Page 27 of the Argus post-war report shows a small-looking cylindrical structure with the caption “Ten Channel Crystal Tuning Unit.” Since few wartime airborne receivers were crystal-tuned, the device was likely a component of a transmitter, but that was about all that could be determined from the photo and caption.

Early in our identification effort we had begun buying illustrated service manuals printed by Bendix during WWII. One day we opened a Bendix RTA-1 manual and found an interior photo clearly showing the component on page 27 of the Argus report.

Eventually we bought an RTA-1 on eBay. The shipping weight was over 50 pounds. It arrived in a box the size of a small refrigerator and packed in several years’ supply of plastic peanuts. The “small” cylindrical component in the Argus report was 10 inches in diameter and about 18 inches long.

The RTA-1 was a voice and data receiver/transmitter used in both military and civilian transport aircraft during WWII and in commercial transports after the war. The tuning component made by Argus takes up fully 30% of the volume of the whole unit.