Page:Popular Science Monthly Volume 91.djvu/968

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952

��Popular Science Monthly

��most used letter in the alphabet, is rightly given the shortest Morse signal; T being the next letter in order of frequency is awarded the next shortest signal, and so on, until we find Z, the least employed letter, deservedly saddled for its laziness with one of the longest Morse signals.

But by Mr. Morse's allocation of English letters, as will be seen on reference to column five of the diagram, only 14 out of the 26 letters are correctly suited. This means great loss of time in transmission. It may be observed in this connection that the Morse code is in use on no less than 95 per cent, of the telegraph lines of the world.

It seems almost a pity that advantage was not taken of the advent of wireless telegraphy to redistribute the Morse sym- bols on the ideal basis here demonstrated.

��Making a Good Outdoor Ground for Wireless Apparatus

THE outside ground wire for the wireless set or other experimental apparatus of the amateur is continually meeting with misfortune. No ordinary joint seems capa- ble of permanency. This is usually due to

���The old and the new methods of making a permanent ground for electrical apparatus

inconvenient locations, especially in crowded cities where the shed or "shop" is likely to be next to an alley fence or in a similarly exposed place.

In our usual thoughtless following after precedent we are likely to believe that the standard grounding joint customarily em- ployed by telephone and electric lighting companies is about the only grounding joint possible. Consequently every time the ground wire gets stripped off its pipe, we replace it with another of exactly the same sort. This usual grounding joint is shown in the illustration. It consists simply of the groundwire wrapped several times

��around the pipe that goes down into the earth, the turns being held in place by oc- casional dabs of solder. Naturally this ar- rangement is not very strong mechanically.

A more satisfactory joint can be made as follows: Take a round file and brighten up the interior of the pipe at the end; then wet some waste and tamp it down into the pipe a distance of about \\i in. Bunch up the end of the ground wire until it fills most of the space above the waste ; then heat the end of the pipe and the bunched-up wire with a soldering torch, at the same time applying a little soldering paste, in order that the solder to come may stick easily. When the end of the pipe becomes hot enough to take the solder readily, apply enough of that material to completely fill the end. This process will naturally en- tirely submerge the bunched-up wire. With a cloth, round off the upper surface of the solder while it is still warm, until it forms a neat cone, with the ground wire coming out of the center as shown in the illustration.

This sort of a ground connection buries the end of the wire inside the pipe, instead of causing it to cling to the exterior as best it can, as with the old way. The end of the pipe may be subjected to very rough treat- ment indeed, without disturbing the wire.

Auto-Transformer in Headlight Circuit on a Magneto

HEADLIGHTS from the Ford magneto are so wired that when one of them burns out the circuit is broken and the other one goes out. This trouble may be easily overcome by the use of a small auto-transformer. Such a transformer may be made in a rectangular form from thin strips of sheet iron }/% in. wide, cut in lengths to make four piles 1 in. high, two of which are 1^2 m - long and the other two 2Y2 in, long. These are all given a coat of shellac varnish and allowed to dry; then they are built up in dovetail fashion after the coils are placed on one of them.

Make two coils of 120 turns each, using No. 20-gage wire — about % lb. will be re- quired. The method of placing the coils on the core and the necessary wiring are illus- trated. Should the device fail to work satisfactorily, reverse the connections of the coils. With this outfit, the burning out of one headlight will not cause any percepti- ble change in the light from the other. It is also possible by winding another coil on

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