November 1947 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.
A month before Bell
Laboratories' announcement of the
transistor invention by Mssrs. Bardeen, Shockley and Brattain,
Radio-Craft magazine editor Hugo Gernsback published a piece extolling the
virtues of a newly developed microtube, aka a "rice-grain" tube. As connected as
Gernsback was in the electronics industry, it is doubtful he knew of the
impending game-changing invention. Commercialization of the transistor took a
few years to get to the point where the devices could be manufactured cheaply
and reliably enough to begin being integrated (pun intended) into products, so
vacuum tubes still reigned for another decade or more. While the microtubes were
designed into such products as portable radios, hearing aids, and other things
in desperate need of size reduction, standard tubes continued to be used in the
majority of things. Even the military and aerospace industries elected largely
to pass on microtubes and instead wait for semiconductors. Still, there was no
guarantee in 1947 that solid state would ever displace vacuum tubes for anything
other than specialty products; it was still a very much unknown realm. Gernsback
quickly embraced transistors after the announcement was made.
A New Milestone in Electronic Developments
The above illustration is a considerably enlarged view of the
National Bureau of Standard's new Microtube. At the right are rice grains, at the
left a bookmatch for comparative size.
By Hugo Gernsback
The Tube Laboratory of the National Bureau of Standards has just announced a
new "rice-grain" radio tube - now known as the microtube.
This new subminiature radio tube is only slightly larger than a rice grain and
only a bit wider than a book match, illustrated on this page. This constitutes possibly
one of the greatest electronic developments in a decade. It certainly is a milestone
in radio from every point of view. The development is so revolutionary that at this
time it is impossible to foresee just how far it may lead us into further radio
Complete technical details of the new tube cannot be given at this time because
the new microtube has important military applications that can-not be revealed at
One of the important contributions which the National Bureau of Standards has
made is in the reduction of microphonic noises and internal tube noises. As every
radio technician knows, microphonics has been one of the great irritants in radio
work and the Tube Division of the National Bureau of Standards is to be congratulated
on this accomplishment, which ranks in importance with the reduction of tube size
The Bureau mentions that these tubes will create profound effects in industrial
and commercial fields, such as, for instance, in electronic computing machines.
Present-day models of such machines use as many as 18,000 tubes in a single machine
and some of the newer present models as well as others now being projected require
as many as 2,000 radio tubes. It can be seen that by using microtubes a tremendous
amount of space will be saved. This is true also in every type of radio where saving
of space is an important factor.
Incidentally, the new tubes have an expected life of 15,000 to 20,000 hours.
While at this time of writing the tubes are not available commercially, they
are now being developed by a large tube manufacturer who is working under a development
Other important future projections of the new microtube can be readily made now
that the new subminiature tube is a reality.
General David Sarnoff in 1921 predicted the eventual use of a wrist-watch size
radio. General Sarnoff was serious when he made his prognostication, which now moves
into the status of a distinct possibility. Indeed, a 5- or more tube superheterodyne
watch size radio receiver now can be built with these new microtubes. There is no
problem today as to the rest of the components which can easily go into a space
the size of a man's wrist watch. The only thing that might baffle a constructor
would be the batteries. However, this need not worry us too much either, because
we can immediately think of a battery substitute.
Remember, these tubes do not use much current; therefore, we can imagine a miniature
electric generator, powered by a watch-spring motor, using the recently perfected,
most powerful Alnico V magnet. Such a subminiature generator becomes a distinct
possibility. You merely wind the watch in the ordinary manner and the generator
will keep running for a short period. It then can be rewound for more power. Thus,
we will have a self-contained radio receiver compressed into the size of an ordinary
watch. The face that normally is the crystal now becomes the loudspeaker diaphragm
or cone, then by holding the wrist radio to the ear we should have clear and sufficiently
loud reproduction to enjoy whatever program we wish to listen to.
Much smaller radios than these can be envisaged also for military purposes, such
as subminiature radars, proximity fuses, handle-talkies, and a host of others. It
has been said that World War II was won chiefly through the instrumentality of radio
and electronics. The submarine war could not have been won if it had not been for
our superiority in radar and associated other electronic techniques. Instant communication
was a most important factor in winning the war. Radar for tracking down enemy aircraft
was THE reason that made possible the aerial victory in the Battle of Britain. Without
it there would not have been enough airplanes at the right spot at the right time,
and the Battle of Britain certainly would have been lost.
If another war should come, we may rest assured that again radio and electronics
will be the outstanding factor. Controlled missiles, in the so-called push-button
war, could not be possible without radio-electronics.
The guided missiles now being perfected to protect our shores and to intercept
other missiles will all contain the new microtubes. Indeed, the guided missile that
can be followed from headquarters by means of television becomes now a distinct
possibility due to the microtube.
For the pocket radio set, which has been in the developmental stage for several
years now, the microtube will also become the most important factor due mainly to
the great saving of space that can be achieved even over the present-day miniature
tubes, still far too big, as we have pointed out a number of times.
There may also come a complete revolution in our radio receiver techniques. Some
years ago we used to manufacture a radio tube that had all the elements of three
tubes contained in one glass envelope. This tube proved too expensive to manufacture
and is no longer made. But with the new microtube, an entirely new possibility,
which the writer advances now, seems economically sound and feasible.
Instead of using five separate tubes in a superheterodyne receiver, five separate
microtubes could all be placed into one envelope much smaller than the present-day
standard tube. The new tube unit would merely have extending from the base the usual
tube prongs, and instead of having five tubes we would have only one. This new multiplex
tube therefore would be five tubes in one.
It would save an enormous amount of space in every radio set and it still would
be cheaper than separate tubes. The wiring would become much simpler, the connections
shorter, the weight less, and the cost would be reduced.
Then, if one of the multiple microtube units fails, the entire multitube simply
would be discarded and a new one plugged in. It would save the service-man an enormous
amount of servicing time if all radio sets would adopt such a multiple tube.
In this discussion we have merely scratched the surface of this new epoch-making
development. In the next few years the microtube can be counted on to revolutionize
many branches of radio and electronics, television not excepted.
Posted November 9, 2020