- Fishpond
Fishpond was the
code name given to an extension to the British H2S airborne radar system fitted to alliedbomber s duringWorld War II . It was designed to give early warning of Germannight fighters approaching in the hemisphere below the carrying aircraft out to a range of 30mile s (48.2km ).The H2S radar was a
navigation al aid designed to give amap -like display of the ground below the aircraft. The display, known as aPlan Position Indicator (PPI), used a scanningelectron beam in aCathode Ray Tube which scanned from the centre of the display to the edge in a direction corresponding to the direction in which the radar's scanning head was pointing. In order that the centre of the display represented the ground immediately beneath the aircraft, the scan had to be delayed to allow for the transmitted radar pulses to travel from the aircraft to the ground and back again. This delay was derived from a simpleradio altimeter .It was realised that during this undisplayed time echoes would be returning from any other aircraft within the vicinity of the bomber. Accordingly a second display was installed in the
radio operator's position which displayed the image suppressed from the navigator's display. This display showed the relatively stationary blips from the bomber formation and, most importantly, the rapidly moving returns from the German night fighters.External links
* [http://website.lineone.net/~norman.groom/r1155.htm Picture of a Lancaster's Fishpond display and R1154/T1154 receiver/transmitter]
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