Editing Loran-C (section)

===Improving systems===
Loran-C had originally been designed to be highly automated, allowing the system to be operated more rapidly than the original LORAN's multi-minute measurement. It was also operated in "chains" of linked stations, allowing a fix to be made by simultaneously comparing two secondaries to a single master. The downside of this approach was that the required electronic equipment, built using 1950s-era tube technology, was very large. Looking for companies with knowledge of seaborne, multi-channel phase-comparison electronics led, ironically, to Decca, who built the AN/SPN-31, the first widely used Loran-C receiver. The AN/SPN-31 weighed over {{convert|100|lbs|kg}} and had 52 controls.{{sfn|Blanchard|1991|p=310}}

Airborne units followed, and an adapted AN/SPN-31 was tested in an [[Avro Vulcan]] in 1963. By the mid-1960s, units with some transistorization were becoming more common, and a chain was set up in [[Vietnam]] to support the United States' [[Vietnam War|war efforts]] there. A number of commercial airline operators experimented with the system as well, using it for navigation on the [[great circle]] route between North America and Europe. However, [[inertial platform]]s ultimately became more common in this role.{{sfn|Blanchard|1991|p=310}}

In 1969, Decca sued the United States Navy for patent infringement, producing ample documentation of their work on the basic concept as early as 1944, along with the "missing" 9f frequency{{efn|Blanchard uses 7f and 9f on different pages.}} at 98&nbsp;kHz that had been set aside for experiments using this system. Decca won the initial suit, but the judgement was overturned on appeal when the Navy claimed "wartime expediency".{{sfn|Blanchard|1991|p=311}}