Radio Broadcast (May-Oct 1922)

A COMPACT PORTABLE WIRELESS SET A Complete Wireless Telephoi ing Station Which May Be C; By ARTHUR IT IS doubtful if any one subject studied by Boy Scouts is as popular as radio. This was true even before radio broadcasting was introduced, creating the nationwide interest it has. In the days when it was necessary to communicate by code, many instances arose which clearly demonstrated that Scouts were able to render great service to mankind not to mention the enjoyment they derived from the pursuit of this very attractive hobby. In times of flood and other disaster, where the telephone and telegraph wires have been demolished, communication has been made possible and relief brought by radio outfits operated by Scouts. During the European War the work done by the Scouts is now a matter of history with which most folks are familiar, but the work of yesteryear is now being far outranked, and what is considered exceptional to-day is seemingly destined to be the commonplace of to-morrow. For instance, who, a year ago, would have thought that a complete wireless telephone station, with its source of power, the necessary wire for the aerial and ground systems, transmitter and receiver, could be limited in weight to approximately fifteen pounds and could be conveniently carried in a single haversack? Surely there were few such folk. It was but a few years ago, when the U. S Army pack transmitter was introduced and caused a great furor in radio circles. It was made up in several units and could be carried from place to place by mules. There were collapsible masts and the spark transmitting unit and the generator unit and the receiving unit, each designed to fit snugly on the back of a mule. The generator was provided with two handles, somewhat similar to those on a coffee mill, and two husky men were kept quite busy cranking up enough "juice" to run the transmitter, which, by the way, had a very limited range. More recent models have been perfected by the Army and one set was made for use in France. However, there were no le Transmitting and Receivirried by a Single Boy Scout H. LYNCH complete stations in the war which could be counted upon to perform as the little complete station which is now available for Scout use. THE "station" equipment IF THE apparatus in the accompanying illustrations is compared in size with the boys surrounding it, little need be said regarding its compactness, and misgivings are likely to present themselves as to the possible value of such a small outfit. In order to make this point very clear let us consider some past performances, just as soon as we have covered the parts which go to make up the "station." First and foremost, there is a regenerative tuner, with a single wave length control and a tickler control. Wherever we find a regenerative circuit we must have vacuum tubes, and in this particular receiving set there is a tube of special construction, designed to operate from the power delivered by a single dry battery of the type ordinarily used for door bells. There is a rheostat, or regulating resistance, connected in this battery circuit, and adjusting it permits variation of the current flowing through the tube in order that any desired intensity may be secured. Vacuum tube operation requires the use of a "B" or "plate" battery, which in this case is in the form of a block just about one third the size of a common red brick. This little battery is made up of a number of individual dry cells in series and is designed to supply a high voltage rather than much power. Such batteries may be counted upon to supply approximately twenty volts, which is sufficient for the plate circuit of the vacuum tube used in this outfit. Of course it is necessary to employ telephone receivers, though this set may be used with amplifiers and a loud speaker when it is used in a permanent location rather than in field work. Except for the aerial and ground wires, which we will consider more thoroughly presently, there is nothing else needed for this transmitting and receiving station. Let us