📡 History of the RCAF AT-7 / AR-6 Radio Set

The AT-7 Transmitter and AR-6 Receiver were part of a uniquely Canadian family of airborne radio equipment built during the Second World War. Produced by RCA Victor (Montreal), Northern Electric, and Canadian Marconi, these sets were designed to meet the Royal Canadian Air Force’s rapidly expanding needs under the British Commonwealth Air Training Plan (BCATP).

Between 1939 and 1945, Canada became one of the largest Allied producers of aircraft radio equipment, building tens of thousands of transmitters, receivers, intercoms, and direction-finding units. The AT-7/AR-6 pairing was one of the standard Canadian HF (high-frequency) communication systems of the period.

🔧 Development and Purpose

Why Canada Designed Its Own Radios

Early in the war, Canada relied heavily on British equipment such as the T1154/R1155.
But Britain could not supply enough for BCATP schools and Canadian-produced aircraft.
So Canada initiated domestic versions:

• similar operating ranges

• simplified for mass production

• tailored for RCAF service conditions

• compatible with both trainers and operational aircraft

The result was the “AT series” transmitters and “AR series” receivers.

📻 AR-6 Receiver (RCAF 10D/1428)

The AR-6 was a rugged HF receiver covering roughly 1.5–18 MHz, depending on variant.
It was designed for reliable long-range communication and for use with DF (direction-finding) loop antennas.

Key Features

• Multi-band operation suitable for both aircraft and marine craft

• Shock-mounted chassis for vibration resistance

• Large illuminated dial for night use

• 24-volt aircraft electrical compatibility

• Often paired with loop aerial control units for homing and navigation

Where It Was Used

• Avro Lancaster (RCAF)

• Avro Anson Mk II (Canadian-built)

• Canso/PBY flying boats

• Blackburn Shark

• Cessna Crane (selected installations)

• RCAF crash boats and marine rescue launches

The receiver was versatile enough that many were reused in the postwar period in marine and coast-station service.

📡 AT-7 Transmitter (RCAF 10D/1267)

The AT-7 was a compact HF aircraft transmitter intended for medium-to-long range communication, functioning on fixed frequency channels selected before flight. It was part of an evolutionary line:

• AT-1 – Early version

• AT-5 / AT-6 – Improved tuning systems

• AT-7 – Wartime standard for Canadian aircraft

Key Features

• Four large coil-box tuning units (the square covers on the panel)

• Red locking toggles for frequency-range changes

• Output designed for trailing and fixed wire aerials

• Built specifically for mass-produced RCAF aircraft

• Operated on 24-volt systems common to Canadian trainers and patrol craft

The AT-7 could send voice (AM) or Morse code (CW), making it useful for both routine communication and SAR (search and rescue) operations.

✈️ Operational Use

Together, the AT-7/AR-6 formed a complete HF communication station used in:

Aircraft

• Canso (PBY-5A) amphibians – for long-range patrol and rescue

• Avro Anson Mk II – especially navigation and wireless training

• Lancaster Mk X (RCAF) – many Canadian-built aircraft carried AR-6 sets

• Blackburn Shark – used for coastal patrol and training

Marine Search & Rescue

Remarkably, the exact same radio rack was also fitted into RCAF crash boats and marine rescue launches—fast vessels used to recover downed airmen on the coasts.
This made maintenance easier: the same spares, the same training, the same procedures.

🛠️ Legacy

The AT-7/AR-6 radios represent an important chapter in Canada’s wartime industrial history. They were:

• Canadian designed

• Canadian built

• Used in Canadian-produced aircraft

• Installed across the BCATP

• Served both air and sea rescue roles

Many surviving examples appear today in museums or private collections, often still wearing the original RCAF green lacquer and 10D-series stores codes.