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 1943 QST magazine 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
New Horizons probe last July.
Astronomy and Amateur Radio
Hitch Your Hobby to a Star
By Hollis M. French, * W1JLK
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 amateur communications.
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 or both.
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.
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 approximately 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 approximately 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 cycle.3
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 astrophysics, 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
astrophysical 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 radio waves.
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 DX.
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 days.
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 so forth.
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 1932.
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.
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 12, 2022
(updated from original post on 4/25/2016)