Page 8 Advertisements Column 1

Evening Star, Issue 22881, 12 February 1938, Page 8

Things to Do and Make By Handicraft A SIMPLE MICROPHONE FOR WIRELESS ENTHUSIASTS A good microphone is, contrary to general belief, quite easy for the handyman to make. Follow these directions given by Handicraft and you will be surprised at the results. THE Reiss type microphone, because It Is simple and gives good results, Is being used by many experimenters throughout the country. To build this type of microphone, you will require the following materials:— I block of wood, 4in. cubed. 2 brass rods, Jin. wide, SJin. long. 1 small sheet of clear mica (6ln. square). Half ounce of fine polished carbon granules. - Take the brass rods to a jeweller and have them gold plated. If you do not Drill another hole Bin. wide from the centre top edge of the window to the top of the block, but be careful not to break through the front edge. This is illustrated in the cross section shown in Fig. 2. Then prepare the mica, which is glued across the window. It must be very thin. The sheet you purchase will be quite thick, so you will have to split it until it is about the thickness of a thin sheet of paper. ‘ , ~ .. The easiest way is to hold the mica on edge under a steady stream of water from the tap and split it with a knife. The water will help to keep the split even. You may have to do this three or four times to get the desired thickness. Cut a piece 41n. square and glue it across the front of the block. When the glue is dry, fix the rods firmly-in their holes, and pour in the carbon granules through the hole shown in Pig. 2 until the “window” (which Is now covered by the mica) is as full as possible. Put a small screw in the hole so that the granules cannot be spilt. The connections to the microphone are made to the rods, and a convenient method is to solder a wire to each rod and connect Fig. 1. wish to use plated rods, highly polished carbon rods will make satisfactory substitutes. The block of wood is the next consideration, and (Fig. 1) shows the necessary preparation. Drill two holes, Jin. wide and 3§in. long from the top so that the edges are about Jin. from the front of the block. These holes take the rods, and are spaced 3Jln. from centre to centre. Next cut an area 3iin. square and Jin. deep from the front and sandpaper the back. This area Is called the “window,” and it will be seen that the “window” will expose the holes drilled for the rods. * 8* U ** pc HOLE FOR POURING IN GRANULES FJG-. S BATTERY li'r£3 is as & 1 MIKE switch FIG. 3 FOR A WINDY DAYj) Fun With a Windmill TTERE Is one way of making a paper XI windmill, although probably you know of a different method; — Fold a square piece of paper (any size) up and across the middle and from corner to corner. Fold the upper and lower edges to the middle, crease, and open. Fold the left and right edges to the middle, crease, and open. Then turn the paper over and fold the comete to the centre A THIMBLE CASE * Something for Girls To make this novel thimble and needle case you will need a small quantity of three-ply, pale blue wool, about a quarter of a yard of narrow yellow ribbon, a fairly line crochet book, and a circle of cream flannel Sin. In diameter. BEGIN at the top of the cream flannel by making a chain of three stitches. Join and double crochet twice into each chain. Next row round do 1 d.c. and 2 d.c. into every alternate stitch, then continue 1 d.c. into every stitch for the next six rounds. ' * Begin the rim of the hat by making two treble into every stitch for the first and second rows. After that make one treble, two treble into every alternate stitch for the next six rows, and finish off. Take the small circle of flannel and buttonhole neatly all the way round. Top sew this piece of flannel to underneath the rim of the hat, leaving just sufficient space through which to slip the thimble into the crown of the hat. Slip two or three needles across the flannel where the opening is so that the thimble is secure, and tie a band, and finish bow around the base of the crown. This will make a very attractive and useful addition to your work basket. _ them to terminals screwed in the back of the block. To operate the microphone, it must be connected in series with a battery, and the primary winding of a transformer. The secondary of the transformer is connected to the amplifier (or to the pick-up terminals of your receiver). The circuit connections are shown in Pig. 3. The transformer should really be a special microphone transformer, but an ordinary audio transformer will serve, although the volume will not be so loud. To give a finished appearance, strips of bakelite can be screwed along the edges to cover up the rough edges of the mica. To prevent damage to the mica put a piece of wire gauze across the top of these strips and hold it in place by four more strips of bakelite screwed on top. Be sure that the wire gauze does not sag and touch the diaphragm. PID2, FIG. I flu. 3. and open. Torn the paper over again. It should look like Pig, I. Next’ bring the middle of each edge to the centre. There will! then be four corners standing up. Prffis these four corners outward and create, and your windmill will appear as in Pig. 2. paste a small circle of paper ii the centre of the windmill to hold the folds in place. Pin it to the end cf a stick (Pig. 31. You can make a moie attractive windmill if you use paper coloured on one side. Begin to fold vith the white side up. ' GARDENING HINT: S A MATCH PROBLEM EE if you can solve this problem before 1 next week:— Arrange five matches on the table, as PROBLEM shown in the illustration. The problem is to add one macch and make 100. Can you do it? The solution will be given next week. r'. //, SC SET WOSt THJS OH lAVN TRY this handy Idea next time you want to elevate the nozzle of your garden hose, but cartiot find a convenient object on which to rest it. Arrange the hose In the way shovn. The spray will be directed upward an*; 1 will not damage tne surface of the lawn . . On some hoses the particular type Jpf nozzle will not alloy it to remain in the desired position whin the water is turned on, but in that casea looped piece of wire fastened near the xozzle to drop over tne