Eureka / Rebecca / BABS / Lucero
Rebecca / Eureka is a simple system designed initially to assist in the delivery of supplies to the Army or Resistance in occupied Europe. The system expanded into blind homing and approach aid for aircraft. Much of the credit for the development of this system must go to Dr.R.Hanbury-Brown and J.W.S.Pringle of the TRE (Telecommunications Research Establishment)

Principles
The Airborne Rebecca equipment radiates about 300 times a second a 4-5 uSec duration interrogating puls on a spot frequency. On receipt of the interrogating pulses the Eureka beacon located on the ground triggers its associated transmitter causing responses to be radiated on a different frequency but at a pulse recurrence frequency of the interrogating transmitter. The returned signal received on both the right and left Rebecca receiver aerials are displayed on a cathode ray tube in which the time-base is synchronised with the original pulse from the Rebecca transmitter and applied to the Y-plates of the cathode ray tube. The received signals are switched into the receiver in synchronism with the switching of the video-frequency output signals to the right and left hand X-plates of the cathode ray tube. In this way, if the beacon is to the right the signal to the right of the time base will have a greater amplitude, in which case a right turn will be necessary to make the signals on either side of the time base equal in amplitude and the aircraft will then be flying directly towards the beacon.

The Eureka transponder was based on a super regenerative receiver with a separate Transmitter valve and powered by a battery operated vibrator. A coding unit which is part of the Eureka beacon periodically causes the width of the beacon response pulses to vary at Morse code intervals for identification. This function may also be manually controlled for transmission of simple messages.
Eureka
(ground station)		 Rebecca
(airborne station)		 BABS Lucero
Eureka Mk I
Eureka Mk II
Eureka Mk II F
Eureka Mk III A
Eureka Mk III B
Eureka Mk III C (AN/PPN-2)
Eureka Mk III T (talking)
Eureka H
BABS Mk II		 Rebecca Mk I
Rebecca Mk II
Rebecca Mk II A (SCR-729 - AN/APN-2)
Rebecca Mk II B
Rebecca Mk II T (talking)
Rebecca Mk III
Rebecca Mk IV
Rebecca H
Lucero II

BABS Mk 1C
BABS MK 2
BABS Mk 2FT
BABS Mk 2M
BABS Mk 2M Tropical
BABS Mk 3F
BABS Mk 3M
BABS Mk 4
BABS Tudor Mk 1

 

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Eureka Mk I

Year of issue 1941
RAF designation TGR 5508
Frequency 217 MHz, single channel
Main items TR 3164
Power unit 286, 289
Aerial system 157
Remarks

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Eureka Mk II

Year if issue 1943
Power unit 254 & TR 3174


Power unit 254A & TR 3174
RAF designation TGRI 5509 (only battery)
TGRI 5666 (battery & mains)
TGRI 5720
Frequency 214-234 MHz, 5 channels
Main items TR 3174 / TR 3558
Power unit 254A
(for TGRI 5509)
Power unit...
(for TGRI 5666)
Aerial system 304A
Remarks Build by Murphy

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Eureka Mk II F

Year if issue 1943
RAF designation FGRI 5596
Frequency Sender 196.5MHz, Receiver 193 MHz
Main items TR 3559
Power unit 254A
Aerial system 350
Remarks Used by fighter command for approaching airplanes with A.I. who were searching for german submarines.

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Eureka Mk III A

Year of issue 1943
RAF designation ARI 5648 / TGR 5671
Frequency 214-234 MHz, 5 Channels
Main items TR 3593 / TR 3514 / TR 3563
Power unit 670
Remarks Build by Cossor

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Eureka Mk III B

Year of issue
RAF designation TGR 5527 / TGR 5714
Frequency sender 216.5 MHz, receiver 213.5 MHz
Main items TR 3514 / TR 3563 / TR 3593
Power unit 515
Aerial system 305
Remarks Ultralight weight version
Tim Bell's smart looking Mk 3B
Complete in transit case.

more photo's on Summer of 44

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Eureka Mk III C

Year of issue 1944
RAF designation ARI 5687
US designation AN/PPN-2
Frequency 214-234 MHz, 5 channels
Main items RT-37/PPN-2
Aerial AS-73/PPN-2
Remarks American version

RT-37/PPN-2            AS-73/PPN-2

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Eureka Mk III T (Talking)

Year of issue
RAF designation TGR 5643
Frequency sender 213.5 MHz
Main items TR 3593
Modulator 210
Power unit type 2
Remarks Ultralight weight version, talking rebecca

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Eureka H

Year of issue 1944
RAF designation MGR 5591
Frequency 214-234 MHz, 20 Channels
Main items TR 3529 / TR 3579
Receiver 188
Transmitter 45A
Modulator 180
Power unit 286
Control unit 222
Remarks Mobile ground station fitted in vehicle, only used with Rebecca H

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BABS Mk II

Year of issue 1944
RAF designation
Frequency 214-234 MHz, 20 Channels
Main items
Remarks Build by Pye

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Rebecca Mk I

Year of issue 1941
RAF designation ARI 5120
Frequency 213 MHz, 1 channel
Main items TR 3161
Rx 55, 300
Tx 43
Indicator unit 6E (or 289)
Switch unit 289 (or 295)
Remarks

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Rebecca Mk II

RAF designation ARI 5506, 5162, 5787
Function The Rebecca Mk. 2 installation is fitted in aircraft as an aid to navigation. The equipment operates in conjunction with a radar ground beacon known as Eureka or BASS. By using Rebecca, the aircraft navigator can home on to the beacon and during his approach, his range from the beacon is continuously displayed.
Year of issue 1943
Indicator type 233


Switch unit type 78A
Frequency range 214 to 234 Mc/s on the following five spot frequencies when operated in conjunction with Eureka
A- 214 Mc/s
B- 219 Mc/s
C- 224 Mc/s
D- 229 Mc/s
E- 234 Mc/s
190.5 to 193 Mc/s and 214 to 234 Mc/s when operated with BABS
Pulse width 5 microsecond
Bandwidth 3 Mc/s
Power input 80V AC supply, 1300 to 2600 c/s
Power output 300 Watts peak, for 5 micrseconds
Power consumption 225 Watts AC, 25 Watts DC
Main items Transmitter-Receiver TR 3173A (or C)
Rx 61
Tx 45A
Modulator 66
Power unit 286
Indicator 233 (or 6E)
switch unit 115, 78A
Junction box 222
Receiver Aerial 184
Transmitter Aerial 308
Aerial 165, 312 (BABS), 186
Remarks Build by Dynatron

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Rebecca Mk IIA (SCR 729 - AN/APN-2)

Year of issue
US designation SCR-729
AN/APN-2
Frequency single preset tx frequency
two preset rx frequency's
Main items Transmitter/Receiver BC 800 (or BC 1345)
Indicator BC 929
Control unit BC 1145
Antenna AN 147, AN 148
.., RC 55
Remarks Modified SCR-729
Aircraft radar beacon and Air to Air IFF
AN/APN-T1 - trainer for SCR-729
Displays 7 IFF codes, BABS & YH Beacons

Indicator BC 929


AN 148

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Rebecca Mk IIB

Year of issue 1944
Indicator type 233


Switch unit type 78A
RAF designation ARI 5594
Frequency 173-176 MHz, see remarks
Main items TR 3576
Rx 159A
Tx 105
Modulator 66
Power unit 286
Indicator 233, 289
Switch unit 115, 78A
Control unit 222A
Aerial system 308
Transmitter Aerial 342
Receiver Aerial 346
Amplifier 178
Oscillator 40
Waveform generator 40
Remarks Modified Mk II, used by Coastal Command, Transport Command and Fleet Air Arm.
Transmitter for 3 Eureka channels and 176 MHz ASV radarbeacon.
Receiver for 177 MHz ASV radarbeacons, 173 MHz BABS radar approach beacons and two Eureka channels
Build by Murphy

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Rebecca Mk II T (talking)

Year of issue 1943
Indicator type 233


Switch unit type 78A
RAF designation ARI 5642
Frequency 214-234 MHz, 20 Channels
Main items TR 3173T / TR 3610
Modulator 198, 211
Power unit 648
Indicator 96 (or 233)
Switch unit 78A, 115
Amplifier A3611
Remarks Talking Rebecca, for use with Eureka Mk II T

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Rebecca Mk III

Year of issue 1943
RAF designation ARI 5161, 5151
Frequency Sender 213.5 MHz, Receiver 216.5 MHz
Main items TR 3182
Indicator 87 (or 98)
switch unit 116
control unit 87
Aerial 180, 181
Remarks Build by Cossor

TR 3182

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Rebecca Mk IV

RAF designation ARI 5610
Function Rebecca Mk. 4 installation is a lightweight miniature airborne interrogator operating over the frequency band 174 to 240 Mc/s. it is a general purpose equipment designed to replace all existing marks of Rebecca and Lucero in service and provides the following facilities
  1. Interrogation of all types of British and American homing and re-supply beacons operating on Coastal, Fighter and Bomber Command frequencies
  2. Interrogation of IFF Mk 3. Mk. 3GR and American equivalents, including AN/APX-l and AN/APX-2
  3. Operation with the shipborne beacon, Type 251M
  4. A blind approach system in conjunction with BABS Mk. 2.
  5. Operation with Walter and similar rescue beacons
  6. Provision for operation with a meter presentation unit. furnishing range, orbit and heading information
Year of issue 1946
Frequency 170-240 MHz, 30 Channels
Main items TR 3624
Rx 211, 6449
Tx 127
Indicator 208
Switch unit 273
control unit 526
Receiver Aerial 184
Transmitter Aerial 308
Remarks Build by EMI

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Rebecca H

Year of issue 1944
Indicator unit type 6A
RAF designation ARI 5543
Frequency 214-234 MHz, 30 Channels
Main items TR 3590 / TR 3577
Rx 61A
Tx 45A
Modulator 179
Power unit 286
Indicator 6A
switch unit 115, 78A
Control unit 222A
Aerial 312, 345
Remarks Special version which needed 2 Eureka beacons, used for photo reconnaissance.
Usual combined with Gee "H"

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BABS Mk 1C

Year if issue
RAF designation FGRI 5115 or 5116
Frequency
Main items
Remarks BA & ASV

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BABS Mk II

Function

A responder beacon providing beam approach facilities in conditions of poor visibility for aircraft fitted with a suitable interrogating device such as Lucero or Rebecca
Frequency Range

Predetermined spot frequencies within the range 214 to 234 Mc/s T and R 5 Mc/s apart
Performance

Range with aircraft flying at l.000 ft.-14 to 20 miles. Both mobile and fixed versions available. The system can respond to approx. 30 aircraft at one time 
Pulse

Normal-5uS (dots) and l2,5uS (dashes)
Danger coding-26uS (dots) and 30uS (dashes)
Equipment

TR-3567 or TR-3567A
Power unit Type 6l9
Rectifier Type 10
Switch, fuse and distribution board
Petrol-electric generator set
Spare monitor receiver assembly
12V, 100 Ah accumulator, etc.
P.R.F

Beam switching alternately every 1/15th second
Selectivity

+/- 2 Mc/s = 6dB down
+/- 5 Mc/s = 10dB down
Sensitivity Receiver: Input of 100 microvolts = twice noise
Aerial system Aerial system Type 349. A rectangular slotted cavity resonator mounted symmetrically in a corner reflector
Output Transmitter radiated power: 15 watts peak
Power Supplies 12 volts, 5 amp.
12 volt accumulator float-charged by small petrol-electric set
Test equipment

WavemeterTypeW-1649
Hydrometer set type B
Output tester  Type 57
Signal generator Type 53
Monitor Type 28
Test set Type 292, or Type 138A
Test meter Type D
Tester insulation Type A
Vehicles and associated equipment 12 cwt. Standard D.R.L.S. van, vehicle, Type 441; monitor aerial

BABS Mk 2FT

Year if issue
RAF designation FGRI 5798
Frequency
Main items
Remarks

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BABS Mk 2M

Year if issue
RAF designation FGRI 5725
Frequency
Main items
Remarks

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BABS Mk 2M Tropical

Year if issue
RAF designation MGRI 5797
Frequency
Main items
Remarks

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BABS Mk 3F

Year if issue
RAF designation FGRI 5755
Frequency
Main items
Remarks

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BABS Mk 3M

Year if issue
RAF designation MGRI 5756
Frequency
Main items
Remarks

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BABS Mk 4

Year if issue
RAF designation FGRI 23014 (5926 = 400Mc/s)
Frequency
Main items
Remarks

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BABS Tudor Mk 1

Year if issue
RAF designation ARI 5385
Frequency
Main items
Remarks

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BABS test equipment

TS  333
Trainer TS   88
TS 335

Lucero II

RAF designation ARI 5645
Function Lucero is a homing, beam approach and IFF interrogator for use with H2S, ASV and AI. It uses the IF amplification stages of the equipment with which it is used and also the display appears on the CRT of the parent equipment. Due to this inter-connection and also to the fact that different marks of the equipment to be interrogated have different carrier frequencies, several variations of Lucero have been produced. The TR 3566A. which here is briefly described, is the Bomber and Coastal Command version, the same basic set being used by both commands. Push-button frequency selector is used by Bomber Command. while Coastal use a functional selector switch.
Year of issue 1944
Type of wave Pulse modulated
Pulse width 5 microseconds
Pulse recurrence frequency 217 c/s
Frequency range
Range Transmitter Receiver
1 171-181 (177) Mc/s 171-181 (176) Mc/s
2 212-226 168-178
3 222-236 210-238
4 222-236 220-238
Main items Transmitter Receiver TR 3566
Power unit 532
Receiving unit 161
Switch unit type 115
transmitter unit type 105
Waveform generator type 3C
Control unit type 222A
Remarks Used by Bomber Command and Fleet Air Arm.
Developed for 1.7 meter beacons by 9 and 3 cm radar (H2S and ASV Mk VI)
some versions switchable to two Eureka channels.

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Reference:
"Radar Development to 1945" E.K.Williams, published by P.Peregrinus
Air Publications & Manuals.

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