There´s Monica and Fishpond... Fishpond Fishpond became part of the H2S system and was operated by the wireless operator. Any aircraft, which stayed into a hemispherical area behind the bomber, would be seen on the display screen as a blip. http://www.qsl.net/pe1ngz/stories/story-parhfinder-navigator.html When was the Fispond used and was it considered any good? At least the crew that went bombing Berlin 1943 ( check the films section ) was questioned on its use.
I would think that it would have been of limited utility as were all rear facing radars of this sort tried by bomber command. Whether it is Monica, Airborne Grocer, AN/APS-13, Village Inn, or several other similar devices all had fairly high false-alarm rates making them more a nusiance than anything else. There were just too many aircraft in the stream and these devices were insufficently sensitive to discriminate between targets. On top of this, since H2S (or the later EHB...Every House in Berlin...which became its eventural successor) was normally mounted under the aircraft amidships a good portion of the rear level with and above the aircraft would be blanked out in any case. Of course, with the Germans often making Schrage Musik attacks from below this might not have been a big disadvantage. Aside from that, many H2S operators only turned on the equipment intermittently for navigation and then the final bomb run. This reduced the chance of a nightfighter homing on its signal and, reduced the ground warning as well. It also made telling spoof raids from real ones harder as generally only the real raids had H2S aircraft in the stream.
