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TAR-224A
CIA spy radio set

TAR-224 was a highly compact self-contained spy radio set, developed around 1970 by AVCO Corporation in Cincinnati (Ohio, USA) for the US Central Intelligence Agency (CIA), as a successor to the ageing GRC-109 (RS-1) of the 1950s. It was intended for communication with field agents operating behind enemy lines. After a long operational life, it was phased out in the late 1980s.
 
The entire unit is completely waterproof, with all switches and controls at the front panel properly sealed, allowing the radio to be stored under harsh conditions for an extended period of time. A plastic lid can be placed over the controls to protect them against dust and dirt. It is held in place by three metal latches at the edges.

The image on the right shows a typical TAR-224A unit, without the optional CS-224 30-channel crystal selector installed. The unit roughly consists of two parts: the receiver (RX) at the left, and the transmitter (TX) at the right.
  
TAR-224a spy radio set (USA)

The radio coverages all frequencies between 2 and 24MHz. The receiver has a Variable Frequency Oscillator (VFO), allowing continuous tuning of all 4 frequency bands, whereas the transmitter is crystal operated. The unit can be powered by an external 12V source that is connected to a 3-pin socket at the front left, or by a special 12V battery pack that is installed behind a watertight panel at the front left. A plastic grip, at the left of the radio, allows the unit to be carried around easily.

The TAR-224 was introduced in 1970 and the user manual was updated once in September 1971. The unit shown here, was probably issued in the early 1970s, and was last inspected in 1976. Most TAR-224 units were used by the CIA on special (overseas) missions [4], but the radios were also used by intelligence services in Europe [1]. It is known to be used on a mission in Angola in 1975. According to CIA communication specialist Teddy Roberts, the TAR-224 was still being used in operational context in 1983, when he trained a unit of US Army Green Barets on its use.
 
TAR-224A with top lid in place TAR-224a spy radio set (USA) TAR-224a spy radio set (USA) TAR-224A front panel Phone/Key sockets and Power socket Adjusting the RX frequency TAR-224A in upright position Carrying the TAR-224A

 
Controls
The image below gives a good view of the TAR-224 controls and connections. The left half of the radio contains the receiver (RX), whilst the right half contains the transmitter (TX). The two sections are separated by a vertical white line at the center. The radio can be powered by an internal 12V battery, but also by an external power source that is connected at the bottom left.


The receiver has a Variable Frequency Oscillator (VFO) that can be adjusted to any frequency between 2 and 24MHz, but the transmitter requires a suitable crystal for each TX frequency. The crystal is inserted into a special socket at the bottm of the TX section. At the top right is room for an expansion unit. As far as we know, the only expansion that was ever released was the CS-224 crystal selector that allowed quick selection of 30 channels (the option is not shown here).
 
Components
Receiver   RX
The left half of the TAR-224 is taken by the receiver (RX). It consists of a colour-coded 4-position BAND selector and a 4-row frequency scale. The frequency can be adjusted by means of a rigged knob just below the frequency scale. The knob has a spring-loaded handle for faster tuning.
 
At the bottom of the front panel are the MODE-selector, the Beat Frequency Oscillator (BFO), AF gain (volume) and RF gain (HF pre-amplifier). When the RF adjustment is set to the leftmost position, the Automatic Gain Control (AGC) is enabled. The receiver also contains the POWER switch and the connectors for external power, microphone, speaker and external morse key.

The frequency scale can be calibrated by setting the MODE-selector to CAL. This enables the built-in reference oscillator, which produces a carrier at 500kHz intervals (3MHz, 3.5MHz, etc.).
  
Adjusting the RX frequency

Once the reference oscillator is selected, tune the receiver to a carrier near a rounded frequency (e.g. 3MHz) and adjust the scale ruler (CAL ADJ) so that its center positions lines up with the frequency. The receiver is suitable for the reception of morse signals (CW) and voice (AM), but can also receive Single Side Band signals (SSB) by the using the built-in Beat Frequency Oscillator (BFO). For normal operation (CW) the BFO should be set to the center position (0). For SSB signals, the BFO knob can be tuned (-) for Lower Side Band (LSB) and (+) for Upper Side Band (USB).
 
Adjusting the RX frequency Band selector The four frequency ranges (yellow selected) Adjusting the BFO (SSB) Phone/Key sockets and Power socket Power/MODE switch (OFF, RX, TX) Connecting antenna and counterpoise Calibrating the scale

 
Transmitter   TX
The transmitter is crystal-operated and is suitable for CM (morse) and AM (voice) communication. A suitable CR-18/U crystal can be inserted in a special socket at the front center. If rapid channel selection is needed, an optional channel selector can be installed in a special slot at the top right. If the selector is not installed, the slot is closed by a thick plexiglass panel. The manual suggests that a synthesizer could be installed as well, but as far as we currently know it was never built.
 
When using the (optional) channel selector, three banks of 10 channels each are available. When a single crystal is inserted into the crystal socket at the front panel, the 30-channel selector is disabled. Two frequency ranges are available via a selector: 2-12MHz and 12-24MHz. In the 12-24MHz mode, the crystal frequency is doubled.

When sending messages in morse code, the TAR-224 was normally used in combination with a burst-encoder in order to avoid detection and interception by a potential eavesdropper. It was probably used with the GRA-71 burst encoder.
  
Using the built-in morse key

Alternatively, a morse key could be connected to one of the 6-pin U-229 connectors at the front left, allowing manual transmission of morse signals. In case of an emergency, the built-in morse key could be used for this as well. The minimum output power for an unmodified TAR-224 is specified at 13W in CW and 4W in AM, but in practice the output power was much higher.
 
The radio shown here delivers 21W in CW and up to 8W in AM [3]. When used for phone (voice), a handset or headset could be connected to one of the 6-pin U-229 sockets at the front left. The (wire) antenna and a suitable counterpoise should be connected to the two snap-on terminals at the right edge of the transmitter.

The TAR-224 has a built-in Antenna Matcher that allows the transmitter to be adjusted for the (wire) antenna in use. This can be done by holding down the morse key whilst manually rotating the antenna tuning knob at the right.
  
Starting the auto-tuner (pull knob)

Alternatively, the Automatic Antenna Tuner (AAT) can be enabled by pulling-out the antenna matcher knob. This engages a novel electronically controlled motor-driven coil mechanism that will try to obtain the highest power output at the best possible Standing Wave Ratio (SWR).
 
TAR-224 with standard NATO-issue handset Using the built-in morse key Selecting the TX range Tuning indicator and battery check Crystal socket with built-in switch Placing a crystal in the socket on the front panel Starting the auto-tuner (pull knob) Connecting antenna and counterpoise

 
Power
The TAR-224 can be powered by any 12V DC source that can deliver 5.9 Amp. The operational voltage range is 10.8 to 13.2V. When using an external DC source, the so-called battery-protection circuit automatically disables the internal battery in order to prevent damage.
 
When a suitable power supply/battery charger is used, it can be used to charge the battery simultaneously. For this purpose, a separate contact is used in the connector and the battery.

The battery itself is a single-unit rechargable 12V accumulator that is installed behind a water-tight door at the front left of the radio. In the battery compartment are three contact pins, marked J1, J2 and J3. The first pin (marked J1) is connected to the +12V whilst J3 is connected to the negative terminal (-) of the battery. The center pin (J2) is for charging the battery.
  
Selecting the internal battery

Please note that the battery-protection circuit uses a latching (bistable) relay. Once the internal battery is switched off, it will remain disabled (even when the external power source is removed) until the RESET POWER button on the front panel is pressed.

Please note that when putting the radio in storage, the power selector at the front panel should be set to the OFF position (left). When closing the radio, an index stub on the inside of the plastic top cover, prevents it from being fitted when the power switch is not in the correct position (OFF). The top cover is locked in place by means of three latches at its sides. When placed in the upright position, the radio can be carried around using the plastic grip at the side.
 
TAR-224 with opened door to the battery compartment Contacts inside the battery compartment External connections Selecting the internal battery Power/MODE switch (OFF, RX, TX) TAR-224A with protective cover (top lid) Index slot to ensure the radio is OFF when the lid is closed TAR-224A with top lid in place

 
Interior
The TAR-224 is a truely compact self-contained transceiver. The entire radio is housed in a die-cast aluminium case that measures approx. 12 x 18.5 x 31 cm and weights just 6 kg. The case is fully waterproof and all controls, connectors and adjustments have watertight gaskets as well.
 
After loosening 10 torx bolts at the edges of the front panel, the entire radio can be lifted out of the case. The image on the right shows the interior of the radio with the front panel facing down. At the left is the transmitter with the coils of the Automatic Antenna Tuner clearly visible (the preotective cover is removed here). At the right is the receiver and (at the front) the internal wiring of the various controls at the front panel.

The construction of the receiver is extremely complex. It is attached to the front panel with just four bolts and can easily be removed.
  
TAR-224A interior

The receiver is connected to the rest of the radio with only one 29-pin connector. After removing the knobs and the four bolts from the front panel, the entire receiver can be lifted from the connector and, hence, the interior. The RX block consists of a series of shielded units that are bolted together. They are wired together via two (green) 14-pin connectors at the side.
 
The image on the right shows the RX unit with the frequency scale facing upwards. The 29-pin connector and the two 14-pins connectors are visible at the left. A separate SMC connector is used for the RF antenna input (at the front).

In order to accomodate the four frequency ranges, a complex construction is used for the Antenna Matching unit, the RF pre-amplifier and the Local Oscillator (LO). These three units are mounted side-by-side in a single enclosure, with a common axle (attached to the BAND selector) running through each compartment.
  
RX unit with its connectors at the left

As each of the three units has to be adjusted differently for each frequency band, four different tuning sections are mounted around the common axle in each compartment. When rotating the BAND-selector at the front panel, the axle turns 90° with each step, selecting a different section.
 
The image on the right shows the interior of the three units. The tuning section are clearly visible at the center of each compartment. The rotation from the BAND-selector is carried over to the common axle by means of a serial of cogwheels and a chain belt at the side of the receiver.

The tuning section is normally closed by a common metal plate that covers the three sections (the cover is not shown here). The signals from the HF pre-amplifier and the Local Oscillator (LO) are fed to the IF-stage that is mounted to the bottom of the receiver unit.
  
RX interior. From left to right: Antenna matching, RF Amplifier and Local Oscillator (LO).

The right half of the TAR-224 contains the transmitter (TX), of which the Automatic Antenna Tuner (ATT) is arguably the most interesting unit. It is mounted in the front right corner of the radio. It consists of a large adjustable capacitor and a very special variable tuning coil.
 
The image on the right shows the ATT after its protective cover has been removed. At the left is the tuning coil. It is connected via a cog wheel mechanism at the bottom, to a synchronized rigged solid metal spool behind it.

At the front right is the electro-motor. It drives the tuning mechanism at 1000 RPM. Also connected to the mechanism is the large tuning capacitor that is just visible behind the motor. When enaging the ATT (by pulling the knob at the front panel), the tuning capacitor and the coil are adjusted for optimum SWR.
  
Clear view of the double winding/unwinding coil

A novel winding/unwinding mechanism is used for the adjustment of the coil. When running, the wiring is moved from the coil to the solid spool and vice versa. As a result the induction of the coil is increased or decreased. When starting the ATT, the mechanism is first fully wound back to the reference position. It then runs forward and will stop when the desired position is reached.
 
Radio removed from the case TAR-224A interior TAR-224A interior (top view) Antenna Tuner (left) and receiver (right) TAR-224A interior TAR-224A interior (side view) TAR-224A interior RX unit with its connectors at the left
Band selector mechanism Receiver internal connector RX interior. From left to right: Antenna matching, RF Amplifier and Local Oscillator (LO). Receiver with IF-stage removed IF-stage TAR-224A interior. The cover of the automatic anenna tuner has been removed. Automatic Antenna Tuner Clear view of the double winding/unwinding coil

 
Connections
The diagram below shows the pin numbering and connections of the connectors at the front left of the TAR-224. The two U-229 sockets (left) are identical [5]. They both are fully wired (A-F) in parallel. The other socket (right) is the socket for the external power source. A suitable connector for the latter is the Amphenol PT06A-8-3S, which is available from distributors like Digi-Key (US).


 
 PHONE/KEY
Pin Function Description
A GND Ground (common wire)
B SPK Speaker (separate, or part of handset/headset)
C PTT Push-to-Talk switch (connects to ground)
D MIC Microphone (separate or as part of handset)
E KEY External (morse) key
F +12V Power supply (output) for external burst encoder

 
 POWER
Pin Function Description
A +12V Power supply (input)
B GND Ground (common wire)
C CHG Charge input (for internal battery)

 
 BATTERY
Pin Function Description
J1 +12V Power supply (input)
J2 CHG Charge input (for internal battery)
J3 GND Ground (common wire)

 

TAR-224 and the CIA
Terry Roberts worked for the CIA for 40 years 1

Teddy Roberts started his professional life back in 1960 when, fresh out of high school, he attended a Radio Intercept Operator's Training in Imperial Beach (California, USA). After passing a Naval communications training later that year, he got his first assignment at the US Naval Communications Facility in Adak (Alaska), where he learned to work with sophisticated high-powered computers, video display terminals and the collection and analysis of communications signals. In 1963 he was transferred to the Naval Communications Station in Honolulu (Hawaii).

In 1964, following his release from the US Navy, Terry entered communications training with the CIA, after which he was assigned to the American Embassy in East Africa. Later that year, whilst being on medical hold for any overseas posting, Terry was temporarily assigned with an engineering office at the CIA's communications training facility.
 
After his medical hold had been cancelled in 1965, he was assigned to a US Embassy in West Africa. In the following years, he worked in several countries including Germany, Libya, Israel, the Phillipines, and China, until he landed in London (UK) for a five-year assignment with the US Embassy. During these years he worked closely with the British Intelligence services in support of NATO war planning programs.

In 1988, he was assigned to CIA Headquarters in Virgina, where he worked as chief of recruitment for the CIA's Office of Communications. A few years later he was assigned as Deputy Chief of Operations of the Communications Area Operations staff for Africa. In 1992, Terry was assigned as associate director of the CIA's Global Network Management Center, planning the CIA's world-wide communication needs on a daily basis, until he retired from the CIA in 1995.

The image on the right shows Terry Roberts holding a TAR0224A in his hands. He used this radio in an operational context in 1983, when training a unit of Army Green Berets on its use.
  
Photograph by Elaine Blaisdell. Copyright 2009, The Journal [4]. Reproduced here with kind permission.

One of his most memorable experiences was his involvement in the arrest of Daulton Lee and his partner in crime Crystopher Boyce, during a three-year tour in Mexico, where he worked in close cooperation with the FBI. Whilst working for US defense contractor TRW, Boyce used a Minox-B spy camera to copy classified government information, which Lee sold to the Soviets. Lee and Boyce were eventually arrested in 1977, and were sentenced to life and 40 years respectively. The story was later told in the 1979 book (and later in the 1985 movie) The Falcon and the Snowman.
 
  1. Thanks to The Journal for allowing us to reproduce part of their 2009 publication [4] and the photograph above. The photograph was made by Elaine Blaisdell, who also wrote the original article.

Help required
Although the TAR-224 was in service for many years during the Cold War, not many of them have appreared on the surplus market, making them into rather rare collector's items. As a result, not much is known about the backgrounds and operational context of these radios. If you have any information that is not listed here, please contact us.

We are also looking for the optional CS-224 Channel Selector that can be installed in the empty slot in the top right corner of the radio.

 
Documentation
  1. Instruction Manual for Radio Set TAR-224
    AVCO Corporation, 15 September 1971.

  2. TAR-224 Inspection Work Sheet for serial number 549
    16 September 1976. 2 pages.

References
  1. Louis Meulstee, TAR-224
    Wireless for the Warrier. Volume 4. September 2004. ISBN 0952063-36-0.

  2. AVCO Corporation, Instruction Manual for Radio Set TAR-224
    80045 PRC 31/570. 15 September 1971.

  3. TAR-224 Inspection Works Sheet
    TAR-224 Serial Number 549. 16 September 1976.

  4. Elaine Blaisdell, In service to his country
    Teddy Roberts spent 40 years working for the CIA around the world.
    The Journal (Website). 28 February 2009. Retrieved November 2012.

  5. Crypto Museum, U-229 connector description
    Crypto Museum website. December 2011.

Further information

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Crypto Museum. Created: Wednesday 21 November 2012. Last changed: Sunday, 14 May 2017 - 07:14 CET.
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