What Radio Readers Want to Know 



Indoor Aerial 



C J., Detroit, Mich., asks : 



Q. 1. Would it be possible to use the light- 

 ing circuits in the house for an aerial, it being 

 understood that the main switch is open? 



A. 1. While not a very efficient aerial sys- 

 tem it might be used under certain conditions. 

 If the wires are not placed in metal conduits 

 or in no way grounded, the system could be 

 used. Nothing but local stations would prob- 

 ably be received. Better run a few wires 

 across a ceiling in the top of the house than 

 to try to use the light wires. 



Q. 2. If the wires could be used, what 

 would be the wave length of the system? 

 The house is a two-story frame house, with 

 one light in the attic and four in the cellar. 



A. 2. It would be impossible for us to 

 estimate the wave-length of the system. 



Q. 3. If the bulbs were unscrewed, could 

 this aerial be used to transmit on by using 

 a small coil? 



A. 3. No. The potential from the coil 

 would be too high for the wiring and would 

 puncture it at such points as fixtures. Similar 

 trouble is experienced where currents are 

 induced in the house wiring from an out- 

 door system of aerial conductors. 



Radio Telephone 



E. J. O'B., Black River Falls, Wis., asks: 



Q. 1. Will you please give me the informa- 

 tion which will enable me to construct a radio 

 telephone set capable of transmitting one- 

 half mile or farther if possible? 



A. 1. We would judge from your letter 

 that you would prefer to have instructions 

 for a set which you could set up yourself, 

 without involving expensive construction 

 costs. For details of larger or more effi- 

 cient sets we would have to refer you to a 

 text book on the subject as it would be far 

 too long to cover in this column. However, 

 there is in vogue a type of radio which will 

 cover the distance which you desire and 

 which is fairly reliable. Such a set consists 

 fundamentally of a transformer, such as 

 would be used for radio telegraphic work, 

 shunted by a carbon micrometer gap. Con- 

 nected across the gap are two small conden- 

 sers in series between which is the primary 

 of an ordinary oscillation transformer. The 

 secondary of the oscillation transformer is 

 connected on one side to the aerial and on the 

 other to the transmitter, the other side of 

 the transmitter being grounded. The conden- 

 sers are about 0.00:ir.m.f. in capacity and the 



transformer about % K.W., and should op- 

 erate on 60 cycles or at a higher frequency if 

 available. The April, 1914 Popular Electricity 

 and World's Advance, page 1,466, has a de- 

 scription of such a set and shows the microm- 

 eter, gap in detail, giving the necessary work- 

 ing drawings. Page 666 of the May, 1914, 

 Modern Electrics and Mechanics, describes a 

 similar set, but omits details of the spark 

 gap. 



Multiple Tuner 



A. F., Rochester, N. Y., asks : 



Q. 1. Is it absolutely necessary to use No. 

 24 wire on the multiple tuner described in 

 the September issue of the World's Advancef 



A. 1. By changing the size of the wire the 

 most important change in the characteris- 

 tics of the tuner will be the wave length, 

 to which it will respond. By increasing the 

 size of the wire the wave length to which 

 the tuner would respond would be decreased.. 

 By using smaller wire the respondent wave 

 length would be increased. In this partic- 

 ular tuner it would be possible to use any 

 size of wire from about No. 23 to No. 28, 

 bearing in mind, of course, the change in the 

 respondent wave length. For your purposes 

 we do not believe this change would be of any 

 great importance to you. 



Q. 2. Is it also necessary to use enameled 

 wire? 



A. 2. Enameled wire permits the greatest 

 number of turns to be placed on the coil and 

 increases the respondent wave-length over 

 that available with other types of windings. 

 Spaced bare wire or single cotton or silk 

 covered wire may be used quite satisfactorily. 



Receiving Set 



E. E. Z., Long Island City, N. Y., asks : 



Q. 1. Please give me the dimensions of a 

 receiving transformer to use with an audion 

 detector to have a range of 200 to 1.500 

 meters. I desire to use switches instead of 

 sliders. 



A. 1. Wind l.'iO turns of No. 28 S. C. C 

 magnet wire on cylinders 5 %: and 4% inche? 

 in diameter respectively and five inches long. 

 You can arrange the taps to suit yourself. 

 On the primary we would suggest that you 

 make arrangements for tuning to every other 

 turn, and on the secondary ten points would 

 be sufficient. 



Q. 2. Please give me the dimensions of a, 

 loading coil to increase the range to 4,000 

 or 5,000 meters. 



A. 2. Wind No. 28 S. C. C. magnet wire 



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