Atwater Kent Models 30, 33, 35, 48 and 49 Radio Service Data Sheet
May 1930 Radio-Craft

May 1930 Radio-Craft [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Craft, published 1929 - 1953. All copyrights are hereby acknowledged.

Interestingly, a couple models of this Atwater Kent radio featured an untuned front end at the antenna interface, possibly because the adjustment range of the provided variable capacitor would not handle an extreme antenna impedance. With as basic as all the RF amplifier stages are, it seems maybe adding a second adjustable capacitor in parallel to facilitate a wider adjustment range would not have been too big of a cost burden compared to the advantage of tuning the input in the presence of all the EMI spewing from crappy electromechanical equipment and minimally filtered transmitters (it was the era of AM, after all). Note the unusual aspect ratio of the case, being much longer than it is deep or high. There are many YouTube videos of people having restored various versions of the radio - models 30, 35, 40, and more.

Atwater Kent Models 30, 33, 35, 48 and 49

These receivers are six-tube sets of the single-dial, battery-operated type. They are often referred to by their factory catalog numbers, to wit: Model 30, No. 8000; Model 35, No. 8100; Model 48, No. 9840; Model 33, No. 8930, Model 49, No. 9860. The models 33 and 49 have a tuned input (four tuned circuits); the models 30, 35 and 48 have an untuned input (three tuned circuits). Models 48 and Models 49 are code numbers showing that a gold-finished panel is used. Models 33 and 49 are so wired that R5 limits the current to V5 and V6 only while V4 is controlled by the additional variable resistor Rx. R in the first stage of these two circuits has the same value as equivalent resistors R1 and R2. C is the regular tuning condenser, in shunt to which is the circuit-balancing variable condenser Ca.

The purpose of the untuned antenna input of the 30, 35 and 48, shown in the larger diagram, is to eliminate the detuning effects of aerials of different constants. If it becomes necessary to change a variable-condenser bank, make certain that the pulleys turn easily on the shafts; if they do not because of a damaged condenser shaft, replace the entire condenser group.

Each belt must be arranged with the eyelets, which clamp the two ends together, at the bottom of the belt loop. Each belt has two small holes; one to fit over a pin on the dial-condenser pulley and the other to fit over the pin on the pulley which is controlled by that belt.