Page:Popular Science Monthly Volume 90.djvu/176

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��Popular Science Monthly

��consist of 12 plates of glass 8 in. by lo in., covered with tinfoil 6 in. by 8 in. Twelve of these plates connected in parallel will afford the required value of capacity. The foil may be attached to the plates by means of melted beeswax. The plates should be y^ in. in thickness.

Q. 2. Will the following described oscillation transformer be suitable for this set? The primary consists of six turns of 5/16 in. edgewise-wound copper strip 5 in. in diameter while the secondary has eight turns of }/2 in. edgewise-wound copper strip 73^ in. in diameter. How far apart should the turns be spaced?

A. 2. Provided the turns are spaced J^ in. the transformer will prove entirely satisfactory for operation at the wavelength of 200 meters.

��Requirements for License E. M. K., South Amboy, N, J., inquires: Q. 1. What are the requirements for securing a license for an amateur sending station?

A. 1. To secure a license for an amateur sending station, the applicant must first possess an amateur first or second-grade license. The examination for this certificate is taken at the U. S. Navy Yard, Brooklyn, N. Y, To obtain an amateur first grade certificate the applicant must have a sufficient knowledge of the adjustment and operation of the apparatus which he wishes to operate and of the regulations of the International Convention of Acts of Congress in so far as they relate to interference with other radio communication and impose certain duties on all grades of operators. The applicant must be able to transmit and receive in the Inter- national Morse Code at a speed sufficient to enable him to recognize distance calls or the official keep-out signals. A speed of at least five words per minute, five letters to the word, must be obtained.

After this license has been secured, you must then communicate with the Government Radio Inspector, Custom House, Bowling Green, New York City, who will send you an application blank to be filled out and in which is fully stated the purpose of the station, the character of the apparatus, the size of the aerial, etc. If satisfactory and in accordance with the requirements for amateur stations, a licensed certificate will be given and a call letter assigned in due time.

Q 2. What are the requirements for a com- mercial license?

A. 2. To qualify' for a commercial first-grade license the applicant must pass a satisfactory ex- amination in the adjustment, operation, and care of commercial wireless telegraph apparatus, including the correction of faults and changes from one wave- length to another. He must be able to transmit and receive in International Morse Code at a speed of at least twenty words per minute. He must have complete knowledge of the use and care of storage batteries or other auxiliary apparatus. He must be fully informed on the International Regulations in force applying to radio communication. He must also know the requirements of the Act of August 13th, 1912.

��Dimensions of a Short Wave Transmitter

R. P. P., Newark, N J., inquires:

Q. 1. Please give the dimensions for an oscillation transformer and condenser to be used with a }/2 K.W. set and an antenna having a wavelength of 170 meters.

A. 1. The primary winding of the oscillation transformer may consist of four turns of 3/16 in. copper tubing or No. 6 D.B.R.C. wire wound on a form 10 in. in diameter, the turns being spaced i in. apart. The corresponding secondary winding may be 8 in. in diameter and comprise 10 turns of the same tubing or wire spaced % in. apart.

The condenser should have a capacity of .008 microfarads and for this you require 12 glass plates J^ in. in thickness, with other dimensions 8 in. by ID in. covered on both sides with tinfoil 6 in. by 8 in. These plates should all be connected in parallel and then immersed in oil.

��Long Distance Receptions from Germany

A. T. Valparaiso, Ind., inquires:

Q. 1. Is an aerial 200 ft. in length 80 ft. in height suitable for the reception of undamped wave stations located in Germany?

A. 1. Yes, provided a supersensitive receiving set is employed.

Q. 2. Can I use a sliding wire tikker for this purpose?

A. 2. To collect enough energy for these far distant stations to make audible the signals on a tikker, it would require an antenna of enormous proportions such as used at the large transatlantic and transpacific stations. Some form of the audion oscillating circuit is required to receive foreign stations on amateur aerials.

Q. 3. Please give a circuit diagram for a long distance receiving set, and data for the construction of the tuner.

A. 3. You had better secure a copy of the November, 1915, issue orthe April, 1916, issue of this magazine and note the articles on long distance receiving apparatus. Also in the book "How to Conduct a Radio Club" (on sale by the Book Department of this magazine) there is described fully the circuits of a long distance receiving set with the complete dimensions for all the coils.

Q. 4. This set is to be used in eastern Pennsyl- vania in a mountainous district. Will the mountains interfere with the workings of the apparatus?

A. 4. Generally, no. Mountains seem to have the most severe effect when they are located near to the transmitting station rather than to the receiving station.

��Licensing a Receiver

P. T. P., Salem, Va., writes:

Q. 1. I am about to erect a receiving station and desire to know if it is necessary for me to inform the Radio Inspector.

A. 1. The inspector need not be informed nor is a station license required for a receiving equipment.

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