The author of this article, Earle Ennis, apparently was the sole employee of the company, the Western Wireless Equipment Company, which conducted this test on January 21, 1911. Although this article claims that this transmission was the first use of radio from an airplane, there actually had been at least one previous successful test, by James McCurdy in New York on August 27, 1910. Interestingly, Jane Morgan's 1967Electronics in the West (Airplane extract)reports that Ennis may have also made an earlier test in June, 1910. However, this account does not mention any previous tests.
The lettering on the transmitter box sitting on Lieutenant Beck's lap reads:
TYPE A-4 AEROPLANE WIRELESS TELEGRAPH SET Developed For WESTERN WIRELESS EQUIPMENT CO.
Journal of Electricity, Power and Gas, April 1, 1911, pages 279-280:
WIRELESS TELEGRAPHY FROM AN AEROPLANE
BY E. E. ENNIS
Wireless telegraphy as a factor in the aerial evolutions of the future in naval and military warfare was thoroughly exploited in a series of experiments conducted for the War Department at the recent aviation meet at San Francisco. At that time it was conclusively proven for the first time that communication can be established between an aeroplane, hundreds of feet in the air, and a ground station, and that messages can be transmitted with absolute accuracy from almost any distance or altitude with practically no interferences from other wireless stations in the vicinity.
From a military standpoint, the results obtained are invaluable. The chief function of the aeroplane in warfare is along the line of scouting duty, and finds its most important place in reporting the position of hostile bodies of troops, making maps of fortifications, locating guns, supply trains, etc. The facility with which such information can be "wirelessed" to headquarters from an aeroplane circling thousands of feet overhead and practically out of range of hostile gun fire, and the value of such information in governing the arrangement, and advance of troops, artillery and fortification construction, makes the wireless the most valuable contribution of the century to the highly advanced science of modern warfare.
The tests were conducted at Selfridge Field and were under the direct charge of Lieutenant Paul W. Beck and representatives of the Western Wireless Equipment Company, who designed and built the apparatus for the experiments. The maximum distance covered was 40 miles and the greatest altitude attained during the tests was 500 feet, at which time Lieutenant Beck, carried as a passenger in a Wright machine, transmitted two complete messages in the Morse code to the wireless station on the aviation field while traveling at an approximate speed of 55 miles per hour. Both messages were received at the field station as well as by other stations, one of which was over 40 miles distant, with absolute clearness and accuracy.
The apparatus used in the experiments was a radical departure from the generally accepted design and embodied many unique ideas in construction and operation. The entire sending instrument, which Lieutenant Beck carried in his lap, weighed but 29 pounds and was enclosed in a small mahogany case with sending key fastened on the top. In constructing the apparatus, cognizance was taken of certain physiological phenomena originally discovered by Professor Fessenden, i.e., when a spark is used which gives a high-pitched musical note, the ear becomes more acutely sensitive to its presence and it can be distinguished at much greater distances than sparks of a lower frequency. The transmitting end was therefore tuned to the highest possible frequency, which gave the set a certain degree of selectivity and eliminated to a great extent the disturbing impulses of extraneous interferences.
The integral instruments consisted in the main of a small storage cell, a high-frequency coil-transformer, an inductive transformer for syntonizing, variable condensers for varying the capacity of the oscillation circuit, a noiseless discharge chamber for the spark and an ordinary telegraph key. The antenna consisted of 95 feet of phosphor-bronze wire, 1/16 of an inch in diameter, formed of seven fine strands inter-twisted and weighing 1½ ounces. When the aeroplane left the ground this was wound around a small drum which unwound at the will of the operator and swung out behind, clear of the propeller. The wire was fastened to the machine by a simple clip attachment, that was easily opened when the aeroplane neared the ground, releasing the antenna and allowing it to drop to the ground, and permitting the machine to land free from possibility of entanglement with tree tops or other objects. The transmitting instruments were properly balanced with the antenna both as to capacity and inductance, before the aeroplane left the ground.
For a ground connection a capacity ground was substituted in the form of the wire stays of the aeroplane. This was found to have ample capacity to act as a counterpoise to the antenna. The strange feature of the demonstration was that at all times the ground was actually higher than the antenna, which is the direct reverse of all other wireless work, where a certain height of the antenna above that of the ground is desired, and which under ordinary conditions is almost imperative. Another point that was noticed was that the higher the aeroplane went the clearer the signals became, which seems to bear out Tesla's theories that stationary waves exist in the earth, the disturbance of which by even minute currents produces extended effects, and that at the altitude of a mile or more above the actual surface of the earth, the globe could be practically belted by wireless waves with comparatively little power.
The steady decrease in the loudness of the signals as the aeroplane traveled away from the field station and the correspondingly steady increase as it returned indicates that with a receiving instrument on the ground properly calibrated and used in conjunction with a sensitive galvanometer and a Wheatstone bridge, it would be quite possible to determine the approximate distance of an aeroplane from a ground station. This would be specially valuable in locating hostile machines communicating with their own troops, especially if used in connection with a directive system like the Belli-Tosini, which is able by the use of an instrument called a radio-goniometer to determine the compass direction of a station in operation.
Merely tentative efforts were made to receive a message aboard an aeroplane during the tests at Selfridge Field, owing to the practical impossibility of hearing any of the signals through the terrific exhaust of the engine. The aeroplane is in its crude state yet, and until the noise is eliminated it is impossible to receive signals from the ground and have them audible in telephone receivers even though as sensitive a detector as the perikon is used. Until such time as a degree of quiet can be obtained in aeroplane motors it will be necessary to use some form of mechanical receiver of the tape or galvanometer type, tuned to the same group frequency as the radiating circuits of the sending station. This could probably be developed to a successful point with the proper experimentation.
Wireless work as applied to aeroplanes is capable of much greater development than as applied to any other field of research. The ability to obtain an almost unlimited wave length, and absolute freedom from interference, added to the small amount of power necessary to reach unbelievable distances, all open up a vista to aeroplane wireless that is as free from limits as the medium through which it works, and will undoubtedly lead to the clearing up of many of the contradictions that hamper the progress of the experts.