November 1935 Radio-Craft
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
The announcement and public demonstration of Senatore Guglielmo Marconi's 'death ray' device was the coming true of some of the worst fears of science fiction aficionados. Application of these newly created centimeter wave 'beams' could roast the flesh of man or beast when generated with great enough power. The diminutive wavelength not only would heat liquids, but also provided a means of detecting and measuring energy reflected off of 'targets' such as aircraft and boats. It applications were endless. Although not called so, one of the article's diagrams looks to be an example of a bistatic radar system. The early magnetron implementation is quite different than the modern cavity arrangement.
The New "Mystery Ray"
This new ray - developed simultaneously by three World Powers - depends upon the beam-effect and reflection of "centimeter"-length or ultra-ultra-short waves to "spot" enemy planes, ships, etc. Fortunately, there are valuable commercial applications for this new tool of warfare and destruction.
The ray transmitter with the dipole antenna at left.
In the past half-year many exciting reports have been published concerning a new invention, which may be used to produce the most perilous of all war weapons, the often predicted - but never presented "death rays." Comments from experts concerning these exciting reports have firmly indicated that death rays are mere daydreams, at least on the basis of present technical progress, and that the existence of these "extremely dangerous" rays may fit well into the realms created by Hollywood studio facilities but not in the world of realities.
Receiver for the rays.
The public mind, however, fascinated by the horrible prospects of these death rays in a future war, took these unconfirmed reports as scientifically verified facts and mystery story authors even started at once to lubricate their typewriters and do their part in confusing the public mind!
Experimental magnetron tube transmitter.
This, quite muddled, situation has recently been even more confused by an interview given to the press by Senatore Guglielmo Marconi concerning a new kind of ray, of which he predicted some extraordinary possibilities through their application in case of war. This interview by the head of Marconi Wireless Ltd. induced its competitor in the world market, the German Radio Corporation (Telefunken Company), to unveil some results of their recently finished secret experiments with a kind of ray similar in its qualities to the mystery rays of Marconi.
Split-magnetron sending-receiving tube.
According to recently printed newspaper reports the U.S.A. Signal Corps also has a mystery ray device in development, which seems to be equal in its qualities to the German and Italian ones. The kind of rays and devices used by the Signal Corps could not be learned, since all details concerning the devices made by the General Electric Co. have been enveloped in great secrecy. While the Signal Corps conducted its first practical tests at the Lighthouse Station on the Navesink Hills near Highland, N.J., a heavy military police line was thrown around the station.
Construction and circuit of the "split magnetron".
These circumstances make the demonstration of the German mystery rays, recently conducted in a suburb of Berlin especially interesting. These demonstrations disclosed to the invited newspapermen, and foreign military attaches, contrary to all expectations - were not units of tremendous dimensions, but tiny devices about as large as a normal match box! The new mystery-ray machines do not operate as has often been predicted with millions of watts, but radiate only a few watts in the form of very short waves (from 5 to 15 centimeters) into the "air." The energy necessary to operate these mystery ray transmitters is provided by regular dry-cell batteries of normal size and weight. The produced beam radiated by these transmitters is as narrow and "confined" as a water pipe of ordinary dimensions, and despite the fact that they are not really death rays, in the sense fiction story writers put it, they are actually able to bring death and destruction to ships and aircraft.
The transmitter compared to match box.
The reason for this ostensibly seeming paradox is explained by the fact that, although these rays do not kill or destroy directly they do so indirectly by furnishing the means to detect and localize airplanes even if hidden by clouds, smoke, snow or rainfall.
Dipole antenna for transmitter.
It is said that these valuable uses are possible through the ability of the mystery rays to penetrate the sight obscuring elements without being absorbed or dispersed as would be the case if a normal light beam (and under certain circumstances, even a strong beam of ultra-red light) was used. These newly utilized rays have, however, the advantage of being as easily reflected as a normal light beam. How these qualities of the newly utilized "ultra-ultra" short-waves may be used for air defense will be shown by the following example.
Transmitter with "wing" reflector.
Along the borderline of the country a great many of these small, mystery-ray transmitters will be fixed atop cast-iron posts or, perhaps, hidden on church towers or tall buildings. The transmitters are so adjusted that their beams are radiated at a slight angle into the sky. Any airplane flying through these invisible "feelers" will reflect the beam back to earth. Since these beams obey the well known optical law, that "the angle of reflection is equal to the angle of incidence," it is easy to install a great many of these receivers in such close proximity that at least one of them may be depended upon to pick up the reflected beam, regardless of how high or how low the plane flies.
Dr. S. Spitz, of Burbank, California, developed this amazing machine, which indicates as a moving spot of light, the location of an airplane; the 'plane's sound automatically actuates the device. The same principle probably could be applied to silent 'planes, the actuation then being obtained by means of centimeter (the "mystery ray" mentioned in this article) waves reflected from the 'plane!
Since the use of so many receivers might create some difficulties in controlling them all at the same time (which is necessary for an efficient air defense) an automatic system, operating similarly to the relays used in automatic telephony, to connect two telephones without help of human hand, will be developed. The various transmitters will be modulated by certain current impulses, and if such a succession of impulses is received, the "telephone" relay will indicate the position of transmitter and the receiver in operation upon a kind of annunciator.
How the ray shows the location of enemy aircraft.
These rays are produced by tiny split-plate magnetron tubes (The split-plate magnetron is illustrated and described in considerable detail in the article, "Super-short Radio Waves," which appeared in the October, 1934, issue of Radio-Craft. - Editor), which are also used for the reception of these rays. The electro-magnet used for these transmitters is of surprisingly small dimensions but produces (through the application of a special high grade of iron) a remarkably strong magnetic field.
The new German ultra-ultra-short-wave receivers and transmitters have been developed by the Drs. H. Scharlau and W. Runge, of the Telefunken Laboratories. As Dr. Runge recently demonstrated, these newly utilized rays may be of great value in piloting incoming ships into foggy harbors. For this purpose two parallel "running" beams are radiated by two transmitters with any desired spread between them. Two receivers are installed aboard the ship to be piloted which are connected to a pilot indicator instrument by means of a bridge circuit. As long as the ship follows the proper direction, the indicator of the pilot instrument will stay at the "on course" line. If the ship shifts more to one side, thus leaving the proper direction, the field strength of one of the very sharply concentrated beams will rise, while the other beam will be received with decreasing strength.
Tugboat being guided into a harbor.
The mystery-ray devices might also be useful for private telephone connections between two points as far distant as sight is possible. If receiver and transmitter are installed on high points, the maximum bridged distance will approach 50 miles. The communication can be kept secret because no reception outside of the very narrow "beam line" between transmitter and receiver is possible.
Posted September 7, 2015