Air traffic control has been in the news lately, on account of my country's declining ability to do it. Well, that's a long-term trend, resulting from decades of under-investment, severe capture by our increasingly incompetent defense-industrial complex, no small degree of management incompetence in the FAA, and long-lasting effects of Reagan crushing the PATCO strike. But that's just my opinion, you know, maybe airplanes got too woke. In any case, it's an interesting time to consider how weird parts of air traffic control are. The technical, administrative, and social aspects of ATC all seem two notches more complicated than you would expect. ATC is heavily influenced by its peculiar and often accidental development, a product of necessity that perpetually trails behind the need, and a beneficiary of hand-me-down military practices and technology. Aviation Radio In the early days of aviation, there was little need for ATC---there just weren't many planes, and technology didn't allow ground-based controllers to do much of value. There was some use of flags and signal lights to clear aircraft to land, but for the most part ATC had to wait for the development of aviation radio. The impetus for that work came mostly from the First World War. Here we have to note that the history of aviation is very closely intertwined with the history of warfare. Aviation technology has always rapidly advanced during major conflicts, and as we will see, ATC is no exception. By 1913, the US Army Signal Corps was experimenting with the use of radio to communicate with aircraft. This was pretty early in radio technology, and the aircraft radios were huge and awkward to operate, but it was also early in aviation and "huge and awkward to operate" could be similarly applied to the aircraft of the day. Even so, radio had obvious potential in aviation. The first military application for aircraft was reconnaissance. Pilots could fly past the front to find artillery positions and otherwise provide useful information, and then return with maps. Well, even better than returning with a map was providing the information in real-time, and by the end of the war medium-frequency AM radios were well developed for aircraft. Radios in aircraft lead naturally to another wartime innovation: ground control. Military personnel on the ground used radio to coordinate the schedules and routes of reconnaissance planes, and later to inform on the positions of fighters and other enemy assets. Without any real way to know where the planes were, this was all pretty primitive, but it set the basic pattern that people on the ground could keep track of aircraft and provide useful information. Post-war, civil aviation rapidly advanced. The early 1920s saw numerous commercial airlines adopting radio, mostly for business purposes like schedule coordination. Once you were in contact with someone on the ground, though, it was only logical to ask about weather and conditions. Many of our modern practices like weather briefings, flight plans, and route clearances originated as more or less formal practices within individual airlines. Air Mail The government was not left out of the action. The Post Office operated what may have been the largest commercial aviation operation in the world during the early 1920s, in the form of Air Mail. The Post Office itself did not have any aircraft; all of the flying was contracted out---initially to the Army Air Service, and later to a long list of regional airlines. Air Mail was considered a high priority by the Post Office and proved very popular with the public. When the transcontinental route began proper operation in 1920, it became possible to get a letter from New York City to San Francisco in just 33 hours by transferring it between airplanes in a nearly non-stop relay race. The Post Office's largesse in contracting the service to private operators provided not only the funding but the very motivation for much of our modern aviation industry. Air travel was not very popular at the time, being loud and uncomfortable, but the mail didn't complain. The many contract mail carriers of the 1920s grew and consolidated into what are now some of the United States' largest companies. For around a decade, the Post Office almost singlehandedly bankrolled civil aviation, and passengers were a side hustle [1]. Air mail ambition was not only of economic benefit. Air mail routes were often longer and more challenging than commercial passenger routes. Transcontinental service required regular flights through sparsely populated parts of the interior, challenging the navigation technology of the time and making rescue of downed pilots a major concern. Notably, air mail operators did far more nighttime flying than any other commercial aviation in the 1920s. The post office became the government's de facto technical leader in civil aviation. Besides the network of beacons and markers built to guide air mail between cities, the post office built 17 Air Mail Radio Stations along the transcontinental route. The Air Mail Radio Stations were the company radio system for the entire air mail enterprise, and the closest thing to a nationwide, public air traffic control service to then exist. They did not, however, provide what we would now call control. Their role was mainly to provide pilots with information (including, critically, weather reports) and to keep loose tabs on air mail flights so that a disappearance would be noticed in time to send search and rescue. In 1926, the Watres Act created the Aeronautic Branch of the Department of Commerce. The Aeronautic Branch assumed a number of responsibilities, but one of them was the maintenance of the Air Mail routes. Similarly, the Air Mail Radio Stations became Aeronautics Branch facilities, and took on the new name of Flight Service Stations. No longer just for the contract mail carriers, the Flight Service Stations made up a nationwide network of government-provided services to aviators. They were the first edifices in what we now call the National Airspace System (NAS): a complex combination of physical facilities, technologies, and operating practices that enable safe aviation. In 1935, the first en-route air traffic control center opened, a facility in Newark owned by a group of airlines. The Aeronautic Branch, since renamed the Bureau of Air Commerce, supported the airlines in developing this new concept of en-route control that used radio communications and paperwork to track which aircraft were in which airways. The rising number of commercial aircraft made in-air collisions a bigger problem, so the Newark control center was quickly followed by more facilities built on the same pattern. In 1936, the Bureau of Air Commerce took ownership of these centers, and ATC became a government function alongside the advisory and safety services provided by the flight service stations. En route center controllers worked off of position reports from pilots via radio, but needed a way to visualize and track aircraft's positions and their intended flight paths. Several techniques helped: first, airlines shared their flight planning paperwork with the control centers, establishing "flight plans" that corresponded to each aircraft in the sky. Controllers adopted a work aid called a "flight strip," a small piece of paper with the key information about an aircraft's identity and flight plan that could easily be handed between stations. By arranging the flight strips on display boards full of slots, controllers could visualize the ordering of aircraft in terms of altitude and airway. Second, each center was equipped with a large plotting table map where controllers pushed markers around to correspond to the position reports from aircraft. A small flag on each marker gave the flight number, so it could easily be correlated to a flight strip on one of the boards mounted around the plotting table. This basic concept of air traffic control, of a flight strip and a position marker, is still in use today. Radar The Second World War changed aviation more than any other event of history. Among the many advancements were two British inventions of particular significance: first, the jet engine, which would make modern passenger airliners practical. Second, the radar, and more specifically the magnetron. This was a development of such significance that the British government treated it as a secret akin to nuclear weapons; indeed, the UK effectively traded radar technology to the US in exchange for participation in US nuclear weapons research. Radar created radical new possibilities for air defense, and complimented previous air defense development in Britain. During WWI, the organization tasked with defending London from aerial attack had developed a method called "ground-controlled interception" or GCI. Under GCI, ground-based observers identify possible targets and then direct attack aircraft towards them via radio. The advent of radar made GCI tremendously more powerful, allowing a relatively small number of radar-assisted air defense centers to monitor for inbound attack and then direct defenders with real-time vectors. In the first implementation, radar stations reported contacts via telephone to "filter centers" that correlated tracks from separate radars to create a unified view of the airspace---drawn in grease pencil on a preprinted map. Filter center staff took radar and visual reports and updated the map by moving the marks. This consolidated information was then provided to air defense bases, once again by telephone. Later technical developments in the UK made the process more automated. The invention of the "plan position indicator" or PPI, the type of radar scope we are all familiar with today, made the radar far easier to operate and interpret. Radar sets that automatically swept over 360 degrees allowed each radar station to see all activity in its area, rather than just aircraft passing through a defensive line. These new capabilities eliminated the need for much of the manual work: radar stations could see attacking aircraft and defending aircraft on one PPI, and communicated directly with defenders by radio. It became routine for a radar operator to give a pilot navigation vectors by radio, based on real-time observation of the pilot's position and heading. A controller took strategic command of the airspace, effectively steering the aircraft from a top-down view. The ease and efficiency of this workflow was a significant factor in the end of the Battle of Britain, and its remarkable efficacy was noticed in the US as well. At the same time, changes were afoot in the US. WWII was tremendously disruptive to civil aviation; while aviation technology rapidly advanced due to wartime needs those same pressing demands lead to a slowdown in nonmilitary activity. A heavy volume of military logistics flights and flight training, as well as growing concerns about defending the US from an invasion, meant that ATC was still a priority. A reorganization of the Bureau of Air Commerce replaced it with the Civil Aeronautics Authority, or CAA. The CAA's role greatly expanded as it assumed responsibility for airport control towers and commissioned new en route centers. As WWII came to a close, CAA en route control centers began to adopt GCI techniques. By 1955, the name Air Route Traffic Control Center (ARTCC) had been adopted for en route centers and the first air surveillance radars were installed. In a radar-equipped ARTCC, the map where controllers pushed markers around was replaced with a large tabletop PPI built to a Navy design. The controllers still pushed markers around to track the identities of aircraft, but they moved them based on their corresponding radar "blips" instead of radio position reports. Air Defense After WWII, post-war prosperity and wartime technology like the jet engine lead to huge growth in commercial aviation. During the 1950s, radar was adopted by more and more ATC facilities (both "terminal" at airports and "en route" at ARTCCs), but there were few major changes in ATC procedure. With more and more planes in the air, tracking flight plans and their corresponding positions became labor intensive and error-prone. A particular problem was the increasing range and speed of aircraft, and corresponding longer passenger flights, that meant that many aircraft passed from the territory of one ARTCC into another. This required that controllers "hand off" the aircraft, informing the "next" ARTCC of the flight plan and position at which the aircraft would enter their airspace. In 1956, 128 people died in a mid-air collision of two commercial airliners over the Grand Canyon. In 1958, 49 people died when a military fighter struck a commercial airliner over Nevada. These were not the only such incidents in the mid-1950s, and public trust in aviation started to decline. Something had to be done. First, in 1958 the CAA gave way to the Federal Aviation Administration. This was more than just a name change: the FAA's authority was greatly increased compared tot he CAA, most notably by granting it authority over military aviation. This is a difficult topic to explain succinctly, so I will only give broad strokes. Prior to 1958, military aviation was completely distinct from civil aviation, with no coordination and often no communication at all between the two. This was, of course, a factor in the 1958 collision. Further, the 1956 collision, while it did not involve the military, did result in part from communications issues between separate distinct CAA facilities and the airline's own control facilities. After 1958, ATC was completely unified into one organization, the FAA, which assumed the work of the military controllers of the time and some of the role of the airlines. The military continues to have its own air controllers to this day, and military aircraft continue to include privileges such as (practical but not legal) exemption from transponder requirements, but military flights over the US are still beholden to the same ATC as civil flights. Some exceptions apply, void where prohibited, etc. The FAA's suddenly increased scope only made the practical challenges of ATC more difficult, and commercial aviation numbers continued to rise. As soon as the FAA was formed, it was understood that there needed to be major investments in improving the National Airspace System. While the first couple of years were dominated by the transition, the FAA's second director (Najeeb Halaby) prepared two lengthy reports examining the situation and recommending improvements. One of these, the Beacon report (also called Project Beacon), specifically addressed ATC. The Beacon report's recommendations included massive expansion of radar-based control (called "positive control" because of the controller's access to real-time feedback on aircraft movements) and new control procedures for airways and airports. Even better, for our purposes, it recommended the adoption of general-purpose computers and software to automate ATC functions. Meanwhile, the Cold War was heating up. US air defense, a minor concern in the few short years after WWII, became a higher priority than ever before. The Soviet Union had long-range aircraft capable of reaching the United States, and nuclear weapons meant that only a few such aircraft had to make it to cause massive destruction. Considering the vast size of the United States (and, considering the new unified air defense command between the United States and Canada, all of North America) made this a formidable challenge. During the 1950s, the newly minted Air Force worked closely with MIT's Lincoln Laboratory (an important center of radar research) and IBM to design a computerized, integrated, networked system for GCI. When the Air Force committed to purchasing the system, it was christened the Semi-Automated Ground Environment, or SAGE. SAGE is a critical juncture in the history of the computer and computer communications, the first system to demonstrate many parts of modern computer technology and, moreover, perhaps the first large-scale computer system of any kind. SAGE is an expansive topic that I will not take on here; I'm sure it will be the focus of a future article but it's a pretty well-known and well-covered topic. I have not so far felt like I had much new to contribute, despite it being the first item on my "list of topics" for the last five years. But one of the things I want to tell you about SAGE, that is perhaps not so well known, is that SAGE was not used for ATC. SAGE was a purely military system. It was commissioned by the Air Force, and its numerous operating facilities (called "direction centers") were located on Air Force bases along with the interceptor forces they would direct. However, there was obvious overlap between the functionality of SAGE and the needs of ATC. SAGE direction centers continuously received tracks from remote data sites using modems over leased telephone lines, and automatically correlated multiple radar tracks to a single aircraft. Once an operator entered information about an aircraft, SAGE stored that information for retrieval by other radar operators. When an aircraft with associated data passed from the territory of one direction center to another, the aircraft's position and related information were automatically transmitted to the next direction center by modem. One of the key demands of air defense is the identification of aircraft---any unknown track might be routine commercial activity, or it could be an inbound attack. The air defense command received flight plan data on commercial flights (and more broadly all flights entering North America) from the FAA and entered them into SAGE, allowing radar operators to retrieve "flight strip" data on any aircraft on their scope. Recognizing this interconnection with ATC, as soon as SAGE direction centers were being installed the Air Force started work on an upgrade called SAGE Air Traffic Integration, or SATIN. SATIN would extend SAGE to serve the ATC use-case as well, providing SAGE consoles directly in ARTCCs and enhancing SAGE to perform non-military safety functions like conflict warning and forward projection of flight plans for scheduling. Flight strips would be replaced by teletype output, and in general made less necessary by the computer's ability to filter the radar scope. Experimental trial installations were made, and the FAA participated readily in the research efforts. Enhancement of SAGE to meet ATC requirements seemed likely to meet the Beacon report's recommendations and radically improve ARTCC operations, sooner and cheaper than development of an FAA-specific system. As it happened, well, it didn't happen. SATIN became interconnected with another planned SAGE upgrade to the Super Combat Centers (SCC), deep underground combat command centers with greatly enhanced SAGE computer equipment. SATIN and SCC planners were so confident that the last three Air Defense Sectors scheduled for SAGE installation, including my own Albuquerque, were delayed under the assumption that the improved SATIN/SCC equipment should be installed instead of the soon-obsolete original system. SCC cost estimates ballooned, and the program's ambitions were reduced month by month until it was canceled entirely in 1960. Albuquerque never got a SAGE installation, and the Albuquerque air defense sector was eliminated by reorganization later in 1960 anyway. Flight Service Stations Remember those Flight Service Stations, the ones that were originally built by the Post Office? One of the oddities of ATC is that they never went away. FSS were transferred to the CAB, to the CAA, and then to the FAA. During the 1930s and 1940s many more were built, expanding coverage across much of the country. Throughout the development of ATC, the FSS remained responsible for non-control functions like weather briefing and flight plan management. Because aircraft operating under instrument flight rules must closely comply with ATC, the involvement of FSS in IFR flights is very limited, and FSS mostly serve VFR traffic. As ATC became common, the FSS gained a new and somewhat odd role: playing go-between for ATC. FSS were more numerous and often located in sparser areas between cities (while ATC facilities tended to be in cities), so especially in the mid-century, pilots were more likely to be able to reach an FSS than ATC. It was, for a time, routine for FSS to relay instructions between pilots and controllers. This is still done today, although improved communications have made the need much less common. As weather dissemination improved (another topic for a future post), FSS gained access to extensive weather conditions and forecasting information from the Weather Service. This connectivity is bidirectional; during the midcentury FSS not only received weather forecasts by teletype but transmitted pilot reports of weather conditions back to the Weather Service. Today these communications have, of course, been computerized, although the legacy teletype format doggedly persists. There has always been an odd schism between the FSS and ATC: they are operated by different departments, out of different facilities, with different functions and operating practices. In 2005, the FAA cut costs by privatizing the FSS function entirely. Flight service is now operated by Leidos, one of the largest government contractors. All FSS operations have been centralized to one facility that communicates via remote radio sites. While flight service is still available, increasing automation has made the stations far less important, and the general perception is that flight service is in its last years. Last I looked, Leidos was not hiring for flight service and the expectation was that they would never hire again, retiring the service along with its staff. Flight service does maintain one of my favorite internet phenomenon, the phone number domain name: 1800wxbrief.com. One of the odd manifestations of the FSS/ATC schism and the FAA's very partial privatization is that Leidos maintains an online aviation weather portal that is separate from, and competes with, the Weather Service's aviationweather.gov. Since Flight Service traditionally has the responsibility for weather briefings, it is honestly unclear to what extend Leidos vs. the National Weather Service should be investing in aviation weather information services. For its part, the FAA seems to consider aviationweather.gov the official source, while it pays for 1800wxbrief.com. There's also weathercams.faa.gov, which duplicates a very large portion (maybe all?) of the weather information on Leidos's portal and some of the NWS's. It's just one of those things. Or three of those things, rather. Speaking of duplication due to poor planning... The National Airspace System Left in the lurch by the Air Force, the FAA launched its own program for ATC automation. While the Air Force was deploying SAGE, the FAA had mostly been waiting, and various ARTCCs had adopted a hodgepodge of methods ranging from one-off computer systems to completely paper-based tracking. By 1960 radar was ubiquitous, but different radar systems were used at different facilities, and correlation between radar contacts and flight plans was completely manual. The FAA needed something better, and with growing congressional support for ATC modernization, they had the money to fund what they called National Airspace System En Route Stage A. Further bolstering historical confusion between SAGE and ATC, the FAA decided on a practical, if ironic, solution: buy their own SAGE. In an upcoming article, we'll learn about the FAA's first fully integrated computerized air traffic control system. While the failed detour through SATIN delayed the development of this system, the nearly decade-long delay between the design of SAGE and the FAA's contract allowed significant technical improvements. This "New SAGE," while directly based on SAGE at a functional level, used later off-the-shelf computer equipment including the IBM System/360, giving it far more resemblance to our modern world of computing than SAGE with its enormous, bespoke AN/FSQ-7. And we're still dealing with the consequences today! [1] It also laid the groundwork for the consolidation of the industry, with a 1930 decision that took air mail contracts away from most of the smaller companies and awarded them instead to the precursors of United, TWA, and American Airlines.

You know sometimes a technology just sort of... comes and goes? Without leaving much of an impression? And then gets lodged in your brain for the next decade? Let's talk about one of those: the iBeacon. I think the reason that iBeacons loom so large in my memory is that the technology was announced at WWDC in 2013. Picture yourself in 2013: Steve Jobs had only died a couple of years ago, Apple was still widely viewed as a visionary leader in consumer technology, and WWDC was still happening. Back then, pretty much anything announced at an Apple event was a Big Deal that got Big Coverage. Even, it turns out, if it was a minor development for a niche application. That's the iBeacon, a specific solution to a specific problem. It's not really that interesting, but the valance of it's Apple origin makes it seem cool? iBeacon Technology Let's start out with what iBeacon is, as it's so simple as to be underwhelming. Way back in the '00s, a group of vendors developed a sort of "Diet Bluetooth": a wireless protocol that was directly based on Bluetooth but simplified and optimized for low-power, low-data-rate devices. This went through an unfortunate series of names, including the delightful Wibree, but eventually settled on Bluetooth Low Energy (BLE). BLE is not just lower-power, but also easier to implement, so it shows up in all kinds of smart devices today. Back in 2011, it was quite new, and Apple was one of the first vendors to adopt it. BLE is far less connection-oriented than regular Bluetooth; you may have noticed that BLE devices are often used entirely without conventional "pairing." A lot of typical BLE profiles involve just broadcasting some data into the void for any device that cares (and is in short range) to receive, which is pretty similar to ANT+ and unsurprisingly appears in ANT+-like applications of fitness monitors and other sensors. Of course, despite the simpler association model, BLE applications need some way to find devices, so BLE provides an advertising mechanism in which devices transmit their identifying info at regular intervals. And that's all iBeacon really is: a standard for very simple BLE devices that do nothing but transmit advertisements with a unique ID as the payload. Add a type field on the advertising packet to specify that the device is trying to be an iBeacon and you're done. You interact with an iBeacon by receiving its advertisements, so you know that you are near it. Any BLE device with advertisements enabled could be used this way, but iBeacons are built only for this purpose. The applications for iBeacon are pretty much defined by its implementation in iOS; there's not much of a standard even if only for the reason that there's not much to put in a standard. It's all obvious. iOS provides two principle APIs for working with iBeacons: the region monitoring API allows an app to determine if it is near an iBeacon, including registering the region so that the app will be started when the iBeacon enters range. This is useful for apps that want to do something in response to the user being in a specific location. The ranging API allows an app to get a list of all of the nearby iBeacons and a rough range from the device to the iBeacon. iBeacons can actually operate at substantial ranges---up to hundreds of meters for more powerful beacons with external power, so ranging mode can potentially be used as sort of a lightweight local positioning system to estimate the location of the user within a larger space. iBeacon IDs are in the format of a UUID, followed by a "major" number and a "minor" number. There are different ways that these get used, especially if you are buying cheap iBeacons and not reconfiguring them, but the general idea is roughly that the UUID identifies the operator, the major a deployment, and the minor a beacon within the deployment. In practice this might be less common than just every beacon having its own UUID due to how they're sourced. It would be interesting to survey iBeacon applications to see which they do. Promoted Applications So where do you actually use these? Retail! Apple seems to have designed the iBeacon pretty much exclusively for "proximity marketing" applications in the retail environment. It goes something like this: when you're in a store and open that store's app, the app will know what beacons you are nearby and display relevant content. For example, in a grocery store, the grocer's app might offer e-coupons for cosmetics when you are in the cosmetics section. That's, uhh, kind of the whole thing? The imagined universe of applications around the launch of iBeacon was pretty underwhelming to me, even at the time, and it still seems that way. That's presumably why iBeacon had so little success in consumer-facing applications. You might wonder, who actually used iBeacons? Well, Apple did, obviously. During 2013 and into 2014 iBeacons were installed in all US Apple stores, and prompted the Apple Store app to send notifications about upgrade offers and other in-store deals. Unsurprisingly, this Apple Store implementation was considered the flagship deployment. It generated a fair amount of press, including speculation as to whether or not it would prove the concept for other buyers. Around the same time, Apple penned a deal with Major League Baseball that would see iBeacons installed in MLB stadiums. For the 2014 season, MLB Advanced Marketing, a joint venture of team owners, had installed iBeacon technology in 20 stadiums. Baseball fans will be able to utilize iBeacon technology within MLB.com At The Ballpark when the award-winning app's 2014 update is released for Opening Day. Complete details on new features being developed by MLBAM for At The Ballpark, including iBeacon capabilities, will be available in March. What's the point? the iBeacons "enable the At The Ballpark app to play specific videos or offer coupons." This exact story repeats for other retail companies that have picked the technology up at various points, including giants like Target and WalMart. The iBeacons are simply a way to target advertising based on location, with better indoor precision and lower power consumption than GPS. Aiding these applications along, Apple integrated iBeacon support into the iOS location framework and further blurred the lines between iBeacon and other positioning services by introducing location-based-advertising features that operated on geofencing alone. Some creative thinkers did develop more complex applications for the iBeacon. One of the early adopters was a company called Exact Editions, which prepared the Apple Newsstand version of a number of major magazines back when "readable on iPad" was thought to be the future of print media. Exact Editions explored a "read for free" feature where partner magazines would be freely accessible to users at partnering locations like coffee shops and book stores. This does not seem to have been a success, but using the proximity of an iBeacon to unlock some paywalled media is at least a little creative, if probably ill-advised considering security considerations we'll discuss later. The world of applications raises interesting questions about the other half of the mobile ecosystem: how did this all work on Android? iOS has built-in support for iBeacons. An operating system service scans for iBeacons and dispatches notifications to apps as appropriate. On Android, there has never been this type of OS-level support, but Android apps have access to relatively rich low-level Bluetooth functionality and can easily scan for iBeacons themselves. Several popular libraries exist for this purpose, and it's not unusual for them to be used to give ported cross-platform apps more or less equivalent functionality. These apps do need to run in the background if they're to notify the user proactively, but especially back in 2013 Android was far more generous about background work than iOS. iBeacons found expanded success through ShopKick, a retail loyalty platform that installed iBeacons in locations of some major retailers like American Eagle. These powered location-based advertising and offers in the ShopKick app as well as retailer-specific apps, which is kind of the start of a larger, more seamless network, but it doesn't seem to have caught on. Honestly, consumers just don't seem to want location-based advertising that much. Maybe because, when you're standing in an American Eagle, getting ads for products carried in the American Eagle is inane and irritating. iBeacons sort of foresaw cooler screens in this regard. To be completely honest, I'm skeptical that anyone ever really believed in the location-based advertising thing. I mean, I don't know, the advertising industry is pretty good at self-deception, but I don't think there were ever any real signs of hyper-local smartphone-based advertising taking off. I think the play was always data collection, and advertising and special offers just provided a convenient cover story. Real Applications iBeacons are one of those technologies that feels like a flop from a consumer perspective but has, in actuality, enjoyed surprisingly widespread deployments. The reason, of course, is data mining. To Apple's credit, they took a set of precautions in the design of the iBeacon iOS features that probably felt sufficient in 2013. Despite the fact that a lot of journalists described iBeacons as being used to "notify a user to install an app," that was never actually a capability (a very similar-seeming iOS feature attached to Siri actually used conventional geofencing rather than iBeacons). iBeacons only did anything if the user already had an app installed that either scanned for iBeacons when in the foreground or registered for region notifications. In theory, this limited iBeacons to companies with which consumers already had some kind of relationship. What Apple may not have foreseen, or perhaps simply accepted, is the incredible willingness of your typical consumer brand to sell that relationship to anyone who would pay. iBeacons became, in practice, just another major advancement in pervasive consumer surveillance. The New York Times reported in 2019 that popular applications were including SDKs that reported iBeacon contacts to third-party consumer data brokers. This data became one of several streams that was used to sell consumer location history to advertisers. It's a little difficult to assign blame and credit, here. Apple, to their credit, kept iBeacon features in iOS relatively locked down. This suggests that they weren't trying to facilitate massive location surveillance. That said, Apple always marketed iBeacon to developers based on exactly this kind of consumer tracking and micro-targeting, they just intended for it to be done under the auspices of a single brand. That industry would obviously form data exchanges and recruit random apps into reporting everything in your proximity isn't surprising, but maybe Apple failed to foresee it. They certainly weren't the worst offender. Apple's promotion of iBeacon opened the floodgates for everyone else to do the same thing. During 2014 and 2015, Facebook started offering bluetooth beacons to businesses that were ostensibly supposed to facilitate in-app special offers (though I'm not sure that those ever really materialized) but were pretty transparently just a location data collection play. Google jumped into the fray in their Signature Google style, with an offering that was confusing, semi-secret, incoherently marketed, and short lived. Google's Project Beacon, or Google My Business, also shipped free Bluetooth beacons out to businesses to give Android location services a boost. Google My Business seems to have been the source of a fair amount of confusion even at the time, and we can virtually guarantee that (as reporters speculated at the time) Google was intentionally vague and evasive about the system to avoid negative attention from privacy advocates. In the case of Facebook, well, they don't have the level of opsec that Google does so things are a little better documented: Leaked documents show that Facebook worried that users would 'freak out' and spread 'negative memes' about the program. The company recently removed the Facebook Bluetooth beacons section from their website. The real deployment of iBeacons and closely related third-party iBeacon-like products [1] occurred at massive scale but largely in secret. It became yet another dark project of the advertising-industrial complex, perhaps the most successful yet of a long-running series of retail consumer surveillance systems. Payments One interesting thing about iBeacon is how it was compared to NFC. The two really aren't that similar, especially considering the vast difference in usable ranges, but NFC was the first radio technology to be adopted for "location marketing" applications. "Tap your phone to see our menu," kinds of things. Back in 2013, Apple had rather notably not implemented NFC in its products, despite its increasing adoption on Android. But, there is much more to this story than learning about new iPads and getting a surprise notification that you are eligible for a subsidized iPhone upgrade. What we're seeing is Apple pioneering the way mobile devices can be utilized to make shopping a better experience for consumers. What we're seeing is Apple putting its money where its mouth is when it decided not to support NFC. (MacObserver) Some commentators viewed iBeacon as Apple's response to NFC, and I think there's more to that than you might think. In early marketing, Apple kept positioning iBeacon for payments. That's a little weird, right, because iBeacons are a purely one-way broadcast system. Still, part of Apple's flagship iBeacon implementation was a payment system: Here's how he describes the purchase he made there, using his iPhone and the EasyPay system: "We started by using the iPhone to scan the product barcode and then we had to enter our Apple ID, pretty much the way we would for any online Apple purchase [using the credit card data on file with one's Apple account]. The one key difference was that this transaction ended with a digital receipt, one that we could show to a clerk if anyone stopped us on the way out." Apple Wallet only kinda-sorta existed at the time, although Apple was clearly already midway into a project to expand into consumer payments. It says a lot about this point in time in phone-based payments that several reporters talk about iBeacon payments as a feature of iTunes, since Apple was mostly implementing general-purpose billing by bolting it onto iTunes accounts. It seems like what happened is that Apple committed to developing a pay-by-phone solution, but decided against NFC. To be competitive with other entrants in the pay-by-phone market, they had to come up with some kind of technical solution to interact with retail POS, and iBeacon was their choice. From a modern perspective this seems outright insane; like, Bluetooth broadcasts are obviously not the right way to initiate a payment flow, and besides, there's a whole industry-standard stack dedicated to that purpose... built on NFC. But remember, this was 2013! EMV was not yet in meaningful use in the US; several major banks and payment networks had just committed to rolling it out in 2012 and every American can tell you that the process was long and torturous. Because of the stringent security standards around EMV, Android devices did not implement EMV until ARM secure enclaves became widely available. EMVCo, the industry body behind EMV, did not have a certification program for smartphones until 2016. Android phones offered several "tap-to-pay" solutions, from Google's frequently rebranded Google Wallet^w^wAndroid Pay^w^wGoogle Wallet to Verizon's embarrassingly rebranded ISIS^wSoftcard and Samsung Pay. All of these initially relied on proprietary NFC protocols with bespoke payment terminal implementations. This was sketchy enough, and few enough phones actually had NFC, that the most successful US pay-by-phone implementations like Walmart's and Starbucks' used barcodes for communication. It would take almost a decade before things really settled down and smartphones all just implemented EMV. So, in that context, Apple's decision isn't so odd. They must have figured that iBeacon could solve the same "initial handshake" problem as Walmart's QR codes, but more conveniently and using radio hardware that they already included in their phones. iBeacon-based payment flows used the iBeacon only to inform the phone of what payment devices were nearby, everything else happened via interaction with a cloud service or whatever mechanism the payment vendor chose to implement. Apple used their proprietary payments system through what would become your Apple Account, PayPal slapped together an iBeacon-based fast path to PayPal transfers, etc. I don't think that Apple's iBeacon-based payments solution ever really shipped. It did get some use, most notably by Apple, but these all seem to have been early-stage implementations, and the complete end-to-end SDK that a lot of developers expected never landed. You might remember that this was a very chaotic time in phone-based payments, solutions were coming and going. When Apple Pay was properly announced a year after iBeacons, there was little mention of Bluetooth. By the time in-store Apple Pay became common, Apple had given up and adopted NFC. Limitations One of the great weaknesses of iBeacon was the security design, or lack thereof. iBeacon advertisements were sent in plaintext with no authentication of any type. This did, of course, radically simplify implementation, but it also made iBeacon untrustworthy for any important purpose. It is quite trivial, with a device like an Android phone, to "clone" any iBeacon and transmit its identifiers wherever you want. This problem might have killed off the whole location-based-paywall-unlocking concept had market forces not already done so. It also opens the door to a lot of nuisance attacks on iBeacon-based location marketing, which may have limited the depth of iBeacon features in major apps. iBeacon was also positioned as a sort of local positioning system, but it really wasn't. iBeacon offers no actual time-of-flight measurements, only RSSI-based estimation of range. Even with correct on-site calibration (which can be aided by adjusting a fixed RSSI-range bias value included in some iBeacon advertisements) this type of estimation is very inaccurate, and in my little experiments with a Bluetooth beacon location library I can see swings from 30m to 70m estimated range based only on how I hold my phone. iBeacon positioning has never been accurate enough to do more than assert whether or not a phone is "near" the beacon, and "near" can take on different values depending on the beacon's transmit power. Developers have long looked towards Bluetooth as a potential local positioning solution, and it's never quite delivered. The industry is now turning towards Ultra-Wideband or UWB technology, which combines a high-rate, high-bandwidth radio signal with a time-of-flight radio ranging protocol to provide very accurate distance measurements. Apple is, once again, a technical leader in this field and UWB radios have been integrated into the iPhone 11 and later. Senescence iBeacon arrived to some fanfare, quietly proliferated in the shadows of the advertising industry, and then faded away. The Wikipedia article on iBeacons hasn't really been updated since support on Windows Phone was relevant. Apple doesn't much talk about iBeacons any more, and their compatriots Facebook and Google both sunset their beacon programs years ago. Part of the problem is, well, the pervasive surveillance thing. The idea of Bluetooth beacons cooperating with your phone to track your every move proved unpopular with the public, and so progressively tighter privacy restrictions in mobile operating systems and app stores have clamped down on every grocery store app selling location data to whatever broker bids the most. I mean, they still do, but it's gotten harder to use Bluetooth as an aid. Even Android, the platform of "do whatever you want in the background, battery be damned," strongly discourages Bluetooth scanning by non-foreground apps. Still, the basic technology remains in widespread use. BLE beacons have absolutely proliferated, there are plenty of apps you can use to list nearby beacons and there almost certainly are nearby beacons. One of my cars has, like, four separate BLE beacons going on all the time, related to a phone-based keyless entry system that I don't think the automaker even supports any more. Bluetooth beacons, as a basic primitive, are so useful that they get thrown into all kinds of applications. My earbuds are a BLE beacon, which the (terrible, miserable, no-good) Bose app uses to detect their proximity when they're paired to another device. A lot of smart home devices like light bulbs are beacons. The irony, perhaps, of iBeacon-based location tracking is that it's a victim of its own success. There is so much "background" BLE beacon activity that you scarcely need to add purpose-built beacons to track users, and only privacy measures in mobile operating systems and the beacons themselves (some of which rotate IDs) save us. Apple is no exception to the widespread use of Bluetooth beacons: iBeacon lives on in virtually every apple device. If you do try out a Bluetooth beacon scanning app, you'll discover pretty much every Apple product in a 30 meter radius. From MacBooks Pro to Airpods, almost all Apple products transmit iBeacon advertisements to their surroundings. These are used for the initial handshake process of peer-to-peer features like Airdrop, and Find My/AirTag technology seems to be derived from the iBeacon protocol (in the sense that anything can be derived from such a straightforward design). Of course, pretty much all of these applications now randomize identifiers to prevent passive use of device advertisements for long-term tracking. Here's some good news: iBeacons are readily available in a variety of form factors, and they are very cheap. Lots of libraries exist for working with them. If you've ever wanted some sort of location-based behavior for something like home automation, iBeacons might offer a good solution. They're neat, in an old technology way. Retrotech from the different world of 2013. It's retro in more ways than one. It's funny, and a bit quaint, to read the contemporary privacy concerns around iBeacon. If only they had known how bad things would get! Bluetooth beacons were the least of our concerns. [1] Things can be a little confusing here because the iBeacon is such a straightforward concept, and Apple's implementation is so simple. We could define "iBeacon" as including only officially endorsed products from Apple affiliates, or as including any device that behaves the same as official products (e.g. by using the iBeacon BLE advertisement type codes), or as any device that is performing substantially the same function (but using a different advertising format). I usually mean the latter of these three as there isn't really much difference between an iBeacon and ten million other BLE beacons that are doing the same thing with a slightly different identifier format. Facebook and Google's efforts fall into this camp.

When we last talked about Troposcatter, it was Pole Vault. Pole Vault was the first troposcatter communications network, on the east coast of Canada. It would not be alone for long. By the time the first Pole Vault stations were complete, work was already underway on a similar network for Alaska: the White Alice Communication System, WACS. Alaska has long posed a challenge for communications. In the 1960s, Western Union wanted to extent their telegraph network from the United States into Europe. Although the technology would be demonstrated shortly after, undersea telegraph cables were still notional and it seemed that a route that minimized the ocean crossing would be preferable---of course, that route maximized the length on land, stretching through present-day Alaska and Siberia on each side of the Bering Strait. This task proved more formidable than Western Union had imagined, and the first transatlantic telegraph cable (on a much further south crossing) was completed before the arctic segments of the overland route. The "Western Union Telegraph Expedition" abandoned its work, leaving a telegraph line well into British Columbia that would serve as one of the principle communications assets in the region for decades after. This ill-fated telegraph line failed to link San Francisco to Moscow, but its aftermath included a much larger impact on Russian interests in North America: the purchase of Alaska in 1867. Shortly after, the US military began its expansion into the new frontier. The Army Signal Corps, mostly to fulfill its function in observing the weather, built and staffed small installations that stretched further and further west. Later, in the 1890s, a gold rush brought a sudden influx of American settlers to Alaska's rugged terrain. The sudden economic importance of Klondike, and the rather colorful personalities of the prospectors looking to exploit it, created a much larger need for military presence. Fortuitously, many of the forts present had been built by the Signal Corps, which had already started on lines of communication. Construction was difficult, though, and without Alaskan communications as major priority there was only minimal coverage. Things changed in 1900, when Congress appropriated a substantial budget to the Washington-Alaska Military Cable and Telegraph System. The Signal Corps set on Alaska like, well, like an army, and extensive telegraph and later telephone lines were built to link the various military outposts. Later renamed the Alaska Communications System, these cables brought the first telecommunication to much of Alaska. The arrival of the telegraph was quite revolutionary for remote towns, who could now receive news in real-time that had previously been delayed by as much as a year [1]. Telegraphy was important to civilians as well, something that Congress had anticipated: The original act authorizing the Alaska Communications System dictated that it would carry commercial traffic as well. The military had an unusual role in Alaska, and one aspect of it was telecommunications provider. In 1925, an outbreak of diphtheria began to claim the lives of children in Nome, a town in far western Alaska on the Seward Peninsula. The daring winter delivery of antidiphtheria serum by dog sled is widely remembered due to its tangential connection to the Iditarod, but there were two sides of the "serum run." The message from Nome's sole doctor requesting the urgent shipment was transmitted from Nome to the Public Health Service in DC over the Alaska Communications System. It gives us some perspective on the importance of the telegraph in Alaska that the 600 mile route to Nome took five days and many feats of heroism---but at the same time could be crossed instantaneously by telegrams. The Alaska Communications System included some use of radio from the beginning. A pair of HF radio stations specifically handled traffic for Nome, covering a 100-mile stretch too difficult for even the intrepid Signal Corps. While not a totally new technology to the military, radio was quite new to the telegraph business, and the ACS to Nome was probably the first commercial radiotelegraph system on the continent. By the 1930s, the condition of the Alaskan telegraph cables had decayed while demand for telephony had increased. Much of ACS was upgraded and modernized to medium-frequency radiotelephone links. In towns small and large, even in Anchorage itself, the sole telephone connection to the contiguous United States was an ACS telephone installed in the general store. Alaskan communications became an even greater focus of the military with the onset of the Second World War. A few weeks after Pearl Harbor, the Japanese attacked Fort Mears in the Aleutian Islands. Fort Mears had no telecommunications connections, so despite the proximity of other airbases support was slow to come. The lack of a telegraph or telephone line contributed to 43 deaths and focused attention on the ACS. By 1944, the Army Signal Corps had a workforce of 2,000 dedicated to Alaska. WWII brought more than one kind of attention to Alaska. Several Japanese assaults on the Aleutian islands represented the largest threats to American soil outside of Pearl Harbor, showing both Alaska's vulnerability and the strategic importance given to it by its relative proximity to Eurasia. WWII ended but, in 1949, the USSR demonstrated an atomic weapon. A combination of Soviet expansionism and the new specter of nuclear war turned military planners towards air defense. Like the Canadian Maritimes in the East, Alaska covered a huge swath of the airspace through which Soviet bombers might approach the US. Alaska was, once again, a battleground. The early Cold War military buildup of Alaska was particularly heavy on air defense. During the late '40s and early '50s, more than a dozen new radar and control sites were built. The doctrine of ground-controlled interception requires real-time communication between radar centers, stressing the limited number of voice channels available on the ACS. As early as 1948, the Signal Corps had begun experiments to choose an upgrade path. Canadian early-warning radar networks, including the Distant Early Warning Line, were on the drawing board and would require many communications channels in particularly remote parts of Alaska. Initially, point-to-point microwave was used in relatively favorable terrain (where the construction of relay stations about every 50 miles was practical). For the more difficult segments, the Signal Corps found that VHF radio could provide useful communications at ranges over 100 miles. VHF radiotelephones were installed at air defense radar stations, but there was a big problem: the airspace surveillance radar of the 1950s also operated in the VHF band, and caused so much interference with the radiotelephones that they were difficult to use. The radar stations were probably the most important users of the network, so VHF would have to be abandoned. In 1954, a military study group was formed to evaluate options for the ACS. That group, in turn, requested a proposal from AT&T. Bell Laboratories had been involved in the design and evaluation of Pole Vault, the first sites of which had been completed two years before, so they naturally positioned troposcatter as the best option. It is worth mentioning the unusual relationship AT&T had with Alaska, or rather, the lack of one. While the Bell System enjoyed a monopoly on telephony in most of the United States [2], they had never expanded into Alaska. Alaska was only a territory, after all, and a very sparsely populated one at that. The paucity of long-distance leads to or from Alaska (only one connected to Anchorage, for example) limited the potential for integration of Alaska into the broader Bell System anyway. Long-distance telecommunications in Alaska were a military project, and AT&T was involved only as a vendor. Because of the high cost of troposcatter stations, proven during Pole Vault construction, a hybrid was proposed: microwave stations could be spaced every 50 miles along the road network, while troposcatter would cover the long stretches without roads. In 1955, the Signal Corps awarded Western Electric a contract for the White Alice Communications System. The Corps of Engineers surveyed the locations of 31 sites, verifying each by constructing a temporary antenna tower. The Corps of Engineers led construction of the first 11 sites, and the final 20 were built on contract by Western Electric itself. All sites used radio equipment furnished by Western Electric and were built to Western Electric designs. Construction was far from straightforward. Difficult conditions delayed completion of the original network until 1959, two years later than intended. A much larger issue, though, was the budget. The original WACS was expected to cost $38 million. By the time the first 31 sites were complete, the bill totaled $113 million---equivalent to over a billion dollars today. Western Electric had underestimated not only the complexity of the sites but the difficulty of their construction. A WECo report read: On numerous occasions, the men were forced to surrender before the onslaught of cold, wind and snow and were immobilized for days, even weeks . This ordeal of waiting was of times made doubly galling by the knowledge that supplies and parts needed for the job were only a few miles distant but inaccessible because the white wall of winter had become impenetrable WACS initial capability included 31 stations, of which 22 were troposcatter and the remainder only microwave (using Western Electric's TD-2). A few stations were equipped with both troposcatter and microwave, serving as relays between the two carriers. In 1958, construction started on the Ballistic Missile Early Warning System or BMEWS. BMEWS was an over-the-horizon radar system intended to provide early warning of a Soviet attack. BMEWS would provide as little as 15 minutes warning, requiring that alerts reach NORAD in Colorado as quickly as possible. One BMEWS set was installed in Greenland, where the Pole Vault system was expanded to provide communications. Similarly, the BMEWS set at Clear Missile Early Warning Station in central Alaska relied on White Alice. Planners were concerned about the ability of the Soviet Union to suppress an alert by destroying infrastructure, so two redundant chains of microwave sites were added to White Alice. One stretched from Clear to Ketchikan where it connected to an undersea cable to Seattle. The other went east, towards Canada, where it met existing telephone cables on the Alaska Highway. A further expansion of White Alice started the next year, in 1959. Troposcatter sites were extended through the Aleutian islands in "Project Stretchout" to serve new DEW Line stations. During the 1960s, existing WACS sites were expanded and new antennas were installed at Air Force installations. These were generally microwave links connecting the airbases to existing troposcatter stations. In total, WACS reached 71 sites. Four large sites served as key switching points with multiple radio links and telephone exchanges. Pedro Dome, for example, had a 15,000 square foot communications building with dormitories, a power plant, and extensive equipment rooms. Support facilities included a vehicle maintenance building, storage warehouse, and extensive fuel tanks. A few WACS sites even had tramways for access between the "lower camp" (where equipment and personnel were housed) and the "upper camp" (where the antennas were located)... although they apparently did not fare well in the Alaskan conditions. While Western Electric had initially planned for six people and 25 KW of power at each station, the final requirements were typically 20 people and 120-180 KW of generator capacity. Some sites stored over half a million gallons of fuel---conditions often meant that resupply was only possible during the summer. Besides troposcatter and microwave radios, the equipment included tandem telephone exchanges. These are described in a couple of documents as "ATSS-4A," ATSS standing for Alaska Telephone Switching System. Based on the naming and some circumstantial evidence, I believe these were Western Electric 4A crossbar exchanges. They were later incorporated into AUTOVON, but also handled commercial long-distance traffic between Alaskan towns. With troposcatter comes large antennas, and depending on connection lengths, WACS troposcatter antennas ranged from 30' dishes to 120' "billboard" antennas similar to those seen at Pole Vault sites. The larger antennas handled up to 50kW of transmit power. Some 60' and 120' antennas included their own fuel tanks and steam plants that heated the antennas through winter to minimize snow accumulation. WACS represented an enormous improvement in Alaskan communications. The entire system was multi-channel with redundancy in many key parts of the network. Outside of the larger cities, WACS often brought the first usable long-distance telephone service. Even in Anchorage, WACS provided the only multi-channel connection. Despite these achievements, WACS was set for much the same fate as other troposcatter systems: obsolescence after the invention of communications satellites. The experimental satellites Telstar 1 and 2 launched in the early 1960s, and the military began a shift towards satellite communications shortly after. Besides, the formidable cost of WACS had become a political issue. Maintenance of the system overran estimates by just as much as construction, and placing this cost on taxpayers was controversial since much of the traffic carried by the system consisted of regular commercial telephone calls. Besides, a general reticence to allocate money to WACS had lead to a general decay of the system. WACS capacity was insufficient for the rapidly increasing long-distance telephone traffic of the '60s, and due to decreased maintenance funding reliability was beginning to decline. The retirement of a Cold War communications system is not unusual, but the particular fate of WACS is. It entered a long second life. After acting as the sole long-distance provider for 60 years, the military began its retreat. In 1969, Congress passed the Alaska Communications Disposal Act. It called for complete divestment of the Alaska Communications System and WACS, to a private owner determined by a bidding process. Several large independent communications companies bid, but the winner was RCA. Committing to a $28.5 million purchase price followed by $30 million in upgrades, RCA reorganized the Alaska Communications System as RCA Alascom. Transfer of the many ACS assets from the military to RCA took 13 years, involving both outright transfer of property and complex lease agreements on sites colocated with military installations. RCA's interest in Alaskan communications was closely connected to the coming satellite revolution: RCA had just built the Bartlett Earth Station, the first satellite ground station in Alaska. While Bartlett was originally an ACS asset owned by the Signal Corps, it became just the first of multiple ground stations that RCA would build for Alascom. Several of the new ground stations were colocated with WACS sites, establishing satellite as an alternative to the troposcatter links. Alascom appears to have been the first domestic satellite voice network in commercial use, initially relying on a Canadian communications satellite [3]. In 1974, SATCOM 1 and 2 launched. These were not the first commercial communications satellites, but they represented a significant increase in capacity over previous commercial designs and are sometimes thought of as the true beginning of the satellite communications era. Both were built and owned by RCA, and Alascom took advantage of the new transponders. At the same time, Alascom launched a modernization effort. 22 of the former WACS stations were converted to satellite ground stations, a project that took much of the '70s as Alascom struggled with the same conditions that had made WACS so challenging to begin with. Modernization also included the installation of DMS-10 telephone switches and conversion of some connections to digital. A series of regulatory and business changes in the 1970s lead RCA to step away from the domestic communications industry. In 1979, Alascom sold to Pacific Power and Light, now for $200 million and $90 million in debt. PP&L continued on much the same trajectory, expanding the Alascom system to over 200 ground stations and launching the satellite Aurora I---the first of a small series of satellites that gave Alaska the distinction of being the only state with its own satellite communications network. For much of the '70s to the '00s, large parts of Alaska relied on satellite relay for calls between towns. In a slight twist of irony considering its long lack of interest in the state, AT&T purchased parts of Alascom from PP&L in 1995, forming AT&T Alascom which has faded away as an independent brand. Other parts of the former ACS network, generally non-toll (or non-long-distance) operations, were split off into then PP&L subsidiary CenturyTel. While CenturyTel has since merged into CenturyLink, the Alaskan assets were first sold to Alaska Communications. Alaska Communications considers itself the successor of the ACS heritage, giving them a claim to over 100 years of communications history. As electronics technology has continued to improve, penetration of microwave relays into inland Alaska has increased. Fewer towns rely on satellite today than in the 1970s, and the half-second latency to geosynchronous orbit is probably not missed. Alaska communications have also become more competitive, with long-distance connectivity available from General Communications (GCI) as well as AT&T and Alaska Communications. Still, the legacy of Alaska's complex and expensive long-distance infrastructure still echoes in our telephone bills. State and federal regulators have allowed for extra fees on telephone service in Alaska and calls into Alaska, both intended to offset the high cost of infrastructure. Alaska is generally the most expensive long-distance calling destination in the United States, even when considering the territories. But what of White Alice? The history of the Alaska Communications System's transition to private ownership is complex and not especially well documented. While RCA's winning bid following the Alaska Communications Disposal Act set the big picture, the actual details of the transition were established by many individual negotiations spanning over a decade. Depending on the station, WACS troposcatter sites generally conveyed to RCA in 1973 or 1974. Some, colocated with active military installations, were leased rather than included in the sale. RCA generally decommissioned each WACS site once a satellite ground station was ready to replace it, either on-site or nearby. For some WACS sites, this meant the troposcatter equipment was shut down in 1973. Others remained in use later. The Boswell Bay troposcatter station seems to have been the last turned down, in 1985. The 1980s were decidedly the end of WACS. Alascom's sale to PP&L cemented the plan to shut down all troposcatter operations, and the 1980 Comprehensive Environmental Response, Compensation, and Liability Act lead to the establishment of the Formerly Used Defense Sites (FUDS) program within DoD. Under FUDS, the Corps of Engineers surveyed the disused WACS sites and found nearly all had significant contamination by asbestos (used in seemingly every building material in the '50s and '60s) and leaked fuel oil. As a result, most White Alice sites were demolished between 1986 and 1999. The cost of demolition and remediation in such remote locations was sometimes greater than the original construction. No WACS sites remain intact today. Postscript: A 1988 Corps of Engineers historical inventory of WACS, prepared due to the demolition of many of the stations, mentions that meteor burst communications might replace troposcatter. Meteor burst is a fascinating communications mode, similar in many ways to troposcatter but with the twist that the reflecting surface is not the troposphere but the ionized trail of meteors entering the atmosphere. Meteor burst connections only work when there is a meteor actively vaporizing in the upper atmosphere, but atmospheric entry of small meteors is common enough that meteor burst communications are practical for low-rate packetized communications. For example, meteor burst has been used for large weather and agricultural telemetry systems. The Alaska Meteor Burst Communications System was implemented in 1977 by several federal agencies, and was used primarily for automated environmental telemetry. Unlike most meteor burst systems, though, it seems to have been used for real-time communications by the BLM and FAA. I can't find much information, but they seem to have built portable teleprinter terminals for this use. Even more interesting, the Air Force's Alaskan Air Command built its own meteor burst network around the same time. This network was entirely for real-time use, and demonstrated the successful transmission of radar track data from radar stations across the state to Elmendorf Air Force base. Even better, the Air Force experimented with the use of meteor burst for intercept control by fitting aircraft with a small speech synthesizer that translated coded messages into short phrases. The Air Force experimented with several meteor burst systems during the Cold War, anticipating that it might be a survivable communications system in wartime. More details on these will have to fill a future article. [1] Crews of the Western Union Telegraph Expedition reportedly continued work for a full year after the completion of the transatlantic telephone cable, because news of it hadn't reached them yet. [2] Eliding here some complexities like GTE and their relationship to the Bell System. [3] Perhaps owing to the large size of the country and many geographical challenges to cable laying, Canada has often led North America in satellite communications technology.

We've talked before about carphones, and certainly one of the only ways to make phones even more interesting is to put them in modes of transportation. Installing telephones in cars made a lot of sense when radiotelephones were big and required a lot of power; and they faded away as cellphones became small enough to have a carphone even outside of your car. There is one mode of transportation where the personal cellphone is pretty useless, though: air travel. Most readers are probably well aware that the use of cellular networks while aboard an airliner is prohibited by FCC regulations. There are a lot of urban legends and popular misconceptions about this rule, and fully explaining it would probably require its own article. The short version is that it has to do with the way cellular devices are certified and cellular networks are planned. The technical problems are not impossible to overcome, but honestly, there hasn't been a lot of pressure to make changes. One line of argument that used to make an appearance in cellphones-on-airplanes discourse is the idea that airlines or the telecom industry supported the cellphone ban because it created a captive market for in-flight telephone services. Wait, in-flight telephone services? That theory has never had much to back it up, but with the benefit of hindsight we can soundly rule it out: not only has the rule persisted well past the decline and disappearance of in-flight telephones, in-flight telephones were never commercially successful to begin with. Let's start with John Goeken. A 1984 Washington Post article tells us that "Goeken is what is called, predictably enough, an 'idea man.'" Being the "idea person" must not have had quite the same connotations back then, it was a good time for Goeken. In the 1960s, conversations with customers at his two-way radio shop near Chicago gave him an idea for a repeater network to allow truckers to reach their company offices via CB radio. This was the first falling domino in a series that lead to the founding of MCI and the end of AT&T's long-distance monopoly. Goeken seems to have been the type who grew bored with success, and he left MCI to take on a series of new ventures. These included an emergency medicine messaging service, electrically illuminated high-viz clothing, and a system called the Mercury Network that built much of the inertia behind the surprisingly advanced computerization of florists [1]. "Goeken's ideas have a way of turning into dollars, millions of them," the Washington Post continued. That was certainly true of MCI, but every ideas guy had their misses. One of the impressive things about Goeken was his ability to execute with speed and determination, though, so even his failures left their mark. This was especially true of one of his ideas that, in the abstract, seemed so solid: what if there were payphones on commercial flights? Goeken's experience with MCI and two-way radios proved valuable, and starting in the mid-1970s he developed prototype air-ground radiotelephones. In its first iteration, "Airfone" consisted of a base unit installed on an aircraft bulkhead that accepted a credit card and released a cordless phone. When the phone was returned to the base station, the credit card was returned to the customer. This equipment was simple enough, but it would require an extensive ground network to connect callers to the telephone system. The infrastructure part of the scheme fell into place when long-distance communications giant Western Union signed on with Goeken Communications to launch a 50/50 joint venture under the name Airfone, Inc. Airfone was not the first to attempt air-ground telephony---AT&T had pursued the same concept in the 1970s, but abandoned it after resistance from the FCC (unconvinced the need was great enough to justify frequency allocations) and the airline industry (which had formed a pact, blessed by the government, that prohibited the installation of telephones on aircraft until such time as a mature technology was available to all airlines). Goeken's hard-headed attitude, exemplified in the six-year legal battle he fought against AT&T to create MCI, must have helped to defeat this resistance. Goeken brought technical advances, as well. By 1980, there actually was an air-ground radiotelephone service in general use. The "General Aviation Air-Ground Radiotelephone Service" allocated 12 channels (of duplex pairs) for radiotelephony from general aviation aircraft to the ground, and a company called Wulfsberg had found great success selling equipment for this service under the FliteFone name. Wulfsberg FliteFones were common equipment on business aircraft, where they let executives shout "buy" and "sell" from the air. Goeken referred to this service as evidence of the concept's appeal, but it was inherently limited by the 12 allocated channels. General Aviation Air-Ground Radiotelephone Service, which I will call AGRAS (this is confusing in a way I will discuss shortly), operated at about 450MHz. This UHF band is decidedly line-of-sight, but airplanes are very high up and thus can see a very long ways. The reception radius of an AGRAS transmission, used by the FCC for planning purposes, was 220 miles. This required assigning specific channels to specific cities, and there the limits became quite severe. Albuquerque had exactly one AGRAS channel available. New York City got three. Miami, a busy aviation area but no doubt benefiting from its relative geographical isolation, scored a record-setting four AGRAS channels. That meant AGRAS could only handle four simultaneous calls within a large region... if you were lucky enough for that to be the Miami region; otherwise capacity was even more limited. Back in the 1970s, AT&T had figured that in-flight telephones would be very popular. In a somewhat hand-wavy economic analysis, they figured that about a million people flew in the air on a given day, and about a third of them would want to make telephone calls. That's over 300,000 calls a day, clearly more than the limited AGRAS channels could handle... leading to the FCC's objection that a great deal of spectrum would have to be allocated to make in-flight telephony work. Goeken had a better idea: single-sideband. SSB is a radio modulation technique that allows a radio transmission to fit within a very narrow bandwidth (basically by suppressing half of the signal envelope), at the cost of a somewhat more fiddly tuning process for reception. SSB was mostly used down in the HF bands, where the low frequencies meant that bandwidth was acutely limited. Up in the UHF world, bandwidth seemed so plentiful that there was little need for careful modulation techniques... until Goeken found himself asking the FCC for 10 blocks of 29 channels each, a lavish request that wouldn't really fit anywhere in the popular UHF spectrum. The use of UHF SSB, pioneered by Airfone, allowed far more efficient use of the allocation. In 1983, the FCC held hearings on Airfone's request for an experimental license to operate their SSB air-ground radiotelephone system in two allocations (separate air-ground and ground-air ranges) around 850MHz and 895MHz. The total spectrum allocated was about 1.5MHz in each of the two directions. The FCC assented and issued the experimental license in 1984, and Airfone was in business. Airfone initially planned 52 ground stations for the system, although I'm not sure how many were ultimately built---certainly 37 were in progress in 1984, at a cost of about $50 million. By 1987, the network had reportedly grown to 68. Airfone launched on six national airlines (a true sign of how much airline consolidation has happened in recent decades---there were six national airlines?), typically with four cordless payphones on a 727 or similar aircraft. The airlines received a commission on the calling rates, and Airfone installed the equipment at their own expense. Still, it was expected to be profitable... Airfone projected that 20-30% of passengers would have calls to make. I wish I could share more detail on these ground stations, in part because I assume there was at least some reuse of existing Western Union facilities (WU operated a microwave network at the time and had even dabbled in cellular service in the 1980s). I can't find much info, though. The antennas for the 800MHz band would have been quite small, but the 1980s multiplexing and control equipment probably took a fare share of floorspace. Airfone was off to a strong start, at least in terms of installation base and press coverage. I can't say now how many users it actually had, but things looked good enough that in 1986 Western Union sold their share of the company to GTE. Within a couple of years, Goeken sold his share to GTE as well, reportedly as a result of disagreements with GTE's business strategy. Airfone's SSB innovation was actually quite significant. At the same time, in the 1980s, a competitor called Skytel was trying to get a similar idea off the ground with the existing AGRAS allocation. It doesn't seem to have gone anywhere, I don't think the FCC ever approved it. Despite an obvious concept, Airfone pretty much launched as a monopoly, operating under an experimental license that named them alone. Unsurprisingly there was some upset over this apparent show of favoritism by the FCC, including from AT&T, which vigorously opposed the experimental license. As it happened, the situation would be resolved by going the other way: in 1990, the FCC established the "commercial aviation air-ground service" which normalized the 800 MHz spectrum and made licenses available to other operators. That was six years after Airfone started their build-out, though, giving them a head start that severely limited competition. Still, AT&T was back. AT&T introduced a competing service called AirOne. AirOne was never as widely installed as Airfone but did score some customers including Southwest Airlines, which only briefly installed AirOne handsets on their fleet. "Only briefly" describes most aspects of AirOne, but we'll get to that in a moment. The suddenly competitive market probably gave GTE Airfone reason to innovate, and besides, a lot had changed in communications technology since Airfone was designed. One of Airfone's biggest limitations was its lack of true roaming: an Airfone call could only last as long as the aircraft was within range of the same ground station. Airfone called this "30 minutes," but you can imagine that people sometimes started their call near the end of this window, and the problem was reportedly much worse. Dropped calls were common, adding insult to the injury that Airfone was decidedly expensive. GTE moved towards digital technology and automation. 1991 saw the launch of Airfone GenStar, which used QAM digital modulation to achieve better call quality and tighter utilization within the existing bandwidth. Further, a new computerized network allowed calls to be handed off from one ground station to another. Capitalizing on the new capacity and reliability, the aircraft equipment was upgraded as well. The payphone like cordless stations were gone, replaced by handsets installed in seatbacks. First class cabins often got a dedicated handset for every seat, economy might have one handset on each side of a row. The new handsets offered RJ11 jacks, allowing the use of laptop modems while in-flight. Truly, it was the future. During the 1990s, satellites were added to the Airfone network as well, improving coverage generally and making telephone calls possible on overseas flights. Of course, the rise of satellite communications also sowed the seeds of Airfone's demise. A company called Aircell, which started out using the cellular network to connect calls to aircraft, rebranded to Gogo and pivoted to satellite-based telephone services. By the late '90s, they were taking market share from Airfone, a trend that would only continue. Besides, for all of its fanfare, Airfone was not exactly a smash hit. Rates were very high, $5 a minute in the late '90s, giving Airfone a reputation as a ripoff that must have cut a great deal into that "20-30% of fliers" they hoped to serve. With the rise of cellphones, many preferred to wait until the aircraft was on the ground to use their own cellphone at a much lower rate. GTE does not seem to have released much in the way of numbers for Airfone, but it probably wasn't making them rich. Goeken, returning to the industry, inadvertently proved this point. He aggressively lobbied the FCC to issue competitive licenses, and ultimately succeeded. His second company in the space, In-Flight Phone Inc., became one of the new competitors to his old company. In-Flight Phone did not last for long. Neither did AT&T AirOne. A 2005 FCC ruling paints a grim picture: Current 800 MHz Air-Ground Radiotelephone Service rules contemplate six competing licensees providing voice and low-speed data services. Six entities were originally licensed under these rules, which required all systems to conform to detailed technical specifications to enable shared use of the air-ground channels. Only three of the six licensees built systems and provided service, and two of those failed for business reasons. In 2002, AT&T pulled out, and Airfone was the only in-flight phone left. By then, GTE had become Verizon, and GTE Airfone was Verizon Airfone. Far from a third of passengers, the CEO of Airfone admitted in an interview that a typical flight only saw 2-3 phone calls. Considering the minimum five-figure capital investment in each aircraft, it's hard to imagine that Airfone was profitable---even at $5 minute. Airfone more or less faded into obscurity, but not without a detour into the press via the events of 9/11. Flight 93, which crashed in Pennsylvania, was equipped with Airfone and passengers made numerous calls. Many of the events on board this aircraft were reconstructed with the assistance of Airfone records, and Claircom (the name of the operator of AT&T AirOne, which never seems to have been well marketed) also produced records related to other aircraft involved in the attacks. Most notably, flight 93 passenger Todd Beamer had a series of lengthy calls with Airfone operator Lisa Jefferson, through which he relayed many of the events taking place on the plane in real time. During these calls, Beamer seems to have coordinated the effort by passengers to retake control of the plane. The significance of Airfone and Claircom records to 9/11 investigations is such that 9/11 conspiracy theories may be one of the most enduring legacies of Claircom especially. In an odd acknowledgment of their aggressive pricing, Airfone decided not to bill for any calls made on 9/11, and temporarily introduced steep discounts (to $0.99 a minute) in the weeks after. This rather meager show of generosity did little to reverse the company's fortunes, though, and it was already well into a backslide. In 2006, the FCC auctioned the majority of Airfone's spectrum to new users. The poor utilization of Airfone was a factor in the decision, as well as Airfone's relative lack of innovation compared to newer cellular and satellite systems. In fact, a large portion of the bandwidth was purchased by Gogo, who years later would use to to deliver in-flight WiFi. Another portion went to a subsidiary of JetBlue that provided in-flight television. Verizon announced the end of Airfone in 2006, pending an acquisition by JetBlue, and while the acquisition did complete JetBlue does not seem to have continued Airfone's passenger airline service. A few years later, Gogo bought out JetBlue's communications branch, making them the new monopoly in 800MHz air ground radiotelephony. Gogo only offered telephone service for general aviation aircraft; passenger aircraft telephones had gone the way of the carphone. It's interesting to contrast the fate of Airfone to to its sibling, AGRAS. Depending on who you ask, AGRAS refers to the radio service or to the Air Ground Radiotelephone Automated Service operated by Mid-America Computer Corporation. What an incredible set of names. This was a situation a bit like ARINC, the semi-private company that for some time held a monopoly on aviation radio services. MACC had a practical monopoly on general aviation telephone service throughout the US, by operating the billing system for calls. MACC still exists today as a vendor of telecom billing software and this always seems to have been their focus---while I'm not sure, I don't believe that MACC ever operated ground stations, instead distributing rate payments to private companies that operated a handful of ground stations each. Unfortunately the history of this service is quite obscure and I'm not sure how MACC came to operate the system, but I couldn't resist the urge to mention the Mid-America Computer Corporation. AGRAS probably didn't make anyone rich, but it seems to have been generally successful. Wulfsberg FliteFones operating on the AGRAS network gave way to Gogo's business aviation phone service, itself a direct descendent of Airfone technology. The former AGRAS allocation at 450MHz somehow came under the control of a company called AURA Network Systems, which for some years has used a temporary FCC waiver of AGRAS rules to operate data services. This year, the FCC began rulemaking to formally reallocate the 450MHz air ground allocation to data services for Advanced Air Mobility, a catch-all term for UAS and air taxi services that everyone expects to radically change the airspace system in coming years. New uses of the band will include command and control for long-range UAS, clearance and collision avoidance for air taxis, and ground and air-based "see and avoid" communications for UAS. This pattern, of issuing a temporary authority to one company and later performing rulemaking to allow other companies to enter, is not unusual for the FCC but does make an interesting recurring theme in aviation radio. It's typical for no real competition to occur, the incumbent provider having been given such a big advantage. When reading about these legacy services, it's always interesting to look at the licenses. ULS has only nine licenses on record for the original 800 MHz air ground service, all expired and originally issued to Airfone (under both GTE and Verizon names), Claircom (operating company for AT&T AirOne), and Skyway Aircraft---this one an oddity, a Florida-based company that seems to have planned to introduce in-flight WiFi but not gotten all the way there. Later rulemaking to open up the 800MHz allocation to more users created a technically separate radio service with two active licenses, both held by AC BidCo. This is an intriguing mystery until you discover that AC BidCo is obviously a front company for Gogo, something they make no effort to hide---the legalities of FCC bidding processes are such that it's very common to use shell companies to hold FCC licenses, and we could speculate that AC BidCo is the Aircraft Communications Bidding Company, created by Gogo for the purpose of the 2006-2008 auctions. These two licenses are active for the former Airfone band, and Gogo reportedly continues to use some of the original Airfone ground stations. Gogo's air-ground network, which operates at 800MHz as well as in a 3GHz band allocated specifically to Gogo, was originally based on CDMA cellular technology. The ground stations were essentially cellular stations pointed upwards. It's not clear to me if this CDMA-derived system is still in use, but Gogo relies much more heavily on their Ku-band satellite network today. The 450MHz licenses are fascinating. AURA is the only company to hold current licenses, but the 246 reveal the scale of the AGRAS business. Airground of Idaho, Inc., until 1999 held a license for an AGRAS ground station on Brundage Mountain McCall, Idaho. The Arlington Telephone Company, until a 2004 cancellation, held a license for an AGRAS ground station atop their small telephone exchange in Arlington, Nebraska. AGRAS ground stations seem to have been a cottage industry, with multiple licenses to small rural telephone companies and even sole proprietorships. Some of the ground stations appear to have been the roofs of strip mall two-way radio installers. In another life, maybe I would be putting a 450MHz antenna on my roof to make a few dollars. Still, there were incumbents: numerous licenses belonged to SkyTel, which after the decline of AGRAS seems to have refocused on paging and, then, gone the same direction as most paging companies: an eternal twilight as American Messaging ("The Dependable Choice"), promoting innovation in the form of longer-range restaurant coaster pagers. In another life, I'd probably be doing that too. [1] This is probably a topic for a future article, but the Mercury Network was a computerized system that Goeken built for a company called Florist's Telegraph Delivery (FTD). It was an evolution of FTD's telegraph system that allowed a florist in one city to place an order to be delivered by by a florist in another city, thus enabling the long-distance gifting of flowers. There were multiple such networks and they had an enduring influence on the florist industry and broader business telecommunications.

I have a rough list of topics for future articles, a scratchpad of two-word ideas that I sometimes struggle to interpret. Some items have been on that list for years now. Sometimes, ideas languish because I'm not really interested in them enough to devote the time. Others have the opposite problem: chapters of communications history with which I'm so fascinated that I can't decide where to start and end. They seem almost too big to take on. One of these stories starts in another vast frontier: northeastern Canada. It was a time, rather unlike our own, of relative unity between Canada and the United States. Both countries had spent the later part of World War II planning around the possibility of an Axis attack on North America, and a ragtag set of radar stations had been built to detect inbound bombers. The US had built a series of stations along the border, and the Canadians had built a few north of Ontario and Quebec to extend coverage north of those population centers. Then the war ended and, as with so many WWII projects, construction stopped. Just a few years later, the USSR demonstrated a nuclear weapon and the Cold War was on. As with so many WWII projects, freshly anxious planners declared the post-war over and blew the dust off of North American air defense plans. In 1950, US and Canadian defense leaders developed a new plan to consolidate and improve the scattershot radar early warning plan. This agreement would become the Pinetree Line, the first of three trans-Canadian radar fences jointly constructed and operated by the two nations. For the duration of the Cold War, and even to the present day, these radar installations formed the backbone of North American early warning and the locus of extensive military cooperation. The joint defense agreement between the US and Canada, solidified by the Manhattan Project's dependence on Canadian nuclear industry, grew into the 1968 establishment of the North American Air Defense Command (NORAD) as a binational joint military organization. This joint effort had to rise to many challenges. Radar had earned its place as a revolutionary military technology during the Second World War, but despite the many radar systems that had been fielded, engineer's theoretical understanding of radar and RF propagation were pretty weak. I have written here before about over-the-horizon radar, the pursuit of which significantly improved our scientific understanding of radio propagation in the atmosphere... often by experiment, rather than model. A similar progression in RF physics would also benefit radar early warning in another way: communications. One of the bigger problems with the Pinetree Line plan was the remote location of the stations. You might find that surprising; the later Mid-Canada and DEW lines were much further north and more remote. The Pinetree Line already involved stations in the far reaches of the maritime provinces, though, and to provide suitable warning to Quebec and the Great Lakes region stations were built well north of the population centers. Construction and operations would rely on aviation, but an important part of an early warning system is the ability to deliver the warning. Besides, ground-controlled interception had become the main doctrine in air defense, and it required not just an alert but real-time updates from radar stations for the most effective response. Each site on the Pinetree Line would require a reliable real-time communications capability, and as the sites were built in the 1950s, some were a very long distance from telephone lines. Canada had only gained a transcontinental telephone line in 1932, seventeen years behind the United States (which by then had three different transcontinental routes and a fourth in progress), a delay owing mostly to the formidable obstacle of the Canadian Rockies. The leaders in Canadian long-distance communications were Bell Canada and the two railways (Canadian Pacific and Canadian National), and in many cases contracts had been let to these companies to extend telephone service to radar stations. The service was very expensive, though, and the construction of telephone cables in the maritimes was effectively ruled out due to the huge distances involved and uncertainty around the technical feasibility of underwater cables to Newfoundland due to the difficult conditions and extreme tides in the Gulf of St. Lawrence. The RCAF had faced a similar problem when constructing its piecemeal radar stations in Ontario and Quebec in the 1940s, and had addressed them by applying the nascent technology of point-to-point microwave relays. This system, called ADCOM, was built and owned by RCAF to stretch 1,400 miles between a series of radar stations and other military installations. It worked, but the construction project had run far over budget (and major upgrades performed soon after blew the budget even further), and the Canadian telecom industry had vocally opposed it on the principle that purpose-built military communications systems took government investment away from public telephone infrastructure that could also serve non-military needs. These pros and cons of ADCOM must have weighed on Pinetree Line planners when they chose to build a system directly based on ADCOM, but to contract its construction and operation to Bell Canada [1]. This was, it turned out, the sort of compromise that made no one happy: the Canadian military's communications research establishment was reluctant to cede its technology to Bell Canada, while Bell Canada objected to deploying the military's system rather than one of the commercial technologies then in use across the Bell System. The distinct lack of enthusiasm on the part of both parties involved was a bad omen for the future of this Pinetree Line communications system, but as it would happen, the whole plan was overcome by events. One of the great struggles of large communications projects in that era, and even today, is the rapid rate of technological progress. One of ADCOM's faults was that the immense progress Bell Labs and Western Electric made in microwave equipment during the late '40s meant that it was obsolete as soon as it went into service. This mistake would not be repeated, as ADCOM's maritimes successor was obsoleted before it even broke ground. A promising new radio technology offered a much lower cost solution to these long, remote spans. At the onset of the Second World War, the accepted theory of radio propagation held that HF signals could pass the horizon via ground wave propagation, curving to follow the surface of the Earth, while VHF and UHF signals could not. This meant that the higher-frequency bands, where wideband signals were feasible, were limited to line-of-sight or at least near-line-of-sight links... not more than 50 miles with ideal terrain, often less. We can forgive the misconception, because this still holds true today, as a rule of thumb. The catch is in the exceptions, the nuances, that during the war were already becoming a headache to RF engineers. First, military radar operators observed mysterious contacts well beyond the theoretical line-of-sight range of their VHF radar sets. These might have been dismissed as faults in the equipment (or the operator), but reports stacked up as more long-range radar systems were fielded. After the war, relaxed restrictions and a booming economy allowed radio to proliferate. UHF television stations, separated by hundreds of miles, unexpectedly interfered with each other. AT&T, well into deployment of a transcontinental microwave network, had to adjust its frequency planning after it was found that microwave stations sometimes received interfering signals from other stations in the chain... stations well over the horizon. This was the accidental discovery of tropospheric scattering. The Earth's atmosphere is divided into five layers. We live in the troposhere, the lowest and thinnest of the layers, above which lies the stratosphere. Roughly speaking, the difference between these layers is that the troposphere becomes colder with height (due to increasing distance from the warm surface), while the stratosphere becomes warmer with height (due to decreasing shielding from the sun) [2]. In between is a local minimum of temperature, called the tropopause. The density gradients around the tropopause create a mirror effect, like the reflections you see when looking at an air-water boundary. The extensive turbulence and, well, weather present in the troposhere also refract signals on their way up and down, making the true course of radio signals reflecting off of the tropopause difficult to predict or analyze. Because of this turbulence, the effect has come to be known as scattering: radio signals sent upwards, towards the troposphere, will be scattered back downwards across a wide area. This effect is noticeable only at high frequencies, so it remained unknown until the widespread use of UHF and microwave, and was still only partially understood in the early 1950s. The locii of radar technology at the time were Bell Laboratories and the MIT Lincoln Laboratory, and they both studied this effect for possible applications. Presaging one of the repeated problems of early warning radar systems, by the time Pinetree Line construction began in 1951 the Lincoln Laboratory was already writing proposals for systems that would obsolete it. In fact, construction would begin on both of the Pinetree Line's northern replacements before the Pinetree Line itself was completed. Between rapid technological development and military planners in a sort of panic mode, the early 1950s were a very chaotic time. Underscoring the ever-changing nature of early warning was the timeline of Pinetree Line communications: as the Pinetree Line microwave network was in planning, the Lincoln Laboratory was experimenting with troposcatter communications. By the time the first stations in Newfoundland completed construction, Bell Laboratories had developed an experimental troposcatter communications system. This new means of long-range communications would not be ready in time for the first Pinetree Line stations, so parts of the original ADCOM-based microwave network would have to be built. Still, troposcatter promised to complete the rest of the network at significantly reduced cost. The US Air Force, wary of ADCOM's high costs and more detached from Canadian military politics, aggressively lobbied for the adoption of troposcatter communications for the longest and most challenging Pinetree Line links. Bell Laboratories, long a close collaborator with the Air Force, was well aware of troposcatter's potential for early warning radar. Bell Canada and Bell Laboratories agreed to evaluate the system under field conditions, and in 1952 experimental sites were installed in Newfoundland. These tests found reliable performance over 150 miles, far longer than achievable by microwave and---rather conveniently---about the distance between Pinetree Line radar stations. These results suggested that the Pinetree Line could go without an expensive communications network in the traditional sense, instead using troposcatter to link the radar stations directly to each other. Consider a comparison laid out by the Air Force: one of the most complex communications requirements for the Pinetree Line was a string of stations running not east-west like the "main" line, but north-south from St. John's, Newfoundland to Frobisher Bay, Nunavut. These stations were critical for detection of Soviet bombers approaching over the pole from the northwest, otherwise a difficult gap in radar coverage until the introduction of radar sites in Greenland. But the stations covered a span of over 1,000 miles, most of it in formidably rugged and remote arctic coastal terrain. The proposed microwave system would require 50 relay stations, almost all of which would be completely new construction. Each relay's construction would have to be preceded by the construction of a harbor or airfield for access, and then establishment of a power plant, to say nothing of the ongoing logistics of transporting fuel and personnel for maintenance. The proposed troposcatter system, on the other hand, required only ten relays. All ten would be colocated with radar stations, and could share infrastructure and logistical considerations. Despite the clear advantages of troposcatter and its selection by the USAF, the Canadian establishment remained skeptical. One cannot entirely blame them, considering that troposcatter communications had only just been demonstrated in the last year. Still, the USAF was footing most of the bill for the overall system (and paying entirely for the communications aspect, depending on how you break down the accounting) and had considerable sway. In 1954, well into construction of the radar stations (several had already been commissioned), the Bell Canada contract for communications was amended to add troposcatter relay in addition to the original microwave scheme. Despite the weaselly contracting, the writing was on the wall and progress on microwave relay stations almost stopped. By the latter part of 1954, the microwave network was abandoned entirely. Bell Canada moved at incredible speed to complete the world's first troposcatter long-distance route, code named Pole Vault. One the major downsides of troposcatter communications is its inefficiency. Only a very small portion of the RF energy reaching the tropopause is reflected, and of that, only a small portion is reflected in the right direction. Path loss from transmitter to receiver for long links is over -200 dB, compared to say -130 dB for a microwave link. That difference looks smaller than it is; dB is a logarithmic comparison and the decrease from -130 dB to -200 dB is a factor of ten million. The solution is to go big. Pole Vault's antennas, manufactured as a rush order by D. S. Kennedy Co. of Massachusetts. 36 were required, generally four per site for transmit and receive in each direction. Each antenna was a 60' aluminum parabolic dish held up on edge by truss legs. Because of the extreme weather at the coastal radar sites, the antennas were specified to operate in a 120 knot wind---or a 100 knot wind with an inch of ice buildup. These were operating requirements, so the antenna had not only to survive these winds, but to keep flexing and movements small enough to not adversely impact performance. The design of the antennas was not trivial; even after analysis by both Kennedy Co. and Bell Canada, after installation some of the rear struts supporting the antennas buckled. All high-wind locations received redesigned struts. To drive the antennas, Radio Engineering Laboratories of Long Island furnished radio sets with 10 kW of transmit power. Both of these were established companies, especially for military systems, but were still small compared to Bell System juggernauts like Western Electric. They had built the equipment for the experimental sites, though, and the timeline for construction of Pole Vault was so short that planners did not feel there was time to contract larger manufacturers. This turn of events made Kennedy Co. and REL the leading experts in troposcatter equipment, which became their key business in the following decade. The target of the contract, signed in January of 1954, was to have Pole Vault operational by the end of that same year. Winter conditions, and indeed spring and fall conditions, are not conducive to construction on the arctic coast. All of the equipment for Pole Vault had to be manufactured in the first half of the year, and as weather improved and ice cleared in the mid-summer, everything was shipped north and installation work began. Both militaries had turned down involvement in the complex and time-consuming logistics of the project, so Bell Canada chartered ships and aircraft and managed an incredibly complex schedule. To deliver equipment to sites as early as possible, icebreaker CCGS D'Iberville was chartered. C-119 and DC3 aircraft served alongside numerous small boats and airplanes. All told, it took about seven months to manufacture and deliver equipment to the Pole Vault sites, and six months to complete construction. Construction workers, representing four or five different contractors at each site and reaching about 120 workers to a site during peak activity, had to live in construction camps that could still be located miles from the station. Grounded ships, fires, frostbite, and of course poor morale lead to complications and delays. At one site, Saglek, project engineers recorded a full 24-hour day with winds continuously above 75 miles per hour, and then weeks later, a gust of 135 mph was observed. Repairs had to be made to the antennas and buildings before they were even completed. In a remarkable feat of engineering and construction, the Pole Vault system was completed and commissioned more or less on schedule: amended into the contract in January of 1954, commissioning tests of the six initial stations were successfully completed February of 1955. Four additional stations were built to complete the chain, and Pole Vault was declared fully operational December of 1956 at a cost of $24.6 million (about $290 million today). Pole Vault operated at various frequencies between 650 and 800 MHz, the wide range allowing for minimal frequency reuse---interference was fairly severe, since each station's signal scattered and could be received by stations further down the line in ideal (or as the case may be, less than ideal) conditions. Frequency division multiplexing equipment, produced by Northern Electric (Nortel) based on microwave carrier systems, offered up to 36 analog voice circuits. The carrier systems were modular, and some links initially supported only 12 circuits, while later operational requirements lead to an upgrade to 70 circuits. Over the following decades, the North Atlantic remained a critical challenge for North American air defense. It also became the primary communications barrier between the US and Canada and European NATO allies. Because Pole Vault provided connections across such a difficult span, several later military communications systems relied on Pole Vault as a backhaul connection. An inventory of the Saglek site, typical of the system, gives an idea of the scope of each of the nine primary stations. This is taken from "Special Contract," a history by former Bell Canada engineer A. G. Lester: (1) Four parabolic antennas, 60 feet in diameter, each mounted on seven mass concrete footings. (2) An equipment building 62 by 32 feet to house electronic equipment, plus a small (10 by 10 feet) diversity building. (3) A diesel building 54 by 36 feet, to house three 125 KVA (kilovolt amperes) diesel driven generators. (4) Two 2500 gallon fuel storage tanks. (5) Raceways to carry waveguide and cables. (6) Enclosed corridors interconnecting buildings, total length in this case 520 feet. Since the Pole Vault stations were colocated with radar facilities, barracks and other support facilities for the crews were already provided for. Of course, you can imagine that the overall construction effort at each site was much larger, including the radar systems as well as cantonment for personnel. Pole Vault would become a key communications system in the maritime provinces, remaining in service until 1975. Its reliable performance in such a challenging environment was a powerful proof of concept for troposcatter, a communications technique first imagined only a handful of years earlier. Even as Pole Vault reached its full operating capability in late 1956, other troposcatter systems were under construction. Much the same, and not unrelated, other radar early warning systems were under construction as well. The Pinetree Line, for all of its historical interest and its many firsts, ended as a footnote in the history of North American air defense. More sophisticated radar fences were already under design by the time Pinetree Line construction started, leaving some Pinetree stations to operate for just four years. It is a testament to Pole Vault that it outlived much of the radar system it was designed to support, becoming an integral part of not one, or even two, but at least three later radar early warning programs. Moreover, Pole Vault became a template for troposcatter systems elsewhere in Canada, in Europe, and in the United States. But we'll have to talk about those later. [1] Alexander Graham Bell was Scottish-Canadian-American, and lived for some time in rural Ontario and later Montreal. As a result, Bell Canada is barely younger than its counterpart in the United States and the early history of the two is more one of parallel development than the establishment of a foreign subsidiary. Bell's personal habit of traveling back and forth between Montreal and Boston makes the early interplay of the two companies a bit confusing. In 1955, the TAT-1 telephone cable would conquer the Atlantic ocean to link the US to Scotland via Canada, incidentally making a charming gesture to Bell's personal journey. [2] If you have studied weather a bit, you might recognize these as positive and negative lapse rates. The positive lapse rate in the troposphere is a major driver in the various phenomenon we call "weather," and the tropopause forms a natural boundary that keeps most weather within the troposphere.