Tuner Type D

This circa 1907 United Wireless crystal radio receiver was most likely designed by early wireless pioneer Harry Shoemaker. Shoemaker was the chief engineer for Lee de Forest’s American Wireless Telegraph Company, and later United Wireless Telegraph Company. 

The Type D tuner had a range of 200-2000 meters and was widely used through WWI. 

The set has two tuning coils inside a mahogany box that measures approximately 12″ x 12″ by 4.25″ high. On the top surface, it has slots for two sliders for tuning ad switches for battery bias and detector-shorting during transmit periods. The batteries, which had to be replaced every three months, were stored inside. On the right hand slide is a third slide tuner. These sliding tuners are recessed, whereas in the later Model Type D, they are raised above the panel and removable for easier cleaning. This set also has two aerial binding posts for the loop antenna on the outer panels. Later, all three binding posts were on the middle top panel. The center binding post was the ground connection.

In questo link sono elencati 15 modelli, di cui 15 con immagini e 0 con schemi.
Elenco delle radio e altri apparecchi della United Wireless Telegraph Co.; New York City, New York