On the Thirtieth Anniversary of Soviet Physics

Soviet Radiophysics over 30 Years

B. A. Vvedenskii and M. I. Ponomarev

Radio engineering is one of the most striking examples of a technical discipline that has maintained very close contact with physics. This is explained above all by the fact that, by its very nature, radio engineering is directly concerned both with electrodynamics (questions of radiation and propagation), and with electronics and electron optics (electron tubes, secondary-emission tubes, cathode-ray devices), and with molecular physics (gas-filled devices, questions of ionization of the upper layers of the atmosphere). Almost always the processes encountered in the field of radio are processes of electrical oscillations (not infrequently accompanied by mechanical oscillations), such as, for example, the oscillations of lumped circuits or the oscillations of distributed systems and of volumes bounded by metallic walls, and oscillations propagating around the entire terrestrial globe under the complex conditions determined by the characteristics of its surface and atmosphere. In a number of important cases, radio engineering, like other branches of technology, must leave the long-familiar ground of linear oscillations and deal—chiefly in connection with oscillations of electronic devices—with nonlinear oscillations. Finally, a number of problems lead to the use of systems in which both electrical and mechanical oscillations occur simultaneously (electroacoustics, the field of piezoelectricity).

The solution of such problems requires, besides considerable physical erudition, also the ability to use the appropriate mathematical apparatus. These and similar circumstances led to the separation from physics of a certain branch discipline called radiophysics, which is, in a sense, a connecting link between physics and radio engineering. Certain areas of radiophysics have in turn become separate; such sections as, for example, electroacoustics and questions of television would be irrational to include in the present survey. Likewise, the question of electronic and ionic devices as a whole now also constitutes an independent field. Finally, it is naturally necessary to delimit the field of radiophysics and

radio engineering. Without intending to give a systematic account of the achievements of Soviet radio engineering, we shall nevertheless indicate below certain moments in its history, when this is required by the demands of continuity in the exposition.

The term “radiophysics” is hardly even two decades old; but in essence radiophysics was born with the work of Hertz, i.e. even before the appearance of the term “radio” and of radio engineering itself, or “wireless telegraphy.” Thanks to the work of the inventor of radio, A. S. Popov, the homeland of radio must, in fairness, be considered Russia; but radiophysics and radio engineering in pre-revolutionary Russia developed weakly. In particular, the growth of radiophysics in old Russia was very strongly hampered by the pre-revolutionary dependence on foreign capital, which in matters of radio was very strong. Only the Naval Department, in the person of its plant in Galernaya Harbor, represented a somewhat gratifying exception, supporting, at times quite fruitfully, the glorious traditions of A. S. Popov.

A certain, and perhaps even significant, revival of work in radiophysics began at the height of the World War of 1914–1918. Here one cannot fail to recall certain technical innovations carried out in Russia at that time, such as, for example, the establishment of radiotelephone communication near Petrograd at the end of 1914; radio-direction-finding stations, in particular for the direction finding of airplanes; radio communication with submarines; the manufacture of the first thermionic instruments and even the creation of an initial theory of the tube generator (N. D. Papaleksi, M. V. Shuleikin, and others). In 1916 M. V. Shuleikin had already published the first mathematical expression for sidebands under modulation; V. P. Vologdin, as early as 1911, began his work on high-frequency machines, which made it possible for the first time to establish radio communication between the USSR and the USA, and which are now successfully used for the purposes of high-frequency hardening of steel products. A. A. Petrovsky’s well-known book The Scientific Foundations of Wireless Telegraphy appeared in 1913.

By the time of the Great October Socialist Revolution there were very few young specialists in the field of radio in the country, although a certain scientific-pedagogical center already existed at the Electrotechnical Institute of Petrograd, later headed by I. G. Freiman. The technical base, in the form of a few radio stations (Khodynka, Detskoye Selo) and laboratories (Petrograd, Odessa), was weak and already obsolete. The radio industry was only just coming into being. Therefore Soviet radio had to develop, if not from the very beginning, then in any case from a low level. However, the healthy shoots that existed by 1917, under Soviet power gave a rapid and abundant growth.

Lenin and Stalin, already at the beginning of the Great October Socialist Revolution, widely used radio means, addressing soldiers and sailors; this was the prototype of our modern radio—

things. The entire development of radio in the Soviet state is inseparably linked with the names of Lenin and Stalin.

Thanks to the constant and devoted support of the Soviet government and, in particular, of V. I. Lenin himself, by the 1920s—greatly to the astonishment of Western Europe—technical achievements began to appear in the Soviet country that were not inferior to foreign ones and, in a number of cases, even surpassed them. A young cadre of our own also emerged and began to grow rapidly.

The genius of V. I. Lenin, of course, could not fail to notice the exceptional possibilities of radio engineering and its significance for the socialism then being built. Vladimir Ilyich’s winged words about a “newspaper without paper and without distances” and about a “meeting with an audience of millions” are known to every Soviet radio engineer. The Soviet government surrounded with exceptional attention the Nizhny Novgorod Radio Laboratory, organized by Vladimir Ilyich’s personal instruction and under the scientific direction of M. A. Bonch-Bruevich. The production by M. A. Bonch-Bruevich, with the energetic participation of P. A. Ostryakov, of the first tubes already of a semi-modern type, both receiving and generator tubes; the construction of radiotelephone radio stations using powerful tubes of original design; and a number of other works won the Nizhny Novgorod Laboratory named after V. I. Lenin a leading position for the period 1918–1926, which was also marked by the Soviet government’s twice awarding the Laboratory the Order of the Red Banner of Labor (1922–1924).

Radio-engineering or radio-physics centers also arose in other cities. Thus, in 1919 M. V. Shuleikin founded a department of radio engineering at the then Higher Technical School (now the Moscow Power Engineering Institute named after V. M. Molotov). In 1920 L. I. Mandelstam and N. D. Papaleksi organized a similar center in Odessa, and A. A. Chernyshev a radio laboratory in Leningrad at the Polytechnic Institute. From 1923, the Central Radio Laboratory arose in Leningrad with the participation of L. I. Mandelstam, N. D. Papaleksi, D. A. Rozhansky, M. A. Bonch-Bruevich, A. F. Shorin, V. P. Vologdin, and others.

The end of the second decade of our century was an epoch of struggle by the electron tube for the leading role in radio engineering. In this connection it is especially important that the production of electron tubes, besides the Nizhny Novgorod Laboratory, began to be mastered in Odessa (N. D. Papaleksi, E. Ya. Shchegolev, K. V. Stakhorsky) and in Leningrad (M. M. Bogoslovsky; there, in particular, S. A. Vekshinsky began his work, whose name is inseparably connected with the subsequent development of the Soviet electron tube). In addition, in a number of places electron tubes for special purposes were being successfully manufactured (in small quantities). This work could not have been successful had it not been preceded by a thorough development of questions of obtaining vacuum, cooling tubes—in particular by water—developing glass-blowing skills, and so on. To this same period belong the first experiments

on sound reinforcement, on various methods of modulation, on the study of the propagation of long waves, and also on questions of ultrashort waves.

Approximately from the middle of the 1920s, in parallel with the emergence and growth of the Soviet radio industry, there also began a clearer demarcation between radio engineering and radiophysics, which subsequently received consistent development in the Stalin five-year plans. The moment described is the moment at which the radiofication of the country began. Radiofication proceeded above all through the construction of separate broadcasting radio stations and communication radio stations. The very first Soviet radio station, built in 1922 by the Nizhny Novgorod Radio Laboratory thanks to the great assistance of V. I. Lenin, was at that time the most powerful in the world.

Since then the Soviet Union has steadily maintained world primacy in powerful radio-broadcasting stations. In the development of these stations, the services of M. A. Bonch-Bruevich, A. L. Mints, and others are especially great. V. P. Vologdin was the creator of the first powerful mercury rectifiers, which provided power for these stations; he also developed the theory of rectifying devices. The works of M. A. Spitsyn and A. M. Kugushev also had substantial importance in the creation of Soviet powerful mercury rectifiers.

The Stalin five-year plans created the Soviet radio industry. Thanks to the exceptionally great assistance of Joseph Vissarionovich Stalin, Soviet radio construction received tremendous development. A number of Soviet radio plants are being created, manufacturing large quantities of broadcasting and communication radio receivers from domestic materials. The country is being covered with a network of radio centers.

It is difficult to overestimate the role of the Soviet radio industry in the Great Patriotic War, when our radio industry contributed to a significant degree to the transformation of the Soviet Army into the most maneuverable army in the world, after Comrade Stalin had defined the role of radio as the most reliable means of communication under the conditions of modern maneuver warfare.

By the time the Soviet radio industry arose, the electron tube had already decisively won for itself the leading role in radio engineering; therefore the Low-Current Trust that was organized at that time paid serious attention to the serial production, aiming at mass production, of electron tubes, from receiving tubes to powerful generator tubes with water cooling. In 1925 Soviet industry was already capable of undertaking the construction of the Tehran radio station. Approximately from this same year the Nizhny Novgorod Radio Laboratory began to work on short waves, thereby joining in the contest then flaring up in world radio engineering between long and short waves. A year later, work on quartz stabilization began. And from approximately this same period, the abundance of purely acoustic questions in the field of electrical communications brought technical acoustics and electroacoustics into being as a separate discipline.

The principle of radio transmission rests upon electromagnetic emission (radiation), whence the very name “radio.” But only systems of conductors in which electromagnetic oscillations take place are capable of radiating electromagnetic energy. Thus, the theory of electromagnetic oscillations is, to a certain extent, the more primary one. Further, the radiated electromagnetic, i.e. oscillatory, energy must reach the receiver, propagating along the surface of the terrestrial globe: hence the theory of the propagation of radio waves. These considerations also determine the basic divisions of radiophysics; the subsequent exposition is constructed accordingly.

OSCILLATIONS OF LUMPED CIRCUITS

In the first stages of the development of radio, exclusively damped oscillations were used: these were almost always linear oscillations, possessing the property that their amplitude depends entirely on the initial conditions, on the “push” that caused these oscillations.

Linear oscillatory systems (“circuits”) consist of a combination of capacitances and inductances and the inevitably present resistance. If neither the capacitance nor the inductance changes with time, then the whole process is governed by a simple and well-studied linear differential equation. Therefore the theory of linear oscillations has existed for a comparatively long time in a very complete form; its conclusions have been brought to the utmost clarity, intelligibility, and technical convenience, and have long since been presented with great completeness in courses, as, for example, in the books of I. G. Freiman, M. A. Bonch-Bruevich, A. I. Berg, B. P. Aseev, and others.

But linear oscillations in radio, just as in any other field, are in essence only a certain abstraction, to which real—nonlinear—oscillations approximate only to a certain degree. Thus, the oscillations of the most ordinary pendulum are already nonlinear if one deals with finite (and not vanishingly small) amplitudes. Electric oscillations are likewise nonlinear if the circuit contains coils with iron; systems that generate undamped oscillations by means of arc generators, electron tubes, and analogous devices are nonlinear in principle.

One cannot think that radio engineers stopped helplessly before the solution of nonlinear problems. By means of approximate calculations, consisting of a more or less skillful combination of elements of elementary theory and direct experience, powerful generators, complex receivers, and many other radio devices were built and are being built (and very successfully). However, this entire very valuable collection of technical “recipes” lacked a unifying idea. The Dutch investigator van der Pol, and also the Englishman Appleton, approached the problem of creating a theory of nonlinear oscillations in radio engineering. The results and conclusions obtained by them are valuable and fruitful, but nevertheless they leave much to be desired with respect to

“rigor (and consequently, also persuasiveness), for intuitive elements play a large role in their reasoning.

Soviet physicists, chiefly those of the schools of L. I. Mandelstam and N. D. Papaleksi, who united and headed work carried out in a number of scientific institutions, succeeded in bringing complete clarity to this problem. The works of N. M. Krylov and N. N. Bogoliubov, Yu. B. Kobzarev, and others contributed substantially to this.

A. A. Andronov showed how well questions of nonlinear oscillations can be investigated by means of methods developed for other purposes by A. M. Lyapunov and Henri Poincaré. The geometrical representations thus obtained (“state curves in the phase plane”) and the method of approximate solution of nonlinear differential equations by expansion in a certain “small parameter” connected with the constants of the system proved to be a very powerful tool not only for solving a number of nonlinear problems, but also for predicting new phenomena in this field.

A rigorous theory was obtained for a number of interesting and important nonlinear phenomena, such as the phenomena of “capture,” or forced synchronization of an oscillating nonlinear system by an external electromotive force; the phenomenon of “pulling” (A. A. Andronov and A. A. Witt, 1930); intermittent generation (G. S. Gorelik, V. A. Kuzovkin, 1932), earlier investigated by S. N. Rzhevkin and B. A. Vvedensky (1921); and others. The phenomenon of “resonance of the \(n\)-th kind,” or, in other words, “autoparametric resonance,” was discovered. From earlier works it followed that in nonlinear systems periodic oscillations may occur also with a frequency smaller (by an integral number of times) than the frequency of the external exciting force. From the point of view of radio physics, this phenomenon was discovered, investigated, and evaluated in essence by L. I. Mandelstam and N. D. Papaleksi and in the works of M. A. Leontovich, S. M. Rytov, M. I. Filippov, E. M. Rubchinsky, A. B. Melikyan, and V. V. Migulin. Since very valuable properties of autoparametric resonance curves were clarified (sharply bounded edges and the existence of a “threshold” and a “ceiling” for the amplitude of the external e.m.f.), “autoparametric filters” were constructed and tested. Resonance of the \(n\)-th kind in systems with two degrees of freedom was theoretically investigated by S. M. Rytov. It is very remarkable that the phenomena of autoparametric resonance proved to be closely connected with the so-called “parametric excitation” of a certain circuit. The latter occurs if the inductance or capacitance of the circuit is changed periodically and with a certain frequency, depending on the parameters of the circuit, by some amount (depending on the damping of the circuit). This excitation also occurs at an excitation frequency not only equal to, but twice, and so on, smaller than the natural frequency of the system. Comparison with autoparametric excitation showed a deep similarity between the two phenomena; under autoparametric action on a nonlinear system there also occurs

in essence, a periodic change of a certain parameter of this system.

Under the action of parametric excitation on a certain nonlinear system, definite stable amplitudes of oscillation are established in the latter (analogously to the usual tube generator), and there is here a resonance of a special kind, called heteroparametric. On the basis of this phenomenon, L. I. Mandelstam and N. D. Papaleksi founded a new type of electrical machine—the “parametric generator.” V. A. Lazarev, A. G. Ryazankin, and others took part in the development of this machine.

G. S. Gorelik developed a general theory of resonance in linear systems both with constant and with periodically varying parameters.

N. M. Krylov, N. N. Bogolyubov, and Yu. B. Kobzarev provided a method for solving nonlinear problems by means of so-called “quasilinear” techniques, which are of considerable interest because of their relative simplicity. K. F. Teodorchik fruitfully developed this method on the basis of the energy principle. Part of these works contains an investigation of the question of the dependence of the frequency of a tube generator on its operating mode, which is very important for the question of quartz-free parametric stabilization of the generator frequency. The works of B. K. Shembel, A. P. Skibarko, G. M. Mikhailov, and B. A. Vvedensky also belong here.

Recently S. M. Rytov, A. M. Prokhorov, and M. E. Zhabotinsky have given a new nonlinear theory of stabilization.

Mathematicians, in the persons of L. S. Pontryagin, A. A. Markov, and others, have also contributed much that is highly valuable for clarifying the question of nonlinear oscillations.

The achievements of the theory began to penetrate into purely technical circles as well; this was greatly facilitated by the appearance of A. A. Andronov and S. E. Khaikin’s book Theory of Oscillations, and also, more recently, by B. P. Aseev’s Nonlinear Radio Engineering and K. F. Teodorchik’s Self-Oscillatory Systems.

The latest works of A. A. Andronov and his students have shown that the methods of nonlinear theory used in radiophysics can be successfully applied to the solution of problems in the theory of regulation.

The problem of modulation of oscillations is closely related to the question of oscillations. Among the earlier works on amplitude modulation, one should note the works of I. G. Klyatskin and A. L. Mints on grid and anode modulation, and the works of P. V. Shmakov. In recent years much attention has been given to frequency and phase modulation, which in a number of cases give significant advantages with respect to freedom from interference. In this field one should note (in historical order) the works of A. M. Kugushev, Pestryakov, G. A. Levin, Yu. M. Gadiev, V. I. Siforov, E. G. Momot, and others. In S. M. Rytov’s monograph, the theory of frequency-modulated oscillations has been deeply and in generalized form dis—

the question of modulation was considered. Questions of radio reception are fruitfully examined in the works of V. I. Siforov, P. I. Kuksenko, N. N. Krylov, L. B. Slepyan, V. A. Kotelnikov, E. G. Momot, and others; G. S. Gorelik gave the theory of superregenerative reception partly jointly with G. Ginz. The works of V. L. Granovskii, V. I. Bunimovich, and others on noise in electronic devices have the most direct bearing on radio reception, especially in the spectrum of ultrahigh frequencies.

OSCILLATIONS OF DISTRIBUTED SYSTEMS AND ELECTROMAGNETIC RADIATION

In the exposition of the preceding section we tacitly assumed that the extent of the oscillating systems constitutes only a very small fraction of the length of the wave to which the frequency of oscillations in this system corresponds (in air). In this case the fundamental phenomenon for questions of radio engineering is not yet clearly revealed—namely, the phenomenon of emission, or radiation. To achieve noticeable radiation, oscillating systems must be sufficiently extended in relation to the length of the wave being radiated. In this case the current and voltage are not identical along the entire length of the system: the system becomes “distributed.” Modern radio engineering employs, in various cases, the most diverse radiating systems: from long-wave networks (antennas), suspended on masts many tens of meters high, to complex systems consisting of a whole grating of vibrators, “highly directional systems.” In recent times parabolic and other directing mirrors (similar to ordinary searchlights), as well as horn systems like those used in acoustics, so-called slot antennas, dielectric antennas, and others have come into wide use. Therefore the efforts of many investigators are directed toward creating the most effective methods for calculating such systems.

As a subordinate task there emerges the problem of supplying oscillatory energy to various radiators from the generator, or from receiving systems to the receiver. Normally this supply is carried out with the aid of “feeders” in the form of lines made of two or more parallel conductors, or in the form of a concentric cable. For the shortest waves, recently simple hollow metal tubes of the corresponding cross-section (“waveguides”) have also been used. The necessity arises of establishing rules for designing such systems under different conditions. Finally, since in the last analysis every radiating system, in itself linear, is necessarily connected with some nonlinear system, be it a generator or a receiver, there also arises the problem of a nonlinear treatment of distributed systems. At the shortest waves even the oscillatory circuits themselves often constitute distributed systems.

The emergence of Soviet radio dates back to the time of the flourishing of the long-wave range, when the greatest, and practi-

... almost the only one—powerful antenna networks were developed, with suspension on tall masts, with grounding systems, counterpoises, with their low radiation resistance and the relatively very large role of their capacitance and active resistance. A number of works by M. V. Shuleikin and his collaborators were devoted to these questions. In the early 1920s D. A. Rozhanskii, and also Brillouin, advanced the principle of calculating radiation resistance by taking into account the reaction of the field created by the radiating system upon that very system (“the method of induced emfs”). Soviet scientists were the first to appreciate the significance of this principle, which was manifested not only in the pioneering work of D. A. Rozhanskii, but especially in the works of I. G. Kliatskin and A. A. Pistol’kors. On this basis the latter gives a calculation of the radiation resistance of multivibrator directive systems, which began to develop as the short-wave range developed.

The theory of the directivity of such systems, as well as the channeling of energy, was studied by M. A. Bonch-Bruevich and V. V. Tatarinov. The latter contributed particularly much to the technical theory of the operation of such systems and of supplying energy to them. His book Short-Wave Antennas, as well as analogous books by A. A. Pistol’kors, M. S. Neiman, and B. P. Aseev, played a major role in the development of this subject. In this same field the works of S. I. Nadenenko are known, in particular on the question of the bandwidth of such antennas. However, to this day there does not exist a truly rigorous and, at the same time, practice-oriented theory of radiating systems of sufficiently general type. Substantial results toward creating a rigorous theory of the single-wire radiator were obtained by V. N. Kessenikh, A. E. Suzan in his works on the oscillations of an ellipsoid under the action of an external force, A. G. Arenberg, who considered the oscillations of a sphere under these conditions (in this case the problem is solved completely), I. I. Vol’man, and M. I. Ponomarev. Important results concerning “sufficiently thin” antennas were obtained by M. A. Leontovich and M. Levin.

A considerable number of works were devoted to the investigation of certain interesting special types of antennas, for example rhombic antennas, including coupled ones, antenna towers with top feed (G. Z. Aizenberg), and others; feeder lines with varying parameters, for which A. R. Vol’pert succeeded in obtaining a sufficiently general solution. The distortion introduced by long lines into the shape of the pulses transmitted along them and the influence of inhomogeneities in a coaxial cable (L. A. Zhekulin), which is important for television devices, were also investigated.

Investigations have been and are being carried out in the field of ultrashort-wave and decimeter antennas of various types, including reflector and horn antennas (M. A. Bonch-Bruevich and V. V. Tatarinov, N. A. Petrov, S. Ya. Turligin and M. I. Ponomarev, B. A. Vvedenskii, E. N. Maizel’s, A. I. Uzkov); M. A. Bonch-Bruevich and, independently, M. S. Neiman almost simultaneously (1938) proposed a new type of antenna in which apertures are used instead of ordinary vibrators.

or slots in a closed oscillating volume (for example, a tube). M. S. Neiman proposed the name “diffraction” for these antennas.

A considerable number of works were devoted to mastering television antennas of the ultrashort-wave range (A. R. Volpert, G. Z. Aizenberg, L. V. Gruzinsky, B. I. Molodov). In the theory of slot antennas, the recent works of A. A. Pistol’kors and Ya. N. Fel’d are of fundamental importance. L. A. Vainshtein calculated the radiation of a system of two semi-infinite parallel planes.

A very interesting question—the possibility of obtaining sharply directed radiation from antennas of small dimensions (relative to the wavelength)—was developed by A. Z. Fradin, who clarified the fundamental disadvantage of small-sized antennas owing to their very small efficiency (not to mention purely technical difficulties). M. S. Neiman and V. I. Bunimovich carried out very interesting and detailed investigations in the field of the theory and technical application of oscillations excited in closed metallic volumes, for example spheres, round cylinders, etc., which M. S. Neiman called “endo-vibrators.”

Oscillations of such systems are of great importance for stabilizing the frequency of ultrashort-wave and decimeter generators; the corresponding investigations were carried out by M. S. Neiman and V. I. Bunimovich independently of analogous foreign investigations, and appeared in print practically simultaneously with the latter.

The achievements of radio engineering at very high frequencies, corresponding to decimeter and centimeter waves, served as an impetus for the study of the propagation of radio waves in tubes (“waveguides”). A number of works by E. M. Studenkov, A. Drabkin, G. V. Kisyun’ko, N. N. Malov, I. I. Vol’man, P. E. Krasnushkin, A. S. Berkman and D. I. Mash, S. Ya. Braude, and others made it possible to develop the theory of waveguides considerably. B. A. Vvedensky and A. G. Arenberg published a monograph summing up the principal, mainly prewar, work on waveguides.

One should also note the works on the excitation of a system of parallel wires by a nonlinear generator (Yu. N. Shchenn, S. P. Strelkov, and others).

PROPAGATION OF RADIO WAVES

In the propagation of radio waves, a very large role is played by the electrical properties of the soil (dielectric permittivity and electrical conductivity), irregularities and, first of all, the spherical shape of the Earth, and, finally, the state of the upper—and, for ultrashort waves, also the lower—layers of the atmosphere.

Owing to two physical phenomena: diffraction when waves bend around irregularities of the soil and overcome the curvature of the Earth, and refraction when waves pass through the inhomogeneous atmosphere, the trajectories of waves are directed approximately along the spherical surface of the Earth, which makes possible the bending around

radio waves around the terrestrial globe. Depending on the distance of radio transmission, one of these phenomena predominates. In transmission over very great distances (on the order of thousands of kilometers), in practice we are dealing only with refraction, and specifically with refraction in the upper layers of the atmosphere, ionized by the action of the sun’s light and also corpuscular radiation. If, however, we confine ourselves to considering propagation over short distances, then the simultaneous action of diffraction and refraction comes to the fore.

The earliest Soviet studies concern the propagation of radio waves in the ionosphere. The beginning of this work was laid by M. V. Shuleikin, who arrived at the necessity of accepting a complex structure of the ionized atmosphere earlier than foreign authors. In the middle of the 1920s, in the radio department of the VEI, investigations were carried out to verify the well-known empirical formula of Austin. But the most substantial investigations belong to the field of short-wave propagation. The first experiments (M. A. Bonch-Bruevich, V. V. Tatarinov, 1924) led to the organization of the Moscow—Tashkent radio communication line and marked the beginning of the development of short-wave communication in the Union. Systematic observations of the passage of short waves were organized around 1927 by the Ministry of Communications (then the People’s Commissariat of Posts and Telegraphs), in parallel with the development of the Union’s trunk radio network. A. N. Shchukin in 1932 generalized the experimental material accumulated by that time in his method for calculating the field strength of short waves; foreign methods of calculation (Eckersley, Namba-Tukada) appeared considerably later.

The ionosphere is a variable agent, since its ionization depends on solar radiation. And the intensity of the solar radiation itself changes not only depending on the season and time of day, but also on the epoch of the cycle of solar activity (the so-called “eleven-year” solar cycle). Since the degree of ionization determines the wave that should be used for radio communication over a given distance and in given geographical latitudes and longitudes, there arises not only the need to know the state of ionization over the entire terrestrial globe, but also to know it for as long a time as possible in advance.

Beginning approximately in 1926, investigation of the ionosphere came to be carried out everywhere by the well-known “radio echo” method; special “ionospheric stations” began to arise, systematically observing and recording the state of the ionosphere. Probably the first published ionospheric investigations in the USSR were the studies carried out in connection with the International Polar Year (1932–1933) in Murmansk by M. A. Bonch-Bruevich. In 1932 there was in operation an experimental ionospheric installation of A. N. Kazantsev and Ya. L. Alpert. Soon analogous work was begun by V. N. Kessenikh and his group in Tomsk; around the middle of the 1930s began

regular operation of a number of other Soviet ionospheric stations. From that time onward a systematic study of the ionosphere began, now in direct connection with the practical operation of radio lines. Very soon the continuously growing demands of operation decisively advanced the organization of work on radio forecasts (the drawing up of calendar schedules of working waves for definite periods in advance); such work was organized both in the system of the Ministry of Communications by K. M. Kosikov, and in the system of the Academy of Sciences of the USSR by M. V. Shuleikin and A. N. Kazantsev.

On the basis of data from ionospheric stations throughout the world, an atlas of “ionization maps” was compiled for a number of years, which now serves for the preparation of radio forecasts. In view of the decisive role of the Sun and its radiation in the behavior of the ionosphere, and consequently also in radio communication, astronomers began to be fruitfully involved in the preparation of radio forecasts; because of the close interconnection between ionospheric and geophysical (geomagnetic, etc.) phenomena, ties with geophysicists also began to be strengthened. In 1934 the Academy of Sciences made the first attempt to unite the efforts of investigators in these fields by organizing a conference on the study of the stratosphere. Later this task came to be addressed by the Scientific Council on Radiophysics and Radio Engineering of the Academy of Sciences of the USSR, whose first chairman was L. I. Mandelstam and whose second was N. D. Papaleksi.

A peculiar type of interference, in which, when receiving one station, the modulation of another, located on the path of propagation, is heard, despite the fact that imperfections of the receiving apparatus are ruled out, was discovered in the USSR, quite independently, in Gorky. S. M. Rytov (1939) investigated this question (and certain related problems) theoretically. Let us also note the studies of L. A. Zhekulin (1940) and V. L. Ginzburg (1942) on the distortion of the shape of a radio pulse in passing through the ionosphere, and the ionospheric studies carried out under the general direction of V. N. Kessenikh and others.

The study of propagation over short distances—or, more precisely, over such distances and in such cases where the influence of the ionosphere may be neglected—is practically important in a number of instances. At especially small distances one may also disregard the influence of the curvature of the terrestrial sphere. By 1917 the theory of this question seemed to rest on quite firm ground. However, V. A. Fock (1926, and in more detail in 1933) noted and corrected substantial inaccuracies in the existing fundamental conclusions. The whole question of the so-called “surface waves” was reconsidered, and the existing law of the dependence of the intensity of the electromagnetic field on distance, both with respect to amplitude and with respect to phase, received its correct expression. From V. A. Fock’s formulas of 1926 there followed, among other things, very important propagation formulas, which in the foreign literature were published by van der Pol and Niessen only in 1930—

1931; in its complete form V. A. Fock’s work appeared in 1933. It should be noted that a formula almost coinciding with van der Pol’s 1931 formula had been obtained and published by M. V. Shuleikin as early as 1923.

In all investigations of this kind, practically all attention was paid only to the amplitude of the electromagnetic field, while the question of phase was touched upon only incidentally. L. I. Mandelstam and N. D. Papaleksi drew attention precisely to the question of phase propagation, thereby in essence opening a new chapter in the theory of radio-wave propagation. As the nearest practical application, they proposed a very effective application to the problems of radio of the interference principle of the usual error and, as a development of it, the measurement of distances by this method. A radio wave emitted by one radio station is received and re-emitted by a second radio station at another frequency (chosen, to avoid interference, for example as \(2/3\) of the fundamental). At the first station the two waves are compared in phase, and the phase shift makes it possible to calculate the distance. The Soviet priority in this question is very notable.

P. A. Ryazin gave a theoretical investigation of the field of a vertical antenna placed above a plane, precisely from the point of view of phase propagation. It turned out that the velocity of propagation, which according to the earlier theory (refuted by V. A. Fock—see above) should differ greatly from the velocity of light, in fact differs from it only very little; this was also experimentally confirmed in a number of cases with the aid of special apparatus developed by E. Ya. Shchegolev (1940). A modification of this apparatus yielded a “radio range finder.” With the aid of similar apparatus, V. V. Migulin and Ya. L. Alpert (1940) studied the phase structure of the field and the effect of irregularities of the soil both near the surface of the earth and during ascent in aerostats.

The works of L. I. Mandelstam and N. D. Papaleksi in this field were awarded the Stalin Prize in 1942.

Among other works related to the problems of the flat Earth, we note G. A. Grinberg’s introduction (1940) of a new method of treating the question (a generalization of the operational-calculus method of this kind by replacing the Laplace transform by a certain other one); this method also permits allowance for refraction. V. A. Fock, M. A. Leontovich, G. A. Grinberg, and E. A. Feinberg (1941–1942) developed theoretically the question of the so-called “shore refraction,” i.e., the change of the wave front when it passes from the sea to the shore (or conversely), which is important for radio direction finding. M. A. Leontovich and, especially, E. A. Feinberg have recently analyzed in detail the very important question of the influence of irregularities of the soil.

Special mention should be made of the role of Soviet physicists in establishing and clarifying the question of the principle of reciprocity, which plays a very large role in radio engineering. L. I. Mandelstam formulated

the reciprocity theorem for a point source as early as 1914; M. I. Sveshnikova corrected certain inaccuracies that existed in the foreign literature, and gave a rigorous derivation both for point dipoles and for antennas of finite dimensions.

The ultrashort-wave range entered radio engineering later than all the others, although it was precisely waves of this range that H. Hertz used in his fundamental experiments, and A. S. Popov also carried out his first experiments in radio communication precisely in this range. The laws of propagation of ultrashort waves (USW) therefore began to be studied comparatively recently. In the first statements on this question, dating from the second half of the 1920s, the view was advanced that USW propagate only as far as the horizon (“quasi-optical” USW), and this view persisted for a very long time. In the Soviet Union, quantitative experiments on the laws of propagation of waves of the meter range were organized, both for ground stations and on airplanes and aerostats, in 1926–1928 by B. A. Vvedenskii with A. G. Arenberg and A. V. Astaf’eva. At that time B. A. Vvedenskii already established the first law of USW propagation over short distances, according to which, owing to the interference of the “direct” and the ground-reflected “rays,” the decrease of the field strength over dry soil proceeds much more rapidly (in the first approximation—quadratically with distance) than for long waves, and is strongly dependent on height. (This regularity was published in the foreign literature only 4–5 years later.) Likewise, the law of diffraction propagation of USW beyond the horizon was also obtained in the USSR in 1933 and published in 1935–1937 (works of B. A. Vvedenskii). Subsequent works by foreign authors (van der Pol, T. Eckersley, and others) introduced additions only in the sense of greater exactness of the conclusions, but not in quantitative respect. The most complete and rigorous theoretical work in the field of diffraction propagation was carried out in recent years by V. A. Fock (1943–1945), who merged into a single general theory the cases of a plane and a spherical Earth. This work of V. A. Fock was awarded the Stalin Prize.

Works on the influence of an “undisturbed” or “linearly inhomogeneous” troposphere in the propagation of radio waves lead, at least for points situated “close” to the surface of the earth, to the possibility of solving the problem as if the rays remained straight (despite refraction in the troposphere), but the Earth were more flat. This is in agreement with the works of B. A. Vvedenskii and M. I. Ponomarev on the geometrical optics of the processes under consideration, and was shown more rigorously, at the suggestion of B. A. Vvedenskii, by M. I. Ponomarev from the standpoint of electrodynamics for rays “pressed to the Earth.” This was shown especially rigorously and convincingly later in a new work by V. A. Fock, carried out from the strict standpoint of classical electrodynamics.

B. A. VVEDENSKII and M. I. PONOMAREV

P. E. Krasnushkin investigated the question of the influence of layered inhomogeneities of the troposphere, proceeding from the concepts and models of the theory of propagation in waveguides. These works are much more rigorous than analogous foreign ones.

The laws of propagation of ultrashort waves under various conditions were studied experimentally in the USSR by many investigators in the system of the Ministry of Communications, and also in the system of other ministries (N. A. Petrov and others). The question of ultrashort-wave communication in cities and in mountainous terrain was studied; the latter—in the works of the complex Elbrus expedition of the Academy of Sciences of the USSR (A. Shchetinin and N. Kaminskii, 1934–1936).

A considerable influence on the development in the USSR of the question of the propagation of radio waves was exerted by the monographs of M. A. Bonch-Bruevich (chiefly on ionospheric propagation, 1934), B. A. Vvedenskii—on propagation in a homogeneous atmosphere (1934), A. N. Shchukin—on the propagation of ultrashort waves (1938), and the general course for higher educational institutions by B. A. Vvedenskii and A. G. Arenberg—especially on the propagation of ultrashort waves (1934 and 1938), and earlier ones—by N. A. Petrov and E. S. Artsimovich—on the propagation of ultrashort waves.

In recent years much attention has been devoted to the question of the radio emission of stars (especially their aggregation in the Galaxy) and of the Sun. During the Academy of Sciences of the USSR expedition at the time of the solar eclipse of May 20 of this year in South America, interesting observations (S. E. Khaikin) were made on the radio emission of the sun.

The physics of oscillations of superhigh frequencies essentially began to develop immediately after Hertz’s experiments. In prerevolutionary Russia P. N. Lebedev and his school devoted much attention to these questions, and P. N. Lebedev obtained waves of 6 mm. After the October Revolution, V. K. Arkad’ev and A. A. Glagoleva-Arkad’eva in Moscow and M. A. Levitskaia in Leningrad went very far in obtaining the shortest possible electromagnetic waves (waves considerably shorter than 1 mm were obtained). These were damped oscillations.

The generation of undamped electromagnetic waves of the decimeter range underwent very considerable development in the USSR. Even in the prerevolutionary period A. L. Mints and N. K. Shchadro obtained undamped oscillations of small wavelength with the aid of arc generators. S. L. Zilitinkevich independently obtained waves several decimeters long by the method of the “retarding field” (i.e., of the Barkhausen type) almost simultaneously with their being obtained in the West. Subsequently oscillations of this type were fruitfully studied by N. A. Kaptsov, A. I. Danilevskii, M. T. Grekhova, V. M. Bovshever, S. D. Gvozdver, V. I. Kalinin, and others.

The first experiments on radio communication in the ultrashort-wave range began with waves of the order of 3 m, generated in the usual way by three-electrode tubes (B. A. Vvedenskii and A. I. Danilevskii, 1922); later the question was placed on a more technical basis by S. Ya. Turlygi-

to M. I. Ponomarev and A. V. Astaf’ev in Moscow and to N. A. Petrov in Leningrad (around 1925).

In the former VZI shortwave laboratory, under the direction of B. A. Vvedenskii, beginning in 1928 experiments were carried out on radiotelephone communication on short waves with aerostats and airplanes, and the propagation of short waves was studied (A. G. Arenberg and A. V. Astaf’ev). In 1930 an experimental shortwave broadcasting station operated there for some time (A. V. Astaf’ev, V. I. Cherenkov). Somewhat later, in the same laboratory, M. T. Grekhova and V. M. Bovsheverov carried out experiments in sharply directed communication on waves of the order of 15 cm between Moscow and Lyubertsy; and in 1933, on the Black Sea, M. A. Sliozberg, E. N. Maizels, V. I. Peisikov, and E. A. Selin, under the direction of B. A. Vvedenskii, tested the propagation of waves of 60 cm over distances of the order of 100 km. The latter work was carried out with the aid of split-anode magnetrons, which in the USSR were introduced independently and approximately simultaneously with the West (1932–1933) (A. A. Slutskin, M. A. Sliozberg, and others). On the basis of the work of this expedition, several models of Soviet decimeter apparatus (using magnetrons), which at the time found practical application, were soon created.

Subsequently, quite stable split-anode magnetrons were constructed, yielding powers of several kilowatts in the decimeter range and used for medical investigations. For the same purposes, powerful generators in the meter range were at one time developed by A. M. Kugushev, P. N. Andreev, and their collaborators. N. F. Alekseev and D. D. Malyarov, under the direction of M. A. Bonch-Bruevich, for the first time applied the principle of multi-cavity magnetrons for the generation of centimeter waves.

Waves of the meter and decimeter ranges were also used to investigate the dielectric properties of various substances by M. A. Tsivil’kovskii, M. I. Filippov, and D. I. Mash, while D. A. Rozhanskii and his collaborators worked on methods for measuring dielectric permittivity and conductivity, and V. V. Tatarinov developed a methodology for electrophysiological investigations. Part of the work of N. N. Malov also belongs here.

Questions of piezo-quartz stabilization began to be developed in the USSR (N. D. Papaleksi, L. D. Rozhanskii, Yu. B. Kobzarev, and others) almost immediately after foreign work in this field appeared. Subsequently, thanks to the work of A. V. Shubnikov and his collaborators, N. G. Kovalenko, and others, Soviet quartz stabilizers made from domestic raw material attained a very high degree of perfection. A considerable number of works were devoted to stabilization based on the principle of magnetic tuning of circuits (L. I. Mandel’shtam and N. D. Papaleksi).

Major successes in the fields of Soviet radio-tube construction, radio materials, radio technology, and further in matters of geological prospecting,

electrophysiology, as well as electron optics and certain other fields, we regard as lying outside the scope of the present sketch.

In concluding our brief survey, we must emphasize that it in no way claims to be exhaustive. Many very important radiophysical works have, for a number of reasons, not been touched upon. Nevertheless, even from what has been presented above it is clear that the principal directions of radiophysics have found energetic and successful expression in the work of Soviet radiophysicists. Almost everywhere Soviet research stands at the level of the achievements of world science, and in many respects surpasses them.

Soviet radiophysics has undoubtedly played, and continues to play, a significant role in the organization and scientific equipment of the Soviet radio industry, which, thanks to the unremitting care of the Party and of the Soviet Government, is approaching the glorious thirtieth anniversary of the Soviet state with great successes.

Soviet radiophysics also has significant achievements, many of which deserve inclusion in the treasury of truly advanced Stalinist science.

Comrade Stalin’s appeal “...not only to catch up with, but also in the near future to surpass, the achievements of science beyond the borders of our country...” inspires Soviet radiophysicists, as it does other Soviet scientists—patriots of the Soviet country—to new and still more fruitful work.