5 ms·

A portion of the original DEW line stations are still in service and retain most of their original structure. However, they are now unmanned, remote controlled,

A portion of the original DEW line stations are still in service and retain most of their original structure. However, they are now unmanned, remote controlled, and infrequently serviced by a first nations contractor that reaches them by helicopter. The construction of the actual stations is fairly interesting as well. Typical stations (e.g. not communications hubs) consisted of two "trains" of modular buildings assembled end-to-end with an elevated "snowbridge" between them. But, perhaps the most interesting thing to say about the DEW line is its communication infrastructure. Because of the impracticality of building line-of-sight repeaters (and even more so laying cable), the DEW line was one of few large-scale applications of troposcatter communications. Each station included four large parabolic antennas aimed nearly horizontally at the stations in each direction, the radio signal reflected off of the troposphere to reach the next station over the horizon. Some larger stations featured additional antennas aimed south, which connected through a series of troposcatter repeaters until conventional telecom infrastructure was available. Troposcatter was sparsely used because it required large antennas, high power, and still suffered from weather and solar impacts. However it was relatively widely used in arctic North America due to the long ranges achievable. Other systems included WHITE ALICE (a military communications system in Alaska that carried civilian phone calls to remote towns for decades), several commercial north-south links built in Canada to provide telephone service to mines, the NA-Thule and other connections in that region (some of which were originally built as part of DEW). Troposcatter also saw limited use over water when cable laying was deemed not worth the price, prominently between the Texas Towers and shore and between Florida and Cuba (where the link remained in service long after laying cable would have been preferable due to embargo and other trade complications).

jcrawfordor 6y ago
Because I can't resist talking about this, one of my hobby topics, a bit more, there's a whole history of radar development occurring in Canada in the early cold war. The DEW line is of major interest because of the huge complexity of building such an ambitious project so far north. Also interesting, though, is the Mid-Canada Line which was built before, and further south than, the DEW line. The MCL pioneered the bistatic radar technology which was used (in a much refined form) in the DEW line. The principle of bistatic radar is this: instead of the transmitter and receiver being at the same position, and thus receiving reflections (this is known as monostatic radar), in a bistatic system the transmitter and receiver are at different locations and detect changes in the signal propagating between them. In the case of the MCL and DEW line, the change observed for is dopplar shift caused by a moving object in the area in between. The use of bistatic radar means that the MCL and DEW line are very literally "lines" with each station transmitting to the next. To overcome limitations of bistatic radar, though, the DEW line made use of both. The AN/FPS-19 search radar was a monostatic system. However, monostatic radar often has poor sensitivity to aircraft at low altitude (thus the expression "under the radar"). The AN/FPS-23 bistatic radar was used to "fill in" sensitivity at low altitude, although an aircraft would have to pass between two stations (and thus be further south) to be detected. An interesting example of bistatic radar that makes for easy learning of the concept because of its small scale is the AN/TPS-39 (one of a number of radars called "tipsies" due to the req number), which was used as a "virtual fence" for surface security at Titan missile silos. In that case the two antennas were only something like 10-20 feet apart and had a distinctive horn shape due to using microwave frequencies. Microwave radar is still used in "virtual fence" intrusion detection applications but enhancements in signal processing technology now allow simpler monostatic applications.
bane 6y ago
Out of curiosity, how were these remote systems powered?
- jcrawfordor 6y ago
  Diesel generators. As you can imagine this created an ongoing logistics need, although that wasn't as big of an issue as it may sound because the stations had relatively large crews and so already required regular delivery of supplies and new personnel. The method depended on the station but it was mostly done by sea or air. Around the same time period the USSR was experimenting with lighthouses and remote monitoring equipment powered by RTGs, and on this side of the iron curtain McMurdo station had a small nuclear reactor. However RTGs produced much too little power for these stations and portable reactors were a very experimental technology that was abandoned for a number of reasons you can likely imagine. The RTGs turned out to be a bad idea as well because they now form a sort of sleeping environmental hazard in much of the arctic region, most of them slipped into the water and presumably the casing is slowly corroding away. As a slightly related fact of interest, due to the ongoing need for crew there is a duplicate of a DEW line station located near Streator, IL which was used for training new personnel before they made the long trip north. It includes a troposcatter link to a small station in another town for training radio operators.

jcrawfordor 6y ago

Because I can't resist talking about this, one of my hobby topics, a bit more, there's a whole history of radar development occurring in Canada in the early cold war. The DEW line is of major interest because of the huge complexity of building such an ambitious project so far north. Also interesting, though, is the Mid-Canada Line which was built before, and further south than, the DEW line. The MCL pioneered the bistatic radar technology which was used (in a much refined form) in the DEW line. The principle of bistatic radar is this: instead of the transmitter and receiver being at the same position, and thus receiving reflections (this is known as monostatic radar), in a bistatic system the transmitter and receiver are at different locations and detect changes in the signal propagating between them. In the case of the MCL and DEW line, the change observed for is dopplar shift caused by a moving object in the area in between. The use of bistatic radar means that the MCL and DEW line are very literally "lines" with each station transmitting to the next. To overcome limitations of bistatic radar, though, the DEW line made use of both. The AN/FPS-19 search radar was a monostatic system. However, monostatic radar often has poor sensitivity to aircraft at low altitude (thus the expression "under the radar"). The AN/FPS-23 bistatic radar was used to "fill in" sensitivity at low altitude, although an aircraft would have to pass between two stations (and thus be further south) to be detected. An interesting example of bistatic radar that makes for easy learning of the concept because of its small scale is the AN/TPS-39 (one of a number of radars called "tipsies" due to the req number), which was used as a "virtual fence" for surface security at Titan missile silos. In that case the two antennas were only something like 10-20 feet apart and had a distinctive horn shape due to using microwave frequencies. Microwave radar is still used in "virtual fence" intrusion detection applications but enhancements in signal processing technology now allow simpler monostatic applications.

bane 6y ago

Out of curiosity, how were these remote systems powered?

jcrawfordor 6y ago
Diesel generators. As you can imagine this created an ongoing logistics need, although that wasn't as big of an issue as it may sound because the stations had relatively large crews and so already required regular delivery of supplies and new personnel. The method depended on the station but it was mostly done by sea or air. Around the same time period the USSR was experimenting with lighthouses and remote monitoring equipment powered by RTGs, and on this side of the iron curtain McMurdo station had a small nuclear reactor. However RTGs produced much too little power for these stations and portable reactors were a very experimental technology that was abandoned for a number of reasons you can likely imagine. The RTGs turned out to be a bad idea as well because they now form a sort of sleeping environmental hazard in much of the arctic region, most of them slipped into the water and presumably the casing is slowly corroding away. As a slightly related fact of interest, due to the ongoing need for crew there is a duplicate of a DEW line station located near Streator, IL which was used for training new personnel before they made the long trip north. It includes a troposcatter link to a small station in another town for training radio operators.