December 1947 Radio-Craft
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
Imagine if engineers used physical
mock-ups of semiconductor substrates with BB-sized metal balls representing electrons
and holes to design the next whiz-bang transistor. You'd think they were insane.
Seventy-three years ago, before powerful computers and software were available to
simulate the physics, engineers were doing just that sort of thing to figure out
how to design vacuum tubes. This "Monthly Review" feature in the December 1947 issue
of Radio Craft magazine has a photo of one of the models. Hills and valleys in the
base represented voltage potentials that influenced the trajectory of the balls.
Pretty clever, really. Also reported was the death of world-famous physicist and
originator of the quantum theory, Mr. Max Planck. He was 89 years old - not bad
for the era. A 1 MW transmitter - the most powerful in the world, was soon
to built by the U.S. in Switzerland. See the page capture for all the news.
Radio Electronics Monthly Review
The experimental model "vacuum tube" in use. The model looks
something like a game table.
A Model "Radio Tube" made of rubber, with "electrons" in the
form of bronze balls tests electronic designs in a single day that would require
3 months otherwise, Westinghouse revealed last month. The new model, it is stated,
is helping to develop new tubes for television and high-frequency radio.
It consists of a very thin sheet of rubber stretched across a frame about the
size of a small dining room table. BB-shot-sized bronze balls simulate electrons;
hills and valleys in the rubber simulate electrical voltage; and wooden blocks act
as tube elements.
Proper arrangement of the hills and valleys direct a ball and control its velocity.
Measuring the time it takes for the ball to roll from one part of the table to another,
enables engineers to calculate the speed of actual electrons in a tube. This determines
the electrical voltage needed for that part of the tube.
To find the proper spacing and optimum shape of tube elements wooden reproductions
of various shapes and sizes of cathodes, grids or anodes are used. They help research
men to find the arrangement that gives the best focusing of electrons.
The model, which can produce approximate replicas of most kinds of tubes, permits
checking the internal design of a tube in one day compared to three months by the
old mathematical trial and error method.
Max Planck, world-famous physicist
and originator of the quantum theory, died October 3, at the age of 89.
Planck is regarded as one of the great scientists of the present generation and
one of the scientific immortals of all time. His quantum theory has contributed
to the advance of science in the same measure as Newton's discovery of the laws
of gravitation or Copernicus' theory of the solar system.
He made his fundamental discovery that radiant energy is not continuous, but
comes in small bundles, whose energy content varies with the frequency of the radiation,
in 1900. In his own words "Radiant heat is not a continuous flow and indefinitely
divisible. It must be defined as a discontinuous mass, made up of units all of which
are similar to one another."
These quanta, which he referred to as "the pennies of the atomic world," are
so small as to be unobservable in studies of large-scale phenomena, but are of great
importance in the study of atomic phenomena, and especially of the physics of the
Most Powerful Radio broadcast station in the world will shortly
be erected at Geneva, Switzerland by the United Nations, it was reported 'on good
authority to Radio-Craft last month. The power will be 1,000 kilowatts.
This station will operate on 250 kc (1200 meters) and has been designed to blanket
all of Europe. Located strategically in Switzerland, it is certain to reach practically
every radio receiver on that continent. Europe has a very large number of crystal
receivers. These normally cannot receive signals farther than from 25 to 50 miles.
It is expected that every crystal set in Europe will be able to receive the new
U. N. broadcast station signals.
The diamond radiation counter in use. Enlarged insert shows diamond
between its electrodes.
Diamonds are more useful as detectors of certain types of atomic
radiation than the standard Geiger-Muller counter the National Bureau of Standards
revealed last month.
To use a diamond as a counter, it is clamped between two small brass electrodes
maintained at a difference in potential of about 1000 volts. When a source of gamma
radiation is brought within range of the diamond, pulses of current occur across
the electrodes, which after amplification may be detected and counted on any suitable
indicating device, such as an oscilloscope, a current meter, a set of headphones,
or a loudspeaker. In apparatus assembled at the Bureau, primary amplification is
effected with minimum loss of original intensity through the use of a triode very
close to the diamond in the circuit. The output from this tube is then applied to
a two-stage amplifier, from which pulses of sufficient magnitude to operate the
detecting instrument are obtained.
The pulse-producing property of the diamond is thought to be a result of its
highly symmetric crystalline structure, characterized by a very regular arrangement
of carbon atoms with relatively large intervening spaces. According to this theory,
when a photoelectron is emitted by a diamond atom as the result of the absorption
of gamma radiation the freed electron is accelerated through the interatomic space
toward the positive electrode. Within a very short distance it acquires such high
velocity that other atoms along its path are ionized by collision with the release
of additional electrons, which in turn are accelerated in the same direction. This
multiplication of charges repeats itself in rapid succession, producing a sudden
avalanche of electrons equivalent to a small pulse of current. The larger the diamond
the more electrons would be involved in the sudden pulse.
Apparently the diamond quickly recovers from its ionized state, as the pulses
registered are extremely sharp. The diamond counter is thus a very fast counter,
capable of indicating a much greater number of pulses per minute than is possible
with the ordinary Geiger-Muller counter.
Diamonds tested in the Bureau's laboratories have been found to have a sensitivity
per unit volume equal to or greater than that of any counter constructed by man.
One of these diamonds, measuring about 1/8-inch on each face, has approximately
the same sensitivity for gamma radiation as a laboratory-constructed Geiger-Muller
counter of the usual type. Many diamonds are larger and would be more sensitive.
Posted December 17, 2020