Editing Gee (navigation) (section)

=== Landing system proposal ===

In October 1937, Robert (Bob) J. Dippy, working at [[Robert Watson-Watt]]'s radar laboratory at [[RAF Bawdsey]] in [[Suffolk]], proposed using two synchronized transmitters as the basis for a [[Instrument approach|blind landing]] system. He envisaged two transmitting antennas positioned about {{Convert|10|mi|km|abbr=}} apart on either side of a runway. A transmitter midway between the two antennas would send a common signal over transmission lines to the two antennas, which ensured that both antennas would broadcast the signal at the same instant.{{sfn|Blanchard|1991|p=297}}

A receiver in the aircraft would tune in these signals and send them to an [[Radar display#A-Scope|A-scope]]-type display, like those used by Chain Home. If the aircraft were properly lined up with the runway, both signals would be received at the same instant, and thus be drawn at the same point on the display. If the aircraft were located to one side or the other, one of the signals would be received before the other, forming two distinct peaks on the display. By determining which signal was being received first, pilots would know that they were closer to that antenna, and would be able to recapture the proper direction by turning away from it.{{sfn|Blanchard|1991|p=297}}{{efn|Although it is not mentioned in available sources, some method of telling the two signals apart would be needed. The solution used on Gee, periodically turning one of them on and off to cause it to oscillate on the display, would work here as well.}}

Watt liked the idea, but at the time, a pressing need for the system was not apparent.{{sfn|Blanchard|1991|p=297}} At the time, the [[RAF]] relied on daylight bombing by tight formations of heavily defended bombers as its primary attack force, so night landings were not a major concern. Landing aids would be useful, but radar work was the more urgent need.{{sfn|Blanchard|1991|p=297}}