Radio Broadcast (May-Oct 1926)

RADIO BROADCAST ADVERTISER 263 Now, I Have Found tioms of Value to the Exchange of Ideas Radio Constructor and suggesOperator eONTRl BUT TONS to this department are welcome and those used will be paid for at the usual rates, that is, from two to ten dollars each. A pri^e of twenty-five dollars is given for the best idea used during each three-month period. The prizewinner for the current period will be announced in the August Radio Broadcast. Manuscripts intended for this department should not exceed about three hundred words in length, and should be typewritten. Little consideration can be given to manuscripts not typewritten. Envelopes should be addressed to this department, Radio Broadcast, Garden City, New York. Verniers and Their Application to Radio THE word "vernier" has come to mean in radio terminology "a slow motion," but in engineering, it has kept its original meaning — to divide into, or measure, small parts. This method was called after its inventor, Pierre Vernier, who died in 1637. After a careful examination of advertisements and descriptions of so-called vernier dials, only one (the Erla) was found that had a true vernier incorporated in its design. In the "Now, I Have Found" department of the February, 1926, Radio Broadcast, page 490, appeared an article on a long-wave receiver, in which a piece of slotted bakelite was used to vary the distance between the coils. This method would be an excellent one for short-wave receivers, and if the bakelite strip were graduated with a scale, and a vernier added on the panel (one such as is shown here), very accurate calibration of the receiver would be possible. Coil positions could be recorded to the fortieth of an inch, or closer even, if a smaller scale is used. To make such a vernier scale, first decide the size of the main scale divisions, then, with a good pair of dividers, divide on this vernier scale, into ten equal parts, a length equal to nine divisions of the main scale. In the illustration, Fig. 1, one quarter of an inch is supposed to be the main scale division. Therefore, the vernier scale which is divided into ten equal parts, lines of the main scale. In the example given, this is at 5 on the vernier. The second decimal point is 5, then. The complete reading is therefore 0.85, as stated above. The application of this vernier arrangement to the long-wave receiver mentioned previously, is a simple matter. The main scale is pasted on the sliding strip of bakelite while the vernier scale is pasted to the panel by the side of the sliding strip. When a station is heard, the coil setting may be jotted down by following the instructions above. It is simple to slide the strip of bakelite along until the required setting is found when tuning-in for a station which has previously been heard and its setting marked down. Douglas H. Nelles, Ottawa, Ontario. A Lateral Basketweave Coil Form DID you ever try to bore a dozen or so perpendicular holes in a small piece of wood to hold the pegs in a form for winding lateral basketweave coils? If yours was the usual experience, you have probably found that a drill press, or jig, is necessary in order to have the pegs stand up at right angles, as must be the case to make a neat looking coil. The following method of making the coil form has proved very satisfactory. Use a piece of wood | inch thick for the base. For the uprights get a pound of 20-penny f > Vernier Scale 10-< 2 3*" >0 v. 1 , I 1 .1 1 1 ! 1 I 1 V — 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 j 1 r 1 1 1 j( 1 1 1 1 | 3 2 1^ 2^ ^0 Main Scale FIG. I is 2\ inches long. Readings to one fortieth of an inch will be possible with the arrangement shown. If the main scale is divided into one-tenth divisions, and the vernier correspondingly changed, readings to one hundredth of an inch will be possible. Referring to the scale shown on this page, we see that the setting is 0.85, and this is the way it is read. First of all the reading on the main scale opposite the zero of the vernier scale is taken. In this instance it is less than 1 — it is something over 0.8. To find out what the second decimal figure is, we glance along the vernier scale and see that one of the division lines on it will be in alignment with one of the division finish nails. These are slipped into holes drilled at the proper points on a circle laid out on the base. The difficulty is to drill the holes perpendicularly. Take a second piece of wood about 4 x 4 x f inches. Drill a hole in its center, using a twist drill just a shade larger in diameter than the nails. Slip a nail through this hole and test with a carpenter's or draughtsman's square to see if it is perpendicular — which it probably will not be at first attempt. Drill other holes until you get one that is perpendicular. Mark it, and use it as a guide or jig, placing it over the base when drilling holes for the uprights. •Jc Tested and approved by Radio Broadcast The LYNCH METALLIZED RESISTOR ■4. The old carbon lamp consumed more current to give less light. Tungsten, which is metal, proved more efficient, more dependable. Metal long has been recognized as the most efficient of electrical conductors. TheLynchMetallized Resistor gives non-arcing, conductive resistance. It marks as great an advance as did the tungsten lamp. Arthur H. Lynch PRICES:.25 to 10 Megohms .50 above .01 to .24 " .75 .001 to .01 " gl.OO Single Mounting .35 Warranted — lutely Noiseless Uependaoie / COMPRISING a concentrated metallized deposit one-thousandth of an inch thick upon a glass core and sealed within a glass tube, each LYNCH Metallized Fixed Resistor wins in the exacting tests of time and service. This better'built product has been endorsed by leading engineers and experimenters and the test laboratories of the leading magazines. If your dealer cannot supply you, it will pay you to wait for the mail — we ship postpaid, and Lynch products are sold on a money-back guarantee. Dealers — Write us! ARTHUR H. LYNCH, Inc. Manufacturers of Radio Devices Fisk Bldg., Broadway &. 57th Street New York, N.Y.