Crufts Laboratory Will Resume Study Of Ionosphere and Long Transmission

This article was written for the CRIMSON by Howard Aiken of Cruft Laboratory, assistant to Harry R. Mimno, assistant professor of Physics and Communication Engineering, who is conducting the experiments hereinafter mentioned.

Cruft Laboratory's study of the ionosphere, which has been in abeyance since 1934 will be resumed as soon as authorization is issued by the Federal Communications Communion, as a result of the amendment this week to section 318 of the Communications Act. The ionosphere is that portion of the atmosphere which reflects radio waves and allows long range transmission.

History of Experiments

Early radio engineers and psysicists were aware that radio signals could be transmitted over long distances, but from a theoretical point of view they could not understand why this is possible. They saw no reason why this energy omitted from a transmitting station should not disappear into free space and be lost to the cart. To explain this difficulty, Sir Oliver Heaviside in England and Arthur E. Kennelly simultaneously proposed the explanation that radio signals are reflected from an ionized layer in the upper atmosphere and the energy thereby returned to the earth.

However, the results of experimentation have shown that the simple hypothesis of Kennelly and Heaviside is not sufficient to represent the conditions that obtain in the upper atmosphere.

Cruft Transmitter

One of the methods used in studying the ionosphere at Cruft Laboratory consists of transmitting energy pulses from a special radio transmitter. These purses rise to the ionosphere and are reflected back to the earth as echoes, where they are received by a special radio receiver. The time elapsed between the transmission and reception of each pulse is recorded and the effective height of the layer may then be computed.

Continuous Operation

Since conditions in the ionosphere are changing constantly it is necessary to take continuous observations over long periods of time in order to obtain representative records. This is difficult to accomplish by manual means except at prohibitive cost. For this reason, Dr. H. R. Mimno of the Graduate School of Engineering, developed special automatic devices to be used for the control of the Cruft Laboratory ionosphere research station. By means of these devices, records can be obtained without the attendance of an operator.

Commission Shutdown

This automatic control operated satisfactorily until 1934 when the staff of Cruft Laboratory was advised by the Federal Communications Commission that either a continuous operator watch must be provided, or the station shut down. The cost of employing an operator being prohibitive, this instruction resulted in an interruption of the experimental research program. The Commission's ruling was based on Section 318 of the Communications Act of 1934, which states that a licensed radio operator must be in charge of a radio transmitter during its operation at all times regardless of its purpose or use.

Legislative Action

In order to relive this situation, Senator David I. Walsh and Congressman Clarence F. Lea of California introduced into the Senate and House of Representatives a bill providing for an amendment to Section 318, making possible the operation of certain classes of radio transmitters without operator attendance. This bill passed the House of Representatives on February 24, 1937, the Senate on March 24, 1937, and will become part of our Communications law as soon as it is signed by President Roosevelt