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Page:Popular Science Monthly Volume 90.djvu/325

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How to Become a Wireless Operator

VI. — Simple Adjustments and Connections By T. M. Lewis

��SKILL in receiving, which includes both the abihty to "copy" Morse and Continental signals rapidly and ac- curately, and facility in the adjustment of the receiving instruments, is one of the most imjKjrtant things for a radio-operator to develop. Knowledge of the transmitting

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apparatus and its manipulation, as well as a clear and firm method of handling the key in sending, is of course essential; but without knowing how to adjust the receiv- ing tuners and detectors so as to get maximum strength signals with the least interference a wireless man soon finds himself in trouble. The only way to gain the needful familiarity is through practice with the apparatus itself; and at the same time the student must realize how and why his instruments work. Unless it is clear to him just what effect will be pro- duced, and why, whenever he makes an adjustment or changes a setting, he will not progress very rapidly.

In the January article of this series it was shown that the detector and stopping condenser previously described could be assembled with either of two types of tuning coil (the "one-slide" and the "tvso- slide" varieties) so that messages could be received from commercial and naval sta- tions hundreds of miles away. Receiving practice gained through use of receiving apparatus in the ways indicated will form a valuable foundation for further advances in the use of more complicated tuning

��arrangements, and the experimenter should familiarize himself with the action of the circuits shown in Fig. 3, 4 and 5 of the last article.

Methods oj Connecting

The method of connection shown in Fig. 5 of the January article is the most effective of all the simple arrangements. It requires a tuning coil with two variable contacts or sliders, in addition to the usual detector, telephones, and stopping-con- denser. This same tuner may of course be used for tests of the single-slider "hook- ups," by using only one of the movable contacts; such trials will demonstrate beyond doubt the fact that, when it is properly adjusted, the two-contact arrange- ment gives louder signals with greater freedom from interference. Somewhat more skill is required to get the best results from the two-slide than from the one-slide apparatus, but the effort is more than repaid.

Sliding-contact tuning coils for use in any of the circuits described may be pur- chased from the wireless supply houses, and will give reasonably good results. It is very easy to make such tuners, since all that is required is a coil about 3 in. in diameter and 8 in. in length, wound with insulated wire of about No. 22 gage and fitted with tw^o contacts which slide along rods supported above paths from which

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the insulation has been scraped. Such instruments have been used in commercial radio-telegraphy, and were very common in the stations of eight or ten years ago. It has been found, however, that the sliding contact upon the coil itself is not particular- ly desirable, since the slider finally wears

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