Comments on the Circuits of the first Transistor Radios

Posted on Feb 5, 2014

The circuitry of the Regency shows some peculiarities. The circuit of the self-oscillating mixer stage, the base bias voltage of the second IF stage from the AF power stage, the unusual IF of 262KHz and the supply voltage of 22. 5 V are all characteristic of the device. Other experimental circuits of the time, as well as the upcoming transistor receivers from 1955 below, deviate from its circuit design

Comments on the Circuits of the first Transistor Radios

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significantly. A great similarity is apparent when comparing the circuit of the "Telefunken TR-1" with the "Regency TR-1" (Fig. 1). After the initial pioneering work in the semiconductor factory at Ulm, it is clear that the Hanover factory became active only after the release of Regency receiver. It could be thought of as follows (but unfortunately there are no relevant authorities):They adapted the Regency`s circuit to their available transistors. Because these were pnp types, the supply voltage needed to be reversed. Also since they had poorer RF characteristics, the IF stages were increased to three and the self-oscillating mixer was replaced by separate mixer and oscillator stages. This was necessary to reduce the mixer transistor noise factor. The intermediate frequency was virtually the same. Of course, the RC components to neutralize the IF stages had to be changed. Moreover, they used the same components values, where possible. (There were, however, scarcely any alternatives. ) The speaker was similar to the Jensen model used in the Regency. The claim that the development and manufacture of the Telefunken TR-1 took place in the summer of 1954 (3), is probably questionable. Whether a pocket portable was seen behind closed doors at the Hannover Fair in March 1955, is yet to be determined (4). A Regency TR-1 (with Intermetall transistors) would be shown at the DG sseldorf Radio Exhibition in 1955 by Intermetall (6)....

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