Page:Popular Science Monthly Volume 88.djvu/337

 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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