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Radio Broadcast
gible to the pilot and strong in the immediate vicinity of the field, but decreasing very rapidly with distance from the field. The experiments extended from various applications of alternating current with relatively low frequency to the use of radio transmitting and relatively high frequencies. This latter method made it possible for the pilot to use the same helmet. Moreover, when a very quiet engine was used, and using 20 amperes of i,ooo-cycle current in the transmitting circuit, signals were heard when the plane was at a height of 6,000 feet, and there were indications of faulty tuning in the receiving circuit, at that.
The proposed set-up of radio beacons and localizers offers some practical difficulties, especially while Congress holds the Post Office Radio Division down to $87,000 a year, as at present. The present Post Office radio chain used for administering the Air Mail consists of only twelve stations (Washington, Hazelhurst, L. I.; Bellefonte, Pa; Cleveland and Bryan, O; Chicago, Iowa City, Omaha, Cheyenne, Wyo. ; Salt Lake City, Utah; Reno, Nev.; and San Francisco). Three of these are Navy stations (Cleveland, Chicago and San Francisco). Since radio beacons and localizers, to be adequate, must be actually on the postal fields, and these three are not on the postal fields, new ones must be provided. Again, some of the postal stations are too far apart, as indicated above, to keep a plane in communication with one station or another. And, once more, since the power of receiving beacon signals is limited, and since a plane steers toward
them, not away from them, provision must be made accordingly. However, if field stations are provided at Chicago and Cleveland, the distances between Chicago and New York are not large: from Chicago to Bryan by air is 178 miles, from Bryan to Cleveland 1 52 miles, from Cleveland to Bellefonte 206 miles and from Bellefonte to Hazelhurst 217 miles.
The transcontinental chain of stations of the Air Mail used for administrative purposes, incidentally, are not identical with the postal stations used for broadcasting agricultural information. There are eight now broadcasting: Washington (the only one using the radiophone); Bellefonte, Omaha, -North Platte, Neb.; Rock Springs, Salt Lake City, Elko, and Reno.1
It is to be noted that in no instance is the broadcasting equipment identical with that required for serving planes en route. So the problems confronting the Radio Division of the Air Mail must comprehend broadcasting administration, communication with planes, interpoint communication and radio beacon and field localization, along with radio equipment of the planes themselves.
Clearly, if the Air Mail, solving these problems, can develop and perfect night flying, it will have done much to advance the cause of aviation in America. And, further than this, it will have contributed a great deal toward demonstrating radio as the super-messenger that neither under the sea, upon the land, nor in the clouds, knows any limitation.
xThe Air Mail expects, by the way, to use the wavebands 1050-1500 for broadcasting, 950-1050 for its beacons and localizers, and 850-950 and 500-525 for its aircraft.