History
The prototype Rebecca I was created by bolting a transmitter on to an A.S.V. (Air-to-Surface Vessel) Mark I receiver. An experimental version of Rebecca I and Eureka I built at T.R.E. was demonstrated at the C-in-C, Army Co-operation Command in the summer of 1941. The Rebecca system interested the Special Operations Executive (S.O.E.) and a number were built for the use of partisans in the underground movement in Europe.
The Airborne Forces Equipment Committee took up development of the system in the summer of 1942, funding low-priority development of a Mark II system intended for use on glider tugs and paratroop aircraft. At the time, it was decided that each Eureka should be able to handle interrogation from up to 40 aircraft at a time. They also selected a design based on several sub-units that would allow the equipment to be changed simply by swapping sub-units out from a common chassis.
Both Rebecca II and Eureka II were developed by Murphy Radio with early pre-production of Rebecca II by Dynatron Radio. A system using a selection of tuned capacitors was used to select the operational frequency, from a set of four. Looking for a controller, Murphy selected a General Post Office 5-position electromechanical system used in their telephone exchange systems. A similar selection of four channels was available in the Eureka units, but these were selected manually. Rebecca was powered off the aircraft mains, while Eureka was battery powered with a lifetime of about six hours.
In testing, Eureka II proved to be too heavy for practical use, so A.C. Cossor was selected to build a Mk. III version. They used US miniature 9000-series tubes for this version and used a much smaller battery with a three hour life. This version sparked US interest, who started production of a number of versions of the Mk. III as the AN/PPN-1 (Eureka), AN/PPN-2 (Portable Eureka) and AN/TPN-1 (Transportable Eureka). The AN/APN-2 (Rebecca), also known as the SCR 729, used a display that saw use for a number of purposes.
When many British military gliders failed to reach their landing zones in Sicily even in excellent conditions, a rushed effort to develop and even smaller and lighter Rebecca III system started. Cossor was again selected for the development, using a super-regenerative receiver and batteries for only 30 minutes of operation. The Rebecca IIIN version was used for strike aircraft in the pacific theatre. These versions used capacitors in all five positions of the rotary switch.
The introduction of the miniature B7G tubes in 1944 led to a new round of development of the Rebecca/Eureka. Dozens of different variations were eventually developed.
Read more about this topic: Rebecca/Eureka Transponding Radar
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