THE WIRELESS WORLD.

Otago Daily Times, Issue 20289, 23 December 1927, Page 5

THE WIRELESS WORLD.

NEWS AND NOTES. By Magna Vox. Items of local interest aro invited by “ Magna Vox ” for publication m this column. It is necessary that such matter should reach this office by luesday ol each week for insertion on the following Friday. ANSWERS TO CORRESPONDENTS. “ Crystal,” Dunedin.—The best method of finding the most sensitive spot on the crystal is to move the cat-whisker about over the surface until the loudest signals are heard. “Detector,” St. Clair.—Try changing the valves about in the sockets, as you mav bo using the poor one as the detector. If you arc not already using a C battery I should advise your adding one at once. , . C. A. V-, Oamaru. —Your charging rate is about two amps., and to charge your battery fully it would need a 36 hours charging. The best and surest test, however, is the hydrometer. Gassing freely is another good indication of a fully-charged battery. “Loop,” Waikoikoi.— Using a loop will certainly do away largely with your trouble, but at the same time you will sacrifice a tremendous amount pt volume; and, with your set, would hardly pick up Dunedin. Try reducing the length of your aerial to about 40ft with the same length of lead-in, and write me again. PRESERVING THE VALVES. Valves should not be burned too brightly or their lives will be shortened. Turn on the rheostats only so far as the point Rt which best reproduction is obtained, io turn the rheostats further than this is to shorten the lives of the valves without any benefit.. By operating the filament of a valve at 95 per cent, of its lated voltage its life will bo doubled. DIRECTLY EARTHED AERIAL. An aerial connected directly to earth is capable of receiving radio waves ot a wave-length-about four times its length ot wire. Thus a single wire 100 ft in length can receive waves of a wave-length of 400 ft, without the addition of the usual tuning inductances in a wireless increase or decrease the wave-length at will. A metre is equivalent to 3..8U, oi, roughly, 3ft 3Jin. CHECKING ELIMINATOR CONSUMPTION. The consumption of an eliminator can easily be checked upon the household electric supply meter during day time reccption when no other current is being taken. If current consumed in one hour does not exceed one division on the “ hundredths dial, then the consumption is satisfactorily low. At this rate tho rotating disc ot tlio motor will only bo perceptibly moving. LEAD IN INSULATORS. The best insulators to use for load-in wires requiring support are t!ie post office or “ petticoat ” pattern, as these give practically perfect insulation in all weathers. Attention should be given to the aerial halyards when necessary in order to keep the wire at a reasonable tautnoss. To prevent halyards making an irritating noise by flapping against the pole during a wind, a crosspiece ot wood can be nailed to the pole a fey feet above the griund, and the passed through a notch in the end befoie fastening them to the pole This should keen the halyards clear ot the pole tor Iheir whole feugth. .Then the™ is the old slogan about having a good, earth many listeners are still handmapping their reception h" not testing other earth con nectfons than the water-pipe, which a sometimes quite good, but not ahvaj". A true constructor is always testing, altering, improving, but the sct-ownor i ho is not a constructor should not let things rest until he is getting the best reception possible with the apparatus, in h possession, and improvements o aerial and earth circuits are within the enpa bilities of most people. A SOLDERING HINT. There is quite a knack in soldering, but it is acquired with a When soldering a joint, hold the tinned part of tho hot iron against the wires to be fastened, and then apply a little: ot the solder to the wire. -C lle vv ill flow over the wire, and, if the iron is then removed, the excess will be removed bv the iron. Use the convenient wiresolder which has a-rosin core. This rosin core first flows over the joint to be soldered and removes the oxide, the solder then flows upon the clean wire. If ordinary wire solder m employed a little flux must first be applied to the joint, and after this the solder. Rosin flux should be used because it is non-acid and does not continue to act on tnc wire after the soldering process is comnleted. Acid flux sometimes leaves green deposits on the wire, and often is responsible for “noisy joints. The rosin flux takes a little time to do its work, and the iron should be held on the joint until the solder “ flows "on the wire. When the iron is removed the joint is not com pleted until tho solder visibly sets oi “freezes.” The process is really easy after one tries it a few times. ADJUSTING A NEUTRALISED SET. If a set with neutralising means is to he operated to the best advantage it is necessary that such neutralising device be properly adjusted. The method ot neutralising a set with one stage ot hjgjj, frequency amplification and some method of regeneration is set out below, and will he found simple and effective. The object of the method is to find an adjustment of the neutralising condenser which will allow the greatest setting of the reaction control to be used without producing oscillation. To begin with, the neutralising condenser and the reaction control are both set at a minimum, and then the tuning condensers are both set so that the two tuned circuits are in step with each other. At these settings it will probably be found that the set is m a state of oscillation, and this state may be observed by touching the grid terminal or those plates of the tuning condenser connected to it, and listening tor the click both on placing the anger in position and on withdrawing it. U will possibly be found that the -et twII only oscillate when the two circuits are in tunc, the presence of oscillation will indicate that they are in this state the capacity of the neutralising condenser should now be gradually increased, testing for oscillation as this is being done, and soon it will be observed that oscillation has ceased, and will not begin again even when the tuning dials are readjusted, ihe next step is to increase the reaction unti the set commences to oscillate again, and then increase the neutralising condenser setting until the oscillations cease. Readjust the tuning condenser slightly, so as to make sure that the set is stable under these conditions. Carry on these operations until it is found that the setting of the neutralising condenser has been increased too much. When this state is reached it will be found that further increases in the capacity of the neutralising condenser will not cause oscillations to cease, but will have the effect of making them stronger. Bring the setting of the neutralising condenser back to the point which is thought to be tho correct adjustment, and it will bo found if this is tho correct point that when the two tuned circuits aro in step and the set is brought to the verge of oscillation by the reaction control, a slight movement of the neutralising condenser in either direction will immediately cause oscillations to be set up. It is desirable to carry out the aboveoperations at some point near tho middle of tho tuning range of the set, and, of courso, it is not necessary to state that the whole set should be in the final state, with all the valves, etc., in the position which they will occupy ultimately. In cases where two-volt or similar valves are used with standard screened coils or other types of intcrvalve coupling, it maybe found that poor signals and other difficulties arise. These may be due to the fact that such couplings were designed primarily f°r six-volt valves. An increase of tho plate voltage of the high-frequency stage may help, and it is often quite worth while increasing the grid-plate capacrty of the high-frequency valves by connecting an ordinary neutralising condenser between tho grid and plate setting it about half in. 'J'he neutralising condensers are then anjusted in the usual manner.

A YOUNG MAN'S BUSINESS. It is surprising when one look?, round and reads of conditions m other counlnt' to note the number of yountr men in the wireless industry. In the broadcasting

services, in trading and manufacture of equipment, in conducting wireless services on ships and of course in the field of the amateur experimenter the same conditions are observed—youth predominates. Yet it is not altogether surprising. Wireless is so young and—particularly in broadcasting its appeal s° strong to energetic and ambitious young men, that one would imagine that it would bo the younger generation that took the lead in development. Wo ail remember tho early days—only four or five years ago—when broadcasting wa s a novellv —tho “plaything of youth”—when parents and friends observed with a kindly if not proud tolerance the strange gadgets used by tho smart boy of tho family to “extract music from tho air.” The boy wa 3 regarded as doing no harm in particular, and occasionally it was thought Ins gadgets might bo the forerunners of something really useful. And while those boys were making up their receiving sets from scraps of wire, cigar boxes, and weird contraptions, other boys were making and operating wireless transmitters. These transmitting equipments sent out tho music that was extracted by the receivers. The number and quality of tho transmitters tho receivers improved and keen business men began to so e prospects of a useful and profitable industry being established, and so the industry commenced and grow up. But the reign of tho young man did not ocaso with tho commercialising of his hobby. Rather his roign in another domain began. For we find to-day tho amateur is still very active in his own domain of experiment, and in tho broadcasting stations, and tho radio shops. The young men aro vastly in the majority. In tho management and direction of tho broadcasting service, too, ono finds the older man but seldom. In an organisation like 31,0, Melbourne, from the general manager down, tho young man is conspicuous. It is so in other broadcasting services also. The history of wireless since Marconi’s classic experiments has many references to voting men’s work. Marconi himself was under 21 when he startled' the world with his transmissions. Do Forest was likewise a youngster when ho pioneered his wireless systems. And our own Australian Ba.sillio, who was responsible for putting wireless on tho Australian map, was erecting wireless stations in Russia- when he was 21. In America one need only mention Armstrong as a classic example of the successful youthful pioneer. We must conclude that there i* something in wireless peculiarly attractive to youthful imagination. Tho scientific foundations and art of broadcasting and other wireless services provide a fascination not found in any other study or industry.