THE WIRELESS WORLD.

Otago Daily Times, Issue 19759, 9 April 1926, Page 6

THE WIRELESS WORLD.

By Magna Vox. Though the Exhibition is drawing toward* it* triumphal close, VLDN continues to extend its feelers to every profitable part of Logan Park. During the week a microphone was placed in the Wellington Court, where weekly concerts are now given to large and appreciative audiences. These •will be on the air regularly, commencing from this evening. Programmes of more than ordinary merit have been transmitted in the last seven days and listeners report that reception has been good. This may be accounted for partly by the fact that the day* are now growing short and the concert each evening is given well after _ sundown. As every radio man knows, night conditions are infinitely better than daylight, and . the weather end atmospheric conditions ruling at present have assisted. Many are asking what will be done with VLDN when the Exhibition closes, but nothing definite seems to have been decided yet. “I have had no instructions or advice,” stated Mr Webb, the announcer, when interviewed. Much money has been spent at the station, and if the original statement of Broadcasters (Ltd.) is to be adhered to, the big set will remain in Dunedin as one of the four stations which Broadcasters will control in New Zealand. If this is done listeners will be able to expect something good in the way of transmissions. There will be no faulty location, no interference from amusements devices, and the concerts will be given under conditions that make for maximum efficiency and consistency. A WIRELESS SLUMP. ‘‘Two things point clearly to a marked decline in the popularity of broadcast receiving in New South Wales. One is the reduction in the number of licenses for sets, compared with an increase in Victoria; another and even stronger manifestation is the cancellation of no fewer than 5352 licenses for February, compared with only 699 in Victoria,” writes a special correspondent from Sydney. “Even allowing for the fact that the Victorians, as a people, are more homeloving than the people of New South Wales, the decline in the popularity of wireless in the latter State is viewed with disquiet by those interested in broadcasting The position has been reflected also in a slump in the sale of wireless receiving apparatus during recent months in Sydney and throughout the State generally. “It is contended by some listeners-in that only trained experimenters can, under existing conditions and with the average sets, remain “constant” on any one station, outside 2FC, one of the leading stations, within the metropolitan area for a whole evening without experiencing annoying interference. _ What the average person wants is a simple set that is moderately ea*y to tune, and that when tuned will 'str.y fixed.’ A QUESTION OF LICENSES. “The belief is expressed that there will ba no big rush for the renewal of licenses as long as local programmes, about which there is nos a great deal of complaint, cannot be enjoyed throughout an evening except by owners of “selective” sets, costing anything from £IC to £IOO. 'the owners of the humble crystal receiver and the onevalve set feel that as they pay their licence fees they are entitled to some consideration. Following the example of Victoria and South Australia, a movement is tow on foot to form an organisation among Jitteners-in for the protection of their interests. Whi'o there are growl? at the programmes pit on the air, the bulk of enthusiasts appear to be satisfied with them, . if only they are permitted to receive the • programmes without continual interference. NEW AUSTRALIAN STATION. On Monday, March £9, Australia’s largest and most powerful radio station was opened by th-» Postmaster-general (Mr W, E. Gibaqn). The first number to be sent on the air'was a song by Mr Alfred O’Shea, who is the highest paid radio artist in the monwealthThe new station, which is at Pennant Hills. just ten miles from the studios in ] Pitt street, is housed in special buildings erected for tho purpose, and is considered the moat complete and powerful station in the Southern Hemisphere. It is capable of developing a power of over 10,000 watts. The main aerial is suspended from the mast 400 ft high,. which has supported the

aerial of the Morse station VIS since 1912. It should be quite effective, nevertheless, as it is twice the height of any other broadcasting _ aerial in Australia, and 20 limes the height of the aerial used by Mr Maclurcan. a well-known expert, in his recent test with England, SOLDERING. In building a radio set the thing which the average man gets into difficulties over is the soldering of the connections. Solder- ■ ing may be an art, but it is an easy art. and one which even some of the most in- ! expert of set builders have conquered. There is one great fundamental rule in successful soldering, and that is cleanliness. Solder will positively not stick to a surface syhich is oily or corroded, or dirty in any way whatever- Fully half of those who have trouble with soldering because the surfaces will not stick, or the solder drops off, have not realised that a clean surface is first essential Another important thing is the condition of the soldering iron itself. Various kinds of irons may be used, but an electric one is by far the best from all points of view. An iron to give satisfactory service must be scrupulously clean and tinned. Tlie flux used should be specially suitable for the material to be soldered, and the solder should also be of a type suitable to be properly worked. ’ GETTING BEST RESULTS. Tuning the radio receiver, like making love, is an art —not that I profess to know anything about the latter, but I’ve read it in story-books (says Mr C. D. Maolurcan, an Australian expert). For the person who is readily satisfied there is nothing really difficult or complex about it. He can listen without much effort to 2BL or 2FC. It is only the chappie that wants the melons in the other fellow’s yard—who wants to listen to Melbourne and Adelaide—that has to go about the business with a certain amount of care. Keeping these ' truths in mind, we find th the tuning the radio set can he accomplished in two widely different ways, the result in both cases being somewhat the same, though the degrees of self-satisfaction provided by the two differ greatly. Perhaps the more generally adopted of the two consist ;i obtaining the services of the technician responsible for the installation or some “radio expert” friend to tune in the various stations, making, at the same time, a list of their call signs, together with the settings of all the knobs and dials corresponding with the best adjustment. The other scheme, tho one that makes thrills go right through you and button up down th= back, is to learn what happens when the dials are twisted or the knobs are twirled, so that tuning becomes a process ! of dial juggling with a purpose. No one j who has not tried it an realise the plea- j sure that comes to the newly-initiated I broadcatcher, who ring just what j happens when any knob is touched, revolves the secondary condenser in the right hand, approaching resonance, as a cat approaches the canary, whilst at the same time passing his left elbow under the right ankle, grasping the reaction firmly between the thumb and forefinger and introducing just that degree of regeneration necessary to lift the distant music from the mire of unwanted signals anj static. But to return to technicalities. The radio receiver, or all of that portion which is tuned, can be divided into what is known as oscillatory circuits. These circuits are the electrical equivalent >f the balance-wheel of a watch, the pendulum of a clock, a violin string, or any other mech ical oscillator. When a current is introduced into one of these oscillatory circuits it surges back and forth through tl. circuit at a frequency which is governed by the constants of the circuits. In the radio set thesi dilatory circuits are composed of coils of wire, iu the form i honeycomb, spider-web, ojjust ingle layers, connected across variable condensers—components too well known to require description. In addition to these coils and idensers, there is always a certai., amount of resistance present (the undesirable factor), and, with poor coils, poor condensers, or poor wiring, this resistance is increased. GOING TO EARTH. An important feature of the receiving set is the “earth” mat is obtained.. Too little attention is given to this side of sec construction by amateurs, wttn tne result

that tho work of the set is often not what it should be. Recently an English expert. Dr R. L. Smith Rose, carried out a series of experiments to determine the most suitable earth system for xeception on the broadcast band of wave lengths. Three systems were tried for the earthing connectionFirst a good water main was available, which lay in damp ground for an uninterrupted length of about 100 yards: second a buried earth was constructed by buying a sheet of tinned iron, 4ft by 3ft, at a depth of 3ft, immediately under the aerial lead ifi; and, thirdly, an experineced earth screen was arranged below the aerial and covering a piece of ground 100 ft long by 30ft wide. . Measurements were made of the received aerial current when using these different types of earth connection, and the effect of varying the arrangement of the earth screen was also investigated. The current received with the buried plate was about 15 per cent, less than that with the water pipe. With a screen comprised of a single insulated wire immediately under the aerial and at a height of 3ft above tho ground, the received current was over 60 per cent greater than with the water pipe connection. With four wires 3ft apart in the screen the received current \yas twice as large as that with the water pipe. It would follow, therefore, that an earth screen has decided advantages over the ordinary earth connection when a 100 ft aerial is used, and it should be noted that the earth screen will, in addition, increase tho selectivity of tho whole receiving system. Four wires may be impracticable, but a practical and highly satisfactory arrangement is to have two insulated wires sft above the ground running parallel to the aerial along the edges of a 30ft space.