Similar Systems
Interestingly, the Germans improvised a system conceptually similar to Oboe, code named Egon, to perform bombing on the Eastern Front on a limited scale. It used two modified Freyas to play the roles of Cat and Mouse; these two Freya Egon sets were located about 150 km apart, and the aircraft carried a two channel IFF to respond to them. Voice radio directed the bombers. Despite the considerable effort the Germans put into other electronic navigation systems, they never took this concept farther.
Along with the range restriction, Oboe had another limitation: it could only really be used by one aircraft at a time. As a result, the British rethought Oboe, and came up with a new scheme named "GEE-H" (or "G-H") based on exactly the same thinking, differing only in having the aircraft carry the transmitter and fitting ground stations with the transponder.
Multiple aircraft could use the two stations in parallel because random noise was inserted into the timing of each aircraft's pulse output. The receiving gear on the aircraft could match its own unique pulse pattern with that sent back by the transponder. Each receive-reply cycle took the transponder 100 microseconds, allowing it to handle a maximum of 10,000 interrogations per second and making "collisions" unlikely. The practical limit was about 80 aircraft at one time.
The name "GEE-H" is confusing, since the scheme was very close to Oboe and not very much like GEE. The name was adopted because the system was based on GEE technologies, operating on the same range of 15 to 3.5 meters / 20 to 85 MHz, and initially used the GEE display and calibrator. The "H" suffix came from the system using the twin-range or 'H' principle of measuring the range from transponders at two ground stations. It was about as accurate as Oboe.
Read more about this topic: Oboe (navigation)
Famous quotes containing the words similar and/or systems:
“Take us generally as a people, we are neither lazy nor idle; and considering how little we have to excite or stimulate us, I am almost astonished that there are so many industrious and ambitious ones to be found; although I acknowledge, with extreme sorrow, that there are some who never were and never will be serviceable to society. And have you not a similar class among yourselves?”
—Maria Stewart (1803–1879)
“No civilization ... would ever have been possible without a framework of stability, to provide the wherein for the flux of change. Foremost among the stabilizing factors, more enduring than customs, manners and traditions, are the legal systems that regulate our life in the world and our daily affairs with each other.”
—Hannah Arendt (1906–1975)