November 1943 QST
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
QST, published December 1915 - present (visit ARRL
for info). All copyrights hereby acknowledged.
It is always nice to read an article that encompasses more than
one of my hobbies, whether it be amateur radio and amateur astronomy
like this one, amateur radio and model rocketry, or amateur radio
and radio controlled airplanes. I don't recall ever seeing an article
that combined astronomy and model airplanes. In this QST
piece, author Hollis French expounds on the necessity for Hams to
understand the effects that atmospheric phenomena, caused primarily
by our sun's periodic and intermittent activity, have on radio signal
propagation. Properties of the ionospheric layers had by 1943 been
pretty well surmised based on cause and effect relationships through
indirect observation since at the time no sounding rockets had been
launched into the upper atmosphere to obtain in situ measurements
of ionization, magnetic fields, and free electron activity. Today's
knowledge of course is much more detailed and formulated thanks
in large part to amateur operators over the succeeding decades.
A contemporary analogy would be comparing what we knew about the
surface of Pluto before and after the
probe last July.
Astronomy and Amateur Radio
Hitch Your Hobby to a Star
By Hollis M. French, * W1JLK
Radio development has entered a stage in which the amateur experimenter
of necessity must become an amateur in other vitally related earth
and sky sciences. He must learn to understand and use new tools
and apparatus in order to make the most effective use of the very-high
and higher frequencies. The factors which govern weather and the
electromagnetic field of the earth -astronomical, meteorological
and topographical - as well as conditions in the ionosphere and
in the upper and lower troposphere all serve to determine the range
of communications just as definitely as do power input, circuit
efficiency or mechanical design of transmitting and receiving components.
After the last war, the radio amateur conquered the oceans; after
this war, he will explore and master the "ocean of air" in which
so much of our power was wasted in other years. Now, while wartime
restrictions hold ordinary "hamming" in abeyance, is the time to
study the science" of astronomy and aërology for their bearing
Radio is not strictly a terrestrial art. With advancing knowledge,
ever closer relations appear between the science of astronomy and
the art of radio communication. These are more evident as we pass
the limitations of the old astronomy of position and enter the fascinating
field of astrophysics, where radiation becomes the foundation of
the science. Leaders in the field of research, such as the Radiation
Laboratory of the Massachusetts Institute of Technology, today employ
astronomers and radio engineers alike among their physicists engaged
in the investigation of the general field of radiation and its manifold
applications to the service of man. In many projects, the astronomer
and the radio engineer must work closely on the same problem.
In the study of the propagation of waves, for instance, we find
ourselves in a field where a thorough understanding of astrophysics
is required to understand observed effects. The sun is a star, and
certain aspects of the behavior of radio waves in the earth's ionosphere
are functions of activities taking place within and upon the surface
of this star. The earth's satellite moon likewise has been accused
of complicity in the changing patterns of wave propagation. We may
well disregard "signals from Mars" or hypothetical influences reaching
us from distant stars, but the amateur will be better informed about
where his signals are going, and why, if he is willing to look into
a few topics of practical astronomy.
We leave for treatment in a later article ·the influences of
the sun upon radio transmissions in the very-high, ultrahigh and
super-high frequencies through variations in temperature, humidity
and gradients of pressure in the lower atmosphere. The resulting
discontinuities between adjacent air masses are potent factors governing
communications, but their discussion properly belongs in the science
of aerology rather than astronomy. The tidal or gravitational effects
of both sun and moon may be considered as belonging to either science
Solar Radiation and the Ionosphere
We examine first, therefore, the direct influences of solar radiation
upon the earth's ionosphere. There are daily, seasonal and long-period
variations of a cyclic nature which affect distant reception of
all radio frequencies and which are directly attributable to solar
radiation. The more familiar of these phenomena are the daylight-to-dark
shifts of transmitting range and the summer-to-winter variations.
Both of these effects we understand to be related to the position
of the sun with respect to the observer's horizon. Similar effects,
differing from the solar influences in degree and in period, have
been traced by H. T. Stetson1 to the position of the
moon in the observer's sky. One explanation of these phenomena postulates
electrostatic fields for sun, moon and earth, with interaction governed
by mutual potential differences. A proved hypothesis applying only
to solar influences is that of the ionization of distinct atmospheric
layers of differing densities.
Many radio amateurs, like the late Ross A. Hull, have included
amateur astronomy in their hobby interests. This article points
out ways in which astronomy serves the advancement of radio.
Succeeding articles on "Aërology and V.H.F. Wave Propagation"
and "The Influence of Topography on V.H.F.-to-S.H.F. Communications
" will further demonstrate the importance of a knowledge of
these related sciences to the radio communications art, and
will discuss the construction and use of instruments for research
and experiment such as the barometer, psychrometer, anemometer,
resistance-type thermometer and hygrometer, recording devices,
the pilot balloon and all the interesting "radiosonde" gear
used in soundings of the lower atmosphere. Other new tools which
will be suggested for the radio amateurs use include contour
maps, the level and theodolite - all strange gadgets to practitioners
of the mike and key, perhaps, but definitely useful in adapting
ourselves to present-day and probable future developments in
We may consider the sun to be an enormous transmitter, with self-contained
power supply, which radiates energy over a broad band of wavelengths
of an order of magnitude so small that, instead of measuring them
in meters and centimeters as we do radio waves, a special unit called
the angstrom is applied. This unit has a value of about one ten-millionth
of a millimeter. The solar band of wavelengths includes heat rays,
light rays, ultraviolet rays, X-rays, gamma rays, and other rays
of yet shorter wavelengths, some of which are of lethal character.
Fortunately for life upon the earth, rays shorter than about 2900
angstroms are filtered out before reaching the surface of the earth
by a transformation in the upper atmosphere brought about by the
ultraviolet portion of the sun's radiation. This upper region, called
the ionosphere, lies between 30 and 250 or more miles above the
surface of the earth - above both the troposphere, or lower atmosphere,
and the stratosphere. Here the separation between atoms is so great
and collisions between them so much rarer than in the denser lower
atmosphere that, when an atom becomes ionized by being robbed of
one or more of its electrons by the action of the ultraviolet rays,
it remains in that condition for a relatively long time. Thus we
have an ionized region of a composition so different from that of
the lower atmosphere that radio waves are refracted differently.
Moreover, there are in the ionosphere itself strata of differing
densities, and therefore of differing indices of refraction, which
constitute a distinct series of layers. This region has been investigated
and, for convenience in comparison, the different layers have been
labeled D, E, F, F1 and F2, according to their
relative average heights above the surface of the earth. (See Fig.
2.) None of these layers remain constant in height, and it is the
variation in their heights, combined with their various refracting,
reflecting and absorbing capabilities, that govern to a very large
extent the conditions of long-distance radio transmissions. The
heights of the ionized strata and the degree of ionization may vary
in accordance with the angle of incidence of the solar rays and
also in accordance with changing conditions within the sun, which
affect the character and amount of its radiation. Diurnal and seasonal
variations arise from the first cause, longer-term cyclic and sporadic
variations from the latter.
Fig. 1 - Relative size of sun, earth and
sunspots. A stream of intensified radiation originating in a
region of sun-spot disturbance traces a curved path through
space by reason of the rotation of the sun combined with the
decreasing velocity of the stream beyond its point of origin.
From an ideal engineering viewpoint, the power supply of our
great solar transmitter appears to be very unstable. It is burning
up. It overheats to such a degree that the atoms of its incandescent
gases are constantly being broken down into simpler structures.
Subatomic energy thus released flies off into space as solar radiation.
While the entire substance of the sun is constantly emitting energy
under enormous pressures and at terrific temperatures and incredible
velocities, there occur also from time to time sudden surges of
even more violent emission - veritable explosions - at isolated
points on the solar surface. (See Fig. 1.) These spots appear relatively
dark against the intensely bright photosphere of the sun, so that
it is easy for observers to watch for their appearance and trace
their course across our field of vision as the sun revolves about
its axis over a period of about twenty-seven days. From these "sunspots,"
beams of intensified solar energy emission are projected to very
great distances. When one of these beams sweeps through our atmosphere,
the normal phenomena of solar radiation are strikingly modified
by the resulting changes in ionization. It is of interest to note
that the streams of sunspot radiation are not necessarily straight-line
beams, as from a searchlight, but generally are scimitar-shaped.
The distortion is caused by the rotational speed of that portion
of the sun's surface from which the rays may be emitted. This characteristic
partly accounts for the fact that efforts to predict precisely the
beginning of the effect upon the atmosphere at the observer's zenith
through observation of meridian passage of a sunspot group have
failed. Terrestrial effects have been observed from 34 hours before
to 86 hours after the time predicted on the basis of straight-line
projection at the speed of light. It is further evident that the
propagation speeds of sunspot emissions are only about one per cent
of light speeds.2
When all or e factors involved are better known and understood,
it should be possible to make reasonably precise predictions of
coming change wave-propagation conditions caused by various forms
of solar radiation. Two cycles, in addition to those of diurnal
and seasonal variations, now are recognized. One of these - the
solar rotational cycle, of approximately 27 days - marks the average
time between reappearances of the same sunspot group at the central
meridian of the sun. The approximate time definition arises from
the fact that the substance of the sun is gaseous and, therefore,
a spot on its surface will not necessarily rotate at a constant
rate. The rotation period at the solar equator is approximately
24.6 days, and this period increases with rising latitude. The principal
appearances of the disturbances known as sunspots are between solar
latitudes 5° and 40°, and the mean rotational period of
this belt is approxi-mately 27 days.
The second solar cycle depends upon the variation in number and
average size of the sunspots. Its duration has been observed to
be approxi-mately 11.1 years from one maximum to the next. There
is, however, a considerable degree of variation in the length of
this average period and there is no sharply defined maximum or minimum
period. Nevertheless, this "sunspot cycle," which has been observed
now for 17 cycles or nearly two hundred years, is the most significant
of all solar cycles, and many terrestrial effects are closely linked
with it. Magnetic storms, earth currents, ionization of the upper
atmosphere, the aurora, solar ultraviolet radiation and sunspots
all increase and decrease together, in the same approximate 11-year
Quantitative measurements of the effects of solar radiation upon
the medium frequencies were commenced by Dr. G. W. Pickard as early
as 1926.4 Correlation of these measurements with the
sunspot numbers on the Wolfer scale was continued by Professor Harlan
True Stetson, Director of the Perkins Observatory (astronomical)
and Professor G. W. Kenrick of Tufts College Electrical Laboratories.5
Sporadic effects of solar eruptions, resulting in "fade-outs" on
the high frequencies, were investigated by Dr. J. H. Dellinger of
the National Bureau of Standards.6 J. A. Pierce, W1JFO,
and Melvin S. Wilson, W1DEI, among others, have published summaries
of observations of solar radiation effects upon the lower portion
of the very-high-frequency range.7 By means of these,
numbers of amateurs, otherwise innocent of any knowledge of astro-physics,
have become familiar with such terms as "Dellinger effect," "skip
distance," "critical frequencies," "virtual height," "aurora skip"
and "sporadic E-layer skip."
Many amateurs undoubtedly will be quite content to accept, at
second-hand, any astro-physical data relative to their hobby. For
those who have a mind to investigate these things for themselves,
to seek out first causes and perhaps to reach a position where they
may be able to make further contributions to the field of knowledge,
there are excellent textbooks on astronomy, such as the two-volume
edition of "Astronomy" by Russell, Dugan and Stewart of Princeton
University Observatory, as well as practical manuals on the construction
of observational gear. One of the best of these is Ingalls' "Amateur
Telescope Making"; another is George Ellery Hale's "Signals from
the Stars," in which he describes a complete solar telescope and
spectrohelioscope of an inexpensive type which, as he says, "can
be built and used by professional or amateur astronomers and geophysicists
and by radio students interested in the possible influence of solar
eruptions on radio transmission."
Fig. 2 - The difficulty man faces in plumbing
the vast depths of the "ocean of air" is indicated by the scale
of this drawing, if the reader remembers that there is yet more
beyond. The drawing attempts to include as many points of information
as possible, scaled against the indicated heights above sea
level. The division by dotted lines roughly separates the horizontally
homogeneous regions of upper and lower atmosphere (not to be
confused with the layers of intensified ionization, not all
of which are shown). Soundings of the ionosphere have been possible
only through spectroscopy and the reflections of high-frequency
The amateur with a truly scientific approach to his hobby will
study all available sources of reliable information and ground himself
thoroughly in the proved fundamental principles of every field of
knowledge having a bearing upon his own research. He will patiently
test each new theory by known facts. He will carefully record the
results of all observations for further study, comparing, analyzing,
separating the unknown factors, and testing over and over again.
A relevant fact omitted may destroy the opportunity for a real contribution
to the development of the art.
The science of radio communications unfortunately has been afflicted
with a lunatic fringe spun from pseudo-scientific hypotheses comparable
to the claims of astrology in the field of astronomy. Some years
ago a "research" article was published in a popular radio magazine
in which the author proposed a lunar theory affecting 5-meter DX
which, in substance, suggested that the moon exerts a tidal effect
upon the earth's atmosphere, as well as upon the earth and the sea,
and that the resulting distortion of the atmospheric layers accounted
for periodic increases in the range of propagation for 56-Mc. waves.
This author counseled his readers therefore to "watch the periods
of time between three and four days before and three and four days
after full moon for long-distance DX (sic) on 5 meters this summer."
What is wrong with this picture? "A little knowledge is a dangerous
thing." The gravitational pull of the sun and moon undoubtedly do
create atmospheric tides and it is conceivable that herein may lie
the explanation for one of the many ways in which the propagation
of electromagnetic waves is affected, although the magnitude of
increases in effective transmitting distance from such a cause is
probably so slight as to be difficult of measurement. However, the
theorist obviously was innocent of knowledge of the simplest astronomical
principles to a degree that enabled him to ignore established facts.
If such an effect is caused at full moon by the alignment of earth,
sun and moon, the tidal effect is even more marked at the time of
new moon, and more still at the periods when either new moon or
full moon happens to coincide with the time of the moon's perigee
(moon's closest approach to the earth). Nevertheless, this lame
lunar theory was widely accepted in the five-meter fraternity, and
many a voice was heard on the air passing it along as the latest
and most scientific explanation for the mysteries of five-meter
The keenest enjoyment of his bobby is experienced by the amateur
when his progress in the art is by means of his own careful study
and research, rather than by a process of thumbing rides on the
vehicles constructed by other minds. It is with the purpose of encouraging
the thoughtful and scientifically minded amateur that these articles
are offered on topics which may at first glance seem to some to
be but slightly related to amateur radio as they have known it.
The following is reprinted from a recent issue of the U. S. Coast
Guard Magazine, a service publication devoted to the interests of
the U. S. Coast Guard:
Among the stranger people on this earth are radiomen. A radioman
is a person either going on or coming off watch.
Contrary to popular belief, radiomen are not crazy. A radioman
has two brains: one perfectly normal brain, which is destroyed during
the process of learning radio, and another which is ill a constant
state of turmoil and is used proficiently in his work. This latter
brain is filled with dots and dashes and procedure signs.
Radiomen are like groundhogs. They seldom see the sun, coming
up topside only on Saturday mornings at the special request of the
commanding officer. If the sun is shining and a radioman sees his
shadow, he goes below and everyone knows there will be six more
Sitting at his typewriter a radioman receives an endless story
of the world flowing through his ears, unable to get out because
both ears are stopped up by headphones. The stuff flows out through
his fingers and is given out as press news, weather messages, and
When conversing with a radioman, do not try to point your story
by asking if he remembers "the message to Garcia," because he will
jump and scream, "What's the number of it? Who sent it? If it's
lost, it didn't come in on my watch!"
Radiomen live on black coffee and cigarettes" All through the
long midnight watches they sit and dit and dah, so tired and weary
of it all and wondering why they ever chose radio as a profession.
When they go off duty they hurry home to their little "ham" radio
sets and just dit and dah to their heart's content.
Girls who fall for radiomen will find they are courted with considerable
sparking, and after they are married will receive much broadcasting
both loud and long.
Radiomen are found on all ships and in all stations and are quite
harmless if left alone, fed occasionally, and given annual leave
so they may rig up new "ham" outfits at home!
* Asst. Technical Editor, QST.
1 H. T. Stetson, "On the Correlation of Radio
Reception with the Moon's Position in the Observer's Sky," Perkins
Observatory Miscellaneous Scientific Papers, Reprint No.8, about
2 "Getting the Signal Across," (by six engineers
of RCA Communications, Inc.) Relay, Sept. 1943.
3 J. H. Dellinger, "Some Contributions of Radio
to Other Sciences," reprinted from the Journal of the Franklin Institute,
Vol. 228, No. I, July, 1939.
4 G. W. Pickard, "Correlation of Radio Reception
with Solar Activity and Terrestrial Magnetism," Proceedings of the
I.R.E., Vol. 15, 1927, Nos. 2 and 9.
5 H. T. Stetson, "Radio Reception and the Sunspot
Cycle," reprint from the Proceedings of the Fifth Pacific Science
Congress, Toronto, 1934.
6 J. H. Dellinger, "A New Cosmic Phenomenon."
QST, Jan. 1936; "High-Frequency Radio Fadeouts Continue," QST, June
1936; "Radio Fadeouts Through 1936," QST. Feb. 1937.
7 J. A. Pierce, "Interpreting 1938's 56-Megacycle
DX." QST, Sept. 1938; M. S. Wilson, "Five-Meter Wave Paths," QST,
August and September, 1941.
Posted April 25, 2016