156 



tion, although the first two letters SR are 

 often used for senior, especially in combina- 

 tion with some other abbreviation indicating 

 the title of the person addressed. The abbre- 

 viation you mention may be of this type. 



Loose Couplers and Stranded Copper. 



R. M. L., Indianapolis, Ind., asks : 



Q. 1. Will you please inform me as to the 

 sizes of the primary and secondary cylinders, 

 also the sizes of the wire primary, and sec- 

 ondary needed to make a loose coupler with 

 which I can receive signals of a 4,000-meter 

 wavelength ? 



A. 1. Make the primar>' 5^ inches in 

 diameter and 16 inches long ; the secondary 

 4}i inches in diameter and 16 inches long also. 

 Wind both coils with No. 28 wire. Use bare 

 wire if possible, if not use single cotton cov- 

 ered magnet wire. 



Q. 2. Will you please inform me whether it 

 is necessary to use a tikker to receive Arling- 

 ton, NAA, when using its new continuous 

 wave set? 



A. 2. Yes, unless you use some other method 

 such as the oscillating audion, which is capa- 

 ble of receiving undamped waves. 



Q. 3. Will you please advise me what kind 

 of wire should be used in the aerial for long 

 distance receiving? 



A. 3. Stranded copper is quite satisfactory. 

 There is made a special seven-strand tinned 

 copper wire for antenna purposes which will 

 work very well. This wire costs about a cent 

 per foot and can be obtained from nearly any 

 wireless supply house. Phosphor bronze is 

 also used and has the advantage of being 

 stronger than copper, and it is also more ex- 

 pensive. 



Trouble With a Half Kilo-Watt 

 Transformer. 



K. T., Scranton, Pa., asks : 



Q. 1. I have built a one-half kilo-watt trans- 

 former of the Type E design for radio work 

 and find that instead of taking five amperes 

 it takes but two or three. I used stove pipe 

 iron instead of silicon steel called for by the 

 designers. Would it be all right to reduce 

 the number of turns on the primary to cause 

 the transformer to take a larger load? 



A. 1. Yes, on the transformer you mention 

 this would be satisfactory. Care should be 

 taken that the safety gap on the secondary is 

 not opened too far, as a higher voltage ^\^ll 

 be induced in the secondary if the primary 

 winding is shortened. Are you sure that you 

 are using the same size condenser on the 

 secondary that is called for by the designers? 



Popular Science Monthly 



Many transformers for radio work were de- 

 signed before the Federal radio law was passed 

 and were intended to be used with a larger 

 condenser than is now permissible. Accord- 

 ingly instead of drawing 5 amperes these trans- 

 formers are only taking 2 or 3 with the lighter 

 load. These transformers are having their 

 primary winding reduced, causing an increase 

 in secondary voltage, and accordingly a larger 

 load on the transformer. We are rather sur- 

 prised to find that your transformer is taking 

 less current than expected, unless it is the 

 condenser question, for in general transform- 

 ers constructed by amateurs are noted for 

 their high current consumption. 



Some Miscellaneous Information. 



H. S., Chicago, 111., asks : 



Q. 1. Would there be any change in the 

 connections of an ordinary receiving set if the 

 set was to be used on wavelength of 10,000 

 meters ? 



A. 1. No, the usual connections with loading 

 coils would be used. 



Q. 2. In receiving long wavelengths is it 

 necessary to load both the primarj^ and sec- 

 ondary circuits ? 



A. 2. Yes. The primary is usually loaded 

 by putting a loading coil in series with the 

 primary of the receiving transformer. The 

 secondary is usually brought up to the long 

 wavelength by shunting the secondary of the 

 tuner by a condenser of large capacity. 



Q. 3. What would be required to load a 

 2,200 meter set up to 10,000 meters? 



A. 3. For the primary wind about No. 26 

 wire on a cylinder 5 inches in diameter and 3 

 feet long. The secondary' would be best loaded 

 b}^ adding a small loading coil in series with 

 the secondary of the receiving transformer 

 and shunting the coils with a variable con- 

 denser of about 0.008 m. f. capacity. 



Q. 4. In the primary circuit is it considered 

 best to put a variable condenser in shunt with 

 only the tuner rather than around both the 

 loading coil and tuner? 



A. 4. Yes. 



Q. 5. How many condenser plate's 12x14 

 inches do I need for a 1 KW. transformer with 

 secondary voltage of 20,000, using a rotary 

 gap? By 12x14 inch plates I mean the size 

 of the glass, the actual surface of metal being 

 only 9x11 inches. The glass is Yf, inch thick. 

 Wavelength 200 meters. 



A. 5. Your set will probably require about 

 six plates. 



Q. 6. What is the best material to use for 

 connecting up the transmitting instruments? 



A. 6. Copper ribbon is about the best thing 

 for general use. 



