Editing Mid-Canada Line (section)

==Construction and service==
[[Image:S-55MidCanadaLine.JPG|thumb|right|[[Sikorsky H-19 Chickasaw]] at the [[Canadian Museum of Flight]] 1988. The aircraft is painted as it would have looked while working on the construction of the Mid-Canada Line]]

Construction started in 1956 and proceeded quickly. By April 1957 the eastern half was operational, and the line was declared fully operational on January 1, 1958. Operations were shortly integrated into the newly formed [[NORAD]]. Even the SEG's revised estimates turned out to be too low, and the fence's final cost is estimated at $224,566,830, {{inflation|CA|224566830|1958|fmt=eq|r=-5}}.{{sfn|Thorne|1979}}

Almost as soon as the units went into operation, a serious problem was seen. Due to the large [[radar cross section]]s seen in forward-scattering radars, even small targets produced detectable signals. This was multiplied if the targets were roughly the same size as the wavelength of the radar, or in this case, tended to be spread out in patterns that were multiples of that wavelength. This problem was triggered by the large flocks of migrating waterfowl during the spring and fall, which created signals so powerful that it rendered the radars useless. Testing on the Spider Web and Eastern Townships systems had both been carried out during the summer, so this had not been noticed.{{sfn|Skolnik|2007|p=38}}

Even before the line became operational, in a repeat of earlier history, a new and more capable line was already under study that would combine the plotting capability of the Pinetree system with the line-breaking capabilities of the MCL, and located much farther north to dramatically improve the detection and response times. Emerging as the [[Distant Early Warning Line]], or DEW, construction started before the MCL had become operational. When the DEW line became operational in 1957, the value of the MCL was eroded, and the RCAF started pressing for it to be dismantled.{{sfn|Thorne|1979}}

Although technically capable, the MCL gave little information for vectoring interceptors to their targets, so these tasks still required the Pinetree radars much farther south. The extra time offered by the MCL was not considered worth the trouble of keeping the line operational. The USAF disagreed, but in spite of their objections, the western half of the line was shut down in January 1964, leaving the eastern half to help defend the industrial areas of Canada and the US. As the [[Soviet Union]] moved their offensive capability to ICBMs it became clear that both the MCL and Pinetree systems were of limited use, and the entire Mid-Canada line was shut down in April 1965. The operations site located at [[Cranberry Portage, Manitoba]], for example, has been converted into a high school and residence since active operations at the site closed in the mid-1960s.{{sfn|Thorne|1979}}

The DEW line stations were sited to provide the best possible view of the horizon, but there remained a minimum detection angle below which aircraft could sneak by without being seen. During early planning, a system like the MCL's towers was considered as gap-fillers between the stations to prevent these sorts of intrusions. As the MCL came online and the problem with birds became clear, the original forward-scatter concept was replaced by one using [[Doppler shift|Doppler filtering]] to ignore anything flying below {{convert|125|mph}}. These [[AN/FPS-23]] "Fluttar" systems did indeed filter out birds, but failed to filter out the [[general aviation aircraft]] flying in the area, including those flying base-to-base for servicing and crew rotations.{{sfn|Skolnik|2007|p=45}} As a result, the false-alarm rate rendered it just as ineffective as the MCL, and it lasted even a shorter time, shut down in 1963.<ref>{{cite web |first=Christian |last=Wolff |title=AN/FPS-23 |url=https://www.radartutorial.eu/19.kartei/11.ancient2/karte042.en.html}}</ref>