REBECCA-EUREKA Mk II SYSTEM [Main Title]

An instructional film shot in 16mm Kodachrome illustrating with the help of intertitles and live action footage the mode of operation for one of the early versions of the REBECCA/EUREKA system of airborne direction-finding equipment and ground-based radio homing beacon issued to British paratrooper pathfinder units and Special Operations Executive (SOE) operatives in Nazi-occupied Europe.

START 10:00:00 Opening titles for this 'Most Secret' film and a roller caption describing the purpose of the portable EUREKA ground homing beacon and the matching airborne REBECCA radio 'interrogator'. Intertitles describing each item of equipment and its function introduce static shots of EUREKA's nickel-iron battery, the power unit, the transmitter and receiver and the EUREKA aerial mounted on telescopic tripod legs. An identical method of illustrating the airborne REBECCA equipment follows, in which are featured the electrical generator on the starboard inner engine of a four-engined Handley Page Halifax transport aircraft and inside the aircraft the voltage control equipment, the main 'on' and 'off' switches and the transmitter/receiver frequency control unit. Mounted on the outside of the aircraft are the port and starboard 'Yagi' directional receiver aerials for REBECCA on either side of the nose and the transmitting aerial array under the fuselage.

10:03:33 Royal Air Force technicians pack the transmitter/receiver and the smaller power supply unit for a mobile EUREKA set into a small wooden box. The ear-piece and cable, the EUREKA aerial and its supporting telescopic tripod legs are wrapped up in rolls of felt. The battery for the EUREKA set is the first item to be packed into a canvas bag, followed by the wooden box and all the other items; rolls of felt and cloth are then wedged into the bag to protect its contents before it is laced up and taken away to a nearby RAF airfield in a Bedford MW 15-cwt signals truck.

10:06:41 The Bedford MW truck draws up next to a Halifax transport aircraft and the canvas bag with the portable Eureka homing beacon is unloaded and presented to a British paratrooper standing in a row with four other comrades. They all board the Halifax; the last one into the aircraft pulls up the crew ladder behind him. Shots of the aircraft, probably a Halifax B.II Series 1 transport modified for duty with airborne forces and SOE, taxiing to take off and inside the cockpit showing the RAF pilot at the flight controls and the flight engineer pushing the throttles to maximum power as the aircraft takes off; the navigator in the bomb aimer's position, looking at a map, the wireless operator at his desk, the aircraft making a shadow over the countryside as it slowly loses height. Red and green lights at a panel marked 'Special Troop Electrical Control' .

10:08:51 A roller caption explains how the EUREKA set is air-dropped by parachute. Inside the Halifax, the warning light changes from red to green and the EUREKA operator drops through an opening in the belly of the aircraft with the bag containing the homing beacon set tethered by a line to his parachute, followed by other members of his 'stick'. The paratroopers land in a drop zone (DZ) located somewhere in the chalk uplands of southern England (Wiltshire/Oxfordshire/Berkshire). Several of them, including the soldier with the EUREKA bag tethered to his parachute, are blown backwards by the wind before they can operate their parachute release catches. Once they sort themselves out, two paratroop signallers hurriedly unpack the canvas bag and erect the EUREKA's tripod aerial and connect the transmitter/receiver and the power unit to the battery. The ear piece for the transmitter/receiver is also plugged in. The airborne signaller in charge sets the EUREKA receiver at frequency band A (out of a choice of five frequency settings) and the transmitter on frequency band B. He flips the 'on' switch on the power unit and checks to see everything is working properly by listening to a signal tone with the ear piece.

10:13:05 A sequence that opens with an air-to-air shot of a Halifax B.II in flight showing the operation of the REBECCA equipment inside the aircraft: the wireless operator switches on the power on the voltage control equipment and the navigator, who is in charge of guiding the aircraft onto the signal emitted by the EUREKA ground set, switches on the REBECCA transmitter/receiver set and the frequency control panel. An animation version of a typical cathode ray tube (CRT) display positioned at eye level for the navigator shows the EUREKA's return signal (on the same pulse repetition frequency as the REBECCA ultra high frequency (UHF) 'interrogating' signal) picked by the aircraft's port-and-starboard 'Yagi' receiver aerials. The CRT display shows how the navigator can easily spot the direction from which the signals made by a EUREKA ground station are being transmitted, in this case either to port (left) or starboard (right) of the course along which the aircraft happens to be flying. In front of the CRT is a transparent celluloid overlay on which there is a left/right range indicator; on the left (port) 0 - 36 miles, on the right (starboard) 0 - 90 miles. The navigator fine-tunes the CRT display with two control buttons, 'focus' and 'gain'. On the transmitter/receiver frequency control panel, he pushes the button that sets the REBECCA transmitter on frequency A (to match the EUREKA's receiving frequency) and pushes the button that sets the REBECCA's receiver on frequency B (to match the EUREKA's transmitting frequency). Once the REBECCA-EUREKA system is in operation, there are live actuality shots of the CRT display showing the ground EUREKA homing beacon at ranges between 90 and 36 miles. As the range closes, the navigator turns the control knob for measuring range between 36 to 0 miles in order to get a more precise reading. The CRT display clearly shows when the EUREKA's signal is either to the port (left) or to the starboard (right) of the direction in which the aircraft is flying. Shots show the navigator informing the pilot through the intercom of the need to change course, illustrated here by a shot of the Halifax's starboard wing (filmed from the cockpit) as it turns to starboard low over the English countryside. The CRT scan shows the aircraft on the correct bearing. For the final approach to the drop zone from where EUREKA is transmitting, the navigator sets the range measurement control knob at 9 to 0 miles; the display on the CRT shows the distance between the aircraft and the EUREKA homing beacon rapidly diminishing.

10:19:14 On the ground, the signaller in charge of the EUREKA picks up his ear piece; an intertitle explains that he can hear the change in pitch the signal makes as the aircraft carrying the REBECCA system approaches. He then taps out a single letter message in Morse code on the EUREKA transmitter to confirm his position. Views of the CRT display inside the Halifax as the range falls off and the single letter Morse message shows up on the return signal. On the ground, the two-man EUREKA team, armed with Sten Mk II sub machine guns, taking up combat positions around their homing beacon. Inside the aircraft, the navigator informs the pilot that they are over the DZ and the light on the 'Special Troop Electrical Control' panel changes from red to green. Paratroopers drop out of the belly exit. A 'stick' of paratroopers floats earthwards at the end of their parachutes and lands on the DZ.

10:21:38 A roller caption explains the importance of preventing any REBECCA and EUREKA equipment from falling into enemy hands in order to avoid the danger of effective German electronic warfare counter-measures resulting from the capture of any intact examples. The method of actuating the push-button demolition charge on the REBECCA;s voltage control equipment and priming the EUREKA's transmitter/receiver unit for destruction are demonstrated for the camera. A complete EUREKA set is seen being blown apart with its small demolition charge. The camera examines the burnt and twisted fragments of metal produced by the explosion.

END 10:23:43

16mm