Page:March 1916 QST.djvu/10

MARCH, 1916



The aerial or antenna is of the “loop-type” consisting of six hard drawn No. 12 copper wires 100 feet long attached to ten foot spreaders at each end extending in a northwesterly direction. Each of the six wires is insulated from the spreaders by three glazed porcelain ball insulators joined in series. Two strain insulators having a tensile strength of 1,000 pounds suspend the aerial between two masts, besides providing a further insulation of 75,000 volts. One of the masts is a steel pole erected on the roof of the house, the top of which is 43 feet above ground. On high ground back of the house, a 40 toot steel tower has been erected having a 16 foot 4 x 4 securely mounted at the top that gives the aerial a height of little over 50 feet at this end. On account of the tower being on high ground, there is a difference of nearly 30 feet in elevation of the two ends.

As to its details of construction, it closely resembles the towers erected on the Lackawanna Railroad Station and the Boston Herald&mdash;but the “United Wireless Station” (WDR) in Detroit, Mich., is the one it is really designed after, although on a much smaller scale. The “rat tail” consists of six phosphor bronze wires of seven strands of No. 22 each, that lead from one aerial to two lightning arresters on the exterior of the building. From the lightning arresters two lengths of high tension pirelli cable serve as “lead-in” wires, connecting the aerial with the apparatus in the operating room.

The apparatus is connected with the earth by means of a heavy stranded copper wire composed of 480 No. 30 B & S. gauge wires the equivalent of a No. 4 single copper conductor. This is soldered to the ends of nine discarded boiler tubes taken from one of the government boats. The tubes are 12 feet long and are laid fan shape in moist ground, giving an exposed surface area of 100 square feet. This gives a ground connection nearly, if not equally as efficient as a connection to city water main&mdash;the absence of which made necessary this extra labor.

The receiving apparatus consists of two rotary variable condensers and one adjustable tin foil condenser contained in a cabinet made of bird’s eye maple stained mahogany with a loose coupler and universal detector mounted on top, together with various switches, etc., that enables any of the instruments to be cut in or out of circuit or to be adjusted to various wave lengths and capacities as desired. The receiving transformer has a range of about 600 meters, but for stations using longer waves than this, a large loading coil (double slide tuning coil) is used that increases the range to about 5,000 meters. This is a coil containing 630 feet of wire wrapped on a cylindrical form 18 inches long and 6 inches in diameter. In the construction of the loose-coupler, red fibre is used throughout; also in connection with the variable and fixed condensers. The variable condensers consist of 16 stationary and 15 movable aluminum plates, while the fixed condenser consists of 64 sheets of tin foil made adjustable by steps. In the detector, galena (found in this locality) has so far proven to be the most sensitive mineral tested out for long distance work. Several pair of Brandes receivers&mdash;including their Navy, Transatlantic and Superior types&mdash;complete the receiving set, and the extra pairs of phones have proven invaluable a great many times when other amateurs and friends have come around to listen-in.

The transmitting apparatus is of the switch-board type. At present it is in course of construction and will probably be some little time before every detail is completed; although actual tests will be possible some time in February. The board is inch and a quarter light pink Tennessee marble 55 x 30 inches divided into three panels and supported by an iron frame above a table on which the receiving apparatus sets. The center panel is 25¾ inches