HELPFUL HINTS

Radio Record, Volume I, Issue 27, 20 January 1928, Page 3

HELPFUL HINTS

SEE IMPROVE YOUR RECEPTION

CRYSTALS {N REFLEX CIRCUITS, For extreme sensitivity there is nothing to beat a galena crystal when used in conjunction with a fine copper catwhisker. Crystals marketed under various names, ending in ‘‘ite," are, in the majority of cases, galena, DULL EMITTERS BURN OUT. Don’t burn dull emitter valves too bright in order to try to get better signals The filaments may not burn cut, but the dull-emitting properties of the valves will be impaired. BES POSITION FOR INDOOR AERIAL, e To obtain the best results, an indoor aerial should be as high as possible. The highest indoor position in any house is immediately beneath the roof tiling. An aerial consisting of six or eight parallel wires, attached to insuletors, screwed to the under-side of the roof framing, is the best possible arYaugement. In actual practice, such an aerial gives excellent resulis, especially if used in conjunction with a fairly seusitive valve receiving set. REFLEX RECEIVERS, e If properly wired, a reflex receiver will perform remarkably well. It must be remembered the valyes in these receivers are doing double duty, as both tadio-frequency ainplifier and audio-fre-quency amplifier at the same time, and therefore cantlot perform at maximum efficiency. But reflex does give good results when used properly.

HAND-CAPACITY EFFECTS, A metal shield will reduce hand capacity effect to a minimum in a set. It has been found that in a well-con-structed, carefully designed set, capacity effects are absent, USE OF BY-PASS CONDENSER. It is a good plan to use such a fixed condenser, although the sect will operate Without. It usually improves the control of the regeneration. RANGE OF CRYSTAL RECEIVER. The consistent range of a crystal receiver is from 10 to 25 miles. However, under freak conditions, receivers of this type have been known to pick up signals of stations some hundred miles away. Much depends upon the quality, length, and height of the aerial. LOOSE VALVE CONTACT, When the valve does not fit properly in its socket, a toothpick or a match. whittled down to form a wedge can be placed between the socket and the yvalye | te hold it tightly in place. | | CRYSTAI SENSITIVITY. | A sensitive spot on a crystal soon loses its sensitiveness; when one spot is exhauted, find another, until the crystal is finished. Keep your fingers off the crystal. CONCERNING CONDENSERS. The fixed condenser in a receiving set should have mica diclectrics for best results. Do not use condensers in which the dielectric is paraffin paper. For the best operation of a set it is important to make sute the condenser is of the proper capacity for the part of the cirsuit for which it is intended. CRYSTAL CUPS, When mounting a crystal in a cup (of the type in which the top or cap is ‘setewed down to hold the crystal in ‘place, you wili sometimes find) especially if you are using a small fragment of crystal, that the latter cannot be fixed tightly even when the cap is screwed home. ‘To get over this difficulty, take a piece of tinfoil and crumple it up in a small pad, place this in the cup first, to raise the crystal up a little, and then screw down the cap. Add more foil if necessary. If the hole in the cap is too large, roll some foil into a little stem, and bend this round into a ting, and lay on the top of the crystal. Or a brass washer haying a smaller hole than that in the crystal cap may be introduced npon the top of the crystal. EARTH CONNECTION, A water-pipe is not the only method of making a good earth connection, A large metal object buried will also answer the purpose of a ground, In some cases, where it is impossible to obtain a good ground connection, a counterpoise is used,

HOME-MADE DRY "BY BATTERIES. These may be constructed by breaking ordinary flashlight batteries in separate cells, and connecting them in series, ‘These batteries usually have from two to three cells, and some extremely larger ones have*four. Each cell will have approximately a yolt and a half. It will, therefore, reqnire 15 of these cells to make a 224 volt "RB" battery. | PLACI: SET NEAR THE GROUND It is not commonly known that it is preferable to place the set near the earth, rather than near the aerial. For exaniple, if you have the choice of an attic or a ground floor room for your wireless room, it is better to choose the latter. ‘Lhe lead-in may be fairly long, but the earth lead should be as short as possible,