Radio Review

Evening Star, Issue 20061, 29 December 1928, Page 16

Radio Review

[By “HENRY”]—

Flashes from Everywhere.

RADIO IN HOSPITAL. Through the instrumentality of the Rev. V. G. Bryan King ami. the generosity of many friends, _ a fivevalve radio set has now been installed in the Dunedin Public Hospital. The introduction of wireless is keenly appreciated by the patients in the institution, and the set will certainly relieve the tedium of hospital life for many unfortunate people. Little imagination i required to realise the boon that this innovation will be in the hospital. While the installation has been completed, funds are still required, the sum of £9 being necessary yet. There is not H slightest doubt that, all radio enthusiasts will rally round and help this deserving cause. Supscrb'tions, which may be sent to Mr King, will bo appreciated. OPERATORS’ CERTIFICATES. The Post and Telegraph Department has issued the new syllabus for the examinations for first and second class certificates tor ‘wireless operators, drawn up under the provisions of the .'lnternational Radio-telegraph Convention, 1927, and all radio operators are advised to acquaint themselves with the subject. Cue of the appendices gives the conditions under which holders of existing certificates may be granted certificates under the new international regulations. Holders of first class certificates are notified that their certificates will remain valid for three years from January 1, 1929. If desired, liret class certificates under the new (1927) regulations will be . issued, provided they submit themselves' lor an examination the scope of which is given. Those, who do not desire to take the examination may receive, without pay incut of fee,' a second class certificate. Existing second class certificates will remain valid for three years Irom January 1, 1929, and those who desire to obtain a first or second class certificate under the new regulations must submit themselves for examination. STOPPING NOISESAs a rule, it is usual to employ a variable condenser on the short waves for controlling reaction. It is impossible to keep such a condenser completely free from dust, and any small particles which become lodged between the two sets ot plates will cause a crackle and scraping noise as the condenser spindle is turned. This trouble may bo removed by inserting a fixed condenser in series with the variable one. The value of this fixed condenser may be in the neighbourhood of .001, although a much smaller one can bo employed if the variable reaction condenser is found to be too large. Incidentally, such a condenser acts as a safeguard for the valves in the event of the Variable condenser becoming shorted, in which case it is possible for valves to be burnt out. As a matter of fact, it is desirable to insert a series condenser for the above reason even on sets . intended for reception on the higher waves. AIRPLANE RADIO. If airplane service tests undertaken by the American Telephone and Telegraph Company between tho ground and a cabin airplane develop a,s rapidly! as some of the recent experiments in radio communication, it will soon be possible for anyone withift reach of a telephone to communicate with anyone yvho may be travelling by airplane. “It may be a matter of five years,” one of the engineers of the above company stated, “ and it may quite possibly' bo a much shorter time, before ■we achieve our object of an actual connection service between an object moving through the air and a station on the ground.” In the present experiments apparatus is being used by means of which the wave-length may be changed instantly, bo .that the most efficient and leastcongested channels may he found Irom moment to moment. WAISTCOAT POCKET SET. PROFESSOR’S AMAZING CLAIMS. Wireless in a waistcoat pocket is tho latest news from Berlin. , I’his claim has been imuß by a proics.->or of Jena University as the result of experiments he has earned out during the [ last twelve months. According to the professor, he uses ultra-short waves, three metres and less, and he believes that also hi_s discoveries wall bo of invaluable service to medicine. He has succeeded, he says with a, fraction of a watt, using ordinary valves, without aerials, in covering distances of nearly sixteen miles, and with higher energy he has covered 250 miles. The professor also says he has succeeded in telephoning by use of these short waves The transmitter is stated to-be no larger than a cigar box, and be has constructed receiver which solves with amazing simplicity the problem of detecting ultra-short waves. MAKESHIFT DRILL. It sometimes occurs that a small hole is required in an ebonite panel, and no drill is available. An ordinary bradawl will make a'very good substitute, and it is surprising how quickly it bores a hole. The method of using it is to rotate the tool backwards and forwards through about half a turn, pressure be-

lug applied to the handle. It is advisable to occasionally lift the point out of the hole and place it back in a different position, so ns to ensure that a really circular hole is made.

UNUSUAL ACCUMULATOR CHARGER. Designed especially for wireless battery charging, an interesting new battery charger has been produced by an English manufacturer. The device has been constructed to overcome certain of the unsatisfactory features of trickle chargers which are widely used mr keeping the filament accumulator charged in wireless sets intended to be operated from wireless mains with a minimum of attention from the owner. The trickle charger, although it has been widely adopted and gives general satisfaction, can be worked only at maximum efficiency when the current withdrawn from the battery in a day t operate the received is approximately equal to that returned to it by tho charger when the receiver is not in use. If a large set is employed almost continuously, however, the amount ot current withdrawn from the battery may easily exceed that returned to it by the charger. The result is that after somedays, or perhaps weeks, the battery is discharged* and must be recharged before the receiver can be used again. This will occur periodically as long as the receiver uses more current than the charger will put back into the battery. Uu the other hand, if the- receiver is a very small one, and it is used lor a comparatively limited period daily, the amount of current withdrawn irom it is far less than that returned by the charger. Tho battery is then drawing current from the chargor for a long period after it is fully charged. Not only does this waste current, but in many forms of chargers it causes unnecessary depreciation of the material in the rectifier. In addition it causes excessive loss of the water from the battery by electrolysis when it is fully charged, and, although an occasional overcharge may not damage a battery, continuous overcharging is likely to reduce seriously its useful life. To overcome these disadvantages • a charger which will charge a battery at a considerably greater rate than a trickle charger has been developed. Associated with it is a switch that will automatically bring tbo charger into operation when the battery is partially discharged, and snatch it off again as soon as the battery becomes fully discharged. Owing to the high charging rate of the device it will keep the accumulator fully charged no matter howlarge the receiver used with it may be, ami at the same time, preventing charging from continuing oucc the battery lias been fully charged, it will reduce the many losses which arc caused by overcharging.

BATTERY ISOLATION. AVOIDING LEAKAGE. There are many users of wireless sets who religiously isolate their l.t. and h.t. batteries by disconnecting the leads to the set, either at the receiver or battery end, each time the set is to be switched off. They prefer this to an ordinary push-pull switch on the front of the panel, stating that they have experienced trouble in the earlier days as the result of leakage inside the set. It is not deemed advisable to discuss the pros and cons of the procedure here, but rather to show how this “ isolation ” idea can be put into operation in an efficient manner, .and gives, in addition, the advantage that all connections—h.t., 1.t., and g.b. (if the lastnamed is used outside the set) —are .broken at the same time with extreme rapidity. Instead of mounting terminals on the strip of ebonite generally provided for that purpose at the back of the cabinet, fix into the hole positions small panel-mounting sockets, and make the receiver connections for the batteries to the soldering tags at the back ct the sockets. The number of sockets required will depend, naturally, upon the number of battery points brought out. As far as the battery leads themselves are concerned, they must be taken to an ebonite strip half an inch wide and a quarter of nn inch thick, and whose length is governed by the number ot terminals it replaces. On this piece of ebonite must be mounted a number of plugs, the holes being drilled so that they coincide exactly with the socket positions. Connected to the nuts and screws at the back of these plugs we have the various battery'leads, either arranged in the form of separate leads or as a multi-way battery cord, whichever fancy dictates. The strip holding the loads and plugs can be withdrawn bodily from the sockets when the set is finished with, and the set is then completely isolated, and by using good quality ebonite for tho strip there is no likelihood of any leakage taking place between tho respective plugs. The idea works admirably in practice. RADIO IN SCHOOLS. UNFAVOURABLE REPORT. . The Director of Education for Sheffield, Percival Sharp, has reported to his committee unfavourably with regard to the proposal to install radio in the schools of Sheffield (states the ‘ Christian Science Monitor’). “I am un-

** Henry" will be pleased to answer any questions through this column relating to th 6 fascinating hobby. Each correspondent must sign his name and address (not necessarily for publication). Kawsy items will be welcomed,

able,’ he says, ,“to recommend the committee to undertake the expense of maintaining the system which has been established as an experiment by certain generous donors for a number of schools, and in general I recommend that no provision for the present be made for any further expenditure in connection with wireless installations in schools.” This verdict is the result of an inquiry conducted by Mr Sharp into the results attained by the existing installations, in view of tho intention of the authority, if radio was successful in the schools already fitted, to extend its use to all schools in the city. Mr Sharp has consulted the head masters and head mistresses of the schools in. conference. lie found a largo measure of general agreement that wireless can properly be regarded as a serious instrument of education if the following criteria can be satisfied:—

(1) That children can listen with the same absence of conscious effort with which they attend to an interesting teacher giving his lesson in person. Tho conscious and tiring effort of the child to pick out and distinguish the message of the wireless was emphasised time after time, as one of the difficulties to bo overcome.

(2) The transmission should bo adapted to the needs of the schools. (3) The speakers should be used to exposition for children. (4) The installations must be kept up to a high degree of technical efficiency, or considerable waste of time and money is inevitable. Mr Sharp says that tho general feeling of head teachers is that tho above conditions would make wireless a serious instrument of education, but that under present conditions it can hardly bo so regarded. Transmission through a loud-speaker, ho said, lacks the personal qualities brought into play by tho teacher speaking in person to his class, and experience shows that it is very difficult indeed to maintain tho attention of young children, or even of older children, unless the matter is extraordinarily good, interesting, well delivered, and with almost perfect reception. Further, in actual practice, reception is by no means perfect. In addition, there is the cost of keeping the outfits in good working order. It is estimated that every forty schools would need the whole time of ono man; for the schools of Sheffield alono would cost £11,(300 per annum. This cost, in Mr Sharp’s opinion, is out of all proportion to tho educational benefits which would accrue.

WHY BROADCAST AT A LOSS? THE AMERICAN VIEWPOINT. In his dedicatory speech at the opening of the new SU,UOU-wati. transmitter, WLW, at Cincinnati, Ohio, Rowel Crosiey, jun., president of the Crosiey Radio Corporation, answered a number of questions bearing on radio which have been put to him by listeners, (reports the ‘New York Times’). “Some people have asked me,” said Mr Crosiey, “ Why do you broadcast?” Do you make any money out of it? Does’it cost you much money? If it is expensive, why do you keep it up? “ Being in the business of nuinuiacturing radio sets, we feel a certain obligation to every radio listener to help in providing the entertainment for which liis receiving set was designed. Of course, it may seem to some that it is similar to an automobile manufacturing concern supplying the gasoline after they had sold the car. And I rather imagine that it is something like that, lor if there were no other source ot supply for gasoline than that which would have to be provided by the automobile manufacturers, I fee! certain that they would be compelled to go into the oil business. ‘‘ But it is more than that. I feel that a broadcasting station is a tremendous means ■of developing goodwill. Goodwill is essential in business. The more friends we are able to. make in providing, an excellent broadcasting service for the greatest possible number of people, the greater the goodwill .we can build up. “To answer the question: ‘ls it expensive to operate a boadcasting station? 1 The last two months our records show that the operating deficit for WLW and WSAI has been 10,000 dollars per month. Of course, it has cost a great deal more than that, but w© do have some revenue which has been deducted from the total operating cost to make the net cost. “Are we justified in spending this much money each month for broadcasting? It is impossible to translate the service that we are rendering into a dollars and cents investment basis, and I can only feel, as I said before, Unit anything which creates goodwill, and so much goodwill, must be worth all the money that wo arc spending for it. “Sometimes I have wondered whether the radio audience does not take this service rendered not only by such stations as ours, but by hundreds of other stations, rather for granted. The listeners do not write as many complimentary letters as they used to. But that is to be expected. We, of course, receive letters from day to day, some of them are brickbats, some of them are bouquets. It is mighty difficult to prepare two complete sets of programmes, to keep two broadcasting stations in operation from morning until late'at night and please everybody.”