The Southwestern Historical Quarterly, Volume 97, July 1993 - April, 1994 Page: 65
754 p. : ill. (some col.), maps, ports. ; 23 cm.View a full description of this periodical.
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The Breakthrough Breadboard 65
four days (and nights) when one had never been conceived (much less
designed), the transistor types to be used had not yet been tested in RF
circuits, and the performance specifications for the radio did not even
exist?
It was scary, even for these experienced engineers used to "impossi-
ble" schedules. Nevertheless, there was no hesitation on their part that
Friday afternoon, even though they could see no clear solution to the
many unique problems associated with designing transistor circuits that
would operate at radio frequencies. We not only did not know the solu-
tions, we did not even comprehend all the problems that lay ahead. Not
exactly your typical Friday afternoon.
In setting up the transistor radio design project, one of the first things
Roger, Ed, Mark, and I did that Friday evening was to calculate gain
(amplification) characteristics requirements for each section of the ra-
dio-the radio frequency as well as the audio frequency amplifiers. This
helped us to set the design goals, or specifications, for each section of
the radio.
In order to acquire a small tuning condenser and a small speaker,
both needed for the radio we were to design, we purchased the smallest
available tube-type radio, an Emerson, first thing on Saturday morning.
From it, we could remove and use those unusually small parts not readily
available from parts supply houses. Other key parts which we would
need for the transistor radio, especially transformers, we would have to
design and fabricate ourselves. This small tube-type radio was six inches
wide, three and a half inches high, and one and a quarter inches deep.
It was called a pocket radio because it could be carried in the pocket of
a large overcoat, a major achievement in the miniaturization of vacuum
tube radios. Such radios required two relatively small, short-life batteries.
One was a one-and-a-half-volt flashlight type called an "A" battery. It was
used to supply current to light the filaments of the tubes. The other bat-
tery was a miniature forty-five-volt type called a "B" battery. It supplied
the other currents, called "plate" circuit current, needed for the tubes to
amplify the received signals.
Our measurements of the operating characteristics of the small tube
radio, before removing the tuning condenser and speaker, confirmed
our calculated gain requirements which would have to be designed into
the various stages of the transistor radio to achieve an adequate signal
output. This signal output would have to be high enough to give an
undistorted, easy-to-hear sound across a normal-sized room. We were
now ready to get on with our design tasks.
We decided to use the proven superheterodyne circuit principles and
divided up the circuit design responsibilities. The superheterodyne-type
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Texas State Historical Association. The Southwestern Historical Quarterly, Volume 97, July 1993 - April, 1994, periodical, 1994; Austin, Texas. (https://texashistory.unt.edu/ark:/67531/metapth117154/m1/93/: accessed April 26, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting Texas State Historical Association.