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 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).
Atwater Kent Models 30, 33, 35, 48 and 49
These receivers are six-tube sets of the singledial, 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.
Posted September 21, 2016
Radio Service Data Sheets
These schematics, tuning instructions, and other data are reproduced from my
collection of vintage radio and electronics magazines. As back in the era, similar
schematic and service info was available for purchase from sources such as
SAMS Photofacts, but these printings
were a no-cost bonus for readers. There are 227 Radio Service Data Sheets as of
December 28, 2020.
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while typing up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
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