160 



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. 



