January 1937 Radio-Craft
[Table of Contents]
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics.
Radio-Craft was published from 1929 through 1953. All copyrights are hereby acknowledged. See all articles
The ability to generate clean, controlled radio waves at 3 THz
in 1937 was about as attainable as putting a man on the moon. That
did not stop scientists and engineers from theorizing how to get
there and what to do once attained. That's the way science progress
happens. An official name had not yet been given to the spectrum
realm, but news reporters conjured up the moniker "mystery rays."
Even scientists called it the "black gap." Both sound a bit hokey
and there is a temptation to poke fun at the renowned technical
ignorance of most media types, but no less a science giant as Albert
Einstein referred to quantum entanglement as "spooky action at a
The big idea of author W.E. Shrage was to exploit and extend
the concept of a cathode ray tube (CRT) to convert streams of electrons
into a visual image to use a photosensitive surface to directly
convert (no mixing to an IF) terahertz radio waves modulated with
audio directly into sound. Only amplification and some filtering
would be necessary. I just checked Amazon and no such radio receivers
are available, so it is safe to assume the idea never progressed
past the conceptual stage. Oh well, on to the next project.
Ultra-Ultra-Microwave "Radio" of the Future
The "black gap" referred to by a well-known scientist, in describing
those extremely high frequencies about which we know so little at
present, threatens soon to become one of the most important bands
of radio communication, if the premises set forth by the author
prove to be true. The methods described are, of course, products
of the imagination, but ...
W. E. Shrage
Fig. A - The waves will be "detected" without
It is common knowledge that radio waves, like those of light,
are electro magnetic in nature. Expressed in the language of the
man in the street, this means that both consist of electric particles.
The only difference between them is the number of "wave-movements"
per second executed by the "electric particles." 'Or as a technician
would express it: the only difference between these two kinds of
waves is in their frequency.
What this relation actually involves will become more impressive
later, when we learn more about the electromagnetic wave-spectrum,
and when we consider the fact that radio (or, as the scientists
call them, Hertzian) waves go down to a wavelength of about 0.01-centimeter
(4/1,000 of an inch).
Nobody, as yet, has been able to generate radio waves of such
an extremely short wavelength (or, at least, not in considerable
quantities), but there is no doubt that, in the future, someone
will surprise us with the news that he has found a method to construct
a transmitter which can generate these Ultra-Microwaves-as we shall
call them, since there is as yet no official name given to them.
A very good indication that many scientists around the globe
are paying attention to these very short waves lies in the fact
that our daily papers have so often had rumors of that bugaboo of
man - the so-called "Mystery Rays." According to these reports,
this "secret brain-child" of science is undergoing intense research
in one or another well-known laboratory; but the explanatory stories
told by some papers are of quite frightful nature.
Inquiries at the laboratories, mentioned in these "baloney" articles,
naturally provoke stern denials in each case. However, they do not
change a bit the real situation, despite the fact that these sensational
stories are written by reporters who do not know what it's all about.
But, since the things they write about are mysteries to them, these
pseudo-science-writers speak and write about "mystery" rays. Science,
however, does not know and does not like "mysteries." Science knows
only of known and unknown facts and, naturally, makes an effort
to find out more about the latter.
Fig. B - This tube converts "invisible" light
into visible rays.
The real story about these so-called "mystery rays" is the fact
that the laboratories mentioned in the sensational articles are
either occupied in learning more about the creation and application
of very short radio waves, down to 0.01-centimeter or "cm." (see
Fig. 1); or they are investigating the wave-range between 0.01-cm.
(Hertzian waves) and 0.00008-cm. (red or low-frequency end of the
spectrum of visible light rays) of which little is so far known.
(The dimension 0.00008-cm. is, as Fig. 2 shows, a tiny part of an
inch, or exactly 1/31,777-in.)
Despite the fact that 1/31,777-in. is not much to talk about,
let's take a chance, and look into the wave-range, even below 0.00008-cm.
At first it may seem unbelievable to some readers; but all of us
are very well acquainted with this wave-range, and what's more,
we know it very well down to 0.00004-cm. wavelength! But this is
not all. Each of us is endowed at birth with means to receive these
tremendously tiny ultra-ultra-microwaves!! The story of this means
is not without a tragical note, for, if friends of ours have trouble
with their "receiver" we say: "What a pity, he (or she) is blind."
Or in case distortion occurs in their "reception," we call them
"near-sighted," or "far-sighted," color-blind, etc. One does not
need to be a scientist to know that this wave-range between 0.00008-
and 0.00004-cm. is the one of visible light, as represented in Fig.
1; note, however, that the frequency limits used in this illustration
are not at all arbitrary ones, in fact, may even overlap.
Governments Are Backing Research
Our discussion has shown us, so far, that we know approximately
what to expect in the wave-range of the shortest of the radio waves,
down to 0.01-cm. We all are quite familiar with the very much shorter
waves of the visible spectrum, as we have seen. But we do not know
very much about that portion of the wave spectrum between the shortest
radio waves (0.01-cm.) and the visible light waves.
As we mentioned before, science does not know much about this
space or gap - at least, not from the point of radio communication
- but there is plenty of research going on in various parts of the
globe to find out more about it.
Fig. C - The principle of Fig. B. can be used
to produce "sound."
And, what is, perhaps, most interesting is the fact that many
of these laboratories are owned by governments which are pleased
to give scientists "with promising ideas" a room in their research
institutes (of course, a room with hermetically closed doors). The
reasons for this great interest are the armies and navies which
hope to find in this unknown realm of the wave spectrum something
which will make a future war more terrible and creepy.
Fig. 1 - The wave spectrum (not in true perspective)
showing the "black gap" with relation to other electrical waves.
The Fight About the "Black Gap"
So far European "science sponsors" have been heavily disappointed,
because there seems to be nothing in this gap "full of darkness"
which can be used to give war machines more power to destroy. The
European scientists, too, had disappointments of their own. They
followed their commercial instincts, instead of considering their
scientific eminence, and, in the hope of someday finding something
in this unknown part of the wave spectrum which could be sold eventually
to munitions makers, etc., did not publish the results of their
In the meantime, American scientists, concerned in this "black
gap" only for its scientific interest, have not only published all
the facts they found, but also have blocked the way to the patent
office for many of the European inventors and scientists by applying,
themselves, for the patents in question!
This happened about a: year ago. Since then, European scientists
have been very busy in their scientific publications "telling the
world" they did everything long before America even thought of these
things! But that's their own trouble. The interesting points in
this fight for fame are, so far as we are concerned, the facts unveiled.
The Photocell - The Starting Point
As we mentioned before, light waves and radio waves are one and
the same thing, but only different in the number of wave-movements
executed per second, and their wavelengths. The elementary proof
that this is true is found in the photoelectric cell. Experiments
with these cells have indicated that an electron emission can be
obtained by directing a light beam, as shown in Fig. 3, upon the
photo-sensitive layer of a photocell.
The photoelectric cell is, therefore, (to speak in terms of radio
technique) nothing but a converter, so to speak, somewhat akin to
the mixer-oscillator stage of the usual superhet. Now, let us look
a little closer into the similarities of these devices.
Fig. 2 - The comparison of centimeter and inch.
The (combined) mixer-and-oscillator stage of the usual superhet.
converts an incoming signal of radio frequency (R.F.) into a signal
of intermediate (lower) frequency (I.F.). The signal remains the
same, but the "form of propagation" changes. About the same thing
happens when we change from an express train into a slowly-moving
local train. A somewhat similar action happens in a photoelectric
cell. A light beam (i.e., an impulse of an extremely high frequency)
is converted into a direct-current impulse (change of "speed," but
signal characteristics remain the same).
This complex conversion happens because the thin chemical layer
of a photoelectric cell acts not only as a converter, but also as
the 2nd-detector, and all by means of a tiny bit of caesium oxide.
By mixing this alkali with other chemicals it was possible to extend
the sensitivity of the photocell far into the wave-range of the
Later on someone found out that the photoelectric effect can
also be obtained when the light beam is thrown, not in the "regular
manner" (directly onto the front of the photo-cell, as in Fig. A)
but also upon the opposite side (as shown in Fig. 4) if only the
photo-sensitive layer is made thin enough to be translucent.
Another important step was taken following an idea, first conceived
by Dr. Zworykin of RCA; namely, to shoot the electrons which were
obtained from a photoelectric cell (with a translucent photo-sensitive
layer) directly upon a fluorescent screen (see Fig. C). How such
a fluorescent screen operates is well known from the cathode-ray
tube, where an electron beam falling upon the fluorescent screen
causes an effect which is referred to as a fluorescent: light. This
design of Dr. Zworykin's may be called an impressive triumph of
modern science over nature's secrets, because he made it possible
to receive invisible "light" in the form of infra-red light and
convert it into visible light. This invention, when applied in the
realm of shipping and the navy, means that it is now possible to
see through fog, because infra-red light is not so readily absorbed
A New Kind of Receiver
But this is not all that makes Dr. Zworykin's invention so important
; he has also opened a way by which the enormous number of frequencies
in the famous "black-gap" can be used for communication, especially
for television transmission.
To understand the full importance of the new device for future
radio communication, let's look again at Dr. Zworykin's wonder-tube,
and compare it with a radio receiver of usual design. This comparison
will give us an idea, how complicated and clumsy our present radio
receivers are in the final analysis.
We need coils and antennas to bring the signal of a transmitter
to the control-grid of the first tube of our receiver. We require
oscillator-mixer circuits to convert the RF, signal received into
an I.F. signal. Then follow the 2nd-detector, the A.F. amplifier
and, finally, the reproducer or "loudspeaker."
Remembering that "radio" waves, and visible or invisible "light"
rays are one and the same thing, but different only in their frequency,
let's see how Dr. Zworykin does the trick.
He needs no coils or tubes in the "input stage"; referring to
Fig. B. only an extremely thin layer of a photo-sensitive chemical
to receive the signal. This layer not only converts the incoming
light signal into an impulse of another frequency, but also rectifies
the signal into a direct current (D,C.) impulse, in the form of
an electron emission. A second thin layer, made of a fluorescent
material, is then used to reverse the conversion process.
However, while the first layer converts a signal downwards in
frequency (transforms light impulse of high frequency into D,C.
impulses of, theoretically, very low frequency), the second layer
of fluorescent characteristic converts a signal of a low frequency
(D.C. impulses) into a high frequency. Or, in other words, it converts
the D.C, electron beam into visible light, which is a signal of
very high frequency.
ToToday we are able to receive and to transmit signals in the
range starting with the infra-red light and ending with the range
of the ultra-violet light. Tomorrow. someone, somewhere, will find
a new photo-sensitive chemical, or a new alloy (in the form of a
combination photoelectric cell and thermo-element) which will do
equivalent tricks in those parts of the wave spectrum which are
as yet unconquered; namely the remaining spot between the outskirts
of the .infra-red rays and the shortest of the short radio waves.
Fig. 3 - The principle of the photoelectric cell
using a reflecting cathode, and an anode rod.
As mentioned before, all the scientists working in this part
of the spectrum have not yet announced their findings, but there
are already certain indications which, when assembled in the proper
order, give us an inkling into the future modes of radio communication,
and the future trends of radio design.
Complicated receivers of today will shrink to a tiny glass ball,
consisting in principle of two chemical layers, or even (and this
is also of great interest) of 2 crystals. p>
A tiny "electron multiplier" arrangement, as it has been described
by Dr. Zworykin and Philo T. Farnsworth, will amplify the signals
received by the first layer (or by the first crystal) employed.
In case optical reception is desired, a fluorescent screen will
transform the amplified electron beam into light impulses. In case
musical reproduction is desired, a second crystal, employed as sound
reproducer, will probably do the trick. The principal design of
such a future radio receiver is shown in Fig. C. Experienced readers
will say: "It must be quite simple to build such a receiver after
Dr. Zworykin did something similar with light rays, and since the
Rochelle-salt crystal-loudspeaker is ready today as standard equipment."
However, it only looks that way. There are quite a number of physical
problems unsolved; but there is firm hope that these will be mastered
in time to come.
Upon consideration of the enormous number of wavelengths, available
in the range of the Ultra-Ultra-Microwaves, everyone can picture
himself in possession of his own receiver and his own wavelength
allotted to him, in a manner similar to the way in which we acquire
today license numbers for our cars. To make this true, another problem
must first be conquered: "How shall we tune these receivers to receive
HoHowever. a solution already exists for this problem, Let's
look how photographers interested in color-photography "tune" their
cameras to "catch" only the image of certain colors of the object
to be recorded. They place filters in front of the lens system.
Colors (or to speak in the language of radio technicians-"frequencies")
not desired by the photographers are "tuned-out" (filtered) by means
of a piece of stained glass and, since we also have to deal with
waves-of this frequency-band, similar tuning methods will probably
Fig. 4 - A photocell having a translucent cathode
which permits light to "pass through."
Finally there is another difficulty to expect. That is the "quasi-optical"
nature of these tiny ultra-ultra-microwaves. Since their frequency
approaches that of visible light, their range will be restricted,
approximately, to a distance corresponding to the optical range
of vision. Antennas of odd form will be required to enjoy programs,
transmitted on these wavelengths, in the apartments of our great
A forecast of such an antenna is shown in Fig. A. As this illustration
indicates, a reflecting mirror, approximately horn shaped, is fastened
at the top of a high post. This form of reflecting mirror is necessary
to receive signals from all directions. And, below this mirror we
see a funnel-shaped or concave device. This funnel contains a large
number of tiny "ultra-ultra-microwave receivers" or receiver cells
- much as the eye of a fly is constructed with innumerable facets,
each of which is an "eye" in itself. They will probably be arranged
in circles, Each circle, containing a great many of these receivers,
is "tuned" by means of suitable filters to a certain frequency;
and the amplified electron-emission will be sent via multiple-wire
cable down to the selector mechanism or control unit and the sound
reproducer in the apartment. Eventually the "tuning" (Le., the movement
of the filters( will be executed by remote-control devices from
This all sounds quite expensive. But we should not forget the
numerous and complicated parts contained in our present-day receivers,
yet how much do we pay for a complete se? Or, for example: in the
beginning of radio, we paid about $50,00 for a radio tube of quite
simple design. What is the present price for a complicated metal
tube? All these price problems are questions concerning only the
competing manufacturers. Our interest is to include amateurs to
think along the lines of the article.
Posted December 4, 2015