The AN/ARC-5 Command Radio Set is a series of radio receivers, transmitters, and accessories carried aboard U.S. Navy aircraft during World War II and for some years afterward. It is described as "a complete multi-channel radio transmitting and receiving set providing communication and navigation facilities for aircraft. The LF-MF-HF components are designed to transmit and receive voice, tone-modulated, and continuous wave (cw) signals." Its flexible design provided AM radiotelephone voice communication and Modulated continuous wave (MCW) and Continuous wave (CW) Morse code modes, all of which are typical capabilities in other Navy aircraft communication sets of the period. It was an improvement of the Navy's ARA/ATA command set. Similar units designated SCR-274-N were used in U.S. Army aircraft. The Army set is based on the ARA/ATA, not the later AN/ARC-5. The ARA/ATA and SCR-274-N series are informally referred to as "ARC-5", despite small differences that render all three series incompatible. Like the AN/ARC-5, the ARA/ATA and SCR-274-N had AM voice communication and two-way MCW and CW Morse code capability.
In accordance with the Joint Electronics Type Designation System (JETDS), the "AN/ARC-5" designation represents the 5th design of an Army-Navy airborne electronic device for radio communications equipment. The JETDS system also now is used to name all Department of Defense electronic systems.
History The AN/ARC-5 command set was used by the US Navy from the latter part of World War II into the post-war era. It was fitted in many different aircraft types for communication between aircraft, navigation, and communication back to base. Units were available that covered much of the MF, HF, and VHF spectrum. Despite the use of octal base vacuum tubes, they were compact, rugged and light weight. Many became surplus after the war and were often converted for amateur radio use. The term 'ARC-5', while correctly applied to the AN/ARC-5 series, has also come to be a generic, though incorrect, term for the ARA/ATA and SCR-274-N command set units, including those designed by the Aircraft Radio Corporation in the late 1930s.
The antecedent of the AN/ARC-5 system was the U.S. Navy's ARA/ATA system, initially deployed in 1940. The designations ARA and ATA are a pre-World War II Navy equipment nomenclature. The major units of the ARA are five receivers covering , each unit with its own dynamotor power supply. The major units of the ATA are five transmitters covering , using a common transmitter dynamotor/screen modulator unit. Most units were made by the Aircraft Radio Corporation (USN manufacturer's code CBY). Many units were also made by Stromberg-Carlson (USN manufacturer's code CCT).
To equip US Army Air Corps planes, the US Army adopted in 1941 a reduced set of radios from the ARA/ATA range. Designated SCR-274-N, these Army radios were electrically almost identical to their ARA/ATA counterparts, except for receiver output and modulator sidetone audio transformer output impedance. Structurally and in appearance, they were virtually identical except for most later units being left unpainted aluminum in contrast to the black wrinkle finish of the Navy sets. The designation SCR-274-N is a pre-World War II Army equipment nomenclature. The Army never acquired the ARA receiver, nor the ATA transmitter. Initially, it did not acquire the transmitter, nor the receiver, but the need to communicate on the common civil airfield frequency of plus the anticipated USAAF use of the AN/ARR-1 homing adapter (see below) compelled adding these units to the SCR-274-N. Early Army units were made by Aircraft Radio Corporation, but the vast majority was made by Western Electric, plus a few by Colonial Radio and others.
In late 1943, the U.S. Navy fielded an improved and more flexible set of its ARA/ATA radios under the new Joint Army-Navy (JAN) nomenclature of AN/ARC-5. Structurally and in appearance, the AN/ARC-5 series is almost identical to the former units but both receivers and transmitters are somewhat different electrically. A receiver and transmitter were added that provide four-channel crystal-controlled VHF-AM operation, along with a rarely encountered set of transmitters that provide coverage of .
The main units of both the Navy and the Army systems were usually installed in three-receiver racks and two-transmitter racks. Units not in service could be stored on board the aircraft, just as one would store tuning units of other types of radio equipment.
Specifications The following is a table of ARA/ATA, SCR-274-N, and AN/ARC-5 major components that could comprise a typical three-receiver, two-transmitter installation, with other configurations also being possible. In addition, several miscellaneous components are listed. A blank in the component ID column indicates that no equivalent unit existed for that system. A.R.C. refers to Aircraft Radio Corporation.
MHz ARA-ATA SCR-274-N AN/ARC-5 Navigation Receiver (Beacon Band) 0.19 - 0.55 CBY-46129 BC-453-() R-23()/ARC-5 Navigation Receiver (Broadcast Band) 0.52 - 1.5 CBY-46145 BC-946-() R-24/ARC-5 Communication Receiver 1.5 - 3.0 CBY-46104 R-25/ARC-5 Communication Receiver 3.0 - 6.0 CBY-46105 BC-454-() R-26/ARC-5 Communication Receiver 6.0 - 9.1 CBY-46106 BC-455-() R-27/ARC-5 Communication Receiver - Four Channel 100 - 156 R-28/ARC-5 Communication Receiver - Continuously Tunable 100 - 125 R-112/ARC-5 Communication Receiver - Continuously Tunable 125 - 156 R-113/ARC-5 Special Use Transmitter 0.5 - 0.8 T-15/ARC-5 Special Use Transmitter 0.8 - 1.3 T-16/ARC-5 Special Use Transmitter 1.3 - 2.1 T-17/ARC-5 Communication Transmitter 2.1 - 3.0 CBY-52232 T-18/ARC-5 Communication Transmitter 3.0 - 4.0 CBY-52208 BC-696-A T-19/ARC-5 Communication Transmitter 4.0 - 5.3 CBY-52209 BC-457-A T-20/ARC-5 Communication Transmitter 5.3 - 7.0 CBY-52210 BC-458-A T-21/ARC-5 Communication Transmitter 7.0 - 9.1 CBY-52211 BC-459-A T-22/ARC-5 Communication Transmitter - Four Channel 100 - 156 T-23/ARC-5 Communication Transmitter - Continuously Tunable 100 - 125 T-89/ARC-5 Communication Transmitter - Continuously Tunable 125 - 156 T-90/ARC-5 Communication Transmitter - Four Channel 100 - 146 T-126/ARC-5 Transmitter Modulator CBY-50083 BC-456-() MD-7/ARC-5 Transmitter Modulator Mount CBY-50084 FT-225-A MT-76/ARC-5 MF/HF Antenna Relay CBY-29125 BC-442-() RE-2/ARC-5 MF/HF Antenna Relay Mount CBY-29126 FT-229-A MT-77/ARC-5 Receiver Adapter, ILS (AN/ARN-9) Audio MX-19/ARC-5 Receiver Adapter, ZB (AN/ARR-1) Power CBY-62036 FT-310-A MX-20/ARC-5 Receiver Adapter, Remote Control Blank CBY-49107 FT-230-A MX-21/ARC-5 Receiver Local Tuning Knob A.R.C. 6743 MC-237 A.R.C. 6743 Receiver Adapter, Local Control Panel CBY-23154 FT-260-A C-24/ARC-5 Nav. Receiver ANT-LOOP Remote Control C-25/ARC-5 Single Tunable Receiver Control Box CBY-23261 BC-473-A C-26/ARC-5 Single Lock-Tuned Receiver Control Box C-27/ARC-5 Single Tunable Receiver Control Mount A.R.C. 7053 FT-235-A MT-4/ARR-2 Three-Receiver Remote Control Box CBY-23251 BC-450-A C-38A/ARC-5 Three-Receiver Remote Control Mount A.R.C. 7054 FT-222-A MT-98/ARC-5 Four-Transmitter Remote Control Box CBY-23243 BC-451-A C-30()/ARC-5 Four-Transmitter Remote Control Mount A.R.C. 7083 FT-228-A MT-80/ARC-5 Three-Receiver Rack CBY-46149 FT-220-A MT-65/ARC-5 Three-Receiver Rack Mount CBY-46150 FT-221-A MT-64/ARC-5 Two-Transmitter Rack CBY-52212 FT-226-A MT-71/ARC-5 Two-Transmitter Rack Mount CBY-52213 FT-227-A MT-70/ARC-5 Audio Jack Box J-22/ARC-5 Audio Jack Box Mount MT-78/ARC-5 Receiver Dynamotor CBY-21531 DM-32-A DY-2()/ARR-2 Transmitter Dynamotor CBY-21626 DM-33-A DY-8/ARC-5 Receiver Remote Tuning Shaft A.R.C. 6151 MC-215-A A.R.C. 6151 Tuning Shaft Right Angle A.R.C. 6357 MC-211-A MX-22/ARR-2 Homing Adapter 234 - 258 ZB-series R-1/ARR-1 R-1/ARR-1 Homing Receiver 234 - 258 R-4()/ARR-2 Notes: () A (basic model) or B (1st revision). () No letter (basic model) or A (revision). () A (basic model) or AM (field modified to remove vacuum capacitor).
LF/MF/HF receivers all use an almost identical 6-tube superhet design: r.f. amplifier (12SK7), converter (12K8), two i.f. stages (two 12SK7's(4), or 12SK7/12SF7(5)), diode detector/BFO (12SR7), and one audio stage (12A6). Transmitters use four tubes: 1626 oscillator, two 1625 finals, and 1629 magic-eye tuning. The latter allows a check of the dial calibration by giving a visual indication, viewable by raising a small cover, when the oscillator's frequency matches that of an internal crystal. (4)ARA and SCR-274-N. (5)AN/ARC-5.
Compatibility between systems Audio frequency receiver output and modulator sidetone impedance for the ARA/ATA and the AN/ARC-5 is 300 to 600 ohms. In the SCR-274-N "-A" version, the receiver and modulator impedance is 4000 ohms, while "-B" and later version units have a 250 ohm tap on the AF transformers which can be connected.
ARA/ATA units and equivalent SCR-274-N units are interchangeable between systems, aside from audio impedance differences. However, AN/ARC-5 units generally are not interchangeable with the units of the earlier systems.
In contrast to ARA and SCR-274-N receivers, all AN/ARC-5 receivers have automatic volume control and a modified tube complement. The AN/ARC-5 navigation receivers have terminals and a switch to connect a DU-series direction finding loop to the receiver, and have a special audio line for an MX-19/ARC-5 adapter to allow the receiver to serve as an LF/MF localizer for the Navy's short-lived AN/ARN-9 Air-Track (related to ZA, ZAX) instrument landing system. These two capabilities were rarely if ever utilized. Otherwise, equivalent receivers of all three systems can interchange as a unit.
Few transmitter components of the AN/ARC-5 are interchangeable with ATA or SCR-274-N equivalent units. Mechanically, the transmitter rear power connector is slightly different, so inserting the wrong transmitter in a rack can damage either the rack or the transmitter power connector. Electrically, AN/ARC-5 transmitters use high-level final amplifier plate modulation, and the output tank circuit is shunt high voltage fed. The two earlier systems use less effective screen modulation, and the output circuit is series high voltage fed. The only electrical components of the AN/ARC-5 transmitter system that are interchangeable with the earlier systems are the dynamotor and the antenna relay.
Unlike earlier systems, none of the AN/ARC-5 control boxes have audio jacks for the microphone, headphone, or key. A separate jack box is used instead. AN/ARC-5 transmitter control boxes contain no Morse key.
Homing adaptors and VHF The broadcast band receiver in all of these command sets is intended to host a homing adapter for the Navy ZB/YE homing system. The homing adapter demodulates a signal near that is modulated with a broadcast band carrier. The output is sent to the broadcast band receiver tuned to the modulating frequency to further demodulate the carrier for voice messages or for a Morse code letter indicating to the pilot his bearing from the homing transmitter. All broadcast band receivers came with a power adapter to supply power to the homing adapter. The adapter under the Navy nomenclature system is the ZB-series. The identical unit under JAN nomenclature is the AN/ARR-1. This system was used by both the Navy extensively and the Army much less so. To put the system into operation on the aircraft, the beacon band receiver would be replaced in the rack by the broadcast band receiver. The antenna post is connected to the output of the homing adapter, and a power cable is connected from the homing adapter to the broadcast band receiver. The normal control that had been used for the beacon band receiver also serves this homing system without further reconfiguration.