March 1948 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.
National defense needs have pushed
back the frontiers of science and technology since time immemorial. Mechanics, chemistry,
medicine, mathematics, psychology, astronomy, electricity, and as of the late nineteenth
century, electronics. Astronomy was useful as a navigational tool and required a
very sophisticated knowledge of geometry and algebra to make it accessible to seafaring
men, cartographers, and land surveyors. Since the early 1900s, radio astronomy has
played a huge role in the advancement of super-sensitive receiver designs. Most
people think of information arriving to them in two or maybe three forms: sound,
visible light, and some (but not many) even consider
radio waves. As over-the-air AM and FM radio broadcasts die out, even fewer people
are aware of radio waves; they certainly don't think of their WiFi or cellphone
signals as radio or anything else for that matter ((i.e.,
oblivious to what makes them work). Certainly, only a very small percentage
ever consider that night sky objects - which of course are there during the daylight
hours, too - emit electromagnetic radiation at frequencies other than those of visible
light. In fact, it has been discovered over the last century that much more information
exists outside the visible light band than within it. Pulsars, black holes, and
much of the history of the universe would not be known if not for the study of energy
other than that which we can see visually. When this article appeared in 1948, Dr.s Arno
Robert Wilson had not yet, using the Bell Telephone Labs sugar scoop antenna
in New Jersey, identified the
cosmic background radiation left over from the universe's creation.
Articles here on RF Cafe which mention the Dr. Robert W. Wilson and Dr. Arno
The Maser & Sugar Scoop Antenna: Receiver for Signals from Space,
Bell Telephone Laboratories Project Echo,
The Amazing Maser: The Jewel That Conquers Space,
Cosmic Radio Signals from Sun and Stars, and
Other related articles: "How
We Listen to Stars and Satellites" - January 1958 Popular Electronics,
Astronomy and the Jodrell Bank Radio Telescope" - February 1958 Radio &
TV News, "Radio Astronomy
- Low Noise Front-Ends" - June 1954 Radio & Television News, "Radar
Explores the Moon" - May 1961 Popular Electronics, "Cosmic Radio Signals from
Sun and Stars" - March 1948 Radio-Craft
Cosmic Radio Signals
From Sun and Stars
Front view of the 25-foot Wurzburg antenna beamed at the sun.
The giant equipment illustrated on our cover and on this page is nothing more
nor less than a radio receiver. Further, it is a radio which receives static only!
Building a receiver to pick up static may seem pursuit of the nonessential, but
the designer of this set went even further. He built it to reject practically all
the crackles and pops we get on our broadcast radios and to receive static on very
high frequencies only - on the wave lengths at which the sun and stars radiate.
Scientists of the Bureau of Standards believe that knowledge of this cosmic static
- particularly of the radio waves generated by the sun - may be very useful to communications
engineers, astronomers, and meteorologists. It may help to expand greatly our knowledge
of the universe, and answer the old question: what effect have the stars and sun
on this world and on human life?
Ordinary static is too well known to the broadcast listener, particularly those
living within range of that great "radio center" of terrestrial static - the Caribbean
thunderstorm region. Individual flashes of lightning there combine to produce steady
crashing, which is transmitted over great distances.
Intensity of atmospheric noise drops off as the frequency increases, and finally
ceases to be a practical problem.
At that point cosmic radio noise takes over. Heard as a low, steady hiss, it
may become an important problem to the listener on high frequencies as radio equipment
is improved. Already advances in design of both v.h.f, and u.h.f. equipment have
greatly reduced internal noise from tubes and other components. High-frequency radio
noise may then become the factor which will limit the sensitivity of FM, television,
microwave telephone, and similar equipment.
FM radio signals suppress this type of static within a certain range of the transmitting
station. At considerable distances from lower-power stations the strength ratio
between the FM program and the cosmic noise might be such as to drown out the program
completely. So the ordinary listener may find noise from the sun and stars an immediate
and practical subject of interest.
The project, which use the great Würzburg parabolic antenna shown here,
will observe and analyze radio noise generated by the sun, determining the range
of frequencies in the solar broadcasting spectrum and the strength at which they
can be received on this planet. It will also attempt to correlate solar noise with
other solar, interstellar, and terrestrial phenomena.
Two of these parabolic mirrors are now installed at the propagation laboratory
of the Bureau of Standards at Sterling, Virginia. Twenty-five feet across, they
can capture a large cross section of the solar energy beamed at the earth. The mirrors
are controlled automatically, like an astronomer's telescope, to follow the sun
constantly through the day. By using 2 receivers, different types of studies can
be undertaken simultaneously, or a broader band of frequencies can be followed.
The first receiver - now being installed - will be used initially for studies ranging
480 to 500 mc.
Solar noise appears to be fundamentally the same as cosmic noise, and is heard
as a steady hiss whenever the operator substitutes a pair of headphones for his
recorder. It has also an undulating component superimposed on the stable noise,
with variations sometimes of great rapidity, which sound like puffs or swishes lasting
a second or less. The swishes sometimes overlap, resulting in a grinding noise.
This may manifest itself on the screen of a standard television set as streaking
or picture jumpiness. Occasionally there are intense, prolonged bursts of solar
transmission lasting several hours (see Sunspots and Radio, by Harlan True Stetson,
in Radio-Craft, February, 1948). These cause a radar to "go blind" when pointed
in the sun's direction.
Like many other important scientific projects, the cosmic-noise study started
as an amateur effort. The existence of cosmic radio waves had long been suspected
- they had even been given a name, the Jansky effect. Among the students of this
effect was an Illinois radio engineer, Grote Reber, who built a large sheet-metal
parabola and for some years spent most of his nights collecting records from various
parts of the sky. Among his important discoveries was that the center of the Milky
Way is a powerful source of cosmic radio energy. His work attracted the attention
of the Bureau of Standards, already interested in the problem of the sun's effect
on radio propagation. Unquestionably the leading student of cosmic radio in the
United States, he was called in to head the solar radio study project, exchanging
his sheet metal parabola for the big Würzburgs. The, home-built mirror, however,
is still doing duty in studies of radiation from the stars. The Bureau, at present
chiefly interested in the sun's broadcasts, has 2 important problems to solve in
the field - of cosmic noise: first, the question of intensities-vs-frequencies -
in other words, on what bands are the stars and star-clouds radiating, and what
bands come in strongest; second, mapping the sky's sources of cosmic signals. The
Milky Way center is already known to be a strong source. Another one is in Cygnus
(the Swan). Cause of the radiations is not definitely known. It has been suggested
that, because of the similarity of the sound produced in the radio receiver, it
may be due to thermal agitation of charged particles. The billions of stars which
constitute our galaxy, say the Bureau's scientists, throw off a large amount of
material which expands and tends to fill from the intervening space as a very thin
gas. These atoms of gas may be ionized by starlight, producing positive and negative
particles which radiate both visible light and radio waves.
A notable feature of the radar method of exploring the heavens is that such areas
of activity may be located even though they may be hidden (as in the case of the
Milky Way center) by dense dark clouds which would baffle astronomers. The "electron
telescope" may extend the knowledge of the astronomer as much as the electron microscope
has already broadened the horizons of the searcher into the realm of the infinitesimally
Practical applications of the new study are expected to be immediate. For example,
a radio sextant might be built which would shoot the sun by noting the direction
of arrival of solar noise. Such an instrument would be a boon to navigation in foggy
areas. Knowledge of solar radiation conditions would also be valuable in short-range
forecasts of radio propagation. But by far the greatest value of the study is likely
to be the gaining knowledge of things not now understood and possibly not dreamed
For example, when Grote Reber pointed his radio telescope at the Milky Way center,
he rather expected to find a center of radio noise intensity. Most galaxies have
a dense central nucleus, but the center of ours - if it exists - is hidden in dark
clouds presumably of cosmic dust. The burst of signal strength from that area confirmed
the suspicions of astronomers, and proved that the radio telescope could make discoveries
denied even to Palomar's great light lens. But no one knows the cause of the intense
source of signals in the constellation of Cygnus. Investigation of this and other
discoveries which are almost certain to be made is likely to give us a new grasp
of the universe, and will more than likely help to give us better radio reception
right on this earth.
Posted January 27, 2015