Page 117 - Build Your Own Transistor Radios a Hobbyists Guide to High-Performance and Low-Powered Radio Circuits

will output signals from the local oscillator (lMHz to 2 MHz) and the RF signal input

(540 kHz to 1,600 kHz). The (455-kHz) IF filter then also will remove/attenuate
signals related to the local oscillator or incoming RF signal.
Commercially Made Transistorized Superheterodyne

Radios

One of the first transistor AM radios, the TR-1, was made by LD.E.A., Inc., Regency
Division, in 1955. The circuit topology of the TR-1 followed closely that of the
vacuum-tube radios that used converter circuits instead of a separate local
oscillator circuit and a mixer circuit (Figure 8-2A).

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FIGURE 8-2A Portable four-tube radio.
In Figure 8-2B, an antenna coil is connected to a grid of the 1RS pentagrid

(five-grid) converter tube, whereas an oscillator coil is coupled to three grids of the
lR5 tube. Thus the local oscillator's signal and the incoming RF radio station signal
are connected to just one vacuum tube. Connected to the plate of the lR5 tube is
the first IF transformer to extract AM signals that have been "mapped" to 455 kHz.