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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.
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