Trans-Oceanic

[1][2] Zenith's founder, Lieutenant Commander Eugene F. McDonald, was a great admirer of advancing technology and believed that his company should include the latest, most practical advances in a sturdy product that would enhance the company's reputation.

[2] McDonald was a keen yachtsman and outdoorsman and wished for a portable radio that would provide entertainment broadcasts as well as being able to tune into weather, marine and international shortwave stations.

He asked his company's engineers to develop prototypes to meet his criteria and by 1940 they had concept sets that were ready for production.

[3][4] A cult-like following[5] has developed around the receivers, with earlier tube or valve versions prized by radio collectors, resulting in the availability of many working models and replacement parts.

During this short production run, some 35,000 units were produced and sales data showed that many were sold to customers in the 'above average' income group.

The first run of approximately 10,000 units had a sailboat-embroidered speaker grille, but after the Pearl Harbor attack, the patriotic Commander ordered the grille cloth changed to depict a bomber vaguely resembling a Boeing B-17 bomber.

The T/O was a dual-powered radio receiver; it could operate from electrical service AC or DC and via a pair of "A" and "B" dry cell batteries for portability.

Inserting the power plug into a socket on the chassis or the side of the radio (depending on model) switched the T/O to battery operation.

It had a redesigned front face and incorporated many frequency coverage and electronic changes ordered by McDonald.

There also was a production run in 1953-54, of 27,218 "militarized" H-500's, designated R-520/URR, ordered by the U.S. government for the Korean conflict.

In the spring of 1954, the 600 series was introduced with its 'slide-rule' type dial and a mains supply cord which coils inside the set on a spring-loaded reel.

During the tube or valve T/O model run, this receiver did not include an 88-108 MHz FM radio band.

Eugene McDonald died in 1958, but he was personally involved in the design changes to 'his' radio to the very end.

Later the 1000-1 and 3000-1 models were introduced with provision for an external power using what was one of the first "wall wart" type power supplies - a transformer, rectifier, and filter capacitor in a box with AC line connector that plugged into and hung from the wall socket.

The electrical design was an improvement in both selectivity and sensitivity, and used modern silicon NPN transistors rather than the previous germanium types.

The internal mechanical design was quite similar to the earlier models, and still used a steel chassis and point-to-point wiring, rather than PC boards.

By the time of the release of the 'R7000' in 1979, fierce competition from Sony in Japan—who, with their digital readout tuning dial had, in many ways, a superior product—meant the end of a famous product line.