ARC-27

Later came the all-in-one control panels like the C-1702 shown below.

Any frequency ( out of 1750 channels) was selected on the dials to the right. Then a preset channel was selected on the left dial, and the red “program” button must be turned to set the pegs on the memory drum. This early control panel works pretty the same as what you see on modern radios and TV sets!

VINTAGE AVIONICS

AN/ARC-27

Radio Set AN/ARC-27 is an AM airborne radio set designed for use in aircraft for air to-air and air-to-ground communications.

The AN/ARC-27 is capable of transmitting and receiving on any one of 1750 channels, spaced 100 kHz, within the frequency range of 225.0 to 399.9 MHz. Audio Frequency bandwidth is 6 kHz

The RF power output of the AN/ARC-27 is 9 watts

Input power requirement is 28 Vdc at 19.1 amps during transmit or 16.5 amp when receiving. During channel switching, the dc current rises to 25.5A, with 200W dissipation in the storage drum panel.

The ARC-27 is capable for 1020 Hz tone modulation.

Weight is 71 pounds ( 38 kg) ….

Major components of the AN/ARC-27 are as follows:

RT-178/ARC-27 .............. Receiver-Transmitter

C-626/ARC-27 ................... Control ( with optional MT-821 mount)

MT-822/ARC-27 ……...... Mount

AS-390/SRC …………... .. Stub Antenna

AN/ARA-25 ………….. … Automatic Direction Finder

The Historic Naval Ships Association has an equipment list, with more details of the ARC-27 like the tube line-up. Also on this site are details for the AN/ARA-25 automatic direction finding antenna, often used together with the AN/ARC-27.

All circuit diagrams can be found here.

Controls

The first generation controls for the ARC27 came in two boxes– one to store the 20 preset channels in motor operated drums, and a second one to select one of them .

The C-626/ARC-27 stores the presets and the C-628 ( shown here) selected one of them.

The interconnections for these panels are shown here

RT-178 / ARC-27 top and bottom ( 1953)

Top- in the middle the third local oscillator with motor, guard receiver and spectrum amplifier.

Bottom (below) - the RF power amp (with 2x 2C39A), the third IF and audio amplifier , the first and second IF with crystals box for the second LO, the RF preamp, the spectrum oscillator at the far right, and the modulator with 829B. De complete set has 55 tubes, and no transistors.