there didn't open until 1965.

Eventually, laws were passed so that the FCC could actually hold auctions to allocate new spectrum frequencies.  This change acknowledged that the radio spectrum had value, and probably a better way to allocate it than political influence was to sell it to the highest bidder. 

And of course, technology wasn't standing still during this time, either.  When the first UHF TV band was opened in 1952, it was viewed as the most wasted part of the "vast wasteland" of TV, in the words of a cynical FCC commissioner.  Originally it covered the entire frequency range from 470 MHz to 890 MHz, with channel numbers designated 14 through 83. Because a TV channel then occupied about 6 MHz, in principle there was room for almost 70 channels in the UHF band.  But for many years, that promise went largely unfulfilled for technical reasons.

It was a considerable challenge to early consumer-TV makers to build a UHF tuner, which is the "front-end" part of the TV that takes the signal from the antenna and converts it down to a reasonably low frequency to be demodulated and used.  Those old UHF tuners were fussy, handmade devices that you tuned with a continuously-rotating knob, like a radio dial.  And they were very subject to interference from other UHF stations.  Because of these problems, the FCC handed out a whole lot fewer UHF frequencies than it looked like at first glance you could fit in that huge range, because if the spectrum got anywhere close to crowded, all the UHF tuners would start picking up the wrong signals and everything would go to pot.  Also, UHF signals didn't carry as far as the lower VHF frequencies (channels 2-13), so a lot of early UHF stations were local low-budget affairs that couldn't afford anything better.

Technical times changed, as they always do, and around 2000 the TV industry made its move to digital broadcasting.  This change, plus advances in tuner design, rendered the old super-cautious FCC allocations pointless.  And with the advent of cable TV, the importance of over-the-air broadcasting began to wane, and once tuning your TV became a job for a computer, the channel numbers no longer had to be irrevocably fixed to particular frequencies, as they had to be with electromechanical tuners. 

Fast-forward to 2012.  The new 5G mobile phone service plan includes the use of a 600-700 MHz band that will allow base-quality service over a much wider area than the current higher-frequency mobile phone cells permit.  The problem was, there were still a lot of TV stations in that frequency range, hanging on to their old UHF TV allocations.  The FCC made them a deal:  if you let us auction off your frequency for 5G, we'll either share some of the profits with you and you can take the money and go off the air, or move to another frequency.  Either way, we've got to clear this band for 5G.  Kind of a spectrum-allocation eminent-domain action, as it were.  Some stations took the money and quit.  Others have been shifting up and down the frequency spectrum in a ten-phase process that will be completed by July of 2020.  While this can be a big deal for the broadcasters, involving costly new transmitters and transmitting antennas, the most that even off-the-air consumers will notice is that a station may go blank, but all you have to do is "rescan" your digital TV, and it will automatically hunt for the new frequency and find it for you.

To a geezer like me, who grew up having to get up off the chair and twiddle with the fine-tune control on the TV tuner every so often, it all seems too easy.  And there's something odd about the fluid shifting going on behind the scenes.  Back when a channel allocation was something to be proud of, stations often incorporated their channel number in their logo.  For example, in Fort Worth, the local independent station was Channel 11, and their logo featured the two numeral 1's as two nattily-dressed guys in little white suits, complete with handkerchiefs in their breast pockets (I may be imagining the handkerchief part, but you get the idea). 

No longer.  It's all as invisible as sewer pipes now, and about as interesting to the average consumer.  But in case you were wondering where your off-the-air station went, this may be part of the explanation.

Sources:  Not being a watcher of TV any longer myself, I learned about this process from an article in the San Jose Mercury-News at https://www.mercurynews.com/2020/04/30/heres-why-you-might-need-to-rescan-your-tv-right-now/.  I also referred to articles from Gizmodo at https://gizmodo.com/5g-is-forcing-hundreds-of-tv-channels-to-change-how-the-1837111135 and Venturebeat at https://venturebeat.com/2019/12/10/the-definitive-guide-to-5g-low-mid-and-high-band-speeds/

and the Wikipedia article on UHF TV broadcasting.  The FCC has a handy map on which you can look up your local TV stations and see what's going on with their channel moves, if any, at https://www.fcc.gov/media/engineering/dtvmaps.  And I got the short version of the KLBJ story from Slate, which summarizes LBJ biographer Robert Caro's extensive research on the matter at https://slate.com/news-and-politics/2007/07/how-lady-bird-and-lyndon-baines-johnson-came-by-their-millions.html. 

The FCC and 5G

When I attended Cornell University in 1976 and 1977 for my master's degree, I took a microwave lab course.  In the lab room where we worked was a large glass desiccator jar, sort of like a clear cookie jar with blue desiccator crystals in the bottom to keep the contents dry.  Inside the main area of the jar were tiny rectangular copper pipes with little connectors on the ends. The pipes were about a quarter of an inch wide or less, some as small as soda straws, and a few inches long.  When I asked one of the professors what this was, he explained that the pipes were millimeter-wave waveguides.  Certain frequencies of millimeter waves were highly absorbed by water, so they had decided to keep the waveguides in a desiccator jar to make sure that they didn't have any absorbed film of water in them that would mess up the measurements they might make with them. 

Back then, millimeter-wave equipment was nothing more than a laboratory curiosity.  In terms of frequencies, millimeter waves range from 30 GHz up to 300 GHz.  Their name comes from the fact that they make waves in air that are between 1 and 10 millimeters long from one peak to the next peak.  Back in the 1970s, they were extremely hard to generate and detect, and nobody but a few scientists had anything to do with them.  The only large corporation that had pursued serious research about millimeter waves was Bell Laboratories, which thought for a while that the future of their network would involve millimeter-wave waveguides crisscrossing the country.  But when Corning and other companies figured out how to make extremely low-loss optical fibers, Bell dropped their millimeter-wave idea and switched to fiber optics, which is how the vast majority of network traffic travels today.

But you can't attach fiber optics to a moving car, or somebody walking down the street, so as newer applications such as virtual reality and the Internet of Things grow, there is a constantly increasing need for more wireless bandwidth.  And millimeter waves will be a key player in the next generation of wireless network technology called 5G.

Last Friday, Apr. 12, the U. S. Federal Communications Commission (FCC) announced that it plans to auction off close to 5 GHz of some millimeter-wave bands that have previously been reserved for other purposes.  These bands are at 37, 39, and 47 GHz.  For many years now, auctions have been the FCC's preferred method of allocating frequencies to private entities, and while such auctions shut out everyone except those well-heeled enough to afford to exploit the frequencies they buy, this process is a lot more transparent and fair than their former practice of simply opening applications to all comers, and waiting to see who gets there first.  And the old process was often subject to political log-rolling.  For example, the way Lyndon B. Johnson obtained control of station KLBJ in Austin and vastly mproved its value in the 1940s does not bear a lot of scrutiny, unless you don't mind finding a lot of political wangling that the then-senator engaged in with the FCC. 

While auctions of radio spectrum allocations are not inherently just proceedings in themselves, they do acknowledge that the spectrum is a limited natural esource, and an auction allows interested parties to express their perceived value of that resource in bids.  We don't often value what we don't pay for, and so an auction tends to ensure that whoever gets the right to use certain frequencies is going to exploit them so as to get their money's worth. 

Even as recently as a decade ago, an auction of millimeter-wave bands wouldn't have attracted much attention, because the technology to generate and receive such waves was way too expensive for consumer products.  But with advances in fabrication methods, microwave technology, and adaptive control of antennas, it's now feasible to start building the micro-cells that millimeter-wave wireless will need.  As you go higher in frequency to around 60 GHz, millimeter waves are increasingly absorbed by oxygen in the air, and even below that frequency they do not propagate very far compared to the longer microwaves that are used for earlier wireless systems.  So this means we will need a whole lot more millimeter-wave base stations than you would need for equivalent coverage at lower frequencies. 

A millimeter-wave base station won't be a two-hundred-foot tower with antennas several feet long hanging from the top.  It will probably take the form of a box or panel just a few feet square, sitting at or near ground level, typically on a utility pole.  They will show up first in big cities where the density of foot and vehicle traffic justifies the installations, and then less dense areas will be covered.  For sparsely populated areas, the FCC has announced it is thinking about allocating some frequencies as low as 600 MHz, whose waves can cover much wider areas, so suburbs and rural regions won't be totally left out in the cold, wireless-wise.

This all assumes that there's nothing harmful to human health regarding the increased amount of millimeter-wave radiation that people will be subjected to as 5G deploys.  There is at least one person with apparently good qualifications who says this isn't so.  Martin L. Pall is a retired professor of biological sciences at Washington State University who has published both refereed journal papers and popular talks saying that Wi-Fi, and in particular millimeter waves, can cause everything from low sperm counts to cancer.  I know enough about electromagnetics to have reason to doubt some of his reasoning as to how this occurs, but interested parties can examine his case here.  If he's right, we ought to go slow on the rollout of 5G, but it looks like instead we'll be performing a massive experiment in which millions of people get exposed—and then we'll see if anything bad happens. 

Sources:  The FCC's news release about their planned 5G auction can be found at

https://docs.fcc.gov/public/attachments/DOC-356984A1.pdf.  I read about the plan in an Associated Press article carried by the Austin American-Statesman on Apr. 13, a version of which can be viewed at the AP website https://www.apnews.com/402d7c2651914d31a4f216f81eadda53.  Dr. M. L. Pall's expression of his concerns regarding the increasing use of Wi-Fi can be read in his paper in Environmental Research vol. 164, pp. 405-416 (July 2018), which is downloadable at https://www.sciencedirect.com/science/article/pii/S0013935118300355.