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RR/E-11
US spy receiver

RR/E-11 was a solid-state clandestine receiver, also known as a spy radio receiver, introduced in 1959 by the US Central Intelligence Agency (CIA), initially as a replacement for the receivers of the RS-11 spy radio set, but later primarily as part of the AS-3 automatic radio station. 1 It was also suitable for stand-alone use, in which case it could be powered externally by either 6 or 12V DC.

The receiver is housed in a die-cast aluminium enclosure that can be plugged straight into the right side of the AT-3 transmitter of the AS-3 radio set. For stand-alone use, an external PSU or a special-purpose battery can be connected to the 9-pin sub-D connector at the left side.

The device features permeability tuning, and allows the frequency to be adjusted from 3 to 12 MHz in a single band with kHz resolution, using the tuning knob in combination with a 5-digit odometer-style readout at the top surface. This is similar to that of the German BN-58 receiver.
  
RR/E-11 receiver

Development of the RR/E-11 started around the same time as that of the AS-3 spy radio set – in 1956 – together with a two-band version – the RR/D-11. The first 150 receivers (RR/E-11 and RR/D-11) were delivered around May 1959, well before the complete AS-3 radio set was taken into production. It seems likely that many of the early units were intended for stand-alone use.

  1. The developer of the AS-3, which was probably also the developer of the RR-E-11, is currently unknown and has been redacted in the documentation released by the CIA [A]. However, given the fact that they were based in New Jersey, it is possible, if not likely, that it was the Radio Corporation of American (RCA) [2].

RR/E-11 receiver
Tuning knob and serial number
1 mm banana plug
DE-9 connector with layout
Tuning scale and knob
Earphone
12V DC power cable
RR/E-11 wired for use
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×
A
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RR/E-11 receiver
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Tuning knob and serial number
A
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1 mm banana plug
A
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DE-9 connector with layout
A
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Tuning scale and knob
A
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Earphone
A
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12V DC power cable
A
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RR/E-11 wired for use

Features
The image below gives an overview of the controls and connections on the body of the RR/E-11 receiver. At the left is the DE-9 socket by which it can be connected to a compatible transmitter, such as the AT-3, in which case power and antenna signal are provided by the transmitter. This socket is also used for powering the receiver externally by means of the supplied 12V cable. 1

In stand-alone configuration, antenna and counterpoise should be connected to the push-in terminals at the top left. A pair of headphones, or a low-impedance earphone, should be connected to the terminals at the front left. The device is turned on by placing the MODE selector to ON or to ON AGC. In the latter case, the Automatic Gain Control (AGC) is enabled as well.

Click to see more

The audio volume is adjusted with the VOL-knob at the centre. Turning it clockwise increases the volume. To its right is the adjustment for the Beat Frequency Oscillator (BFO), which is needed for the reception of CW (morse) signals. In fully counter-clockwise position, the BFO is disabled.

The reception frequency is adjusted with the circular metal knob at the right. It has a foldable grip and should be collapsed when stowing the receiver. Turning the knob engages an internal gearbox that drives a set of three coil cores, plus the odometer-style readout at the top surface.

Note that although the receiver has an accurate odometer-style frequency adjustment, the actual frequency to which it is tuned may differ substantially from what is shown in the window. This is particularly the case in extremely hot or cold environments, when it may off by > 25 kHz [A].

MODE selector
The MODE selector has the following settings:

  • OFF
    Device completely switch OFF
  • ON
    Device ON (AGC disabled)
  • ON AGC
    Device ON, AGC enabled
  1. In some situations cables for connection to a 6V car battery were supplied instead.

Tuning knob and serial number
1 mm banana plug
Connecting the headphones
MODE selector
DE-9 connector with layout
Tuning scale and knob
Tuning scale
Adjusting the volume
B
×
B
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Tuning knob and serial number
B
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1 mm banana plug
B
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Connecting the headphones
B
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MODE selector
B
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DE-9 connector with layout
B
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Tuning scale and knob
B
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Tuning scale
B
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Adjusting the volume

Accessories
12V DC power cable
Each RR/E-11 receiver was supplied with a cable – similar to the reproduction shown here – that allowed it to be powered from an external 12V DC power source, so that it could be used stand-alone (i.e. without a compatible transmitter).

The cable mates with the 9-pin socket at the left side, and has clips for connection to, say, a car battery. A different cable was optionally available for use with 6V batteries. In addion, the existing 12V cable could be modified use with 6V DC.

  
12V DC power cable

Headphones
It is currently unknown what type of earphone or headphones was supplied with the RR/E-11, but it is likely that it was similar to the earpiece shown in the image on the right, or a pair of stethoscope tubes with this speaker armature.

The earphone is connected to the two terminals at the front, by means of 1 mm banana-plugs, such as the ones shown here.
  
Earphone




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Interior
The device is housed in a die-cast aluminium enclosure that consists of two parts: the main body which acts as the top, and a flat bottom panel that is bolted to the main body with 8 recessed screws. After loosening them, the bottom panel can be removed, as shown in the image above.

The most prominent feature of the receiver is the multi-stage permeability tuning unit, that is fitted at the top left, and takes about 1/3rd of the total space. It consists of three long coils of which the cores are moved in tandem by a high-precision cogwheel-driven gear mechanism.

The advantage of permeability tuning is that it is nearly linear over the entire 3 to 12 MHz range. The remaining errors are corrected by means of nine adjustable stubs that form the mechanical equivalent of a correction curve. When adjusting the frequency the curve is traced by a 'finger'.
  
Tuning mechanism

The tuning correction mechanism – visible in the image above – is very similar to the one that was used in the contemporary German BN-58 (FE-8) receiver, which was part of the European SP-15 stay-behind spy radio set. The BN-58 was not only smaller but also more stable and sensitive. 1

The electronic circuits are spread over 3 high-quality expoxy-based printed circuit boards: a small one with the power circuitry, a larger one with RF-stage, VFO and LO, and a long one with IF-stages, BFO, AM detector, AGC and AF-stage.

The image on the right shows part of the IF-strip on the largest PCB. The transistors – mostly early types from Philco – are fitted in a metal clips and their legs are soldered to mounting posts at the upper edge of the board. The boards are inter­connected with teflon wiring and are protected against moisture by a thin conformal coating.
  
IF-stages

Note that the output stage of the audio amplifier – the rightmost part of the IF-board – contains a miniature transformer, fitted in a clip at the upper right corner, that allows both high- and low-impedance headphones to be used. The audio is also available on the 9-pin socket at the left.

  1. The BN-58 was developed by Wandel & Golterman in Germany, and had two frequency bands: 2.5-9.1 and 9.1-24 MHz. It can be regarded as the German equivalent of the CIA's RR/D-11 (the two-band version of the RR/E-11). It uses a crystal-based local oscillator (LO), whereas the LO of the RR/E-11 is free-running.

Interior after removing the bottom panel
Interior, top view
Permeability tuning precision adjustments
Tuning mechanism
Tuning gear box
RF Transistors
IF-stages
RF-stage and local oscillator (LO) -- at the front the detector and AF amplifier
Transistor detail
CW tuning capacitor and volume potentiometer
Power board, IF strip, mechanical filter and Local Oscillator
Audio amplifier with output transformer
Power board removed from the enclosure
IF-stip removed from the enclosure
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C
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Interior after removing the bottom panel
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Interior, top view
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Permeability tuning precision adjustments
C
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Tuning mechanism
C
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Tuning gear box
C
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RF Transistors
C
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IF-stages
C
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RF-stage and local oscillator (LO) -- at the front the detector and AF amplifier
C
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Transistor detail
C
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CW tuning capacitor and volume potentiometer
C
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Power board, IF strip, mechanical filter and Local Oscillator
C
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Audio amplifier with output transformer
C
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Power board removed from the enclosure
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IF-stip removed from the enclosure

Click to see more



Block diagram
Below is the preliminary block diagram based on our observations whilst restoring the RR/E-11 in our collection. At the left are input filter, RF pre-amplifier, first mixer and band filter, all of which are adjusted in tandem when turning the frequency tuning knob at the right side. The signal from 2nd mixer is passed to a multi-stage IF-strip, via a mechanical filter that is mounted between the RF and IF boards. It is visible as a long cilinder when looking at the interior from the bottom side.

Preliminary block diagram based on observations

A Beat Frequency Oscillator (BFO) is present for the reception of CW (morse) signals. Its signal is injected somewhere in the IF-strip, and can be suppressed by turning its adjustable capacitor fully counter-clockwise, in which case its blades are shorted by a small contact strip. At the top right is the power circuit, part of which converts an external 12V supply to the internal 6V DC.


Restoration
When we obtained the RR/E-11 featured here – in June 2020 – it was not in working condition. In fact, when connected to a 12V (or 6V) power source, it consumed approx. 10 mA, but was other­wise dead. No sound in the headphones. At first sight, the interior seemed to be in original state, but a closer inspection revealed that there had been earlier (failed) attempts to repair the unit.

The tuning unit had been removed, and in the processed of doing so, two of the wires to the tuning coils had come off. But apart from that, all parts were still present and were originals.

After a suitable 12V cable was made for the 9-pin socket at the left, it was powered up for the first time. Although 6V was present at the MODE selector, none of the transistors on the RF and IF PCBs was supplied with a sensible voltage, which led to the conclusion that something was wrong in the power circuit. It turned out to be a broken germanium diode on the small power board.
  
Power board

This board is fitted in front of the IF-strip, close to the front edge of the enclosure, and can easily be removed. The diode was replaced by a universal AA119 germanium diode, and the device was tested again. This time it worked, and was even receiving signals, but a new problem emerged.

An annoying 'motor boat' sound could be heared through the headphones, even with the volume fully turned down. And with the oscilloscope it was clearly visible on power rail of the IF-board.

It turned out to be an unwanted oscillation effect in the power circuit, probably caused by ageing of the components, and was fixed by placing a low-ESR electrolytic capacitor be­tween the power rail and ground. By soldering it directly to the terminals of the red and black wires on the small power board shown above, it turned out to be effective and could easily be hidden from view.
  
Broken wires in the tuning section

After this modification, the receiver was stable and was able to demodulate the signal from our test generator, which was running at 6 MHz. It was insensitive though, and the scale was approx. 200 kHz of as well. The sensitivity problem was caused by the broken wires of the tuning coils.

As a result, the band filter between the first and second IF mixer was not aligned in tandem with the variable frequency oscillator (VFO), resulting in poor signal strength. Luckily it was possible to deduce where the broken wires had once been soldered to, and after refitting them to the upper right coil, the filter was once again operational.

It was unclear why the scale was so far off. It is known from CIA documentation that at very low or high temperatures, the frequency can be off by > 25 kHz [A], but that does not explain the observed 200 kHz error at room temperature.
  
Tuning mechanism

It seems therefore likely that during an earlier repair attempt, the odometer-style scale had been turned whilst the tuning meachanism and its gearbox had been removed temporarily from the enclosure. By loosening the clamp to the left of the big cogwheel, the scale could be turned without moving the tuning coils, and was roughly set to the desired position. The clamp was then fastened again, and the remaining error was corrected by readjusting the local oscillator (LO).

In the process of restoring the receiver, the following has been done:

  • Rubber feet replaced
  • Black ink removed from front panel
  • Diode replaced in power circuit
  • Capacitor replaced in power circuit
  • Tuning coil L1 rewired
  • Scale calibrated (was 200 kHz off)
  • Local oscillator calibrated
  • Tuning gear box oiled and greased
  • 12V power cable added
  • Headphones added
Power board
Power board removed from the enclosure
IF-stip removed from the enclosure
Audio amplifier with output transformer
Broken wires in the tuning section
Repaired tuning section
Power board, IF strip, mechanical filter and Local Oscillator
D
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D
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Power board
D
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Power board removed from the enclosure
D
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IF-stip removed from the enclosure
D
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Audio amplifier with output transformer
D
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Broken wires in the tuning section
D
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Repaired tuning section
D
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Power board, IF strip, mechanical filter and Local Oscillator

Connections
Peripheral socket   DE-9
At the left side of the RR/E-11 receiver is a rectangular metal stub with an embedded 9-pin D-type male connector. When the receiver is used as part of the AS-3 radio set, this part is plugged into the right side of the AT-3 transmitter. In that case, power and antenna signal are supplied by the transmitter. In addition the (line) audio output of the receiver is available on this connector. It is passed by the transmitter to the (optional) TP-3 printer (that can be plugged into the left side).

  1. Antenna
  2. Ground
  3. n.c.
  4. n.c.
  5. Jumper to 6 when used with 12V DC
  6. +6V DC input
  7. n.c.
  8. +12V DC input
  9. Audio output
Specifications
  • Frequency
    3 - 12 MHz
  • Modulation
    Phone (AM), Morse (CW)
  • Power
    6 or 12V DC
Documentation
  1. RR/E-11 Operating Instructions
    CIA, Date unknown, but probably around 1958/1959.
     Better quality scan, but without images
  1. Partly declassified on 29 May 2014. CIA-RDP78-03330A000600460001-0.

References
  1. Louis Meulstee, RR/E-11
    Wireless for the Warrior - Volume 4 Supplement, Chapter 142.
    October 2017. Retrieved June 2020.

  2. Pete McCollum, The AS-3 HF Radio Set
    Personal correspondence. Retrieved June 2020.

  3. H. Keith Melton, CIA Special Weapons & Equipment: Spy Devices of the Cold War
    New York, 1993. ISBN 0-8069-8732-4. Page 19.

  4. CIA, RR/E11
    Date unknown. Partly declassified on 29 May 2014.
    CIA-RDP78-03330A000600460002-9.
Further information
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Crypto Museum. Created: Saturday 27 June 2020. Last changed: Thursday, 03 September 2020 - 10:35 CET.
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