Friday, May 1, 2015

Experimental Wireless Station 1XX

The Radio Club at Brown University dates to the end of the First World War when the United States government lifted restrictions on the private operation of wireless equipment. Student amateur radio operators formed the new club during the Fall semester in 1919.

An early transmitter used on campus was described as "a ½ KW rotary spark set and a two step amplifier" in the September 1920 QST magazine. One of the call signs used was 1LAU which was assigned to student Herbert R. Grimshaw. The emissions from the crude transmitters used by amateurs during this time caused stations in the same geographic area to interfere with each other. President of the club E. Standish Palmer proposed a system for managing the problem:
"Providence has considerable QRM [interference] to overcome and some sort of a control station is being considered. Palmer suggests different hours for the different classes of communication and a visiting committee to go to the stations of the various amateurs who overstep and tune them up. This is a good idea. Help the young fellows out in every way possible. Make them feel as though we are helping and not trying to dictate to them."
Another transmitter was a home-made set with two vacuum tubes. The alternator used to generate the alternating current is not shown in the photo below. It produces an Interrupted Continuous Wave (I.C.W.) which, like the rotary spark gap described above, was used to send Morse code. These transmitters were not capable of voice communications.

Transmitter of station 1XX
Credit: QST, April 1921.

A detailed description of the transmitter and a key to the schematic below can be found in the April 1921 QST. The students describe operating the transmitter at the physical limits of the components. The alternator was run at an "abnormal speed" and a "considerably higher potential" was applied to the vacuum tubes above the voltage that they were rated for. Adjustment procedures are given to prevent the Western Electric VT-2 tubes from getting "red hot."

Schematic of station 1XX
Credit: QST, April 1921.

At this time amateurs were restricted to using wavelengths shorter than 200 meters (frequencies above 1.5 MHz) to prevent interference with commercial and government stations. The club then received an Experimental Class license to operate the Special Land Station 1XX in October of 1920. This allowed operation at longer wavelengths up to 600 meters (frequencies as low as 500 KHz.)

The transmitter generally had a range of about 900 miles, but there are reports of it being heard in Oregon at a distance of 2,500 miles. During one Trans-Atlantic test in December of 1922 it was distinctly heard in France, some 3,500 miles distant.

Tran-Atlantic Amateur Tests Successful
Credit: Wireless Age, February 1923

The club mailing address was given as Wilson Hall (constructed 1891) which housed the Physical Laboratory and the Department of Physics. The transmitter was likely operated from this location. The aerial was a "flat-top T with a spreader in the center" that was "hung between a steel tower at one end and the ridge of one of the halls at Brown at the other." The photo below of Wilson Hall predates the wireless experiments so it does not show any indication of an antenna on the building.

Wilson Hall, Brown University
Credit: Brown University Library

An article in the Christian Science Monitor (February 19, 1916) announced that the University was offering a new course in "practical and experimental wireless telegraphy." It describes an "outfit... of the latest type" capable of receiving transatlantic messages. "The towers, which are now in place on University and Haxey [sic] halls, will support a 450-foot long aerial." University Hall is about 450 feet from Maxcy Hall, with Wilson Hall between the two and adjacent to Maxcy. The photo below shows an aerial tower on Maxcy. The building at right is Littlefield Hall which dates the photo to after 1925. It is not clear from the student's description if they made use of this tower for their wireless station. It is possible that this tower was only used for courses and the students may have had a second aerial adjacent or nearby.

Maxcy Hall
Credit: Brown University Library

The license for experimental station 1XX expired in October of 1925. After that date the students would have used their personally issued radio licenses for transmitting on the amateur wavelengths below 200 meters. During this era shortwave radio came into widespread use which would have necessitated building a different kind of transmitter with a much shorter antenna.

There is more information about the history of the Brown Radio Club that I've collected at The club is still active today.

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